Silicon carbide fibers are considered ideal reinforcing materials for ceramic matrix composites due to their excellent mechanical properties and high-temperature performance.Different types of fibers necessitate indiv...Silicon carbide fibers are considered ideal reinforcing materials for ceramic matrix composites due to their excellent mechanical properties and high-temperature performance.Different types of fibers necessitate individual investigation due to variations in their composition and fabrication processes.This study presents a comprehensive investigation into evolution of the mechanical properties,surface microstructure,and composition of Shicolon-Ⅱ fibers subjected to argon heat treatment at temperatures ranging from 1300℃to 1700℃.The Shicolon-Ⅱ fibers are composed of small-sized β-SiC grains,SiC_(x)O_(y) amorphous phase,and a minor amount of graphite microcrystals.Following treatment in an argon atmosphere at 1300℃,the fibers maintain a monofilament tensile strength of 3.620 GPa,corresponding to a retention of 98.32%.This strength diminishes to 2.875 GPa,equating to a retention of 78.08%,after treatment at 1500℃.The reduction in mechanical properties of the fibers can be ascribed to the decomposition of the amorphous phase and the growth of β-SiC grains.Furthermore,creep resistance is an essential factor influencing the long-term performance of composite materials.After treatment at temperatures above 1400℃,the high-temperature creep resistance of the fibers is significantly enhanced due to growth of β-SiC grains.This study offers valuable theoretical insights into high-temperature applications of second-generation fibers,contributing to an enhanced understanding of their performance under extreme conditions.展开更多
The TiB+TiC dual-reinforced B_(4)C/TC4 composite was in-situ fabricated via incorporating 0.5wt%B_(4)C reinforcement during the laser melting deposition process.Different heat treatments of annealing and solid solutio...The TiB+TiC dual-reinforced B_(4)C/TC4 composite was in-situ fabricated via incorporating 0.5wt%B_(4)C reinforcement during the laser melting deposition process.Different heat treatments of annealing and solid solution were used to regulate the microstructure,mechanical properties,and corrosion properties of B_(4)C/TC4 composite.Results show that with the increase in temperature from 500℃to 800°C,partial lamellarα-Ti in the as-deposited sample is gradually transformed into equiaxedα-Ti,accompanied by the disappearance of basketweave microstructure.At 1100°C,a small portion of TiC phase suffers fusion.This composite exhibits the optimal combination of strength and plasticity after annealing at 500℃for 4 h followed by furnace cooling,which is attributed to the stress release effect and the refined basketweave microstructure.However,this composite shows a decline in corrosion resistance after various heat treatments due to grain coarsening and micro-galvanic corrosion.展开更多
Heat treatment is applied towood to improve various properties of thematerial.Thepresent study focuses on the colour changes of wood veneer samples due to heat treatment.Native wood species fromJapan and Europe,such a...Heat treatment is applied towood to improve various properties of thematerial.Thepresent study focuses on the colour changes of wood veneer samples due to heat treatment.Native wood species fromJapan and Europe,such as Japanese oak(Quercus mongolica var.crispula),field maple(Acer campestre)and Scots pine(Pinus sylvestris)were used in the experiments.A laboratory-type oven was used to apply the heat at a temperature of 190○C,in the presence of oxygen,for different periods,gradually increasing from 5 to 40 min.The CIELab system(a colour space defined by the International Commission on Illumination)and Near Infrared Spectroscopy(NIR)were employed to evaluate the colour modifications on the samples.As expected,the heat treatment affected the colour of the samples.The lightness index decreased across the three wood species during the treatment.The chroma coordinates changed for pine and maple,while little change occurred in Japanese oak.The overall total colour differences reached their maximum at the final 40-min interval for all wood types.Based on the NIR evaluation,it was found that drastic thermal denaturation of cellulose was unlikely to occur,and the changes in the intermolecular interaction of water affected the colour of the specimens.The data and information of this study could be useful for industrial applications where the veneer of such species is desired.Such heat-treated veneers can be considered as value-added products in furniture manufacturing as well as restoration of furniture units where such veneer is used as an overlay.展开更多
Laser welding is a highly promising joining method for Al alloys.However,certain limitations such as elevated thermal input and keyhole instability are associated with its application in medium-thickness aluminium all...Laser welding is a highly promising joining method for Al alloys.However,certain limitations such as elevated thermal input and keyhole instability are associated with its application in medium-thickness aluminium alloy plates.To address these issues,circular oscillating laser welding combined with post-weld heat treatment was employed to improve the formation quality and mechanical properties of the welds.The effects of the frequency of circular oscillating laser on the forming quality,microstructure,and properties of the welds were analyzed.At an oscillation frequency of 200 Hz,the grain size in the weld zone was reduced compared to single laser welding,and the maximum tensile strength of the weld was observed to reach(264.96±1.33)MPa,representing approximately 61.19%of the base metal.Following the post-weld heat treatment of"solid solution and artificial aging",the grain boundary segregation was diminished.Nanoscale precipitated phases are present in the weld zone.Furthermore,the tensile strength was augmented to(386.35±5.65)MPa,representing approximately 89.23%of the strength of the base metal.The results of this study can provide a theoretical basis and technological reference for the circular oscillating laser welding of medium-thickness 2219-T 6 aluminium alloy plates.展开更多
The effect of different intermediate annealing heat treatments on the surface microstructures and anodic oxide film structures of rolled Al-5.6Mg sheets was studied.The results show that when the continuous annealing ...The effect of different intermediate annealing heat treatments on the surface microstructures and anodic oxide film structures of rolled Al-5.6Mg sheets was studied.The results show that when the continuous annealing is used to control microstructures of the sheets instead of the static state annealing in the intermediate annealing process,the surface grain size of the sheets can be reduced by about 65.7%,and the size of the Mg precipitation phase(Mg_(2)Al_(3))can be reduced by about 67%.Under the combined influence of grain size,precipitation phase,and texture,the highest glossiness can be obtained,which is attributed to continuous intermediate annealing and stabilization annealing at low temperature.The uniform grain and precipitation structures is beneficial to reducing the inhomogeneous dissolution of the oxide film and to obtain the anodic oxide film with uniform thickness and high glossiness.展开更多
