The driving force for using powder metallurgy(PM)mostly relies on its near net-shape ability and cost-performance ratio.The automotive application is a main market of PM industry,requiring parts with competitive mecha...The driving force for using powder metallurgy(PM)mostly relies on its near net-shape ability and cost-performance ratio.The automotive application is a main market of PM industry,requiring parts with competitive mechanical or functional performance in a mass production scale.As the automobile technology transforms from traditional internal combustion engine vehicles to new energy vehicles,PM technology is undergoing significant changes in manufacturing and materials development.This review outlines the challenges and opportunities generated by the changes in the automotive technology for PM.Low-cost,high-performance and light-weight are critical aspects for future PM materials development.Therefore,the studies on PM lean-alloyed steel,aluminum alloys,and titanium alloy materials were reviewed.In addition,PM soft magnetic composite applied to new energy vehicles was discussed.Then new opportunities for advanced processing,such as metal injection molding(MIM)and additive manufacturing(AM),in automotive industry were stated.In general,the change in automotive industry raises sufficient development space for PM.While,emerging technologies require more preeminent PM materials.Iron-based parts are still the main PM products due to their mechanical performance and low cost.MIM will occupy the growing market of highly flexible and complex parts.AM opens a door for fast prototyping,great flexibility and customizing at low cost,driving weight and assembling reduction.展开更多
Die wall lubrication was applied on warm compaction powder metallurgy in hope to reduce the concentration level of the admixed lubricant since lubricant is harmful to the mechanical property of the sintered materials....Die wall lubrication was applied on warm compaction powder metallurgy in hope to reduce the concentration level of the admixed lubricant since lubricant is harmful to the mechanical property of the sintered materials. Iron-based samples were prepared by die wall lubricated warm compaction at 135 ℃ and 175 ℃, using polytetrafluoroethylene (PTFE) emulsion as die wall lubricant. A compacting pressure of 700 MPa and 550 MPa were used. The admixed lubricant concentration ranging from 0 to 0.6 wt.% was used in this study. Compared with non-die wall lubricated samples, the die wall lubricated samples have higher green densities. Results show that in addition to the decrease in ejection forces, green density of the compacts increased linearly with the decrease in admixed lubricant content. Mechanical property of the sintered compacts increase sharply when the admixed lubricant concentration reduced to 0.125 wt.% or less. Ejection force data indicated that samples with die wall lubrication show lower ejection forces when compared with samples without die wall lubrication. No scoring was observed in all experiments even for samples contain no admixed lubricant. Our results indicated that under experimental condition used in this study, no matter at which compaction pressure, compaction temperature, graphite and lubricant contents in the powder the die wall lubricated warm compaction would give the highest green density and lowest ejection force. It can be concluded that combination of die wall lubrication and warm compaction can provide P/M products with higher density and better quality. It is a feasible way to produce high performance P/M parts if suitable die wall lubrication system was applied.展开更多
In this work,a novel ultrahigh-strength Al-10Zn-3.5Mg-1.5Cu alloy was fabricated by powder metallurgy followed by hot extrusion.Investigations on microstructural evolution and mechanical properties of the fabricated s...In this work,a novel ultrahigh-strength Al-10Zn-3.5Mg-1.5Cu alloy was fabricated by powder metallurgy followed by hot extrusion.Investigations on microstructural evolution and mechanical properties of the fabricated samples were carried out.The results show that the grain size of sintered samples matches with the powder particles after ball milling.The relative densities of sintered and hot extruded samples reach 99.1%and 100%,respectively.Owing to the comprehensive mechanism of grain refinement,aging and dispersion strengthening,the ultimate tensile strength,yield strength and elongation of the Al-10Zn-3.5Mg-1.5Cu alloy after hot extrusion and subsequent heat treatment achieve 810 MPa,770 MPa and 8%,respectively.展开更多
Massive vanadium additions as hard phases in powder metallurgy high-speed steels(PM HSS)lead to higher cost and bad machinability.In this study,ultrahigh alloy PM HSS with CPM121(10W-5Mo-4Cr-10V-9Co,wt.%)as the basic ...Massive vanadium additions as hard phases in powder metallurgy high-speed steels(PM HSS)lead to higher cost and bad machinability.In this study,ultrahigh alloy PM HSS with CPM121(10W-5Mo-4Cr-10V-9Co,wt.%)as the basic composition,was directly compacted and activation sintered with near-full density(>99.0%)using pre-oxidized and ball-mixed element and carbide powders.Niobium-alloyed steels(w(V)+w(Nb)=10 wt.%)show higher hardness and wear resistance,superior secondary-hardening ability and temper resistance.But excess niobium addition(>5 wt.%)leads to coarsened carbides and deteriorated toughness.EPMA results proved that niobium tends to distribute in MC carbides and forces element W to form M6C and WC carbides.Further,the role of rotary forging on properties of niobium-alloyed steels(S3)was researched.After rotary forging with deformation of 40%,the bending strength and fracture toughness of niobium-alloyed steels could be further improved by 20.74%and 43.86%compared with those of sample S3 without rotary forging,respectively.展开更多
