Only a few studies have reported the efects of electrochemical hydrogenation on the tensile mechanical properties of additively manufactured Ti–6Al–4V alloy,in all of them the alloy was processed by laser powder-bed...Only a few studies have reported the efects of electrochemical hydrogenation on the tensile mechanical properties of additively manufactured Ti–6Al–4V alloy,in all of them the alloy was processed by laser powder-bed fusion.Furthermore,the efects of either hot isostatic pressing(HIP)or heat treatment(HT)post-treatments on the mechanical properties were not reported.Here,the Young’s modulus,ultimate tensile stress,and uniform(homogeneous)strain of as-built electron beam melted(EBM)Ti–6Al–4V alloys were studied using small tensile specimens before and after electrochemical hydrogenation,as well as before and after secondary processes of HIP at 920℃ and HT at 1000℃.The tensile properties of all hydrogenated alloys were signifcantly degraded compared to their non-hydrogenated counterparts.The yield stress could not be determined for all hydrogenated alloys,as failure occurred at a strain below 0.2%ofset.The uniform strain of the hydrogenated alloys was less than 1%,compared to 1%–5%for the non-hydrogenated alloys.The fracture mode of the hydrogenated alloys after HIP and HT revealed cleavage fracture,indicating increased brittleness.In the as-built hydrogenated alloy,the fracture mode varied with location:brittle fracture occurred near the surface due to the formation of a hydride layer,while a more ductile fracture with dimples was observed below this layer.展开更多
The present work reports the effect of thermal induced porosity(TIP)on the high-cycle fatigue(HCF)and very high-cycle fatigue(VHCF)behaviors of hot-isostatic-pressed(HIPed)Ti-6Al-4V alloy from gasatomized powder.The r...The present work reports the effect of thermal induced porosity(TIP)on the high-cycle fatigue(HCF)and very high-cycle fatigue(VHCF)behaviors of hot-isostatic-pressed(HIPed)Ti-6Al-4V alloy from gasatomized powder.The results show that the residual pores in the as-HIPed powder compacts present no obvious effect on the HCF life.The regrowth of the residual pores can be observed after solution heat treatment.The pore location ranks the most harmful for the fatigue life compared with the other initiating defects.The maximum stress intensity factors were calculated.The plastic zone size of fine granular area(FGA)is much less than the characteristic size of the microstructure,and the crucial size of the internal pores in this study is about 40μm.The failure types of fatigue specimens in the VHCF regime were classified,and the competition of different failure types was described based on the modified Poisson distribution.展开更多
To increase the adhesion strength between the coating and the substrate, sintered Ti（C,N）-based cermets were selected and deposited with monolayer TiN using a multiarc ion-plating technique; subsequently, hot isosta...To increase the adhesion strength between the coating and the substrate, sintered Ti（C,N）-based cermets were selected and deposited with monolayer TiN using a multiarc ion-plating technique; subsequently, hot isostatic pressing （HIPhag） treatment was performed at 1000℃ using nitrogen pressure up to 110 MPa. The mechanical properties of cermets after a coating process and subsequent HIPing treatment have been evaluated with respect to the hardness, the residual stress, and the coating adhesion. The results show that atter the HIPing process, there was a higher increase ha critical load ha the TiN-coated cermets with lower surface roughness compared with those with higher surface roughness. In all cases, the residual stress was found to be compressive. The effects of substrate surface roughness and posttreatment on the adhesion strength of the coatings were thus investigated. It was also fotmd that the HIPing posttreatment process is well suited for hacreasing the adhesion strength between the coating and the substrate.展开更多
60NiTi alloy is considered to be a promising material for specialized bearing and gear applications due to its high hardness,strength,and low modulus.However,fabricating 60NiTi through conventional processing methods ...60NiTi alloy is considered to be a promising material for specialized bearing and gear applications due to its high hardness,strength,and low modulus.However,fabricating 60NiTi through conventional processing methods is challenging due to the brittleness and poor workability.In this study,60NiTi with high relative density was successfully fabricated directly from pre-alloyed powder through hot isostatic pressing.The effects of solution and aging treatments on microstructure and mechanical properties were systematically studied by advanced characterization techniques.The hot-isostatic-pressed 60NiTi showed low average hardness and elastic strain due to the formation of a soft Ni_(3)Ti phase and B2 NiTi matrix.Solution treatment above 1000℃dissolved the Ni_(3)Ti phase and promoted the formation of nanoscale Ni_(4)Ti_(3)precipitates,which significantly improved the hardness,strength,and elastic strain of 60NiTi.The formation of the Ni_(4)Ti_(3) phase can be mainly attributed to the driving forces induced by the chemical supersaturation and mechanical stress concentration.Finally,the phase transformation mechanisms during heat treatment and compression test were discussed.展开更多
The hot compressive deformation behavior of hot isostatically pressed Ti-47.5Al-2Cr-2Nb-0.2W-0.2B alloy using gas atomization powders was systematically investigated and the processing map was obtained in the temperat...The hot compressive deformation behavior of hot isostatically pressed Ti-47.5Al-2Cr-2Nb-0.2W-0.2B alloy using gas atomization powders was systematically investigated and the processing map was obtained in the temperature range of 1323-1473 Kand strain rate range of 0.001-0.5s^（-1）.The calculated activation energy in the above variational ranges of temperature and strain rate possesses a low activation energy value of approximately 365.6kJ/mol based on the constitutive relationship models developed with the Arrhenius-type constitutive model respectively considering the strain rate and deformation temperature.The hot working flow behavior during the deformation process was analyzed combined with the microstructural evolution.Meanwhile,the processing maps during the deformation process were established based on the dynamic material model and Prasad instability criterion under different deformation conditions.Finally,the optimal hot processing window of this alloy corresponding to the wide temperature range of 1353-1453 Kand the low strain rate of 0.001-0.1s^（-1） was obtained.展开更多
