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
To tackle the common issue of green defects in material extrusion(MEX)additive manufacturing(AM)cemented carbides,warm isostatic pressing(WIP)was introduced to eliminate defects of MEX WC-9Co cemented carbide greens,t...To tackle the common issue of green defects in material extrusion(MEX)additive manufacturing(AM)cemented carbides,warm isostatic pressing(WIP)was introduced to eliminate defects of MEX WC-9Co cemented carbide greens,thereby improving both microstructure uniformity and mechanical properties of sintered bodies.The results indicate that WIP reduces defects in MEX greens,thus decreasing the dimensions and numbers of defects,modifying shapes of pores within sintered bodies,while preserving surface quality and shape characteristics.Compared with WC-9Co prepared via MEX followed by debinding and sintering(DS),the hardness of WC-9Co prepared using MEX-WIP-DS does not change significantly,ranging HV_(30)1494-1508,the transverse rupture strength increases by up to 49.3%,reaching 2998-3514 MPa,and the fracture toughness remains high,ranging 14.8-17.0 MPa·m^(1/2).The mechanical properties surpass comparable cemented carbides fabricated through other AM methods and are comparable to those produced by powder metallurgy.The integration of green WIP into MEX-DS broadens the MEX processing window,and improves the overall mechanical properties of MEX AM WC-Co cemented carbides.展开更多
To investigate the effect of microstructure evolution on corrosion behavior and strengthening mechanism of Mg-1Zn-1Ca(wt.%)alloys,as-cast Mg-1Zn-1Ca alloys were performed by equal channel angular pressing(ECAP)with 1 ...To investigate the effect of microstructure evolution on corrosion behavior and strengthening mechanism of Mg-1Zn-1Ca(wt.%)alloys,as-cast Mg-1Zn-1Ca alloys were performed by equal channel angular pressing(ECAP)with 1 and 4 passes.The corrosion behavior and mechanical properties of alloys were investigated by optical microscopy(OM),scanning electron microscopy(SEM),electron backscatter diffraction(EBSD),electrochemical tests,immersion tests and tensile tests.The results showed that mechanical properties improved after ECAP 1 pass;however,the corrosion resistance deteriorated due to high-density dislocations and fragmented secondary phases by ECAP.In contrast,synchronous improvement in the mechanical properties and corrosion resistance was achieved though grain refinement after ECAP 4 passes;fine grains led to a significant improvement in the yield strength,ultimate tensile strength,elongation,and corrosion rate of 103 MPa,223 MPa,30.5%,and 1.5843 mm/a,respectively.The enhanced corrosion resistance was attributed to the formation of dense corrosion product films by finer grains and the barrier effect by high-density grain boundaries.These results indicated that Mg-1Zn-1Ca alloy has a promising potential for application in biomedical materials.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,the interaction between deformation and precipitates during multiple equal channel angular pressing(ECAP)deformations and inter-pass aging combination and its effect on the mechanical properties of 7050 ...In this study,the interaction between deformation and precipitates during multiple equal channel angular pressing(ECAP)deformations and inter-pass aging combination and its effect on the mechanical properties of 7050 aluminum alloy are studied.The result show that ECAP induces numerous substructures and dislocations,effectively promoting the precipitation of theηʹphase exhibiting a bimodal structure during inter-pass aging.Following inter-pass aging and subsequent ECAP,the decrease in grain size(4.8μm)is together with the increase in dislocation density(1.24×10^(15) m^(−2))due to the pinning effect of the precipitated phase.Simultaneously,the dislocation motion causes the second phase particles to become even finer and more diffuse.The synergistic effects of precipitation strengthening,fine grain strengthening,and dislocation strengthening collectively enhance the high strength of aluminum alloys,with ultimate tensile strength and yield strength reaching approximately 610 and 565 MPa,respectively.Meanwhile,ductility remains largely unchanged,primarily due to coordinated grain boundary sliding and the uniform and fine dispersion of second phase particles.展开更多
Pure titanium fabricated by powder metallurgy generally encounters problems including low relative density and low strength,which limits its application performance.This work proposed a multi-step pressing(MSP)techniq...Pure titanium fabricated by powder metallurgy generally encounters problems including low relative density and low strength,which limits its application performance.This work proposed a multi-step pressing(MSP)technique for developing highstrength pure titanium.The MSP processes of spherical Ti powders of 15–53μm,53–105μm,and 75–180μm were systematically investigated through multi-particle fnite element method(MPFEM)compared with conventional one-step pressing(OSP)technique.The relative density,phase constitution,microstructure,and compressive mechanical properties of the sintered bulk