The performances of magnesium alloys remain insufficient to further enhance the application potential of ultralight magnesium alloys.In this work,a Mg-8Li-3Y-2Zn alloy was prepared through vacuum melting and subsequent...The performances of magnesium alloys remain insufficient to further enhance the application potential of ultralight magnesium alloys.In this work,a Mg-8Li-3Y-2Zn alloy was prepared through vacuum melting and subsequent heat treatment at 300,450,and 500°C.The material properties of the resulting samples were assessed through microstructural observation,tensile testing,electrical conductivity measurements,and electromagnetic shielding effectiveness(EMI-SE)testing.The influence of the Mg-8Li-3Y-2Zn alloy microstructure on its mechanical and electromagnetic shielding properties in different states was investigated.It was found that the as-cast alloy containsα-Mg,β-Li,Mg_(3)Zn_(3)Y_(2),and Mg_(12)ZnY phases.Following heat treatment at 500℃(HT500),the blockα-Mg phase transformedfine needle-shapes,its tensile strength increased to 263.7 MPa,and its elongation reached 45.3%.The mechanical properties of the alloy were significantly improved by the synergistic effects imparted by the needle-shapedα-Mg phase,solid solution strengthening,and precipitation strengthening.The addition of Y and Zn improved the EMI-SE of Mg-8Li-1Zn alloy,wherein the HT500 sample exhibits the highest SE,maintaining a value of 106.7–76.9 dB in the frequency range of 30–4500 MHz;this performance has rarely been reported for electromagnetically shielded alloys.This effect was mainly attributed to the multiple reflections of electromagnetic waves caused by the severe impedance mismatch of the abundant phase boundaries,which were in turn provided by the dual-phase(α/β)and secondary phases.Furthermore,the presence of nano-precipitation was also believed to enhance the absorption of electromagnetic waves.展开更多
Laser additively manufactured(LAM)Ni-based superalloys commonly exhibit low strength and high residual stress in the as-built state,requiring post-heat treatment to improve mechanical properties.We propose a modified ...Laser additively manufactured(LAM)Ni-based superalloys commonly exhibit low strength and high residual stress in the as-built state,requiring post-heat treatment to improve mechanical properties.We propose a modified heat treatment(MHT)process that only involves a single-step aging at 650℃ for 4 h to achieve high strength,high ductility,and low residual stress simultaneously in a laser powder bed fusion(LPBF)-processed Inconel 718(IN718)alloy.The MHT treated alloy exhibits comparable tensile strength(1368 MPa)to the conventional solution plus two-step aging(SA)treated alloy(1398 MPa),while the tensile elongation(∼21.7%for MHT treated alloy and 13.4%for SA treated alloy)is 60%higher and the residual stress(∼195 MPa)is 20%lower than the SA treated alloy.The balanced high performance of the MHT IN718 alloy was mainly attributed to the precipitation of abundantγ’’phase with a size of∼5 nm,while the original nano-sized Laves precipitates and dislocation cells were mostly retained.The finer size and higher fraction ofγ”of the MHT sample mainly result from the dislocation structure and compositional variations in the as-built IN718,which promotes precipitation during aging.The retention of Laves phase,and cellular dislocation network in the MHT alloy also contributes to work hardening during tension and suspends the occurrence of necking.This study unveils a unique strengthening and toughening mechanism in the Ni-based superalloy produced by LAM with the presence of abundant Laves precipitates and provides a simple,low energy-consumption and cost-effective heat treatment route for achieving desirable mechanical properties.展开更多
The high strength and stability of the full-lamellar structure guarantee the industrial application of theβ-solidifyingγ-TiAl alloys.However,it is a huge challenge to design an alloy with good hot-deformability as w...The high strength and stability of the full-lamellar structure guarantee the industrial application of theβ-solidifyingγ-TiAl alloys.However,it is a huge challenge to design an alloy with good hot-deformability as well as the full-lamellar structure.The low-cost Ti-42.5Al-2Mn-0.4Mo-0.1B-0.1C(at.%)alloy was designed,which undergoes bothβandαsingle-phase region during the solidification.It is found that the full-lamellar structure can be obtained by the solution heat treatment at 1230℃ for 20 min and then aging treatment at 800℃ for 3 h.Interestingly,a new microstructure,namely,the pearlitic-like microstructure(PM)induced by theα_(2)/γ→βo+γcellular reaction was observed when the aging temperature is increased to above 800℃.The volume fraction of the PM is gradually increased from 0%to 25.5%,65%,and 94%according to elevated aging temperature from 800 to 900,1000,and 1050℃,respectively.The mechanism of the reducedα_(2)/γlamellae and PM formation was discussed regarding the heterogeneous distribution ofβstabilizing elements and the interface energy stored inα_(2)/γlamellae.展开更多
The thermotropic liquid crystal polyester(TLCP)fiber is an increasingly important strategic high-performance fiber.In this paper,the TLCP was prepared by two-step melt polymerization using 4-hydroxybenzoic acid(HBA)an...The thermotropic liquid crystal polyester(TLCP)fiber is an increasingly important strategic high-performance fiber.In this paper,the TLCP was prepared by two-step melt polymerization using 4-hydroxybenzoic acid(HBA)and 6-hydroxy-2-naphthoic acid(HNA)as comonomers at a molar ratio of 7∶3.The structure of TLCP was confirmed by the Fourier transform infrared(FTIR)spectrometer and nuclear magnetic resonance(NMR)spectrometer.The thermal and rheological properties of TLCP before and after heat treatment were analyzed systematically by the differential scanning calorimeter(DSC),dynamic mechanical analyzer(DMA)and high-temperature rotational rheometer.The results revealed that the melting temperature,glass transition temperature and melt viscosity of the TLCP increased significantly after heat treatment.It indicates that the crystallization of the TLCP is perfect,and solid-phase condensation occurs during heat treatment,which increases its molecular mass.In conclusion,heat treatment at a temperature below but close to the melting temperature can effectively regulate the structure and properties of the TLCP,and the results of this study can provide a reference for the high strengthening of TLCP fibers.展开更多
Due to the gradually prominent impact of fracture characteristics and serrated yielding in the application of nickel-based superalloys,the hot tensile properties of Inconel 718 superalloy were studied,including fractu...Due to the gradually prominent impact of fracture characteristics and serrated yielding in the application of nickel-based superalloys,the hot tensile properties of Inconel 718 superalloy were studied,including fracture behavior,mechanical properties,and plastic behavior.The experiments adopted three heat treatment regimes and two tensile directions.Results show that various heat treatments make grain sizes different.The larger-sized grains make the vertical surface uneven,which also decrease the number of grain boundaries and carbides,restricting the occurrence of dimples and ultimately reducing the material plasticity.The reduced grain boundaries can decrease dislocations,increase the demand for thermal activation energy,and transform the serration mode of serrated yielding.In addition,various heat treatments also make precipitates different.Carbides can promote the formation of dimples.The needle-shaped δ phase precipitates at grain boundaries and twin boundaries,and slightly inclines towards the rolling direction.Therefore,its pinning effect is outstanding along the transverse direction,which can affect the dimple aggregation and the dislocation movement,ultimately exhibiting anisotropy in fracture characteristics,mechanical properties,and serrated yielding.展开更多
The effect of holding time of double annealing process on the microstructure and mechanical properties of Ti-5Al-5Mo-5V1Cr-1Fe(Ti55511)alloy was investigated.Results reveal that the shape and size of the primaryα(α_...The effect of holding time of double annealing process on the microstructure and mechanical properties of Ti-5Al-5Mo-5V1Cr-1Fe(Ti55511)alloy was investigated.Results reveal that the shape and size of the primaryα(α_(p))phase are predominantly influenced by the holding time at the first stage.With the prolongation of holding time,the long strip of α_(p) is transformed into a short rod due to the terminal migration mechanism,leading to the broadening growth,and the growth of α_(p) slows down when the holding time is over 2 h.The volume fraction of α_(p) is mainly affected by the holding time of the second stage:with the prolongation of holding time,the volume fraction of α_(p) is increased,which is accompanied by the precipitation of the secondaryα(α_(s)).The mechanical properties of Ti55511 alloy are influenced by bothα_(p) andαs.Tensile results indicate that the optimal holding time of double annealing is 1-4 h for the first stage and 0.5-2 h for the second stage.展开更多
