The two-pass equal channel angular extrusion (ECAE) process was introduced into strain-induced melt activation (SIMA) to predeform a ZK60 alloy with rare earth (RE) addition. Microstructure evolution of ECAE-formed ZK...The two-pass equal channel angular extrusion (ECAE) process was introduced into strain-induced melt activation (SIMA) to predeform a ZK60 alloy with rare earth (RE) addition. Microstructure evolution of ECAE-formed ZK60+RE alloy during reheating was investigated. Furthermore, tensile properties of thixoforged components were determined. The results show that the SIMA process can produce ideal microstructures, and spheroidized solid particles with little entrapped liquid can be obtained. With prolonging holding time, the size of solid particles increases and the degree of spheroidization is improved. The tensile properties of the thixoforged ZK60+RE samples are close to those of two-pass ECAE-formed samples.展开更多
The effects of T6 heat treatment on thixoforged A356 and A380 aluminium alloys were studied.Low superheat casting(LSC)technique was carried out to prepare proper specimens for thixoforging process.The samples were pou...The effects of T6 heat treatment on thixoforged A356 and A380 aluminium alloys were studied.Low superheat casting(LSC)technique was carried out to prepare proper specimens for thixoforging process.The samples were poured at 20°C above their liquidus temperatures which provided the formation of equiaxed grains instead of dendritic growth.Produced billets were reheated for varied time from 20 to 80 min and thixoforged with 50%deformation rate.After thixoforging process,the samples were T6 heat treated for both A356 and A380 alloys.The microstructural evaluation and hardness alteration of thixoforged,solution treated and aged specimens were examined comparatively by using optical microscopy,scanning electron microscopy with energy-dispersive X-ray spectroscopy and Brinell hardness equipment.T6 heat treatment provided relatively uniform microstructure with newly formed precipitates that are Mg2Si and Al2Cu for A356 and A380 billets,respectively.Accordingly,hardness after artificial aging was increased considerably and reached HB 93 for A356 and HB 120 for A380 alloys.展开更多
Thixoforging is a type of semi-solid metal processing at high solid fraction (0.7<φs<1), which involves the processing of alloys in the semi-solid state.Tooling has to be adapted to this particular process to b...Thixoforging is a type of semi-solid metal processing at high solid fraction (0.7<φs<1), which involves the processing of alloys in the semi-solid state.Tooling has to be adapted to this particular process to benefit shear thinning and thixotropic behaviour of such semi-solid material.Tooling parameters, such as the forming speed and tool temperature, have to be accurately controlled because of their influence on thermal exchanges between material flow and tool.These thermal exchanges influence the high-cracking tendency and the rheology of the semi-solid material during forming, which affects parts properties and therefore their quality.Extrusion tests show how thermal exchanges influence quality of thixoforged parts made of 7075 aluminium alloys at high solid fraction by modifying process parameters like forming speed, tool temperature and tool thermal protector.Thus an optimum in terms of thermal exchanges has to be found between surface quality and mechanical properties of the part.A direct application is the evaluation of surface quality of thixoforged thin wall parts made of 7075 aluminium alloy.展开更多
Semisolid billet of AZ80 magnesium alloy was prepared by new strain induced melt activated (new SIMA) process and thixoforging experiment was performed.The results show that after as-cast AZ80 magnesium alloy is proce...Semisolid billet of AZ80 magnesium alloy was prepared by new strain induced melt activated (new SIMA) process and thixoforging experiment was performed.The results show that after as-cast AZ80 magnesium alloy is processed by equal channel angular extrusion, microstructure is refined well due to heavy dynamic recrystallization occurring in severe plastic deformation.Compared with semisolid isothermal treatment and conventional SIMA, semisolid billet with fine and spheroidal grains are achieved in new SIMA.Thixoforging process of semisolid billet prepared by new SIMA has many advantages such as good surface quality of final component, high ability to fill cavity and net-shape.The fine and spheroidal grains and high mechanical properties such as tensile strength of 298 MPa and elongation of 28% can be developed in final part thixoforged.展开更多