pure titanium were characterized.Simulation results demonstrate that the MSP technique signifcantly increases the relative density of green compacts by 3.2%,3.3%,and 5.2%,respectively,compared with OSP technique.Experimental results indicate the relative density of the sintered specimens prepared by MSP spherical powders increases by 5.4%,4.5%,and 4.5%,respectively,compared to OSP,and the yield strength improves by 16%,13%,and 18%.For the sintered specimens prepared by MSP irregular powder of 15–53μm,the relative density increases by 6.0%and the yield strength increases by 15%.The enhancement of relative density and yield strength is mainly because the MSP technique mitigates stress concentration between powder particles.Compared to spherical powder,irregular powder exhibits stronger mechanical interlocking owing to the greater propensity for displacement and deformation,which facilitates mutual wedging and interlocking,resulting in superior strength performance.展开更多
Objective:To explore the effects of acupoint catgut embedding combined with auricular point pressing with beans on symptom management self-efficacy and quality of life in patients with nonalcoholic steatohepatitis(NAS...Objective:To explore the effects of acupoint catgut embedding combined with auricular point pressing with beans on symptom management self-efficacy and quality of life in patients with nonalcoholic steatohepatitis(NASH)of liver depression and spleen deficiency type.Methods:Sixty patients with NASH of liver depression and spleen deficiency type admitted to our hospital from January 2021 to December 2023 were selected and divided into an acupoint catgut embedding group(n=30)and a combined group(n=30)using the envelope lottery method.The acupoint catgut embedding group received acupoint catgut embedding intervention,while the combined group received auricular point pressing with beans on the basis of the acupoint catgut embedding group.The two groups were compared in terms of TCM syndrome scores,symptom management self-efficacy[Chronic Disease Self-Efficacy Scale(CDSES)],and quality of life[Chronic Liver Disease Questionnaire(CLDQ)].Results:After intervention,the combined group had lower TCM syndrome scores for both primary and secondary symptoms compared to the acupoint catgut embedding group(P<0.05).The combined group also had higher scores in all dimensions and total score of the CDSES compared to the acupoint catgut embedding group(P<0.05).Similarly,the combined group had higher scores in all dimensions and total score of the CLDQ compared to the acupoint catgut embedding group(P<0.05).Conclusion:Acupoint catgut embedding combined with auricular point pressing with beans can effectively improve TCM symptoms,enhance symptom management self-efficacy,and improve quality of life in patients with NASH of liver depression and spleen deficiency type.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
Microstructure evolution and texture development and their effects on mechanical properties of a Mg-Gd-Y-Zr alloy during equal channel angular pressing（ECAP） were investigated.It is found that the microstructure is ...Microstructure evolution and texture development and their effects on mechanical properties of a Mg-Gd-Y-Zr alloy during equal channel angular pressing（ECAP） were investigated.It is found that the microstructure is still inhomogeneous after four passes,and two zones,namely the fine grain zone（FGZ） and the coarse grain zone（CGZ） are formed.The grain refinement occurs mainly by particle-stimulated nucleation（PSN） mechanism,which led to a more random texture after four passes of ECAP.In the ECAP-processed alloy,the strength did not increase while the ductility was enhanced dramatically compared with the as-received condition.The change of ductility of this alloy was discussed in terms of texture and second phase particles.展开更多
Commercial ZK60 Mg alloy was processed by multi-pass equal-channel angular pressing（ECAP） and subsequent aging to investigate the effect of grain refinement and second-phase redistribution on its corrosion behavior....Commercial ZK60 Mg alloy was processed by multi-pass equal-channel angular pressing（ECAP） and subsequent aging to investigate the effect of grain refinement and second-phase redistribution on its corrosion behavior. Electrochemical tests show that the fine-grained samples after more ECAP passes have higher corrosion current densities（Jcorr） in the polarization curves, lower charge-transfer resistance（Rt） values in the EIS plots. The severe plastic deformation decreases the alloy corrosion resistance besides the well-known strengthening and toughening. Scanning Kelvin probe（SKP） measurement shows that the anodic and cathode sites are homogeneously distributed on the surface of the fine-grained alloy, which inhibits localized corrosion. The SKP potential, having linear relationship with the corrosion potential（φcorr）, decreases with increasing the ECAP pass. Furthermore, the post-ECAP aging can slightly improve the corrosion resistance of the fine-grained ZK60 Mg alloy and enhance the comprehensive performances, due to the stress relief and uniform distribution of second-phase particles.展开更多