In this study,non-equiatomic Fe_(70)Co_(7.5)Cr_(7.5)Ni_(7.5)V_(7.5) medium-entropy alloys(MEAs)with different carbon contents were prepared via mechanical ball-milling,cold pressing and vacuum sintering.The microstruc...In this study,non-equiatomic Fe_(70)Co_(7.5)Cr_(7.5)Ni_(7.5)V_(7.5) medium-entropy alloys(MEAs)with different carbon contents were prepared via mechanical ball-milling,cold pressing and vacuum sintering.The microstructural evolution,mechanical properties and wear resistance of the MEAs were investigated.Fe_(70)Co_(7.5)Cr_(7.5)Ni_(7.5)V_(7.5) exhibited a bodycentered cubic(bcc)structure withσphase precipitation.After adding 4 at%and 8 at%carbon,the phase composition of the alloys was transformed to bcc+MC+σand bcc+MC+M_(23)C_(6),respectively.The mechanical properties and wear resistance were observed to be significantly enhanced by the formation of carbides.Increasing the carbon content,the corresponding bending strength and hardness increased from 1520 to 3245 MPa and HRC 57.2 to HRC 61.4,respectively.Further,the dominant wear mechanism changed from the adhesion wear to the abrasion wear.Owing to the evenly distributed carbides and precipitated nanocarbides,Fe_(64.4)Co_(6.9)Cr_(6.9)Ni_(6.9)V_(6.9)C_(8) revealed an extremely low specific wear rate of 1.3×10^(−6) mm_(2)/(N·m)under a load of 10 N.展开更多
The extruded plate of powder metallurgy AA2024 aluminum alloy was successfully solid-state joined by friction stir welding(FSW) to demonstrate potential applications in the aerospace and automotive industries. For det...The extruded plate of powder metallurgy AA2024 aluminum alloy was successfully solid-state joined by friction stir welding(FSW) to demonstrate potential applications in the aerospace and automotive industries. For determining the optimal processing parameters of FSW, the microstructure, mechanical properties, and fracture behavior of FSW joints were evaluated. When the processing parameters were optimized with 2000 r/min rotation speed and100 mm/min traverse speed, high quality welds were achieved. The ultimate tensile strength yield strength and elongation of the joint can reach 415 MPa(85% of the base metal strength), 282 MPa, and 9.5%, respectively. The hardness of the joint gradually decreased from the alloy matrix to the heat-affected zone. The lowest strength and hardness appeared near the heat-affected zone because of the over-aging caused by heat flow from repeated stirring during FSW. The average grain size of the stir zone(2.15 μm) was smaller than that of the base metal(4.43 μm) and the heat-affected zone(5.03 μm), whose grains had <110> preferred orientation.展开更多
The high cycle fatigue response of a high V-alloyed powder metallurgy tool steel （AISI 11） with different inclusion sizes was studied. Two materials of this grade at a similar hardness of about HRC 60 were subjected...The high cycle fatigue response of a high V-alloyed powder metallurgy tool steel （AISI 11） with different inclusion sizes was studied. Two materials of this grade at a similar hardness of about HRC 60 were subjected to axial loading fatigue tests, tensile tests and fracture toughness measurements to investigate their mechanical properties. Large inclusion above 70 ~rn is indicated to be responsible for the tensile fracture which happens before yielding. The fatigue strength obtained up to 107 cycles is found to decrease from approximately 1 538 MPa to 1000 MPa with the inclusion size increasing above 30 Izm. The internally induced crack initiation is mainly attributed to the surface compressive residual stress of 300-450 MPa. Fractographic evaluation demonstrates that the crack initiation and propagation controlling factors of the two materials are almost the same, indicating that the two factors would be insignificantly affected by the inclusion size level. Paris sizes of the two materials both show a tendency to decrease as the ratio of stress intensity factor of crack origin to factor of fish-eye increases. The investigation into the relationship between stress intensity factors and fatigue life of the two materials further indicates that the high cycle fatigue behavior of AISI 11 is controlled by crack propagation.展开更多
Metal matrix composites tiles based on Ti-6Al-4V(Ti64)alloy,reinforced with 10,20,and 40(vol%)of either TiC or TiB particles were made using press-and-sinter blended elemental powder metallurgy(BEPM)and then bonded to...Metal matrix composites tiles based on Ti-6Al-4V(Ti64)alloy,reinforced with 10,20,and 40(vol%)of either TiC or TiB particles were made using press-and-sinter blended elemental powder metallurgy(BEPM)and then bonded together into 3-layer laminated plates using hot isostatic pressing(HIP).The laminates were ballistically tested and demonstrated superior performance.The microstructure and properties of the laminates were analyzed to determine the effect of the BEPM and HIP processing on the ballistic properties of the layered plates.The effect of porosity in sintered composites on further diffusion bonding of the plates during HIP is analyzed to understand the bonding features at the interfaces between different adjacent layers in the laminate.Exceptional ballistic performance of fabricated structures was explained by a significant reduction in the residual porosity of the BEPM products by their additional processing using HIP,which provides an unprecedented increase in the hardness of the layered composites.It is argued that the combination of the used two technologies,BEPM and HIP is principally complimentary for the materials in question with the abilities to solve the essential problems of each used individually.展开更多
Mr. La Huapei, a senior engineer equivalent to professor, the former deputy chief engineer in Beijing Central Engineering and Research Institute for Nonferrous Metallurgical Industries (ENFI), is now a senior adviser ...Mr. La Huapei, a senior engineer equivalent to professor, the former deputy chief engineer in Beijing Central Engineering and Research Institute for Nonferrous Metallurgical Industries (ENFI), is now a senior adviser for the Institute.展开更多
A new process recycling rhodium from organic waste containing rhodium in acetic acid industry is developed. Use the special affinity of base metal sulfides (FeS, Ni2S3 , CuS, etc.) on platinum group metals, adopting h...A new process recycling rhodium from organic waste containing rhodium in acetic acid industry is developed. Use the special affinity of base metal sulfides (FeS, Ni2S3 , CuS, etc.) on platinum group metals, adopting high nickel matte trapping-aluminothermic activation method to recovery rhodium from incinerator residue of organic rhodium waste. The method is shorter process, lower equipment requirement, and the higher activity of rhodium black. In pyrometallurgy enrichment process,the recovery rate of rhodium reached 94.65%, the full flow of rhodium recovery rate was 92.04%.展开更多