Nd-Fe-B hot-pressed(HP) magnet prepared from melt-spun MQU-F flakes features coarse grains(CG)with the average size of both 200 nm(CGS) and 700 nm(CGL) at flake boundary.The grain growth at the flake boundary of Nd2 F...Nd-Fe-B hot-pressed(HP) magnet prepared from melt-spun MQU-F flakes features coarse grains(CG)with the average size of both 200 nm(CGS) and 700 nm(CGL) at flake boundary.The grain growth at the flake boundary of Nd2 Fe14B/α-Fe composite HP magnet before and after diffusion of low-melting-point Pr82Cu18 phase was investigated,revealing the indispensable role of surface RE-rich phase of meltspun flakes in the formation of CG in HP magnet.The dominant role of surface oxygen content of melt-spun flakes in the formation of CGL has been clarified with etching method.The HP magnet prepared from the etched flakes with dramatically decreased oxygen content exhibits the CG regions merely with homoge neous equiaxed CGS at flake boundary.Consequently,the coercivity(μ0 Hc) shows significant increase while remanent magnetization(μ0 Mr) inappreciable change.Further investigation with sieving method reveals the elimination of CGL via removal of the fine Nd-Fe-B flakes smaller than 54 μm due to their much higher oxygen content,confirming the dominant role of oxygen content in the formation of CGL.The quantitative analysis on the magnetic properties of the above HP magnets reveals the monotonic increase of coercivity(μ0 Hc) and negligible change of remanent magnetization(μ0 Mr) with decreased oxygen contents of Nd-Fe-B flakes.The maximum value of coercivity(μ0 Hc) increases from2.26 to 2.47 T as the oxygen content decreases from 0.1692 wt% to 0.079 wt%.展开更多
Hot isostatic pressing (HIP) temperature has a significant impact on the service performance of powder metallurgy titanium alloys. In this study, a high-temperature titanium alloy, Ti-6.5Al-3.5Mo-1.5Zr-0.3Si, was prep...Hot isostatic pressing (HIP) temperature has a significant impact on the service performance of powder metallurgy titanium alloys. In this study, a high-temperature titanium alloy, Ti-6.5Al-3.5Mo-1.5Zr-0.3Si, was prepared under different HIP temperatures (880–1000℃), and the microstructural evolution and mechanical properties were systematically investigated. The results demonstrated that the HIPed alloys were predominantly composed of more than 80 vol.% α phase and a small amount of β phase, and their phase compositions were basically unaffected by the HIP temperatures. Under the typical single-temperature-maintained HIP (STM-HIP) regime, the microstructure of alloy significantly coarsened as the HIP temperature increased, and the alloy strength exhibited an obvious linear negative correlation with the HIP temperature. On the basis of Hall–Petch relation, the prediction model of grain size was established, and the mathematical equation between HIP temperature and grain size (d=M(T_(HIP-N)^(-2))) was deduced. Furthermore, a possible evolution mechanism of microstructure was proposed, which could be divided into the decomposition of initial α′ martensite for as-received powder, formation of the globular α grains in prior particle boundaries (PPBs) region, and precipitation of the platelet α grains in non-PPBs region. For these alloys prepared by the dual-temperature-maintained HIP (DTM-HIP) regime, although their tensile properties were comparable to that of alloy prepared by STM-HIP regime with same high-temperature holding stage, higher proportion of globular α grains occurred due to more recrystallization nucleation during the low-temperature holding stage, which probably provided a solution for improving the dynamic service performance of HIPed alloys.展开更多
The microstructure,micro-hardness,and tensile properties of interface between hot isostatic pressing densified low alloy steel and Inconel 690 cladding were investigated during the aging process at 600℃.The results s...The microstructure,micro-hardness,and tensile properties of interface between hot isostatic pressing densified low alloy steel and Inconel 690 cladding were investigated during the aging process at 600℃.The results show that the interface region can be divided into four zones from base metal to deposited metal:carbon-depleted zone(CDZ),partial melting zone(PMZ),planar growth zone(PGZ),and brownish feature zone(BFZ).Dimensions of these zones do not significantly change during aging.However,type I carbides noticeably increase in size in the PMZ,and precipitates clearly occur in the PGZ.The main reason for their growth and occurrence is continuous carbon migration.The highest micro-hardness appears in the PGZ and BFZ regions,which is related to carbon accumulation and precipitates in these regions.Tensile failure occurs on the base metal side due to the high strength mismatch between these two materials.The CDZ,composed of only ferrite,has lower strength and fractures at the boundary between CDZ and base metal.The ultimate tensile strength decreases by only 50 MPa after aging for 1500 h,and the interface region maintains high strength without significant deformation.展开更多
To enhance the mechanical properties of Mo alloys prepared through laser powder bed fusion(LPBF),a hot isostatic pressing(HIP)treatment was used.Results show that following HIP treatment,the porosity decreases from 0....To enhance the mechanical properties of Mo alloys prepared through laser powder bed fusion(LPBF),a hot isostatic pressing(HIP)treatment was used.Results show that following HIP treatment,the porosity decreases from 0.27%to 0.22%,enabling the elements Mo and Ti to diffuse fully and to distribute more uniformly,and to forming a substantial number of low-angle grain boundaries.The tensile strength soars from 286±32 MPa to 598±22 MPa,while the elongation increases from 0.08%±0.02%to 0.18%±0.02%,without notable alterations in grain morphology during the tensile deformation.HIP treatment eliminates the molten pool boundaries,which are the primary source for premature failure in LPBFed Mo alloys.Consequently,HIP treatment emerges as a novel and effective approach for strengthening the mechanical properties of LPBFed Mo alloys,offering a fresh perspective on producing high-performance Mo-based alloys.展开更多