Heat treatment processes, such as annealing and quenching, are crucial in determining residual stress evolution, microstructural changes and mechanical properties of metallic materials, with residual stresses playing ...Heat treatment processes, such as annealing and quenching, are crucial in determining residual stress evolution, microstructural changes and mechanical properties of metallic materials, with residual stresses playing a greater role in the performance of components. This paper investigates the effect of heat treatment on residual stresses induced in AISI 1025, manufactured using LENS. Finite element model was developed and simulated to analyze residual stress development. AISI 1025 samples suitable for tool and die applications in Fused Deposition Modelling (FDM) filament production, were fabricated using Laser Engineered Net Shaping (LENS) process, followed by heat treatment where annealing and quenching processes were done. The material’s microstructure, residual stress and hardness of heat-treated samples under investigation, were compared against the as-built samples. The results indicated that after annealing, tensile residual stresses were reduced by 93%, resulting in a reduced crack growth rate, compared to the as-built sample, although the hardness was reduced significantly by 25%. On the other hand, high tensile residual stresses of 425 ± 14 MPa were recorded after quenching process with an improvement of hardness by 21%.展开更多
Sugarcane bagasse(SCB)is a promising natural fiber for bio-based composites,but its high moisture absorption and poor interfacial adhesion with polymer matrices limit mechanical performance.While chemical treatments h...Sugarcane bagasse(SCB)is a promising natural fiber for bio-based composites,but its high moisture absorption and poor interfacial adhesion with polymer matrices limit mechanical performance.While chemical treatments have been extensively explored,limited research has addressed how thermal treatment alone alters the surface properties and reinforcing behavior of SCB fibers.This study aims to fill that gap by investigating the effects of heat treatment on SCB fiber structure and its performance in starch/poly(vinyl alcohol)(PVA)composites.Characterization techniques including Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and scanning electron microscopy(SEM)were employed to analyze changes in fiber morphology,surface chemistry,and crystallinity.Mechanical properties were assessed via tensile,flexural,and impact testing,and moisture absorption was also evaluated.Composites reinforced with SCB fibers treated at 200○C exhibited significantly superior mechanical properties compared to those prepared with untreated or differently treated fibers.The tensile,flexural,and impact performance of the composites were 15.13,19.37 MPa,and 7.28 J/m,respectively.Composites treated at this temperature also retained better mechanical properties after exposure to humidity.These findings demonstrate that heat treatment is a simple and sustainable method to improve the durability and mechanical performance of nature fiber-reinforced composites,expanding their potential for environmentally friendly material applications.展开更多
The development of cost-effective titanium alloys with outstanding mechanical properties has always been a primary concern of the modern aerospace industry.However,the intrinsic sensitivity of theirαprecipitates to h...The development of cost-effective titanium alloys with outstanding mechanical properties has always been a primary concern of the modern aerospace industry.However,the intrinsic sensitivity of theirαprecipitates to heat treatments proliferates the manufacturing costs to achieve desirable strength and ductility,especially in engineering occasions.In current work,a silicide-containingα+βTi-5Al-7.5V-0.5Mo-0.5Zr-0.5Si(TC5751S)alloy has been evidenced to exhibit advanced mechanical properties with reduced sensitivity to heat treatments.It is noted that more nano-scale secondaryα(αs)precipitate with a simultaneous dissolution in micron-scale primaryα(αp)and(Ti,Zr)_(5)Si_(3)silicides in the current alloy as the solution temperature increases.However,this alloy shows excellent and stabilized strength-ductility synergy in all cases(ultimate tensile strength:1335±30 MPa,yield strength:1245±30 MPa,fracture strain:9.6%±0.5%)irrespective of the aforementioned variations in the microstructure.This stabilized strength and ductility of TC5751S are rationalized based on the compensation mechanisms be-tween the contributions from silicide and heterogeneousαprecipitates.The quantitative analysis unveils that the increased α_(s)/β phase boundary strengthening(σ_(PB))is approximately offset by the decrease in silicide strengthening(σ_(silicide))due to silicide dissolution with increasing solution temperatures,leading to the strength of TC5751S in a dynamic equilibrium state.Simultaneously,the dissolution of silicides re-duces the cracking tendency and complements the ductility loss due to α_(p) reduction and α_(s) precipitation,leading to the ductility insensitive to heat treatments.Therefore,the compensating role of silicides to the effects of heterogeneousαprecipitates on both the strength and ductility of titanium alloys has been well-verified in our work,providing a novel pathway to the development of high-performance titanium alloys friendly to processing strategies.展开更多
WE43MEO magnesium foils(thickness≤200μm)were successfully produced via hot rolling.The initially extruded material was heat treated at 450℃for 2 h to achieve a more homogenous microstructure.Afterwards the sheets w...WE43MEO magnesium foils(thickness≤200μm)were successfully produced via hot rolling.The initially extruded material was heat treated at 450℃for 2 h to achieve a more homogenous microstructure.Afterwards the sheets were hot rolled at 480℃in two to five rolling passes to achieve a uniform thickness of less than 200μm and finally heat treated(T5 and T6 heat treatment).After foil rolling and final heat treatment the microstructural und texture evolution as well as resulting mechanical properties were investigated.Therefore,the samples were quenched directly after foil rolling and the final heat treatment.The foil rolling led either to a deformation microstructure(two and three passes)or globular grains(four and five passes)depending on the number of rolling passes.As main recrystallisation mechanisms continuous dynamic recrystallisation(CDRX)and twinning induced dynamic recrystallisation(TDRX)were identified.The resulting textures revealed the activation of non-basal slip of<c+a>-dislocations during prior foil rolling.As a result of the rolling,the strength increased and the elongation decreased compared to the extruded and heat-treated state.Furthermore,it was found that a T6 temper increased corrosion resistance of the tested WE43MEO foils.展开更多
Microstructure and corrosion resistance of an as-cast Mg-14Li-8Zn(in wt.%,LZ148)alloy subjected to solid solution treatment(T4)and aging treatment(T6)were investigated.The results revealed that the large eutectic MgLi...Microstructure and corrosion resistance of an as-cast Mg-14Li-8Zn(in wt.%,LZ148)alloy subjected to solid solution treatment(T4)and aging treatment(T6)were investigated.The results revealed that the large eutectic MgLi_(2)Zn(θ’)phase formed in as-cast LZ148 alloy were completely dissolved intoβ-Li matrix after T4 treatment,and meanwhile nanoθ’phase could be rapidly precipitated in T4 sample,and then theθ’nanoprecipitates transformed into MgLiZn(θ)phase with a moderate size after T6 treatment.The as-cast sample presented the worst corrosion resistance due to the occurrence of strong micro-galvanic effect between the cathodic eutecticθ’phase and anodicβ-Li matrix.After T4 treatment,the corrosion resistance of as-cast LZ148 alloy was dramatically improved,which was primarily ascribed to the trivial micro-galvanic effect due to the absence of noble eutecticθ’phase.In addition,the dispersed MgLi2Zn nano-precipitates and/or the homogenized distribution of alloying elements in matrix were also beneficial for the improved corrosion resistance of T4 sample.Furthermore,the lower local strain energy in the matrix of T4 sample could also contribute to the excellent corrosion resistance.However,the precipitatedθphases in T6 sample were detrimental to further improve corrosion performance due to the reactivated micro-galvanic effect.At last,the main compositions of surface film on the three samples were also revealed in detail,attributing to the different corrosion resistance of three samples as well.展开更多