(CrFeCoNi)high-entropy alloy(HEA)was reinforced with various contents of WC particles from 5 wt%to 20 wt%,and prepared by powder metallurgy.The mixed powders were compacted under 700 MPa and then sintered at 1200℃in ...(CrFeCoNi)high-entropy alloy(HEA)was reinforced with various contents of WC particles from 5 wt%to 20 wt%,and prepared by powder metallurgy.The mixed powders were compacted under 700 MPa and then sintered at 1200℃in a vacuum furnace for 90 min.Density,phase composition,and microstructure of sintered samples were investigated.Hardness,compressive strength,wear resistance and coefficient of thermal expansion(CTE)were estimated.The results revealed the improvement of the density with the addition of WC.XRD results revealed the formation of new FCC chromium carbide phases.Scanning electron microscopy(SEM)results show a good distribution of the carbide phases over the alloy matrix.The CTE was decreased gradually by increasing the WC content.Compressive strength was improved by WC addition.A mathematical model was established to predict the behavior of the strength of the HEA samples.The hardness of the investigated HEAs was increased gradually with the increasing of WC content about 20.35%.Also,the wear rate of HEA without WC is 1.70×10^(−4)mm^(3)/(N·m),which is approximately 4.5 times the wear rate of 20 wt%WC HEA(3.81×10^(−5)mm^(3)/(N·m)),which means that wear resistance was significantly improved with the increase of WC content.展开更多
A titanium alloy containing continuous oxygen gradient was prepared by powder metallurgy(P/M) and the composition–property relationship was studied on a single sample. The alloy was sintered with layered powder of di...A titanium alloy containing continuous oxygen gradient was prepared by powder metallurgy(P/M) and the composition–property relationship was studied on a single sample. The alloy was sintered with layered powder of different oxygen contents via vacuum sintering and spark plasma sintering(SPS), respectively. After subsequent heat treatments, high-throughput characterizations of the microstructures and mechanical properties by localized measurements were conducted. The Ti-7% Mo(molar fraction) alloy with an oxygen content ranging from 1.3×10^(-3) to 6.2×10^(-5)(mass fraction) was obtained, and the effects of oxygen on the microstructural evolution and mechanical properties were studied. The results show that SPS is an effective way for fabricating fully dense Ti alloy with a compositional gradient. The average width of α′ phase coarsens with the increase of the content of oxygen. The content of α″ martensitic phase also increases with the content of oxygen. At oxygen contents of 3×10^(-3) and 4×10^(-3)(mass fraction), the Ti alloys present the lowest microhardness and the lowest elastic modulus, respectively. The results also indicate that the martensitic phases actually decrease the hardness of Ti-7Mo alloy, and oxygen effectively hardens the alloy by solid solution strengthening. Therefore, the high-throughput characterization on a microstructure with a gradient content of oxygen is an effective method for rapidly evaluating the composition–property relationship of titanium alloys.展开更多
Although casting is commonly used to process aluminum alloys, powder metallurgy remains a promising technique to develop aluminum based materials for structural and functional applications. The possibility to synthesi...Although casting is commonly used to process aluminum alloys, powder metallurgy remains a promising technique to develop aluminum based materials for structural and functional applications. The possibility to synthesize Al-Mg-Zr alloys through mechanical alloying and spark plasma sintering techniques was explored. Al-10Mg-5Zr and Al-5Mg-1Zr alloyed powders were synthesized through wet ball milling the appropriate amount of elemental powders. The dried milled powders were spark plasma sintered through passing constant pulsed electric current with fixed pulse duration at a pressure of 35 MPa. The samples were vacuum sintered at 450, 500, 550, 600 and 620 ℃ for 10, 15 and 20 min. The Al-10Mg-5Zr alloy displays poor densification at lower sintering temperatures of 450, 500, 550 and 600 ℃. Its sinterability is improved at a temperature of 620 ℃ whereas sintering temperatures higher than 620 ℃ leads to partial melting of the alloy. It is possible to sinter the Al-5Mg-1Zr alloy at 450, 500 and 550 ℃. The increase of sintering temperature improves its densification and increases its hardness. The Al-5Mg-IZr alloy displays better densification and hardness compared to Al-10Mg-5Zr alloys.展开更多
Mechanical properties of the warm compacted iron base powder metallurgy materials were compared with those of conventional cold compacted materials. Factors such as compaction temperature, lubricant concentration and ...Mechanical properties of the warm compacted iron base powder metallurgy materials were compared with those of conventional cold compacted materials. Factors such as compaction temperature, lubricant concentration and lubricant′s property were studied. A lubricant for warm compaction powder metallurgy was developed. An iron based powder metallurgy material with a green density of 7.31 g/cm 3 (a relative density of 92.5%) can be obtained by pressing the powder at 700 MPa and 175 ℃. The sintered materials have a density of 7.2 g/cm 3, an elongation of 2.1% and a tensile strength of 751 MPa compared to 546 MPa using conventional cold compaction with the same lubricant and 655 MPa using warm compaction with other lubricant. Compact density and mechanical properties were influenced strongly by the compacting temperature. Although the best quality compacts can be obtained at 175 ℃, warm compaction within 165 to 185 ℃ can give high density compacts. Evidence shows that compact density depends on the friction coefficient of the lubricant.展开更多