A powder thixoforging route combined with slurry based mixing process was proposed to fabricate graphene nanoplatelets(GNPs) reinforced magnesium matrix composites(MgMCs). The originally spherical and ball-milled ZK60...A powder thixoforging route combined with slurry based mixing process was proposed to fabricate graphene nanoplatelets(GNPs) reinforced magnesium matrix composites(MgMCs). The originally spherical and ball-milled ZK60 powders were used as matrices, respectively.The mixing of 0.05 wt.% GNPs with the spherical powder led to GNPs clusters and degraded the mechanical properties of the composite.In contrast, with the addition of an optimal content(0.1 wt.%) of GNPs, the composite fabricated from ball-milled powder achieved a joint enhancement in tensile yield strength(52%) and fracture toughness(19%), demonstrating a pronounced strengthening efficiency of 650% and a good balance between strength and toughness. The ball-milled powder endowed the composite with a homogenous distribution of GNPs and a denser microstructure with reduced Mg-Zn eutectics, and the thixoforging process offered a well-bonded Mg/GNP interface, making full use of the strengthening and toughening potential of GNPs. Theoretical predication based on a modified shear-lag model suggested that load transfer dominated the strengthening mechanisms. In-situ tensile tests verified that crack deflection, secondary cracks and GNPs bridging mainly accounted for the toughening mechanisms. A numerical model with consideration of GNPs orientations was also established to understand the toughening effect from GNPs bridging.展开更多
Cooling slope casting has been applied to aluminium casting alloys for producing ingots with non-dendritic microstructure.Semi-solid forming of the AA7075 was studied via cooling slope casting,reheating and thixoforgi...Cooling slope casting has been applied to aluminium casting alloys for producing ingots with non-dendritic microstructure.Semi-solid forming of the AA7075 was studied via cooling slope casting,reheating and thixoforging processes in order to determine the effect of semi-solid casting on the microstructure of the alloy.AA7075 ingots with non-dendritic microstructure were produced with cooling slope pouring.Castings were characterized by light microscopy,image analysis,scanning electron microscopy and EDS analysis.The resulting structures are promising in terms of grain size and sphericity.It was realized that grain coarsening may occur very suddenly in the reheating process.Cooling slope castings were obtained with 30°and 60°inclination angles,and in comparison,60°castings showed better results.Moreover,by using short reheating periods,semi-solid forging causes trace formation in the solid grains.展开更多
Although thixoforming of low melting point alloys as aluminum or magnesium is now an industrial reality,thixoforming of high melting point alloys as steel is still at the research level.High working temperature,die we...Although thixoforming of low melting point alloys as aluminum or magnesium is now an industrial reality,thixoforming of high melting point alloys as steel is still at the research level.High working temperature,die wearing and production rate are problems that must be solved and are under investigation.The aim of this work is to evaluate the thermal and mechanical loadings applied to the tools during the steel thixoforging process in order to determine whether classical hot-work tool steel can be an appropriate tool material.This evaluation has been realized thanks to experimental trials and to simulations on the finite elements code Forge2008.The effect of the loadings on the tool's failure modes are highlighted and compared with the ones observed in classical hot forging.Beyond this,the failure modes of hot-work tool steel,the X38CrMoV5 or H11,were presented.展开更多
A thixoforging process of the 9Cr18 steel was conducted in a designed setup, and a kind of multi-diameter component was fabricated. The effects of the forming temperature and the strain rate on the solid-/liquid-phase...A thixoforging process of the 9Cr18 steel was conducted in a designed setup, and a kind of multi-diameter component was fabricated. The effects of the forming temperature and the strain rate on the solid-/liquid-phase flow behavior were discussed. The results showed that functional gradient properties of the 9Cr18 steel could be obtained after thixoforging. Changes of microstructure along radial direction could be obtained. Solid austenite was retained after fast cooling, and the liquid film enriched in alloying elements was extruded outside to form a dendrite skin layer. As temperature increased, more molten liquid formed during thixoforging. A heterogeneous flow phenomenon was activated as free liquid channels were formed. The macro-separation of solid and liquid phases was critical for the formation of functional gradient properties. Above 1300 ℃, full dendrite skin layer could be formed. The strain rate affected the thixotropic property via influencing the deformation time of thixoforging. In the presence of lower strain rates, there was more time for the flow of liquid metal, which was the key to the extension of the thixotropic stage. High temperatures and low strain rates contributed to the formation of full skin layer for the designed specimen. The average thickness of skin layer for current specimen could be over 1000 ktm when thixoforged at 1340 ℃ and under a strain rate of 0.02 s^-1.展开更多