Fe(Al,Ta)/Fe_(2)Ta(Al)eutectic composites with solidification rates of 6,20,30,and 80μm/s were prepared by a modified Bridgman directional solidification technology.The coarse Fe_(2)Ta(Al)Laves phase was precipitated...Fe(Al,Ta)/Fe_(2)Ta(Al)eutectic composites with solidification rates of 6,20,30,and 80μm/s were prepared by a modified Bridgman directional solidification technology.The coarse Fe_(2)Ta(Al)Laves phase was precipitated at the eutectic colony boundary during the solidification process,which can affect the stability of microstructure and properties of the composites.The coarse Laves phase was refined using different heat treatment processes in the present paper.The influences of different heat treatment parameters on the Laves phase content,lamella/rod spacing,and mechanical properties were investigated in detail.In addition,the corrosion behaviors of Fe(Al,Ta)/Fe_(2)Ta(Al)eutectic composites before and after being annealed heat treatment in a 3 g/L Na_(2)S_(2)O_(3)solution were also studied.It is shown that both the content of Laves phase and lamella/rod spacing are gradually decreased after heat treatment.Micro-hardness is decreased,while the yield strength,compressive strength,and corrosion resistance are improved.The optimum heat treatment process is selected as well.展开更多
Creep is one of the most typical failure modes for the turbine blades of an aero-engine.The microstructure of the turbine blades after long-term service can be adjusted by rejuvenation heat treatment(RHT)to restore it...Creep is one of the most typical failure modes for the turbine blades of an aero-engine.The microstructure of the turbine blades after long-term service can be adjusted by rejuvenation heat treatment(RHT)to restore its creep properties.In this work,a series of RHT experiments were carried out on a directionally solidified(DS)nickel-based superalloy under different solution temperatures and primary aging temperatures based on the standard heat treatment(SHT)process parameters to investigate the mechanism of temperature influence on DS's microstructure after RHT.It is indicated that a more uniform microstructure can be obtained under higher solution temperatures and lower primary aging temperatures compared to the SHT process.Furthermore,by employing the image processing methods to quantify microstructural parameters,a comprehensive indicator parameter for the RHT effect(marked as Prej)was proposed to characterize the effects of RHT on DS superalloy's microstructure and creep property combined with the entropy weight method.Based on this,a regression model to describe the relationship between RHT process parameters and Prej was constructed by using the response surface methodology(RSM).It is revealed that the optimal solution temperature and primary aging temperature for this DS superalloy are 1283°C and 1095°C,respectively.Then the conclusion was validated through complete creep experiments on the DS superalloy,which showed the creep life after RHT reaches 95.5%of the SHT specimen,and the total life has increased by 20.6%.展开更多
The hardenability of steel is crucial for its durability and performance in engineering applications,significantly influencing mechanical properties such as hardness,strength,and wear resistance.As the engineering fie...The hardenability of steel is crucial for its durability and performance in engineering applications,significantly influencing mechanical properties such as hardness,strength,and wear resistance.As the engineering field continuously demands higher-performance steel materials,a deep understanding of the key influencing factors on hardenability is crucial for developing quality steel that meets stringent application requirements.The effects of some specific elements,including carbon(C),vanadium(V),molybdenum(Mo),and boron(B),as well as heat treatment process parameters such as austenitizing temperature,austenitizing holding time,and cooling rate,were examined.It aims to elucidate the interactions among these factors and their influence on steel hardenability.For each influencing factor,the heat treatment procedure,characteristic microstructure resulting from it,and corresponding Jominy end quench curves were discussed.Furthermore,based on the continuous development of big data technology in the field of materials,the use of machine learning to predict the hardenability of steel and guide the design of steel material was also introduced.展开更多
In the directed energy deposition(DED)process with high heat input,repeated heating and cooling cycles in the deposited layers have a signifcant efect on the microstructure.Because of the diferences in the cyclic numb...In the directed energy deposition(DED)process with high heat input,repeated heating and cooling cycles in the deposited layers have a signifcant efect on the microstructure.Because of the diferences in the cyclic numbers and peak temperatures from the lower layer to the upper layer,inhomogeneous microstructures are formed in the as-built components.In this work,a cyclic heat treatment(CHT)with gradual cooling was used to simulate the thermal process during the DED process of Ti-5Al-3Mo-3V-2Cr-2Zr-1Nb-1Fe(Ti5321)near-βTi alloy.The efect of CHT on the microstructural evolution,especially the spheroidization ofαphase,was investigated.As the CHT cycle increased,the volume fraction ofαphase gradually increased from 35.9%after 1 cycle to 60.9%after 100 cycles,and the length ofαphase frst increased and then gradually decreased,while the width ofαphase increased slowly.The aspect ratio ofαphase decreased from 9.90±3.39 after 1 cycle to 2.37±0.87 after 100 cycles,implying that CHT inducedαphase spheroidization.This phenomenon resulted from both the boundary splitting mechanism and the termination migration mechanism during CHT.The evolution of microstructure afects its mechanical properties.As the CHT cycles increased,the hardness increased overall,from 342.8±5.3 HV after 1 cycle to 400.3±3.4 HV after 100 cycles.This work provides a potential method to tailor the microstructure of near-βTi alloys by heat treatment alone,especially for non-deformable additively manufactured metal components.展开更多
基金National Natural Science Foundation of China(52172108)National Key R&D Program of China(2022YFB3707700)Strategic Priority Research Program of the Chinese Academy of Sciences(XDC0144005)。
文摘Silicon carbide fibers are considered ideal reinforcing materials for ceramic matrix composites due to their excellent mechanical properties and high-temperature performance.Different types of fibers necessitate individual investigation due to variations in their composition and fabrication processes.This study presents a comprehensive investigation into evolution of the mechanical properties,surface microstructure,and composition of Shicolon-Ⅱ fibers subjected to argon heat treatment at temperatures ranging from 1300℃to 1700℃.The Shicolon-Ⅱ fibers are composed of small-sized β-SiC grains,SiC_(x)O_(y) amorphous phase,and a minor amount of graphite microcrystals.Following treatment in an argon atmosphere at 1300℃,the fibers maintain a monofilament tensile strength of 3.620 GPa,corresponding to a retention of 98.32%.This strength diminishes to 2.875 GPa,equating to a retention of 78.08%,after treatment at 1500℃.The reduction in mechanical properties of the fibers can be ascribed to the decomposition of the amorphous phase and the growth of β-SiC grains.Furthermore,creep resistance is an essential factor influencing the long-term performance of composite materials.After treatment at temperatures above 1400℃,the high-temperature creep resistance of the fibers is significantly enhanced due to growth of β-SiC grains.This study offers valuable theoretical insights into high-temperature applications of second-generation fibers,contributing to an enhanced understanding of their performance under extreme conditions.