In comparison with the conventional equal channel angular pressing（ECAP） process,a comprehensive study of influence of twist extrusion（TE） process on consolidating pure aluminum powder in tubes（PITs） by equal ch...In comparison with the conventional equal channel angular pressing（ECAP） process,a comprehensive study of influence of twist extrusion（TE） process on consolidating pure aluminum powder in tubes（PITs） by equal channel angular pressing and torsion（ECAPT） was conducted via three-dimensional（3D） finite element simulation,experimental investigation and theoretical analysis.Simulation results revealed that during the consolidation of aluminum powder particles by ECAPT,TE process played a significant role of back pressure.Due to the torsional shear and high hydrostatic pressure exerted by twist channel,both the magnitude and homogeneity of the effective strain were increased markedly.After one pass of ECAPT process using a square channel with an inner angle of 90° and a twist slope angle of 36.5° at 200℃,commercial pure aluminum powder particles were successfully consolidated to nearly full density.Simulation and experimental results showed good agreement.In the microstructure observations,grains were greatly refined.At the same time,porosities were effectively eliminated by shrinking in size and breaking into small ones.Microhardness test indicated that strain distribution of ECAPT-processed billet was more homogeneous with respect to the ECAP-processed one.All these improvements may be attributed to the extreme intense shear strain induced during ECAPT and the increase in self-diffusion coefficient of aluminum due to the back pressure exerted by TE process.展开更多
Laboratory-scale carbon anodes were produced by a new method of high temperature mould pressing, and their physico-chemical properties were studied. The influence of mould pressing conditions and coal pitch addition o...Laboratory-scale carbon anodes were produced by a new method of high temperature mould pressing, and their physico-chemical properties were studied. The influence of mould pressing conditions and coal pitch addition on the bulk density, crushing strength, and oxidation resistance was analyzed. The mierostructure of carbon anodes was investigated by scanning electron microscopy （SEM）, and the mechanism of producing carbon anodes by high-temperature mould pressing was analyzed. The results show that when the anodes are produced by high-temperature mould pressing, coal pitch can expand into the coke particles and fill the pores inside the particles, which is beneficial for improving the quality of prebaked anodes. The bulk density of carbon anodes is 1.64-1.66 g/cm3, which is 0.08-0.12 g/cm3 higher than that of industrial anodes, and the oxidation resistance of carbon anodes is also significantly improved.展开更多
A combined method of selective laser sintering （SLS） and cold isostatic pressing （CIP） was applied to manufacturing metal parts rapidly. Finite element method was used to predict final dimensions and decrease cost...A combined method of selective laser sintering （SLS） and cold isostatic pressing （CIP） was applied to manufacturing metal parts rapidly. Finite element method was used to predict final dimensions and decrease cost. The simulations of CIP of selective laser sintered parts were carried out by Drucker-Prager-Cap constitutive model with ABAQUS computer program. The property of metal powder was measured by CIP experiments. The results show the rubber bag and the friction coefficient have little influence on results of simulations. The parts only have uniform shrinkage and have no obvious distortion in shape. The results of simulations show a good agreement with the experimental results and the calculated results, indicating that the Drucker-Prager-Cap model is an effective model to simulate CIP process. The simulations could give a useful direction to forming process of the CIP of selective laser sintered components. K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
Uniaxial compressive experiments of ultrafine-grained Al fabricated by equal channel angular pressing(ECAP) method were performed at wide temperature and strain rate range. The influence of temperature on flow stress,...Uniaxial compressive experiments of ultrafine-grained Al fabricated by equal channel angular pressing(ECAP) method were performed at wide temperature and strain rate range. The influence of temperature on flow stress, strain hardening rate and strain rate sensitivity was investigated experimentally. The results show that both the effect of temperature on flow stress and its strain rate sensitivity of ECAPed Al is much larger than those of the coarse-grained Al. The temperature sensitivity of ultrafine-grained Al is comparatively weaker than that of the coarse-grained Al. Based on the experimental results, the apparent activation volume was estimated at different temperatures and strain rates. The forest dislocation interactions is the dominant thermally activated mechanism for ECAPed Al compressed at quasi-static strain rates, while the viscous drag plays an important role at high strain rates.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