The semi-solid filling-plastic flowing integrated forging process of semi-solid 6061 Al alloy was simulated by commercial finite element software DEFORM-3D.Temperature,fluid and stress-strain fields were considered in...The semi-solid filling-plastic flowing integrated forging process of semi-solid 6061 Al alloy was simulated by commercial finite element software DEFORM-3D.Temperature,fluid and stress-strain fields were considered in numerical simulation.The simulation results show that the plastic deformation of billet of the ends is higher than that of billet in the straight cylinder.The value of plastic deformation varies with loading mode and plastic deformation fields at the stage of increasing pressure to constant value.When the thixoforging experiments were performed at 590 ℃,15 mm/s of punch velocity and 46 MPa of pressure side urn,it gets the filling wholly and dense internal organization of semi-solid thixoforging parts is gotten.Finite element analysis results are compatible with experimental ones.展开更多
Magnesium matrix composites(MgMCs)have always suffered low strengthening efficiency and poor ductility due to the difficulties in pursuing the well-bonded interface.Herein,graphene nanoplatelets(GNPs)were decorated wi...Magnesium matrix composites(MgMCs)have always suffered low strengthening efficiency and poor ductility due to the difficulties in pursuing the well-bonded interface.Herein,graphene nanoplatelets(GNPs)were decorated with magnesium oxide nanoparticles(MgO NPs)through chemical co-precipitation and then incorporated into AZ91 alloy to fabricate MgMCs via powder thixoforging.The effect of MgO on the interface of the Mg/graphene system was investigated based on the first-principles calculations,and the result indicated that modifying GNPs with MgO NPs was helpful in improving the Mg-GNP interface bonding.The interface structural analysis revealed that the MgO NPs were firmly bonded with both GNPs andα-Mg through the distortion area bonding and semi-coherent interfacial bonding,severing as a bridge to fasten the interface bonding of composites.In addition,the MgO NPs on GNPs acted as a barrier to prevent GNPs from seriously reacting with the AZ91 alloy.As a result,the AZ91/MgO@GNPs composite was endowed with enhancements of 31%and 10%in the yield strength,and increments of 71%and 61%in elongation compared with the AZ91 alloy and AZ91/GNPs composite,respectively,exhibiting a more significant potential in optimizing the strength-toughness tradeoffcompared with the AZ91/GNPs.Moreover,the possible strengthening and toughening mechanisms were also discussed in detail.This work offers a relatively novel surface modification strategy to modulate the Mg-GNP interface for a simultane-ous improvement of strength and ductility.展开更多
To form complex box-shape parts with large wall-thickness difference,a directly thixoforged technology of 2A14 alloy with low-cost and short-process was proposed and verified.The results showed that complex components...To form complex box-shape parts with large wall-thickness difference,a directly thixoforged technology of 2A14 alloy with low-cost and short-process was proposed and verified.The results showed that complex components were successfully thixoforged.Solid grains in the microstructure of the thixoforged parts exhibited a large deformation degree.This led to an obvious improvement in the mechanical properties of the thixoforged parts.No obvious liquid segregation was found in the microstructure.High mechanical properties were obtained in the thixoforged 2A14 alloy components.The yield strength varied from 157.1 to 187.3 MPa,the ultimate tensile strength varied from 268.2 to 316.6 MPa,and the elongation varied from 7.8%to 24.9%.Increase in plastic deformation degree caused by larger size and less round grains is beneficial to the mechanical properties of the thixoforged components.展开更多
A new processing technology,powder thixoforming,for preparation of particle reinforced metal matrix composites was proposed and 6061 aluminum alloy was prepared by powder thixoforging.6061 ingots were first prepared b...A new processing technology,powder thixoforming,for preparation of particle reinforced metal matrix composites was proposed and 6061 aluminum alloy was prepared by powder thixoforging.6061 ingots were first prepared by cold-pressing the atomized 6061 alloy powders,and then the ingots were partially remelted followed by thixoforging.The effects of reheating time,mould temperature and reheating temperature on microstructure and mechanical properties of the thixoforged alloys were investigated.The results indicate that all of the three parameters have large effects on the microstructure and mechanical properties.Owing to the microstructure changes,the fracture regime varies with the processing parameters.Furthermore,cracks always initiate from shrinkage porosities and inclusions,and then propagate either along the secondarily solidified structures or primary particles.The ultimate tensile strength,elongation and hardness of the resulting alloy are up to 196 MPa,11.0%and HV 55.7 respectively.展开更多