In this study,we developed an in-situ hot-pressing sintering(HPS)device that can be coupled to a lab-oratory X-ray microscope,offering laboratory-available observation of the morphology evolution.With the help of this...In this study,we developed an in-situ hot-pressing sintering(HPS)device that can be coupled to a lab-oratory X-ray microscope,offering laboratory-available observation of the morphology evolution.With the help of this device,in-situ three-dimensional(3D)visualizations of the microstructural evolution of 7055 aluminum alloys during the HPS process were conducted.The 3D results revealed that the twodimensional(2D)methods usually underestimated sintering neck width and exhibited significant standard deviation in statistical analysis.Benefiting from the precise microstructure characterization of the insitu 3D methods,the diffusion activation energy for the sintering of 7055 alloys was calculated,and the quantitative relationship between the sintering temperature and the sintering process was constructed.Moreover,it was experimentally found an accelerative effect of satellite particles on the sintering process,and its mechanisms were discussed.The satellite particles enhanced the curvature near the sintering neck and thus increased the sintering driving stress,promoting the densification process.These findings provide new insights for optimizing sintering processes.展开更多
Laser powder bed fusion(LPBF)technology offers a promising solution to the fabricability challenges of titanium alloys;however,it introduces defects such as porosity and cracking.Here,we evaluated the effectiveness of...Laser powder bed fusion(LPBF)technology offers a promising solution to the fabricability challenges of titanium alloys;however,it introduces defects such as porosity and cracking.Here,we evaluated the effectiveness of hot isostatic pressing(HIP)in eliminating defects and enhancing the overall properties of LPBF Ti-6Al-4V alloy.Our findings indicated that LPBF Ti-6Al-4V alloy after HIP established better corrosion resistance and ductility.These improvements could be related to the decomposition ofαʹphase and the elimination of internal defects within alloy matrix.Furthermore,the application prospect of LPBF Ti-6Al-4V alloy in spent fuel reprocessing environment was expounded.展开更多
In order to solve the problems of traditional long sintering time and relatively low density of synthesized Al_(4)SiC_(4),Al_(4)SiC_(4) was prepared via hot pressing sintering using aluminum powder,silicon carbide pow...In order to solve the problems of traditional long sintering time and relatively low density of synthesized Al_(4)SiC_(4),Al_(4)SiC_(4) was prepared via hot pressing sintering using aluminum powder,silicon carbide powder,flake graphite,and pretreated synthetic Al_(4)C_(3) as raw materials.The phase composition of the Al_(4)C_(3) specimen,which was prepared by pretreating aluminum powder and flake graphite at different temperatures,was investigated.The effects of the heat treatment temperature and duration on the phase composition,microstructure,physical properties,and oxidation resistance of the Al_(4)SiC_(4) specimen were also explored.The results show that under the condition of firing at 1650℃ for 3 h,the Al_(4)SiC_(4) specimen exhibits an apparent porosity of 13.1%,a bulk density of 2.88 g·cm^(-3),a cold compressive strength as high as 63.23 MPa,and a mass loss rate of 1.2%.The preparation of relatively-high-density Al_(4)SiC_(4) ceramics by hot pressing sintering has potential industrial application prospects.展开更多
Al-doped ZnO （AZO） target was prepared by hot pressing using ZnO and Al2O3 powder in mass ratio of 98：2.The effects of hot pressing conditions including temperature,pressure and preserving time on relative density ...Al-doped ZnO （AZO） target was prepared by hot pressing using ZnO and Al2O3 powder in mass ratio of 98：2.The effects of hot pressing conditions including temperature,pressure and preserving time on relative density were investigated.Pore evolution and phase structure change during densification process were studied.The results show that AZO target with super high relative density of 99% was prepared by two-stage hot pressing method under pressure of 35MPa,temperature of 1 050℃ and 1 150℃ with preserving time of 1 h,respectively.At temperature around 1 050℃,the number of isolated pore wasminimum.At temperature lower than 900℃,there existed Al2O3 phase.At temperature higher than 1 000℃,ZnAl2O4 phase was generated and its content was increased with temperature increasing.Hot pressing method had the advantage over pressureless sintering that the content of ZnAl2O4 was lower and sintering temperature could be also lower.With increasing the hot pressing temperature and preserving time,the electric resistivity of AZO target decreased greatly.A low resistivity of 3 10-3 cm was achieved under the temperature of 1 100℃,pressure of 35MPa and preserving time of 10 h.展开更多
WC-6MoxC-0.47Cr3C2-0.28VC binderless carbide was prepared by hot pressing （1700 °C, 20 MPa）. The sample was observed and analyzed by scanning electron microscopy, energy dispersive X–ray spectroscopy and X–ra...WC-6MoxC-0.47Cr3C2-0.28VC binderless carbide was prepared by hot pressing （1700 °C, 20 MPa）. The sample was observed and analyzed by scanning electron microscopy, energy dispersive X–ray spectroscopy and X–ray diffraction. The results show that during the hot pressing process, W atoms dissolve substantially into the MoxC crystal lattices; whilst, the reverse dissolution of Mo atoms into the WC crystal lattices takes place. Consequently, the main phase and binder phase structure are formed. The phase compositions of the main phase and binder phase are a WC-based solid solution containing Mo and a Mo2C-based solid solution containing W, respectively. The isotropic dissolution and precipitation of W and Mo atoms do not result in substantial carbide coarsening. The mechanism for the densification was discussed.展开更多