基金Tianjin Municipal Natural Science Foundation(23JCYBJC00040)National Natural Science Foundation of China(52175369)。
文摘The TiB+TiC dual-reinforced B_(4)C/TC4 composite was in-situ fabricated via incorporating 0.5wt%B_(4)C reinforcement during the laser melting deposition process.Different heat treatments of annealing and solid solution were used to regulate the microstructure,mechanical properties,and corrosion properties of B_(4)C/TC4 composite.Results show that with the increase in temperature from 500℃to 800°C,partial lamellarα-Ti in the as-deposited sample is gradually transformed into equiaxedα-Ti,accompanied by the disappearance of basketweave microstructure.At 1100°C,a small portion of TiC phase suffers fusion.This composite exhibits the optimal combination of strength and plasticity after annealing at 500℃for 4 h followed by furnace cooling,which is attributed to the stress release effect and the refined basketweave microstructure.However,this composite shows a decline in corrosion resistance after various heat treatments due to grain coarsening and micro-galvanic corrosion.
文摘Heat treatment is applied towood to improve various properties of thematerial.Thepresent study focuses on the colour changes of wood veneer samples due to heat treatment.Native wood species fromJapan and Europe,such as Japanese oak(Quercus mongolica var.crispula),field maple(Acer campestre)and Scots pine(Pinus sylvestris)were used in the experiments.A laboratory-type oven was used to apply the heat at a temperature of 190○C,in the presence of oxygen,for different periods,gradually increasing from 5 to 40 min.The CIELab system(a colour space defined by the International Commission on Illumination)and Near Infrared Spectroscopy(NIR)were employed to evaluate the colour modifications on the samples.As expected,the heat treatment affected the colour of the samples.The lightness index decreased across the three wood species during the treatment.The chroma coordinates changed for pine and maple,while little change occurred in Japanese oak.The overall total colour differences reached their maximum at the final 40-min interval for all wood types.Based on the NIR evaluation,it was found that drastic thermal denaturation of cellulose was unlikely to occur,and the changes in the intermolecular interaction of water affected the colour of the specimens.The data and information of this study could be useful for industrial applications where the veneer of such species is desired.Such heat-treated veneers can be considered as value-added products in furniture manufacturing as well as restoration of furniture units where such veneer is used as an overlay.
基金Projects(E2024203001,E2024203049,E2024203071)supported by the Hebei Natural Science Foundation of ChinaProject(236Z1805G)supported by the S&T Program of Hebei,China。
文摘Laser welding is a highly promising joining method for Al alloys.However,certain limitations such as elevated thermal input and keyhole instability are associated with its application in medium-thickness aluminium alloy plates.To address these issues,circular oscillating laser welding combined with post-weld heat treatment was employed to improve the formation quality and mechanical properties of the welds.The effects of the frequency of circular oscillating laser on the forming quality,microstructure,and properties of the welds were analyzed.At an oscillation frequency of 200 Hz,the grain size in the weld zone was reduced compared to single laser welding,and the maximum tensile strength of the weld was observed to reach(264.96±1.33)MPa,representing approximately 61.19%of the base metal.Following the post-weld heat treatment of"solid solution and artificial aging",the grain boundary segregation was diminished.Nanoscale precipitated phases are present in the weld zone.Furthermore,the tensile strength was augmented to(386.35±5.65)MPa,representing approximately 89.23%of the strength of the base metal.The results of this study can provide a theoretical basis and technological reference for the circular oscillating laser welding of medium-thickness 2219-T 6 aluminium alloy plates.
文摘The effect of different intermediate annealing heat treatments on the surface microstructures and anodic oxide film structures of rolled Al-5.6Mg sheets was studied.The results show that when the continuous annealing is used to control microstructures of the sheets instead of the static state annealing in the intermediate annealing process,the surface grain size of the sheets can be reduced by about 65.7%,and the size of the Mg precipitation phase(Mg_(2)Al_(3))can be reduced by about 67%.Under the combined influence of grain size,precipitation phase,and texture,the highest glossiness can be obtained,which is attributed to continuous intermediate annealing and stabilization annealing at low temperature.The uniform grain and precipitation structures is beneficial to reducing the inhomogeneous dissolution of the oxide film and to obtain the anodic oxide film with uniform thickness and high glossiness.
基金supported by the National Natural Sci-ence Foundation of China[No.51564032]Yunnan Provin-cial Department of Education Science Research Fund Project[KKPH202132005]the Analysis and Testing Founda-tion of Kunming University of Science and Technology[2022M20212130086].