The phenomena of die wall lubricated warm compaction of non-lubricant admixed iron powders were researched, and its mechanism of densification was discussed. Water atomized powder obtained from the Wuhan Iron and Stee...The phenomena of die wall lubricated warm compaction of non-lubricant admixed iron powders were researched, and its mechanism of densification was discussed. Water atomized powder obtained from the Wuhan Iron and Steel Corporation was used. With compacting and sintering, compared with cold compaction, the density of warm compacted samples increases by 0.07 - 0. 22 g/cm^3 at the same pressed pressure. The maximum achievable green density of warm compacted samples is 7.12 g/cm^3 at 120℃, and the maximum sintered density is 7.18 g/cm^3 at 80℃. Compared with cold compaction, the ejection force of warm compaction is smaller; the maximum discrep- ancy is about 7 kN. The warm compacted mechanism of densification of iron powders can be obtained： heating the powder contributes to improving plastic deformation of powder particles, and accelerating the mutual filling and rearrangement of powder particles.展开更多
Fe-Cr-Mo-Ni-C-Co alloy was quenched in liquid nitrogen and held for 24 h.Hardness tester,OM,XRD,SEM were used to investigate the mechanical properties and microstructures of the alloy.The results show that the hardnes...Fe-Cr-Mo-Ni-C-Co alloy was quenched in liquid nitrogen and held for 24 h.Hardness tester,OM,XRD,SEM were used to investigate the mechanical properties and microstructures of the alloy.The results show that the hardness increases by 1-2(HRC)and the compressive strength decreases slightly after cryogenic treatment.The increase in hardness is attributed to the transformation from austenite to martensite and the precipitation of the very tiny carbideη-Fe2C.The decrease in compressive strength is caused by residual stress.The great amount of carbides,such as Cr7C3 and Fe2MoC,in the alloy and the obvious difference in thermal expansion coefficient between these carbides and the matrix at the cryogenic temperatures lead to this residual stress.The microscopy of cryogenic martensite is different from that of the non-cryogenic martensite.The cryogenic martensite is long and fine;while the non-cryogenic martensite is short and coarse.There is obvious surface relief of the cryogenic martensite transformation.It is not orientational of this kind surface relief and the boundary of this surface relief is smooth and in a shape of butterfly.The surface relief in the non-cryogenic martensite is wide and arranged in parallel,and the boundary of surface relief is not smooth.These characteristics may imply different growth ways of the two kinds of martensite.展开更多
The green and sintered densities,and tensile strength of sintered P/M steels produced by cold compaction,warm compaction,warm compaction combined with die wall lubrication(DWL)were measured under various compaction pr...The green and sintered densities,and tensile strength of sintered P/M steels produced by cold compaction,warm compaction,warm compaction combined with die wall lubrication(DWL)were measured under various compaction pressures using polytetrafluoroethylene(PTFE)emulsion as the die wall lubricant.The effects of warm compaction on the mechanical properties were studied.The tensile fracture behaviors of cold compaction and warm compaction were studied using scanning electron microscope(SEM).The results show that the density of sintered P/M steel prepared by warm compaction or warm compaction with DWL is higher than that by cold compaction under all compaction pressures.Meanwhile,the highest tensile strength is obtained by combination of warm compaction and die wall lubrication under all compaction pressures.The SEM results show that the fracture modes of the sintered samples prepared by cold compaction and warm compaction at 700 MPa are the mixed mode of ductile fracture and brittle fracture,and obvious dimples can be found in some regions.The fracture of sample prepared by cold compaction is uneven and has irregular and big pores,but that by warm compaction is relatively even and the pores are round mostly,and the samples have many obvious dimples on the whole fracture surface.展开更多
The effects of the addition of Mo on the densification mechanism, microstructure evolution and mechanical strength of blended elemental powder metallurgy Ti-Mo alloy were investigated in this work. The results show th...The effects of the addition of Mo on the densification mechanism, microstructure evolution and mechanical strength of blended elemental powder metallurgy Ti-Mo alloy were investigated in this work. The results show that the addition of Mo hinders the densification of Ti-Mo alloy due to the low diffusion rate of Mo atoms in β-Ti matrix, and the increase of Mo content worsens the sinterability of Ti-Mo alloy. However, the addition of Mo can also refine the microstructure of Ti-Mo alloy greatly, and raising sintering temperature can effectively increase the alloy density without grain coarsening. When neglecting the relative density factor, the addition of Mo refines the microstructure, and improves the mechanical strength by Hall-Petch relationship.展开更多
Surface tensions of slag addition Mg O and Si O2 based on conventional 70%CaF 2-30%Al2O3 and 60%Ca F2-20%Ca O-20%Al2O3(mass fraction) at 1300 °C, 1400 °C and 1500 °C were investigated. Influence mechani...Surface tensions of slag addition Mg O and Si O2 based on conventional 70%CaF 2-30%Al2O3 and 60%Ca F2-20%Ca O-20%Al2O3(mass fraction) at 1300 °C, 1400 °C and 1500 °C were investigated. Influence mechanism of Mg O and Si O2 on slag surface tension was also analyzed. Results indicate that surface tension decreases with the increase of Mg O content in the case of the Mg O content(mass fraction) less than 8%, however, when Mg O content(mass fraction) is from 8% to 30%, surface tension increases with the increase of Mg O content. When Si O2 content(mass fraction) is from 2% to 8%, surface tension decreases with the increase of Si O2 content. Additionally, the relationship between surface tension and optical basicity is a monotonically increasing linear function. Research findings can provide important reference for slag design and the study of slag-metal interfacial tension.展开更多