Cu50Zr40Ti10 bulk amorphous alloys were fabricated by hot pressing gas-atomized Cu50Zr40Ti10 amorphous powder under different consolidation conditions without vacuum and inert gas protection. The consolidation conditi...Cu50Zr40Ti10 bulk amorphous alloys were fabricated by hot pressing gas-atomized Cu50Zr40Ti10 amorphous powder under different consolidation conditions without vacuum and inert gas protection. The consolidation conditions of the Cu50Zr40Ti10 amorphous powder were investigated based on an L9（34） orthogonal design. The compression strength and strain limit of the Cu50Zr40Ti10 bulk amorphous alloys can reach up to 1090.4 MPa and 11.9 %, respectively. The consolidation pressure significantly influences the strain limit and compression strength of the compact. But the mechanical properties are not significantly influenced by the consolidation temperature. In addition, the preforming pressure significantly influences not the compression strength but the strain limit. The optimum consolidation condition for the Cu50Zr40Ti10 amorphous powder is first precompacted under the pressure of 150 MPa, and then consolidated under the pressure of 450 MPa and the temperature of 380 °C.展开更多
The 2024Al/Gr/SiC hybrid composite plates with 5%-10% SiC particles （volume fraction） and 3%-6% flaky graphite （Gr） （volume fraction） were fabricated by vacuum hot pressing and hot extrusion processing. The effe...The 2024Al/Gr/SiC hybrid composite plates with 5%-10% SiC particles （volume fraction） and 3%-6% flaky graphite （Gr） （volume fraction） were fabricated by vacuum hot pressing and hot extrusion processing. The effects of SiC and Gr on the microstructures and mechanical properties of the composites aged at 160, 175 and 190℃ were studied by optical microscopy, scanning electron microscopy （SEM）, and hardness and tensile tests. The results indicate that the SiC particles have a more obvious effect on accelerating the aging response as compared with the Gr. Both the tensile strength and elongation are reduced by the Gr and SiC particles added into the matrix, while the Gr has a more negative influence on the elongation than the SiC particles. The tensile strength （ab）, yield stress （as） and elongation （δ） of the 2024Al/3Gr/10SiC composite aged at 165℃ for 8 h are 387 MPa, 280.3 MPa and 5.7%, respectively. The hybrid composites are characterized by ductile fracture, which is associated with the ductile fracture of the matrix and the tearing of the interface between the matrix and the particles.展开更多
Diffusion bonding between aluminum and copper was performed by vacuum hot pressing at temperatures between 623 and 923 K through two thermal processes： hot compression under the deformation rate of 0.2 mrrdmin for 10...Diffusion bonding between aluminum and copper was performed by vacuum hot pressing at temperatures between 623 and 923 K through two thermal processes： hot compression under the deformation rate of 0.2 mrrdmin for 10 rain at pre-set temperatures, and additional pressing at 0.2 mm/min for 20 rain during furnace cooling. After analyzing interface, the feasible diffusion bonding temperature was suggested as 823 K. The three major intermetallic layers generated during diffusion bonding process were identified as AIECu, AlCu＋AlaCu4 and Al4Cu9. Furthermore, local hardness values ofAlECU, AlCu＋AlaCu4 and Al4Cu9 layers average at （4.97±0.05）, （6.33±0.00） and （6.06±0.18） GPa, respectively.展开更多
The effects of temperature and pressure on density, microstructure and mechanical properties of powder compacts during hot isostatic pressing（HIPping） were investigated. Optimized HIPping parameters of temperature r...The effects of temperature and pressure on density, microstructure and mechanical properties of powder compacts during hot isostatic pressing（HIPping） were investigated. Optimized HIPping parameters of temperature range from 900 to 940℃, pressure over 100 MPa and holding time of 3 h, were obtained. Tensile properties after different heat treatments show that both the geometry of samples and cooling rate have a significant influence on mechanical properties. Finite element method was used to predict the temperature field distribution during HIPped sample cooling, and the experimental results are in agreement with simulation prediction. The interaction of HIPping parameters was analyzed based on the response surface methodology（RSM） in this study.展开更多
The aim of this work was to study the influence of the processing route on the microstructural constituents,hardness andtribological(wear and friction)behavior of Ti6Al4V biomedical alloy.In this sense,three different...The aim of this work was to study the influence of the processing route on the microstructural constituents,hardness andtribological(wear and friction)behavior of Ti6Al4V biomedical alloy.In this sense,three different processing routes were studied:conventional casting,hot pressing and selective laser melting.A comprehensive metallurgical,mechanical and tribologicalcharacterization was performed by X-ray diffraction analysis,Vickers hardness tests and reciprocating ball-on-plate wear tests ofTi6Al4V/Al2O3sliding pairs.The results showed a great influence of the processing route on the microstructural constituents andconsequent differences on hardness and wear performance.The highest hardness and wear resistance were obtained for Ti6Al4Valloy produced by selective laser melting,due to a markedly different cooling rate that leads to significantly different microstructurewhen compared to hot pressing and casting.This study assesses and confirms that selective laser melting is potential to producecustomized Ti6Al4V implants with improved wear performance.展开更多
The Bi0.5Na0.02Sb1.48-xInxTe3alloys（x =0.02-0.20） were synthesized by vacuum melting and hot pressing methods at 753 K,60 MPa for 30 min.Effects of Na and In dual partial substitutions for Sb on the thermoelectric p...The Bi0.5Na0.02Sb1.48-xInxTe3alloys（x =0.02-0.20） were synthesized by vacuum melting and hot pressing methods at 753 K,60 MPa for 30 min.Effects of Na and In dual partial substitutions for Sb on the thermoelectric properties were investigated from 300 to 500 K.Substituting Sb with Na and In can enhance the Seebeck coefficient effectively near room temperature.The electrical resistivity of the Na and In dual-doping samples is higher within the whole test temperature range.The Bi0.5Na0.02Sb1.48-xInxTe3samples（x = 0.02,0.06） play a great role in optimizing the thermal conductivity.As for the Bi0.5Na0.02Sb1.46In0.02Te3alloy,the minimum value of thermal conductivity reaches 0.53 W·m-1·K-1at 320 K.The thermoelectric performance of the Na and In dualdoped samples is greatly improved,and a figure of merit ZT of 1.26 is achieved at 300 K for the Bi0.5Na0.02Sb1.42In0.06Te3,representing 26%enhancement with respect to ZT = 1.0 of the undoped sample.展开更多