文摘The performances of magnesium alloys remain insufficient to further enhance the application potential of ultralight magnesium alloys.In this work,a Mg-8Li-3Y-2Zn alloy was prepared through vacuum melting and subsequent heat treatment at 300,450,and 500°C.The material properties of the resulting samples were assessed through microstructural observation,tensile testing,electrical conductivity measurements,and electromagnetic shielding effectiveness(EMI-SE)testing.The influence of the Mg-8Li-3Y-2Zn alloy microstructure on its mechanical and electromagnetic shielding properties in different states was investigated.It was found that the as-cast alloy containsα-Mg,β-Li,Mg_(3)Zn_(3)Y_(2),and Mg_(12)ZnY phases.Following heat treatment at 500℃(HT500),the blockα-Mg phase transformedfine needle-shapes,its tensile strength increased to 263.7 MPa,and its elongation reached 45.3%.The mechanical properties of the alloy were significantly improved by the synergistic effects imparted by the needle-shapedα-Mg phase,solid solution strengthening,and precipitation strengthening.The addition of Y and Zn improved the EMI-SE of Mg-8Li-1Zn alloy,wherein the HT500 sample exhibits the highest SE,maintaining a value of 106.7–76.9 dB in the frequency range of 30–4500 MHz;this performance has rarely been reported for electromagnetically shielded alloys.This effect was mainly attributed to the multiple reflections of electromagnetic waves caused by the severe impedance mismatch of the abundant phase boundaries,which were in turn provided by the dual-phase(α/β)and secondary phases.Furthermore,the presence of nano-precipitation was also believed to enhance the absorption of electromagnetic waves.
基金financially supported by the Ministry of Science and Technology of China via the National Key Research&Development Plan(Nos.2022YFB3707105 and 2020YFA0405900)Jiangsu Department of Science and Technology via Provincial Key Research&Development(Industrial Foresight and Key Core Technology,No.BE2021037)+1 种基金Department of the National Science Foundation of China(No.52204390)the Natural Science Foundation of Jiangsu Province(No.BK20202010).
文摘Laser additively manufactured(LAM)Ni-based superalloys commonly exhibit low strength and high residual stress in the as-built state,requiring post-heat treatment to improve mechanical properties.We propose a modified heat treatment(MHT)process that only involves a single-step aging at 650℃ for 4 h to achieve high strength,high ductility,and low residual stress simultaneously in a laser powder bed fusion(LPBF)-processed Inconel 718(IN718)alloy.The MHT treated alloy exhibits comparable tensile strength(1368 MPa)to the conventional solution plus two-step aging(SA)treated alloy(1398 MPa),while the tensile elongation(∼21.7%for MHT treated alloy and 13.4%for SA treated alloy)is 60%higher and the residual stress(∼195 MPa)is 20%lower than the SA treated alloy.The balanced high performance of the MHT IN718 alloy was mainly attributed to the precipitation of abundantγ’’phase with a size of∼5 nm,while the original nano-sized Laves precipitates and dislocation cells were mostly retained.The finer size and higher fraction ofγ”of the MHT sample mainly result from the dislocation structure and compositional variations in the as-built IN718,which promotes precipitation during aging.The retention of Laves phase,and cellular dislocation network in the MHT alloy also contributes to work hardening during tension and suspends the occurrence of necking.This study unveils a unique strengthening and toughening mechanism in the Ni-based superalloy produced by LAM with the presence of abundant Laves precipitates and provides a simple,low energy-consumption and cost-effective heat treatment route for achieving desirable mechanical properties.
基金the Jihua Laboratory Scientific Research Project(No.X210291TL210)the National Natural Science Foundation of China(No.51971215).
文摘The high strength and stability of the full-lamellar structure guarantee the industrial application of theβ-solidifyingγ-TiAl alloys.However,it is a huge challenge to design an alloy with good hot-deformability as well as the full-lamellar structure.The low-cost Ti-42.5Al-2Mn-0.4Mo-0.1B-0.1C(at.%)alloy was designed,which undergoes bothβandαsingle-phase region during the solidification.It is found that the full-lamellar structure can be obtained by the solution heat treatment at 1230℃ for 20 min and then aging treatment at 800℃ for 3 h.Interestingly,a new microstructure,namely,the pearlitic-like microstructure(PM)induced by theα_(2)/γ→βo+γcellular reaction was observed when the aging temperature is increased to above 800℃.The volume fraction of the PM is gradually increased from 0%to 25.5%,65%,and 94%according to elevated aging temperature from 800 to 900,1000,and 1050℃,respectively.The mechanism of the reducedα_(2)/γlamellae and PM formation was discussed regarding the heterogeneous distribution ofβstabilizing elements and the interface energy stored inα_(2)/γlamellae.
基金National Key Research and Development Program of China (No.2021YFB3700105)。
文摘The thermotropic liquid crystal polyester(TLCP)fiber is an increasingly important strategic high-performance fiber.In this paper,the TLCP was prepared by two-step melt polymerization using 4-hydroxybenzoic acid(HBA)and 6-hydroxy-2-naphthoic acid(HNA)as comonomers at a molar ratio of 7∶3.The structure of TLCP was confirmed by the Fourier transform infrared(FTIR)spectrometer and nuclear magnetic resonance(NMR)spectrometer.The thermal and rheological properties of TLCP before and after heat treatment were analyzed systematically by the differential scanning calorimeter(DSC),dynamic mechanical analyzer(DMA)and high-temperature rotational rheometer.The results revealed that the melting temperature,glass transition temperature and melt viscosity of the TLCP increased significantly after heat treatment.It indicates that the crystallization of the TLCP is perfect,and solid-phase condensation occurs during heat treatment,which increases its molecular mass.In conclusion,heat treatment at a temperature below but close to the melting temperature can effectively regulate the structure and properties of the TLCP,and the results of this study can provide a reference for the high strengthening of TLCP fibers.
基金National Natural Science Foundation of China(52175353)Shanxi Province Key Research and Development Program(202102150401002)Shanxi Province Major Science and Technology Special Project(202101110401009)。
文摘Due to the gradually prominent impact of fracture characteristics and serrated yielding in the application of nickel-based superalloys,the hot tensile properties of Inconel 718 superalloy were studied,including fracture behavior,mechanical properties,and plastic behavior.The experiments adopted three heat treatment regimes and two tensile directions.Results show that various heat treatments make grain sizes different.The larger-sized grains make the vertical surface uneven,which also decrease the number of grain boundaries and carbides,restricting the occurrence of dimples and ultimately reducing the material plasticity.The reduced grain boundaries can decrease dislocations,increase the demand for thermal activation energy,and transform the serration mode of serrated yielding.In addition,various heat treatments also make precipitates different.Carbides can promote the formation of dimples.The needle-shaped δ phase precipitates at grain boundaries and twin boundaries,and slightly inclines towards the rolling direction.Therefore,its pinning effect is outstanding along the transverse direction,which can affect the dimple aggregation and the dislocation movement,ultimately exhibiting anisotropy in fracture characteristics,mechanical properties,and serrated yielding.