FVS1212/FVS0812 material was prepared by adding FVS1212 powder into FVS0812 powder. The structure and mechanical properties of materials were studied by means of X-Ray, tensile measurement, OM and SEM. The results sho...FVS1212/FVS0812 material was prepared by adding FVS1212 powder into FVS0812 powder. The structure and mechanical properties of materials were studied by means of X-Ray, tensile measurement, OM and SEM. The results show that adding proper content FVS1212 powders can improve the tensile strength of FVS0812 aluminum at room temperature and elevated temperature, and that the elongation of FVS1212/FVS0812 material is better than that of FVS1212 aluminum.展开更多
基金Project(51625404)supported by the National Science Fund for Distinguished Young Scholars,China。
文摘The driving force for using powder metallurgy(PM)mostly relies on its near net-shape ability and cost-performance ratio.The automotive application is a main market of PM industry,requiring parts with competitive mechanical or functional performance in a mass production scale.As the automobile technology transforms from traditional internal combustion engine vehicles to new energy vehicles,PM technology is undergoing significant changes in manufacturing and materials development.This review outlines the challenges and opportunities generated by the changes in the automotive technology for PM.Low-cost,high-performance and light-weight are critical aspects for future PM materials development.Therefore,the studies on PM lean-alloyed steel,aluminum alloys,and titanium alloy materials were reviewed.In addition,PM soft magnetic composite applied to new energy vehicles was discussed.Then new opportunities for advanced processing,such as metal injection molding(MIM)and additive manufacturing(AM),in automotive industry were stated.In general,the change in automotive industry raises sufficient development space for PM.While,emerging technologies require more preeminent PM materials.Iron-based parts are still the main PM products due to their mechanical performance and low cost.MIM will occupy the growing market of highly flexible and complex parts.AM opens a door for fast prototyping,great flexibility and customizing at low cost,driving weight and assembling reduction.
文摘Die wall lubrication was applied on warm compaction powder metallurgy in hope to reduce the concentration level of the admixed lubricant since lubricant is harmful to the mechanical property of the sintered materials. Iron-based samples were prepared by die wall lubricated warm compaction at 135 ℃ and 175 ℃, using polytetrafluoroethylene (PTFE) emulsion as die wall lubricant. A compacting pressure of 700 MPa and 550 MPa were used. The admixed lubricant concentration ranging from 0 to 0.6 wt.% was used in this study. Compared with non-die wall lubricated samples, the die wall lubricated samples have higher green densities. Results show that in addition to the decrease in ejection forces, green density of the compacts increased linearly with the decrease in admixed lubricant content. Mechanical property of the sintered compacts increase sharply when the admixed lubricant concentration reduced to 0.125 wt.% or less. Ejection force data indicated that samples with die wall lubrication show lower ejection forces when compared with samples without die wall lubrication. No scoring was observed in all experiments even for samples contain no admixed lubricant. Our results indicated that under experimental condition used in this study, no matter at which compaction pressure, compaction temperature, graphite and lubricant contents in the powder the die wall lubricated warm compaction would give the highest green density and lowest ejection force. It can be concluded that combination of die wall lubrication and warm compaction can provide P/M products with higher density and better quality. It is a feasible way to produce high performance P/M parts if suitable die wall lubrication system was applied.
基金Project(FRF-GF-19-012AZ)supported by the Fundamental Research Funds for the Central Universities,China。
文摘In this work,a novel ultrahigh-strength Al-10Zn-3.5Mg-1.5Cu alloy was fabricated by powder metallurgy followed by hot extrusion.Investigations on microstructural evolution and mechanical properties of the fabricated samples were carried out.The results show that the grain size of sintered samples matches with the powder particles after ball milling.The relative densities of sintered and hot extruded samples reach 99.1%and 100%,respectively.Owing to the comprehensive mechanism of grain refinement,aging and dispersion strengthening,the ultimate tensile strength,yield strength and elongation of the Al-10Zn-3.5Mg-1.5Cu alloy after hot extrusion and subsequent heat treatment achieve 810 MPa,770 MPa and 8%,respectively.
基金Projects(51771237,51704257)supported by the National Natural Science Foundation of ChinaProject(2019JJ60019)supported by the Joint Fund of Hunan Province,ChinaProject(17QDZ25)supported by the School Level Fund of Xiangtan University,China。
文摘Massive vanadium additions as hard phases in powder metallurgy high-speed steels(PM HSS)lead to higher cost and bad machinability.In this study,ultrahigh alloy PM HSS with CPM121(10W-5Mo-4Cr-10V-9Co,wt.%)as the basic composition,was directly compacted and activation sintered with near-full density(>99.0%)using pre-oxidized and ball-mixed element and carbide powders.Niobium-alloyed steels(w(V)+w(Nb)=10 wt.%)show higher hardness and wear resistance,superior secondary-hardening ability and temper resistance.But excess niobium addition(>5 wt.%)leads to coarsened carbides and deteriorated toughness.EPMA results proved that niobium tends to distribute in MC carbides and forces element W to form M6C and WC carbides.Further,the role of rotary forging on properties of niobium-alloyed steels(S3)was researched.After rotary forging with deformation of 40%,the bending strength and fracture toughness of niobium-alloyed steels could be further improved by 20.74%and 43.86%compared with those of sample S3 without rotary forging,respectively.