基金supported by the Pazy Foundation of the Israel Atomic Energy Commission and the Israeli Council of Higher Education(Grant No.322/20)。
文摘Only a few studies have reported the efects of electrochemical hydrogenation on the tensile mechanical properties of additively manufactured Ti–6Al–4V alloy,in all of them the alloy was processed by laser powder-bed fusion.Furthermore,the efects of either hot isostatic pressing(HIP)or heat treatment(HT)post-treatments on the mechanical properties were not reported.Here,the Young’s modulus,ultimate tensile stress,and uniform(homogeneous)strain of as-built electron beam melted(EBM)Ti–6Al–4V alloys were studied using small tensile specimens before and after electrochemical hydrogenation,as well as before and after secondary processes of HIP at 920℃ and HT at 1000℃.The tensile properties of all hydrogenated alloys were signifcantly degraded compared to their non-hydrogenated counterparts.The yield stress could not be determined for all hydrogenated alloys,as failure occurred at a strain below 0.2%ofset.The uniform strain of the hydrogenated alloys was less than 1%,compared to 1%–5%for the non-hydrogenated alloys.The fracture mode of the hydrogenated alloys after HIP and HT revealed cleavage fracture,indicating increased brittleness.In the as-built hydrogenated alloy,the fracture mode varied with location:brittle fracture occurred near the surface due to the formation of a hydride layer,while a more ductile fracture with dimples was observed below this layer.
基金financially supported by the Natural Science Foundation of Shanxi Province,China(No.201901D211085)the Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi(STIP)
文摘The present work reports the effect of thermal induced porosity(TIP)on the high-cycle fatigue(HCF)and very high-cycle fatigue(VHCF)behaviors of hot-isostatic-pressed(HIPed)Ti-6Al-4V alloy from gasatomized powder.The results show that the residual pores in the as-HIPed powder compacts present no obvious effect on the HCF life.The regrowth of the residual pores can be observed after solution heat treatment.The pore location ranks the most harmful for the fatigue life compared with the other initiating defects.The maximum stress intensity factors were calculated.The plastic zone size of fine granular area(FGA)is much less than the characteristic size of the microstructure,and the crucial size of the internal pores in this study is about 40μm.The failure types of fatigue specimens in the VHCF regime were classified,and the competition of different failure types was described based on the modified Poisson distribution.
基金This work was financially supported by the National Natural Science Foundation of China (No. 50074017).
文摘To increase the adhesion strength between the coating and the substrate, sintered Ti（C,N）-based cermets were selected and deposited with monolayer TiN using a multiarc ion-plating technique; subsequently, hot isostatic pressing （HIPhag） treatment was performed at 1000℃ using nitrogen pressure up to 110 MPa. The mechanical properties of cermets after a coating process and subsequent HIPing treatment have been evaluated with respect to the hardness, the residual stress, and the coating adhesion. The results show that atter the HIPing process, there was a higher increase ha critical load ha the TiN-coated cermets with lower surface roughness compared with those with higher surface roughness. In all cases, the residual stress was found to be compressive. The effects of substrate surface roughness and posttreatment on the adhesion strength of the coatings were thus investigated. It was also fotmd that the HIPing posttreatment process is well suited for hacreasing the adhesion strength between the coating and the substrate.
文摘60NiTi alloy is considered to be a promising material for specialized bearing and gear applications due to its high hardness,strength,and low modulus.However,fabricating 60NiTi through conventional processing methods is challenging due to the brittleness and poor workability.In this study,60NiTi with high relative density was successfully fabricated directly from pre-alloyed powder through hot isostatic pressing.The effects of solution and aging treatments on microstructure and mechanical properties were systematically studied by advanced characterization techniques.The hot-isostatic-pressed 60NiTi showed low average hardness and elastic strain due to the formation of a soft Ni_(3)Ti phase and B2 NiTi matrix.Solution treatment above 1000℃dissolved the Ni_(3)Ti phase and promoted the formation of nanoscale Ni_(4)Ti_(3)precipitates,which significantly improved the hardness,strength,and elastic strain of 60NiTi.The formation of the Ni_(4)Ti_(3) phase can be mainly attributed to the driving forces induced by the chemical supersaturation and mechanical stress concentration.Finally,the phase transformation mechanisms during heat treatment and compression test were discussed.
基金the financial supports from the National Natural Science Foundation of China(Grant Nos.51301157 and 51434007)the National High Technology Research and Development Program of China 863 Program(Grant No.2013AA031103)
文摘The hot compressive deformation behavior of hot isostatically pressed Ti-47.5Al-2Cr-2Nb-0.2W-0.2B alloy using gas atomization powders was systematically investigated and the processing map was obtained in the temperature range of 1323-1473 Kand strain rate range of 0.001-0.5s^（-1）.The calculated activation energy in the above variational ranges of temperature and strain rate possesses a low activation energy value of approximately 365.6kJ/mol based on the constitutive relationship models developed with the Arrhenius-type constitutive model respectively considering the strain rate and deformation temperature.The hot working flow behavior during the deformation process was analyzed combined with the microstructural evolution.Meanwhile,the processing maps during the deformation process were established based on the dynamic material model and Prasad instability criterion under different deformation conditions.Finally,the optimal hot processing window of this alloy corresponding to the wide temperature range of 1353-1453 Kand the low strain rate of 0.001-0.1s^（-1） was obtained.