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supported by the Key Project of Chinese Academy of Engineering(No.2019-XZ-11)the General Project of Chinese Academy of Engineering(No.2023-XY-18)+1 种基金the Open Fund of National Joint Engineering Research Center for Abrasion Control and Molding of Metal Materials of China(No.HKDNM201907)the Independent Project of State Key Laboratory of Powder Metallurgy,China。
文摘To tackle the common issue of green defects in material extrusion(MEX)additive manufacturing(AM)cemented carbides,warm isostatic pressing(WIP)was introduced to eliminate defects of MEX WC-9Co cemented carbide greens,thereby improving both microstructure uniformity and mechanical properties of sintered bodies.The results indicate that WIP reduces defects in MEX greens,thus decreasing the dimensions and numbers of defects,modifying shapes of pores within sintered bodies,while preserving surface quality and shape characteristics.Compared with WC-9Co prepared via MEX followed by debinding and sintering(DS),the hardness of WC-9Co prepared using MEX-WIP-DS does not change significantly,ranging HV_(30)1494-1508,the transverse rupture strength increases by up to 49.3%,reaching 2998-3514 MPa,and the fracture toughness remains high,ranging 14.8-17.0 MPa·m^(1/2).The mechanical properties surpass comparable cemented carbides fabricated through other AM methods and are comparable to those produced by powder metallurgy.The integration of green WIP into MEX-DS broadens the MEX processing window,and improves the overall mechanical properties of MEX AM WC-Co cemented carbides.
基金financially supported by the National Natural Science Foundation of China(No.52374395)the Natural Science Foundation of Shanxi Province,China(Nos.20210302123135,202303021221143)+5 种基金the Scientific and Technological Achievements Transformation Guidance Special Project of Shanxi Province,China(Nos.202104021301022,202204021301009)the Central Government Guided Local Science and Technology Development Projects,China(No.YDZJSX20231B003)the Ministry of Science and Higher Education of the Russian Federation for financial support under the Megagrant(No.075-15-2022-1133)the National Research Foundation(NRF)grant funded by the Ministry of Science and ICT of Korea through the Research Institute of Advanced Materials(No.2015R1A2A1A01006795)the China Postdoctoral Science Foundation(No.2022M710541)the Research Project supported by Shanxi Scholarship Council of China(No.2022-038)。
文摘To investigate the effect of microstructure evolution on corrosion behavior and strengthening mechanism of Mg-1Zn-1Ca(wt.%)alloys,as-cast Mg-1Zn-1Ca alloys were performed by equal channel angular pressing(ECAP)with 1 and 4 passes.The corrosion behavior and mechanical properties of alloys were investigated by optical microscopy(OM),scanning electron microscopy(SEM),electron backscatter diffraction(EBSD),electrochemical tests,immersion tests and tensile tests.The results showed that mechanical properties improved after ECAP 1 pass;however,the corrosion resistance deteriorated due to high-density dislocations and fragmented secondary phases by ECAP.In contrast,synchronous improvement in the mechanical properties and corrosion resistance was achieved though grain refinement after ECAP 4 passes;fine grains led to a significant improvement in the yield strength,ultimate tensile strength,elongation,and corrosion rate of 103 MPa,223 MPa,30.5%,and 1.5843 mm/a,respectively.The enhanced corrosion resistance was attributed to the formation of dense corrosion product films by finer grains and the barrier effect by high-density grain boundaries.These results indicated that Mg-1Zn-1Ca alloy has a promising potential for application in biomedical materials.
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Project(52275350)supported by the National Natural Science Foundation of ChinaProject(0301006)supported by the International Cooperative Scientific Research Platform of SUES,China。
文摘In this study,the interaction between deformation and precipitates during multiple equal channel angular pressing(ECAP)deformations and inter-pass aging combination and its effect on the mechanical properties of 7050 aluminum alloy are studied.The result show that ECAP induces numerous substructures and dislocations,effectively promoting the precipitation of theηʹphase exhibiting a bimodal structure during inter-pass aging.Following inter-pass aging and subsequent ECAP,the decrease in grain size(4.8μm)is together with the increase in dislocation density(1.24×10^(15) m^(−2))due to the pinning effect of the precipitated phase.Simultaneously,the dislocation motion causes the second phase particles to become even finer and more diffuse.The synergistic effects of precipitation strengthening,fine grain strengthening,and dislocation strengthening collectively enhance the high strength of aluminum alloys,with ultimate tensile strength and yield strength reaching approximately 610 and 565 MPa,respectively.Meanwhile,ductility remains largely unchanged,primarily due to coordinated grain boundary sliding and the uniform and fine dispersion of second phase particles.