文摘The effect of holding time of double annealing process on the microstructure and mechanical properties of Ti-5Al-5Mo-5V1Cr-1Fe(Ti55511)alloy was investigated.Results reveal that the shape and size of the primaryα(α_(p))phase are predominantly influenced by the holding time at the first stage.With the prolongation of holding time,the long strip of α_(p) is transformed into a short rod due to the terminal migration mechanism,leading to the broadening growth,and the growth of α_(p) slows down when the holding time is over 2 h.The volume fraction of α_(p) is mainly affected by the holding time of the second stage:with the prolongation of holding time,the volume fraction of α_(p) is increased,which is accompanied by the precipitation of the secondaryα(α_(s)).The mechanical properties of Ti55511 alloy are influenced by bothα_(p) andαs.Tensile results indicate that the optimal holding time of double annealing is 1-4 h for the first stage and 0.5-2 h for the second stage.
文摘Heat treatment processes, such as annealing and quenching, are crucial in determining residual stress evolution, microstructural changes and mechanical properties of metallic materials, with residual stresses playing a greater role in the performance of components. This paper investigates the effect of heat treatment on residual stresses induced in AISI 1025, manufactured using LENS. Finite element model was developed and simulated to analyze residual stress development. AISI 1025 samples suitable for tool and die applications in Fused Deposition Modelling (FDM) filament production, were fabricated using Laser Engineered Net Shaping (LENS) process, followed by heat treatment where annealing and quenching processes were done. The material’s microstructure, residual stress and hardness of heat-treated samples under investigation, were compared against the as-built samples. The results indicated that after annealing, tensile residual stresses were reduced by 93%, resulting in a reduced crack growth rate, compared to the as-built sample, although the hardness was reduced significantly by 25%. On the other hand, high tensile residual stresses of 425 ± 14 MPa were recorded after quenching process with an improvement of hardness by 21%.
文摘Sugarcane bagasse(SCB)is a promising natural fiber for bio-based composites,but its high moisture absorption and poor interfacial adhesion with polymer matrices limit mechanical performance.While chemical treatments have been extensively explored,limited research has addressed how thermal treatment alone alters the surface properties and reinforcing behavior of SCB fibers.This study aims to fill that gap by investigating the effects of heat treatment on SCB fiber structure and its performance in starch/poly(vinyl alcohol)(PVA)composites.Characterization techniques including Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and scanning electron microscopy(SEM)were employed to analyze changes in fiber morphology,surface chemistry,and crystallinity.Mechanical properties were assessed via tensile,flexural,and impact testing,and moisture absorption was also evaluated.Composites reinforced with SCB fibers treated at 200○C exhibited significantly superior mechanical properties compared to those prepared with untreated or differently treated fibers.The tensile,flexural,and impact performance of the composites were 15.13,19.37 MPa,and 7.28 J/m,respectively.Composites treated at this temperature also retained better mechanical properties after exposure to humidity.These findings demonstrate that heat treatment is a simple and sustainable method to improve the durability and mechanical performance of nature fiber-reinforced composites,expanding their potential for environmentally friendly material applications.
基金supported by the National Key Research and Development Program of China(No.2021YFB3702604)the National Natural Science Foundation of China(No.52001258).
文摘The development of cost-effective titanium alloys with outstanding mechanical properties has always been a primary concern of the modern aerospace industry.However,the intrinsic sensitivity of theirαprecipitates to heat treatments proliferates the manufacturing costs to achieve desirable strength and ductility,especially in engineering occasions.In current work,a silicide-containingα+βTi-5Al-7.5V-0.5Mo-0.5Zr-0.5Si(TC5751S)alloy has been evidenced to exhibit advanced mechanical properties with reduced sensitivity to heat treatments.It is noted that more nano-scale secondaryα(αs)precipitate with a simultaneous dissolution in micron-scale primaryα(αp)and(Ti,Zr)_(5)Si_(3)silicides in the current alloy as the solution temperature increases.However,this alloy shows excellent and stabilized strength-ductility synergy in all cases(ultimate tensile strength:1335±30 MPa,yield strength:1245±30 MPa,fracture strain:9.6%±0.5%)irrespective of the aforementioned variations in the microstructure.This stabilized strength and ductility of TC5751S are rationalized based on the compensation mechanisms be-tween the contributions from silicide and heterogeneousαprecipitates.The quantitative analysis unveils that the increased α_(s)/β phase boundary strengthening(σ_(PB))is approximately offset by the decrease in silicide strengthening(σ_(silicide))due to silicide dissolution with increasing solution temperatures,leading to the strength of TC5751S in a dynamic equilibrium state.Simultaneously,the dissolution of silicides re-duces the cracking tendency and complements the ductility loss due to α_(p) reduction and α_(s) precipitation,leading to the ductility insensitive to heat treatments.Therefore,the compensating role of silicides to the effects of heterogeneousαprecipitates on both the strength and ductility of titanium alloys has been well-verified in our work,providing a novel pathway to the development of high-performance titanium alloys friendly to processing strategies.
文摘WE43MEO magnesium foils(thickness≤200μm)were successfully produced via hot rolling.The initially extruded material was heat treated at 450℃for 2 h to achieve a more homogenous microstructure.Afterwards the sheets were hot rolled at 480℃in two to five rolling passes to achieve a uniform thickness of less than 200μm and finally heat treated(T5 and T6 heat treatment).After foil rolling and final heat treatment the microstructural und texture evolution as well as resulting mechanical properties were investigated.Therefore,the samples were quenched directly after foil rolling and the final heat treatment.The foil rolling led either to a deformation microstructure(two and three passes)or globular grains(four and five passes)depending on the number of rolling passes.As main recrystallisation mechanisms continuous dynamic recrystallisation(CDRX)and twinning induced dynamic recrystallisation(TDRX)were identified.The resulting textures revealed the activation of non-basal slip of<c+a>-dislocations during prior foil rolling.As a result of the rolling,the strength increased and the elongation decreased compared to the extruded and heat-treated state.Furthermore,it was found that a T6 temper increased corrosion resistance of the tested WE43MEO foils.
基金Tplied Basic Research Foundation of Guangdong Province(Grant Nos.2024A1515030065,2023A1515012299 and2023A1515010075)Basic and Applied Basic ResearchProject of Guangzhou(Grant Nos.2024A04J6299 and202201011454)+3 种基金Young Talent Support Project·of Guangzhou Association for Science and Technology(Grant No.QT2024-012)National Natural Science Foundation of China(Grant Nos.52101283 and 52101132)Young Elite Scientist Spon-sorship Program by CAST(Grant No.YESS20230412)National College Students Innovation and EntrepreneurshipTraining Program(Grant No.xj2024118450706)。
文摘Microstructure and corrosion resistance of an as-cast Mg-14Li-8Zn(in wt.%,LZ148)alloy subjected to solid solution treatment(T4)and aging treatment(T6)were investigated.The results revealed that the large eutectic MgLi_(2)Zn(θ’)phase formed in as-cast LZ148 alloy were completely dissolved intoβ-Li matrix after T4 treatment,and meanwhile nanoθ’phase could be rapidly precipitated in T4 sample,and then theθ’nanoprecipitates transformed into MgLiZn(θ)phase with a moderate size after T6 treatment.The as-cast sample presented the worst corrosion resistance due to the occurrence of strong micro-galvanic effect between the cathodic eutecticθ’phase and anodicβ-Li matrix.After T4 treatment,the corrosion resistance of as-cast LZ148 alloy was dramatically improved,which was primarily ascribed to the trivial micro-galvanic effect due to the absence of noble eutecticθ’phase.In addition,the dispersed MgLi2Zn nano-precipitates and/or the homogenized distribution of alloying elements in matrix were also beneficial for the improved corrosion resistance of T4 sample.Furthermore,the lower local strain energy in the matrix of T4 sample could also contribute to the excellent corrosion resistance.However,the precipitatedθphases in T6 sample were detrimental to further improve corrosion performance due to the reactivated micro-galvanic effect.At last,the main compositions of surface film on the three samples were also revealed in detail,attributing to the different corrosion resistance of three samples as well.