基金Project supported by the Ningbo Science and Technology Major (2017B10002,2019B10093)the National Natural Science Foundation of China (51671207,51301192)Zhejiang Province Technology Application Research (LGG19E010001)。
文摘Nd-Fe-B hot-pressed(HP) magnet prepared from melt-spun MQU-F flakes features coarse grains(CG)with the average size of both 200 nm(CGS) and 700 nm(CGL) at flake boundary.The grain growth at the flake boundary of Nd2 Fe14B/α-Fe composite HP magnet before and after diffusion of low-melting-point Pr82Cu18 phase was investigated,revealing the indispensable role of surface RE-rich phase of meltspun flakes in the formation of CG in HP magnet.The dominant role of surface oxygen content of melt-spun flakes in the formation of CGL has been clarified with etching method.The HP magnet prepared from the etched flakes with dramatically decreased oxygen content exhibits the CG regions merely with homoge neous equiaxed CGS at flake boundary.Consequently,the coercivity(μ0 Hc) shows significant increase while remanent magnetization(μ0 Mr) inappreciable change.Further investigation with sieving method reveals the elimination of CGL via removal of the fine Nd-Fe-B flakes smaller than 54 μm due to their much higher oxygen content,confirming the dominant role of oxygen content in the formation of CGL.The quantitative analysis on the magnetic properties of the above HP magnets reveals the monotonic increase of coercivity(μ0 Hc) and negligible change of remanent magnetization(μ0 Mr) with decreased oxygen contents of Nd-Fe-B flakes.The maximum value of coercivity(μ0 Hc) increases from2.26 to 2.47 T as the oxygen content decreases from 0.1692 wt% to 0.079 wt%.
基金support from CAS Project for Young Scientists in Basic Research(YSBR-025)and the Technology Innovation(RCJJ-145-24-39)R.P.Guo acknowledges the financial support from the National Natural Science Foundation of China(No.52401104)+1 种基金the Fundamental Research Program of Shanxi Province(No.202203021221072)the China Postdoctoral Science Foundation(No.2024M753298).
文摘Hot isostatic pressing (HIP) temperature has a significant impact on the service performance of powder metallurgy titanium alloys. In this study, a high-temperature titanium alloy, Ti-6.5Al-3.5Mo-1.5Zr-0.3Si, was prepared under different HIP temperatures (880–1000℃), and the microstructural evolution and mechanical properties were systematically investigated. The results demonstrated that the HIPed alloys were predominantly composed of more than 80 vol.% α phase and a small amount of β phase, and their phase compositions were basically unaffected by the HIP temperatures. Under the typical single-temperature-maintained HIP (STM-HIP) regime, the microstructure of alloy significantly coarsened as the HIP temperature increased, and the alloy strength exhibited an obvious linear negative correlation with the HIP temperature. On the basis of Hall–Petch relation, the prediction model of grain size was established, and the mathematical equation between HIP temperature and grain size (d=M(T_(HIP-N)^(-2))) was deduced. Furthermore, a possible evolution mechanism of microstructure was proposed, which could be divided into the decomposition of initial α′ martensite for as-received powder, formation of the globular α grains in prior particle boundaries (PPBs) region, and precipitation of the platelet α grains in non-PPBs region. For these alloys prepared by the dual-temperature-maintained HIP (DTM-HIP) regime, although their tensile properties were comparable to that of alloy prepared by STM-HIP regime with same high-temperature holding stage, higher proportion of globular α grains occurred due to more recrystallization nucleation during the low-temperature holding stage, which probably provided a solution for improving the dynamic service performance of HIPed alloys.
基金Major Scientific and Technological Project of Gansu(22ZD6GA008)Excellent Doctorate Project of Gansu(23JRRA806)National Natural Science Foundation of China(52175325,51961024,52071170)。
文摘The microstructure,micro-hardness,and tensile properties of interface between hot isostatic pressing densified low alloy steel and Inconel 690 cladding were investigated during the aging process at 600℃.The results show that the interface region can be divided into four zones from base metal to deposited metal:carbon-depleted zone(CDZ),partial melting zone(PMZ),planar growth zone(PGZ),and brownish feature zone(BFZ).Dimensions of these zones do not significantly change during aging.However,type I carbides noticeably increase in size in the PMZ,and precipitates clearly occur in the PGZ.The main reason for their growth and occurrence is continuous carbon migration.The highest micro-hardness appears in the PGZ and BFZ regions,which is related to carbon accumulation and precipitates in these regions.Tensile failure occurs on the base metal side due to the high strength mismatch between these two materials.The CDZ,composed of only ferrite,has lower strength and fractures at the boundary between CDZ and base metal.The ultimate tensile strength decreases by only 50 MPa after aging for 1500 h,and the interface region maintains high strength without significant deformation.
基金National Natural Science Foundation of China(52105385)Stable Support Plan Program of Shenzhen Natural Science Fund(20220810132537001)+2 种基金Guangdong Basic and Applied Basic Research Foundation(2022A1515010781)Joint Fund of Henan Province Science and Technology R&D Program(225200810002)Fundamental Research Funds of Henan Academy of Sciences(240621041)。
文摘To enhance the mechanical properties of Mo alloys prepared through laser powder bed fusion(LPBF),a hot isostatic pressing(HIP)treatment was used.Results show that following HIP treatment,the porosity decreases from 0.27%to 0.22%,enabling the elements Mo and Ti to diffuse fully and to distribute more uniformly,and to forming a substantial number of low-angle grain boundaries.The tensile strength soars from 286±32 MPa to 598±22 MPa,while the elongation increases from 0.08%±0.02%to 0.18%±0.02%,without notable alterations in grain morphology during the tensile deformation.HIP treatment eliminates the molten pool boundaries,which are the primary source for premature failure in LPBFed Mo alloys.Consequently,HIP treatment emerges as a novel and effective approach for strengthening the mechanical properties of LPBFed Mo alloys,offering a fresh perspective on producing high-performance Mo-based alloys.