基金Project(2016YFB0700300)supported by the National Key Research and Development Program of China。
文摘In this study,non-equiatomic Fe_(70)Co_(7.5)Cr_(7.5)Ni_(7.5)V_(7.5) medium-entropy alloys(MEAs)with different carbon contents were prepared via mechanical ball-milling,cold pressing and vacuum sintering.The microstructural evolution,mechanical properties and wear resistance of the MEAs were investigated.Fe_(70)Co_(7.5)Cr_(7.5)Ni_(7.5)V_(7.5) exhibited a bodycentered cubic(bcc)structure withσphase precipitation.After adding 4 at%and 8 at%carbon,the phase composition of the alloys was transformed to bcc+MC+σand bcc+MC+M_(23)C_(6),respectively.The mechanical properties and wear resistance were observed to be significantly enhanced by the formation of carbides.Increasing the carbon content,the corresponding bending strength and hardness increased from 1520 to 3245 MPa and HRC 57.2 to HRC 61.4,respectively.Further,the dominant wear mechanism changed from the adhesion wear to the abrasion wear.Owing to the evenly distributed carbides and precipitated nanocarbides,Fe_(64.4)Co_(6.9)Cr_(6.9)Ni_(6.9)V_(6.9)C_(8) revealed an extremely low specific wear rate of 1.3×10^(−6) mm_(2)/(N·m)under a load of 10 N.
基金Project(92066205) supported by the National Natural Science Foundation of ChinaProject(JCKY61420052008)supported by the National Defense Science and Technology Key Laboratory Foundation,China+2 种基金Project(311021013)supported by Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai),ChinaProject(FRF-MP-20-52) supported by the Fundamental Research Funds for the Central Universities,ChinaProject(075-15-2021-612) support from the Government of the Russian Federation。
文摘The extruded plate of powder metallurgy AA2024 aluminum alloy was successfully solid-state joined by friction stir welding(FSW) to demonstrate potential applications in the aerospace and automotive industries. For determining the optimal processing parameters of FSW, the microstructure, mechanical properties, and fracture behavior of FSW joints were evaluated. When the processing parameters were optimized with 2000 r/min rotation speed and100 mm/min traverse speed, high quality welds were achieved. The ultimate tensile strength yield strength and elongation of the joint can reach 415 MPa(85% of the base metal strength), 282 MPa, and 9.5%, respectively. The hardness of the joint gradually decreased from the alloy matrix to the heat-affected zone. The lowest strength and hardness appeared near the heat-affected zone because of the over-aging caused by heat flow from repeated stirring during FSW. The average grain size of the stir zone(2.15 μm) was smaller than that of the base metal(4.43 μm) and the heat-affected zone(5.03 μm), whose grains had <110> preferred orientation.
基金Project(2007BAE51B05)supported by the National Key Technologies Research and Development Program of China
文摘The high cycle fatigue response of a high V-alloyed powder metallurgy tool steel （AISI 11） with different inclusion sizes was studied. Two materials of this grade at a similar hardness of about HRC 60 were subjected to axial loading fatigue tests, tensile tests and fracture toughness measurements to investigate their mechanical properties. Large inclusion above 70 ~rn is indicated to be responsible for the tensile fracture which happens before yielding. The fatigue strength obtained up to 107 cycles is found to decrease from approximately 1 538 MPa to 1000 MPa with the inclusion size increasing above 30 Izm. The internally induced crack initiation is mainly attributed to the surface compressive residual stress of 300-450 MPa. Fractographic evaluation demonstrates that the crack initiation and propagation controlling factors of the two materials are almost the same, indicating that the two factors would be insignificantly affected by the inclusion size level. Paris sizes of the two materials both show a tendency to decrease as the ratio of stress intensity factor of crack origin to factor of fish-eye increases. The investigation into the relationship between stress intensity factors and fatigue life of the two materials further indicates that the high cycle fatigue behavior of AISI 11 is controlled by crack propagation.
基金funding from the NATO Agency Science for Peace and Security (#G5787)Ballistic investigations were co-financed by Military University of Technology in Warsaw under research project UGB 829/2023/WATSeparate works made in G.V.Kurdyumov Institute for Metal Physics of N.A.S.of Ukraine were partially financially supported by N.A.S.of Ukraine within the frames of project#III09-18。
文摘Metal matrix composites tiles based on Ti-6Al-4V(Ti64)alloy,reinforced with 10,20,and 40(vol%)of either TiC or TiB particles were made using press-and-sinter blended elemental powder metallurgy(BEPM)and then bonded together into 3-layer laminated plates using hot isostatic pressing(HIP).The laminates were ballistically tested and demonstrated superior performance.The microstructure and properties of the laminates were analyzed to determine the effect of the BEPM and HIP processing on the ballistic properties of the layered plates.The effect of porosity in sintered composites on further diffusion bonding of the plates during HIP is analyzed to understand the bonding features at the interfaces between different adjacent layers in the laminate.Exceptional ballistic performance of fabricated structures was explained by a significant reduction in the residual porosity of the BEPM products by their additional processing using HIP,which provides an unprecedented increase in the hardness of the layered composites.It is argued that the combination of the used two technologies,BEPM and HIP is principally complimentary for the materials in question with the abilities to solve the essential problems of each used individually.
文摘Mr. La Huapei, a senior engineer equivalent to professor, the former deputy chief engineer in Beijing Central Engineering and Research Institute for Nonferrous Metallurgical Industries (ENFI), is now a senior adviser for the Institute.