基金Funded by the Key Industry Innovation Chain(Group)Project of Shaanxi Province,China(No.2019ZDLGY 04-04)the Project of Yulin Science and Technology Bureau(No.2023-CXY-197)。
文摘Fe(Al,Ta)/Fe_(2)Ta(Al)eutectic composites with solidification rates of 6,20,30,and 80μm/s were prepared by a modified Bridgman directional solidification technology.The coarse Fe_(2)Ta(Al)Laves phase was precipitated at the eutectic colony boundary during the solidification process,which can affect the stability of microstructure and properties of the composites.The coarse Laves phase was refined using different heat treatment processes in the present paper.The influences of different heat treatment parameters on the Laves phase content,lamella/rod spacing,and mechanical properties were investigated in detail.In addition,the corrosion behaviors of Fe(Al,Ta)/Fe_(2)Ta(Al)eutectic composites before and after being annealed heat treatment in a 3 g/L Na_(2)S_(2)O_(3)solution were also studied.It is shown that both the content of Laves phase and lamella/rod spacing are gradually decreased after heat treatment.Micro-hardness is decreased,while the yield strength,compressive strength,and corrosion resistance are improved.The optimum heat treatment process is selected as well.
基金Supported by National Natural Science Foundation of China(Grant No.52275142)Science Center for Gas Turbine Project(Grant Nos.P2022-AIII-003-001,P2022-B-III-005-001)+1 种基金National Science and Technology Major Project(Grant Nos.J2019-IV-0009-0077,Y2022-IV-0002-0019,J2019-IV-0008-0076)National Basic Scientific Research Project(Grant No.JCKY2021601B204)。
文摘Creep is one of the most typical failure modes for the turbine blades of an aero-engine.The microstructure of the turbine blades after long-term service can be adjusted by rejuvenation heat treatment(RHT)to restore its creep properties.In this work,a series of RHT experiments were carried out on a directionally solidified(DS)nickel-based superalloy under different solution temperatures and primary aging temperatures based on the standard heat treatment(SHT)process parameters to investigate the mechanism of temperature influence on DS's microstructure after RHT.It is indicated that a more uniform microstructure can be obtained under higher solution temperatures and lower primary aging temperatures compared to the SHT process.Furthermore,by employing the image processing methods to quantify microstructural parameters,a comprehensive indicator parameter for the RHT effect(marked as Prej)was proposed to characterize the effects of RHT on DS superalloy's microstructure and creep property combined with the entropy weight method.Based on this,a regression model to describe the relationship between RHT process parameters and Prej was constructed by using the response surface methodology(RSM).It is revealed that the optimal solution temperature and primary aging temperature for this DS superalloy are 1283°C and 1095°C,respectively.Then the conclusion was validated through complete creep experiments on the DS superalloy,which showed the creep life after RHT reaches 95.5%of the SHT specimen,and the total life has increased by 20.6%.
基金supported by the National Natural Science Foundation of China(Nos.52122408 and 52071023)Hong-hui Wu also thanks the financial support from the Fundamental Research Funds for the Central Universities(University of Science and Technology Beijing,Nos.FRF-TP-2021-04C1 and 06500135)supported by USTB MatCom of Beijing Advanced Innovation Center for Materials Genome Engineering.
文摘The hardenability of steel is crucial for its durability and performance in engineering applications,significantly influencing mechanical properties such as hardness,strength,and wear resistance.As the engineering field continuously demands higher-performance steel materials,a deep understanding of the key influencing factors on hardenability is crucial for developing quality steel that meets stringent application requirements.The effects of some specific elements,including carbon(C),vanadium(V),molybdenum(Mo),and boron(B),as well as heat treatment process parameters such as austenitizing temperature,austenitizing holding time,and cooling rate,were examined.It aims to elucidate the interactions among these factors and their influence on steel hardenability.For each influencing factor,the heat treatment procedure,characteristic microstructure resulting from it,and corresponding Jominy end quench curves were discussed.Furthermore,based on the continuous development of big data technology in the field of materials,the use of machine learning to predict the hardenability of steel and guide the design of steel material was also introduced.
基金sponsored by the National Natural Science Foundation of China(No.52271108)the Foundation of Xi’an Key Laboratory of High-Performance Titanium Alloy(No.NIN-HTL-2022-02)+2 种基金the Natural Science Foundation of Shanghai(No.21ZR1445100)the Shanghai Science and Technology Development Funds(No.22QB1406500)the ECU DVC Strategic Research Support Fund(No.23965).
文摘In the directed energy deposition(DED)process with high heat input,repeated heating and cooling cycles in the deposited layers have a signifcant efect on the microstructure.Because of the diferences in the cyclic numbers and peak temperatures from the lower layer to the upper layer,inhomogeneous microstructures are formed in the as-built components.In this work,a cyclic heat treatment(CHT)with gradual cooling was used to simulate the thermal process during the DED process of Ti-5Al-3Mo-3V-2Cr-2Zr-1Nb-1Fe(Ti5321)near-βTi alloy.The efect of CHT on the microstructural evolution,especially the spheroidization ofαphase,was investigated.As the CHT cycle increased,the volume fraction ofαphase gradually increased from 35.9%after 1 cycle to 60.9%after 100 cycles,and the length ofαphase frst increased and then gradually decreased,while the width ofαphase increased slowly.The aspect ratio ofαphase decreased from 9.90±3.39 after 1 cycle to 2.37±0.87 after 100 cycles,implying that CHT inducedαphase spheroidization.This phenomenon resulted from both the boundary splitting mechanism and the termination migration mechanism during CHT.The evolution of microstructure afects its mechanical properties.As the CHT cycles increased,the hardness increased overall,from 342.8±5.3 HV after 1 cycle to 400.3±3.4 HV after 100 cycles.This work provides a potential method to tailor the microstructure of near-βTi alloys by heat treatment alone,especially for non-deformable additively manufactured metal components.