基金supported by the National Key Research&Development Plan(No.2021YFA1600702)the National Natural Science Foundation of China(Nos.92263201,52301155,and 52001161).
文摘In this study,we developed an in-situ hot-pressing sintering(HPS)device that can be coupled to a lab-oratory X-ray microscope,offering laboratory-available observation of the morphology evolution.With the help of this device,in-situ three-dimensional(3D)visualizations of the microstructural evolution of 7055 aluminum alloys during the HPS process were conducted.The 3D results revealed that the twodimensional(2D)methods usually underestimated sintering neck width and exhibited significant standard deviation in statistical analysis.Benefiting from the precise microstructure characterization of the insitu 3D methods,the diffusion activation energy for the sintering of 7055 alloys was calculated,and the quantitative relationship between the sintering temperature and the sintering process was constructed.Moreover,it was experimentally found an accelerative effect of satellite particles on the sintering process,and its mechanisms were discussed.The satellite particles enhanced the curvature near the sintering neck and thus increased the sintering driving stress,promoting the densification process.These findings provide new insights for optimizing sintering processes.
基金supported by the National Natural Science Foundation of China(Nos.52101105,52373321)the IMR Innovation Fund(2023-PY03)the LingChuang Research Project of China National Nuclear Corporation(CNNC-LCKY-202274).
文摘Laser powder bed fusion(LPBF)technology offers a promising solution to the fabricability challenges of titanium alloys;however,it introduces defects such as porosity and cracking.Here,we evaluated the effectiveness of hot isostatic pressing(HIP)in eliminating defects and enhancing the overall properties of LPBF Ti-6Al-4V alloy.Our findings indicated that LPBF Ti-6Al-4V alloy after HIP established better corrosion resistance and ductility.These improvements could be related to the decomposition ofαʹphase and the elimination of internal defects within alloy matrix.Furthermore,the application prospect of LPBF Ti-6Al-4V alloy in spent fuel reprocessing environment was expounded.
文摘In order to solve the problems of traditional long sintering time and relatively low density of synthesized Al_(4)SiC_(4),Al_(4)SiC_(4) was prepared via hot pressing sintering using aluminum powder,silicon carbide powder,flake graphite,and pretreated synthetic Al_(4)C_(3) as raw materials.The phase composition of the Al_(4)C_(3) specimen,which was prepared by pretreating aluminum powder and flake graphite at different temperatures,was investigated.The effects of the heat treatment temperature and duration on the phase composition,microstructure,physical properties,and oxidation resistance of the Al_(4)SiC_(4) specimen were also explored.The results show that under the condition of firing at 1650℃ for 3 h,the Al_(4)SiC_(4) specimen exhibits an apparent porosity of 13.1%,a bulk density of 2.88 g·cm^(-3),a cold compressive strength as high as 63.23 MPa,and a mass loss rate of 1.2%.The preparation of relatively-high-density Al_(4)SiC_(4) ceramics by hot pressing sintering has potential industrial application prospects.
基金Project(31001) supported by the Technology Development Foundation of Ministry of Science and Technology,China
文摘Al-doped ZnO （AZO） target was prepared by hot pressing using ZnO and Al2O3 powder in mass ratio of 98：2.The effects of hot pressing conditions including temperature,pressure and preserving time on relative density were investigated.Pore evolution and phase structure change during densification process were studied.The results show that AZO target with super high relative density of 99% was prepared by two-stage hot pressing method under pressure of 35MPa,temperature of 1 050℃ and 1 150℃ with preserving time of 1 h,respectively.At temperature around 1 050℃,the number of isolated pore wasminimum.At temperature lower than 900℃,there existed Al2O3 phase.At temperature higher than 1 000℃,ZnAl2O4 phase was generated and its content was increased with temperature increasing.Hot pressing method had the advantage over pressureless sintering that the content of ZnAl2O4 was lower and sintering temperature could be also lower.With increasing the hot pressing temperature and preserving time,the electric resistivity of AZO target decreased greatly.A low resistivity of 3 10-3 cm was achieved under the temperature of 1 100℃,pressure of 35MPa and preserving time of 10 h.
基金Project (51074189) supported by the National Natural Science Foundation of ChinaProject (20100162110001) supported by Research Fund for the Doctoral Program of Higher Education of ChinaProject (2011BAE09B02) supported by the National Key Technology R&D Program of China
文摘WC-6MoxC-0.47Cr3C2-0.28VC binderless carbide was prepared by hot pressing （1700 °C, 20 MPa）. The sample was observed and analyzed by scanning electron microscopy, energy dispersive X–ray spectroscopy and X–ray diffraction. The results show that during the hot pressing process, W atoms dissolve substantially into the MoxC crystal lattices; whilst, the reverse dissolution of Mo atoms into the WC crystal lattices takes place. Consequently, the main phase and binder phase structure are formed. The phase compositions of the main phase and binder phase are a WC-based solid solution containing Mo and a Mo2C-based solid solution containing W, respectively. The isotropic dissolution and precipitation of W and Mo atoms do not result in substantial carbide coarsening. The mechanism for the densification was discussed.