基金supports from the National Natural Science Foundation of China(No.52404382)the Key Research and Development Project of Shaanxi Province(No.2023-YBGY-090).
文摘Pure titanium fabricated by powder metallurgy generally encounters problems including low relative density and low strength,which limits its application performance.This work proposed a multi-step pressing(MSP)technique for developing highstrength pure titanium.The MSP processes of spherical Ti powders of 15–53μm,53–105μm,and 75–180μm were systematically investigated through multi-particle fnite element method(MPFEM)compared with conventional one-step pressing(OSP)technique.The relative density,phase constitution,microstructure,and compressive mechanical properties of the sintered bulk pure titanium were characterized.Simulation results demonstrate that the MSP technique signifcantly increases the relative density of green compacts by 3.2%,3.3%,and 5.2%,respectively,compared with OSP technique.Experimental results indicate the relative density of the sintered specimens prepared by MSP spherical powders increases by 5.4%,4.5%,and 4.5%,respectively,compared to OSP,and the yield strength improves by 16%,13%,and 18%.For the sintered specimens prepared by MSP irregular powder of 15–53μm,the relative density increases by 6.0%and the yield strength increases by 15%.The enhancement of relative density and yield strength is mainly because the MSP technique mitigates stress concentration between powder particles.Compared to spherical powder,irregular powder exhibits stronger mechanical interlocking owing to the greater propensity for displacement and deformation,which facilitates mutual wedging and interlocking,resulting in superior strength performance.
文摘Objective:To explore the effects of acupoint catgut embedding combined with auricular point pressing with beans on symptom management self-efficacy and quality of life in patients with nonalcoholic steatohepatitis(NASH)of liver depression and spleen deficiency type.Methods:Sixty patients with NASH of liver depression and spleen deficiency type admitted to our hospital from January 2021 to December 2023 were selected and divided into an acupoint catgut embedding group(n=30)and a combined group(n=30)using the envelope lottery method.The acupoint catgut embedding group received acupoint catgut embedding intervention,while the combined group received auricular point pressing with beans on the basis of the acupoint catgut embedding group.The two groups were compared in terms of TCM syndrome scores,symptom management self-efficacy[Chronic Disease Self-Efficacy Scale(CDSES)],and quality of life[Chronic Liver Disease Questionnaire(CLDQ)].Results:After intervention,the combined group had lower TCM syndrome scores for both primary and secondary symptoms compared to the acupoint catgut embedding group(P<0.05).The combined group also had higher scores in all dimensions and total score of the CDSES compared to the acupoint catgut embedding group(P<0.05).Similarly,the combined group had higher scores in all dimensions and total score of the CLDQ compared to the acupoint catgut embedding group(P<0.05).Conclusion:Acupoint catgut embedding combined with auricular point pressing with beans can effectively improve TCM symptoms,enhance symptom management self-efficacy,and improve quality of life in patients with NASH of liver depression and spleen deficiency type.
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.
文摘Microstructure evolution and texture development and their effects on mechanical properties of a Mg-Gd-Y-Zr alloy during equal channel angular pressing（ECAP） were investigated.It is found that the microstructure is still inhomogeneous after four passes,and two zones,namely the fine grain zone（FGZ） and the coarse grain zone（CGZ） are formed.The grain refinement occurs mainly by particle-stimulated nucleation（PSN） mechanism,which led to a more random texture after four passes of ECAP.In the ECAP-processed alloy,the strength did not increase while the ductility was enhanced dramatically compared with the as-received condition.The change of ductility of this alloy was discussed in terms of texture and second phase particles.
基金Project(BK20131373)supported by the Natural Science Foundation of Jiangsu ProvinceChina
文摘Commercial ZK60 Mg alloy was processed by multi-pass equal-channel angular pressing（ECAP） and subsequent aging to investigate the effect of grain refinement and second-phase redistribution on its corrosion behavior. Electrochemical tests show that the fine-grained samples after more ECAP passes have higher corrosion current densities（Jcorr） in the polarization curves, lower charge-transfer resistance（Rt） values in the EIS plots. The severe plastic deformation decreases the alloy corrosion resistance besides the well-known strengthening and toughening. Scanning Kelvin probe（SKP） measurement shows that the anodic and cathode sites are homogeneously distributed on the surface of the fine-grained alloy, which inhibits localized corrosion. The SKP potential, having linear relationship with the corrosion potential（φcorr）, decreases with increasing the ECAP pass. Furthermore, the post-ECAP aging can slightly improve the corrosion resistance of the fine-grained ZK60 Mg alloy and enhance the comprehensive performances, due to the stress relief and uniform distribution of second-phase particles.