基金the National High Technology Research and Development Program of China(863 Program): (2012AA063203, 2012AA063204, 2012AA063207)
文摘A new process recycling rhodium from organic waste containing rhodium in acetic acid industry is developed. Use the special affinity of base metal sulfides (FeS, Ni2S3 , CuS, etc.) on platinum group metals, adopting high nickel matte trapping-aluminothermic activation method to recovery rhodium from incinerator residue of organic rhodium waste. The method is shorter process, lower equipment requirement, and the higher activity of rhodium black. In pyrometallurgy enrichment process,the recovery rate of rhodium reached 94.65%, the full flow of rhodium recovery rate was 92.04%.
文摘(CrFeCoNi)high-entropy alloy(HEA)was reinforced with various contents of WC particles from 5 wt%to 20 wt%,and prepared by powder metallurgy.The mixed powders were compacted under 700 MPa and then sintered at 1200℃in a vacuum furnace for 90 min.Density,phase composition,and microstructure of sintered samples were investigated.Hardness,compressive strength,wear resistance and coefficient of thermal expansion(CTE)were estimated.The results revealed the improvement of the density with the addition of WC.XRD results revealed the formation of new FCC chromium carbide phases.Scanning electron microscopy(SEM)results show a good distribution of the carbide phases over the alloy matrix.The CTE was decreased gradually by increasing the WC content.Compressive strength was improved by WC addition.A mathematical model was established to predict the behavior of the strength of the HEA samples.The hardness of the investigated HEAs was increased gradually with the increasing of WC content about 20.35%.Also,the wear rate of HEA without WC is 1.70×10^(−4)mm^(3)/(N·m),which is approximately 4.5 times the wear rate of 20 wt%WC HEA(3.81×10^(−5)mm^(3)/(N·m)),which means that wear resistance was significantly improved with the increase of WC content.
基金Project(2014CB6644002)supported by the National Basic Research Program of ChinaProject(2015CX004)supported by the Innovation-driven Plan in Central South University,China+2 种基金Project(51301203)supported by the National Natural Science Foundation of ChinaProject(2014M551827)supported by the National Science Foundation for Post-doctoral Scientists of ChinaProject(2014GK3078)supported by the Science and Technology Planning of Hunan Province,China
文摘A titanium alloy containing continuous oxygen gradient was prepared by powder metallurgy(P/M) and the composition–property relationship was studied on a single sample. The alloy was sintered with layered powder of different oxygen contents via vacuum sintering and spark plasma sintering(SPS), respectively. After subsequent heat treatments, high-throughput characterizations of the microstructures and mechanical properties by localized measurements were conducted. The Ti-7% Mo(molar fraction) alloy with an oxygen content ranging from 1.3×10^(-3) to 6.2×10^(-5)(mass fraction) was obtained, and the effects of oxygen on the microstructural evolution and mechanical properties were studied. The results show that SPS is an effective way for fabricating fully dense Ti alloy with a compositional gradient. The average width of α′ phase coarsens with the increase of the content of oxygen. The content of α″ martensitic phase also increases with the content of oxygen. At oxygen contents of 3×10^(-3) and 4×10^(-3)(mass fraction), the Ti alloys present the lowest microhardness and the lowest elastic modulus, respectively. The results also indicate that the martensitic phases actually decrease the hardness of Ti-7Mo alloy, and oxygen effectively hardens the alloy by solid solution strengthening. Therefore, the high-throughput characterization on a microstructure with a gradient content of oxygen is an effective method for rapidly evaluating the composition–property relationship of titanium alloys.
基金Project(ARP-28-122) supported by King Abdul Aziz City for Science and Technology (KAC ST) of Kingdom of Saudi Arabia
文摘Although casting is commonly used to process aluminum alloys, powder metallurgy remains a promising technique to develop aluminum based materials for structural and functional applications. The possibility to synthesize Al-Mg-Zr alloys through mechanical alloying and spark plasma sintering techniques was explored. Al-10Mg-5Zr and Al-5Mg-1Zr alloyed powders were synthesized through wet ball milling the appropriate amount of elemental powders. The dried milled powders were spark plasma sintered through passing constant pulsed electric current with fixed pulse duration at a pressure of 35 MPa. The samples were vacuum sintered at 450, 500, 550, 600 and 620 ℃ for 10, 15 and 20 min. The Al-10Mg-5Zr alloy displays poor densification at lower sintering temperatures of 450, 500, 550 and 600 ℃. Its sinterability is improved at a temperature of 620 ℃ whereas sintering temperatures higher than 620 ℃ leads to partial melting of the alloy. It is possible to sinter the Al-5Mg-1Zr alloy at 450, 500 and 550 ℃. The increase of sintering temperature improves its densification and increases its hardness. The Al-5Mg-IZr alloy displays better densification and hardness compared to Al-10Mg-5Zr alloys.
文摘Mechanical properties of the warm compacted iron base powder metallurgy materials were compared with those of conventional cold compacted materials. Factors such as compaction temperature, lubricant concentration and lubricant′s property were studied. A lubricant for warm compaction powder metallurgy was developed. An iron based powder metallurgy material with a green density of 7.31 g/cm 3 (a relative density of 92.5%) can be obtained by pressing the powder at 700 MPa and 175 ℃. The sintered materials have a density of 7.2 g/cm 3, an elongation of 2.1% and a tensile strength of 751 MPa compared to 546 MPa using conventional cold compaction with the same lubricant and 655 MPa using warm compaction with other lubricant. Compact density and mechanical properties were influenced strongly by the compacting temperature. Although the best quality compacts can be obtained at 175 ℃, warm compaction within 165 to 185 ℃ can give high density compacts. Evidence shows that compact density depends on the friction coefficient of the lubricant.