基金Project (50874045) supported by the National Natural Science Foundation of ChinaProjects (200902472, 20080431021) supported by the China Postdoctoral Science FoundationProject (10A044) supported by the Research Foundation of Education Bureau of Hunan Province of China
文摘Cu50Zr40Ti10 bulk amorphous alloys were fabricated by hot pressing gas-atomized Cu50Zr40Ti10 amorphous powder under different consolidation conditions without vacuum and inert gas protection. The consolidation conditions of the Cu50Zr40Ti10 amorphous powder were investigated based on an L9（34） orthogonal design. The compression strength and strain limit of the Cu50Zr40Ti10 bulk amorphous alloys can reach up to 1090.4 MPa and 11.9 %, respectively. The consolidation pressure significantly influences the strain limit and compression strength of the compact. But the mechanical properties are not significantly influenced by the consolidation temperature. In addition, the preforming pressure significantly influences not the compression strength but the strain limit. The optimum consolidation condition for the Cu50Zr40Ti10 amorphous powder is first precompacted under the pressure of 150 MPa, and then consolidated under the pressure of 450 MPa and the temperature of 380 °C.
文摘The 2024Al/Gr/SiC hybrid composite plates with 5%-10% SiC particles （volume fraction） and 3%-6% flaky graphite （Gr） （volume fraction） were fabricated by vacuum hot pressing and hot extrusion processing. The effects of SiC and Gr on the microstructures and mechanical properties of the composites aged at 160, 175 and 190℃ were studied by optical microscopy, scanning electron microscopy （SEM）, and hardness and tensile tests. The results indicate that the SiC particles have a more obvious effect on accelerating the aging response as compared with the Gr. Both the tensile strength and elongation are reduced by the Gr and SiC particles added into the matrix, while the Gr has a more negative influence on the elongation than the SiC particles. The tensile strength （ab）, yield stress （as） and elongation （δ） of the 2024Al/3Gr/10SiC composite aged at 165℃ for 8 h are 387 MPa, 280.3 MPa and 5.7%, respectively. The hybrid composites are characterized by ductile fracture, which is associated with the ductile fracture of the matrix and the tearing of the interface between the matrix and the particles.
基金Project (10037273) supported by the Ministry of Knowledge Economy, Korea
文摘Diffusion bonding between aluminum and copper was performed by vacuum hot pressing at temperatures between 623 and 923 K through two thermal processes： hot compression under the deformation rate of 0.2 mrrdmin for 10 rain at pre-set temperatures, and additional pressing at 0.2 mm/min for 20 rain during furnace cooling. After analyzing interface, the feasible diffusion bonding temperature was suggested as 823 K. The three major intermetallic layers generated during diffusion bonding process were identified as AIECu, AlCu＋AlaCu4 and Al4Cu9. Furthermore, local hardness values ofAlECU, AlCu＋AlaCu4 and Al4Cu9 layers average at （4.97±0.05）, （6.33±0.00） and （6.06±0.18） GPa, respectively.
文摘The effects of temperature and pressure on density, microstructure and mechanical properties of powder compacts during hot isostatic pressing（HIPping） were investigated. Optimized HIPping parameters of temperature range from 900 to 940℃, pressure over 100 MPa and holding time of 3 h, were obtained. Tensile properties after different heat treatments show that both the geometry of samples and cooling rate have a significant influence on mechanical properties. Finite element method was used to predict the temperature field distribution during HIPped sample cooling, and the experimental results are in agreement with simulation prediction. The interaction of HIPping parameters was analyzed based on the response surface methodology（RSM） in this study.
基金supported by FTC through the projects PTDC/EMS-TEC/5422/2014 and EXCL/EMS-TEC/ 0460/2012the grant SFRH/BPD/112111/2015+1 种基金supported by FCT with the reference project UID/EEA/04436/2013by FEDER funds through the COMPETE 2020-Programa Operacional Competitividade e Internacionalizacao (POCI) with the reference project POCI-01-0145FEDER-006941.
文摘The aim of this work was to study the influence of the processing route on the microstructural constituents,hardness andtribological(wear and friction)behavior of Ti6Al4V biomedical alloy.In this sense,three different processing routes were studied:conventional casting,hot pressing and selective laser melting.A comprehensive metallurgical,mechanical and tribologicalcharacterization was performed by X-ray diffraction analysis,Vickers hardness tests and reciprocating ball-on-plate wear tests ofTi6Al4V/Al2O3sliding pairs.The results showed a great influence of the processing route on the microstructural constituents andconsequent differences on hardness and wear performance.The highest hardness and wear resistance were obtained for Ti6Al4Valloy produced by selective laser melting,due to a markedly different cooling rate that leads to significantly different microstructurewhen compared to hot pressing and casting.This study assesses and confirms that selective laser melting is potential to producecustomized Ti6Al4V implants with improved wear performance.
基金financially supported by the National Natural Science Foundation of China (No. 51161009)the Research Project of Jiangxi Provincial Education Department (No. GJJ13722 and GJJ11615)
文摘The Bi0.5Na0.02Sb1.48-xInxTe3alloys（x =0.02-0.20） were synthesized by vacuum melting and hot pressing methods at 753 K,60 MPa for 30 min.Effects of Na and In dual partial substitutions for Sb on the thermoelectric properties were investigated from 300 to 500 K.Substituting Sb with Na and In can enhance the Seebeck coefficient effectively near room temperature.The electrical resistivity of the Na and In dual-doping samples is higher within the whole test temperature range.The Bi0.5Na0.02Sb1.48-xInxTe3samples（x = 0.02,0.06） play a great role in optimizing the thermal conductivity.As for the Bi0.5Na0.02Sb1.46In0.02Te3alloy,the minimum value of thermal conductivity reaches 0.53 W·m-1·K-1at 320 K.The thermoelectric performance of the Na and In dualdoped samples is greatly improved,and a figure of merit ZT of 1.26 is achieved at 300 K for the Bi0.5Na0.02Sb1.42In0.06Te3,representing 26%enhancement with respect to ZT = 1.0 of the undoped sample.