基金Project(51401177)supported by the National Natural Science Foundation of ChinaProject(13KJD430005)supported by the Natural Science Foundation of Jiangsu Higher Education Institutions of ChinaProject(JSKLEDC201309)supported by Jiangsu Key Laboratory of Large Engineering Equipment Detection and Control,China
文摘In comparison with the conventional equal channel angular pressing（ECAP） process,a comprehensive study of influence of twist extrusion（TE） process on consolidating pure aluminum powder in tubes（PITs） by equal channel angular pressing and torsion（ECAPT） was conducted via three-dimensional（3D） finite element simulation,experimental investigation and theoretical analysis.Simulation results revealed that during the consolidation of aluminum powder particles by ECAPT,TE process played a significant role of back pressure.Due to the torsional shear and high hydrostatic pressure exerted by twist channel,both the magnitude and homogeneity of the effective strain were increased markedly.After one pass of ECAPT process using a square channel with an inner angle of 90° and a twist slope angle of 36.5° at 200℃,commercial pure aluminum powder particles were successfully consolidated to nearly full density.Simulation and experimental results showed good agreement.In the microstructure observations,grains were greatly refined.At the same time,porosities were effectively eliminated by shrinking in size and breaking into small ones.Microhardness test indicated that strain distribution of ECAPT-processed billet was more homogeneous with respect to the ECAP-processed one.All these improvements may be attributed to the extreme intense shear strain induced during ECAPT and the increase in self-diffusion coefficient of aluminum due to the back pressure exerted by TE process.
基金Project(090302012)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(50934005)supported by the National Natural Science Foundation of China
文摘Laboratory-scale carbon anodes were produced by a new method of high temperature mould pressing, and their physico-chemical properties were studied. The influence of mould pressing conditions and coal pitch addition on the bulk density, crushing strength, and oxidation resistance was analyzed. The mierostructure of carbon anodes was investigated by scanning electron microscopy （SEM）, and the mechanism of producing carbon anodes by high-temperature mould pressing was analyzed. The results show that when the anodes are produced by high-temperature mould pressing, coal pitch can expand into the coke particles and fill the pores inside the particles, which is beneficial for improving the quality of prebaked anodes. The bulk density of carbon anodes is 1.64-1.66 g/cm3, which is 0.08-0.12 g/cm3 higher than that of industrial anodes, and the oxidation resistance of carbon anodes is also significantly improved.
基金Project(2007AA03Z115) supported by the High-Tech Research and Development Program of China
文摘A combined method of selective laser sintering （SLS） and cold isostatic pressing （CIP） was applied to manufacturing metal parts rapidly. Finite element method was used to predict final dimensions and decrease cost. The simulations of CIP of selective laser sintered parts were carried out by Drucker-Prager-Cap constitutive model with ABAQUS computer program. The property of metal powder was measured by CIP experiments. The results show the rubber bag and the friction coefficient have little influence on results of simulations. The parts only have uniform shrinkage and have no obvious distortion in shape. The results of simulations show a good agreement with the experimental results and the calculated results, indicating that the Drucker-Prager-Cap model is an effective model to simulate CIP process. The simulations could give a useful direction to forming process of the CIP of selective laser sintered components. K
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Projects(11272267,11102168,10932008)supported by the National Natural Science Foundation of ChinaProject(B07050)supported by Northwestern Polytechnical University
文摘Uniaxial compressive experiments of ultrafine-grained Al fabricated by equal channel angular pressing(ECAP) method were performed at wide temperature and strain rate range. The influence of temperature on flow stress, strain hardening rate and strain rate sensitivity was investigated experimentally. The results show that both the effect of temperature on flow stress and its strain rate sensitivity of ECAPed Al is much larger than those of the coarse-grained Al. The temperature sensitivity of ultrafine-grained Al is comparatively weaker than that of the coarse-grained Al. Based on the experimental results, the apparent activation volume was estimated at different temperatures and strain rates. The forest dislocation interactions is the dominant thermally activated mechanism for ECAPed Al compressed at quasi-static strain rates, while the viscous drag plays an important role at high strain rates.
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.