文摘The phenomena of die wall lubricated warm compaction of non-lubricant admixed iron powders were researched, and its mechanism of densification was discussed. Water atomized powder obtained from the Wuhan Iron and Steel Corporation was used. With compacting and sintering, compared with cold compaction, the density of warm compacted samples increases by 0.07 - 0. 22 g/cm^3 at the same pressed pressure. The maximum achievable green density of warm compacted samples is 7.12 g/cm^3 at 120℃, and the maximum sintered density is 7.18 g/cm^3 at 80℃. Compared with cold compaction, the ejection force of warm compaction is smaller; the maximum discrep- ancy is about 7 kN. The warm compacted mechanism of densification of iron powders can be obtained： heating the powder contributes to improving plastic deformation of powder particles, and accelerating the mutual filling and rearrangement of powder particles.
文摘Fe-Cr-Mo-Ni-C-Co alloy was quenched in liquid nitrogen and held for 24 h.Hardness tester,OM,XRD,SEM were used to investigate the mechanical properties and microstructures of the alloy.The results show that the hardness increases by 1-2(HRC)and the compressive strength decreases slightly after cryogenic treatment.The increase in hardness is attributed to the transformation from austenite to martensite and the precipitation of the very tiny carbideη-Fe2C.The decrease in compressive strength is caused by residual stress.The great amount of carbides,such as Cr7C3 and Fe2MoC,in the alloy and the obvious difference in thermal expansion coefficient between these carbides and the matrix at the cryogenic temperatures lead to this residual stress.The microscopy of cryogenic martensite is different from that of the non-cryogenic martensite.The cryogenic martensite is long and fine;while the non-cryogenic martensite is short and coarse.There is obvious surface relief of the cryogenic martensite transformation.It is not orientational of this kind surface relief and the boundary of this surface relief is smooth and in a shape of butterfly.The surface relief in the non-cryogenic martensite is wide and arranged in parallel,and the boundary of surface relief is not smooth.These characteristics may imply different growth ways of the two kinds of martensite.
基金Project (MKPT-2004-09ZD) supported by the National Key Technological Research and Development Program of ChinaProject (040117) supported by the Innovative Engineering Program of Central South University
文摘The green and sintered densities,and tensile strength of sintered P/M steels produced by cold compaction,warm compaction,warm compaction combined with die wall lubrication(DWL)were measured under various compaction pressures using polytetrafluoroethylene(PTFE)emulsion as the die wall lubricant.The effects of warm compaction on the mechanical properties were studied.The tensile fracture behaviors of cold compaction and warm compaction were studied using scanning electron microscope(SEM).The results show that the density of sintered P/M steel prepared by warm compaction or warm compaction with DWL is higher than that by cold compaction under all compaction pressures.Meanwhile,the highest tensile strength is obtained by combination of warm compaction and die wall lubrication under all compaction pressures.The SEM results show that the fracture modes of the sintered samples prepared by cold compaction and warm compaction at 700 MPa are the mixed mode of ductile fracture and brittle fracture,and obvious dimples can be found in some regions.The fracture of sample prepared by cold compaction is uneven and has irregular and big pores,but that by warm compaction is relatively even and the pores are round mostly,and the samples have many obvious dimples on the whole fracture surface.
文摘The effects of the addition of Mo on the densification mechanism, microstructure evolution and mechanical strength of blended elemental powder metallurgy Ti-Mo alloy were investigated in this work. The results show that the addition of Mo hinders the densification of Ti-Mo alloy due to the low diffusion rate of Mo atoms in β-Ti matrix, and the increase of Mo content worsens the sinterability of Ti-Mo alloy. However, the addition of Mo can also refine the microstructure of Ti-Mo alloy greatly, and raising sintering temperature can effectively increase the alloy density without grain coarsening. When neglecting the relative density factor, the addition of Mo refines the microstructure, and improves the mechanical strength by Hall-Petch relationship.
基金Project(51274266)supported by the National Natural Science Foundation of ChinaProject(N120502002)supported by the Fundamental Research Funds for Central Universities of ChinaProject(LR2013009)supported by the Program for Liaoning Excellent Talents in University,China
文摘Surface tensions of slag addition Mg O and Si O2 based on conventional 70%CaF 2-30%Al2O3 and 60%Ca F2-20%Ca O-20%Al2O3(mass fraction) at 1300 °C, 1400 °C and 1500 °C were investigated. Influence mechanism of Mg O and Si O2 on slag surface tension was also analyzed. Results indicate that surface tension decreases with the increase of Mg O content in the case of the Mg O content(mass fraction) less than 8%, however, when Mg O content(mass fraction) is from 8% to 30%, surface tension increases with the increase of Mg O content. When Si O2 content(mass fraction) is from 2% to 8%, surface tension decreases with the increase of Si O2 content. Additionally, the relationship between surface tension and optical basicity is a monotonically increasing linear function. Research findings can provide important reference for slag design and the study of slag-metal interfacial tension.
文摘FVS1212/FVS0812 material was prepared by adding FVS1212 powder into FVS0812 powder. The structure and mechanical properties of materials were studied by means of X-Ray, tensile measurement, OM and SEM. The results show that adding proper content FVS1212 powders can improve the tensile strength of FVS0812 aluminum at room temperature and elevated temperature, and that the elongation of FVS1212/FVS0812 material is better than that of FVS1212 aluminum.