Tensile properties of a thixoforged A356 alloy were measured and compared with those of rheocast and gravity cast alloys with the same composition.In the thixoforging process,A356 rheocast alloy produced by stirring m...Tensile properties of a thixoforged A356 alloy were measured and compared with those of rheocast and gravity cast alloys with the same composition.In the thixoforging process,A356 rheocast alloy produced by stirring method was reheated to 600 °C or 610 °C,held for 10 min,and then 50% deformation was applied.Microstructure,tensile properties and fracture surfaces of produced specimens were then investigated.Results obtained show that tensile strength,yield strength and elongation-to-failure of thixoforged samples formed at lower temperature are higher than those of samples formed at higher temperature.By increasing temperature,in the case of thixoforged samples,tensile fracture path is changed from trans-primary alpha phase to inter-primary alpha phase.Differences observed in the tensile fracture path and improvement in the mechanical properties due to thixoforging process is attributed to microstructural changes as well as morphological aspects of silicon phase.展开更多
The effects of punch velocity on the microstructures and tensile properties of Mg2 Sip/AM60 B composite were investigated.In comparison,the tensile properties of the permanent mold casting of this composite were also ...The effects of punch velocity on the microstructures and tensile properties of Mg2 Sip/AM60 B composite were investigated.In comparison,the tensile properties of the permanent mold casting of this composite were also analyzed.The results indicate that the punch velocity obviously influences the microstructure through changing the secondary solidification behaviors and semisolid deformation mechanisms.The variations of the microstructures and deformation mechanisms are responsible for the changes in tensile properties and fracture modes of the composites.The best comprehensive tensile properties of this composite are obtained under the punch velocity of 60 mm/s.The resulting ultimate tensile strength and elongation of the composite are found to be 198 MPa and 10.2%,respectively.The excellent tensile properties of the thixoforged composite are ascribed to the elimination of porosities and the work hardening.展开更多
Thixoforging of steels is a potential forming technology,which aims at producing near-net-shaped components with good quality from high strength steels in one forging step.The thixoforging process parameters such as b...Thixoforging of steels is a potential forming technology,which aims at producing near-net-shaped components with good quality from high strength steels in one forging step.The thixoforging process parameters such as billet temperature,temperature distribution after reheating,argon gas pressure,transportation time and forging load were investigated on the thixoforging of non axis-symmetric parts of steel grade X210CrW12.The experimental and numerical study of the material flow and tool temperature load reveal the areas of intensive tool wear,thus being useful for further tool design.Hardened hot working steel X38CrMoV5-1 as a tool bulk material with protecting thin films of TiAlN/γ-Al2O3 shows good experimental results at 170 forging cycles.展开更多
文摘The two-pass equal channel angular extrusion (ECAE) process was introduced into strain-induced melt activation (SIMA) to predeform a ZK60 alloy with rare earth (RE) addition. Microstructure evolution of ECAE-formed ZK60+RE alloy during reheating was investigated. Furthermore, tensile properties of thixoforged components were determined. The results show that the SIMA process can produce ideal microstructures, and spheroidized solid particles with little entrapped liquid can be obtained. With prolonging holding time, the size of solid particles increases and the degree of spheroidization is improved. The tensile properties of the thixoforged ZK60+RE samples are close to those of two-pass ECAE-formed samples.
文摘The effects of T6 heat treatment on thixoforged A356 and A380 aluminium alloys were studied.Low superheat casting(LSC)technique was carried out to prepare proper specimens for thixoforging process.The samples were poured at 20°C above their liquidus temperatures which provided the formation of equiaxed grains instead of dendritic growth.Produced billets were reheated for varied time from 20 to 80 min and thixoforged with 50%deformation rate.After thixoforging process,the samples were T6 heat treated for both A356 and A380 alloys.The microstructural evaluation and hardness alteration of thixoforged,solution treated and aged specimens were examined comparatively by using optical microscopy,scanning electron microscopy with energy-dispersive X-ray spectroscopy and Brinell hardness equipment.T6 heat treatment provided relatively uniform microstructure with newly formed precipitates that are Mg2Si and Al2Cu for A356 and A380 billets,respectively.Accordingly,hardness after artificial aging was increased considerably and reached HB 93 for A356 and HB 120 for A380 alloys.
基金University of Liège,Walloon Region (First Europe Program Convention n°"NEP" 415824,THIXALU Project and MAGAL Project) and the COST 541 for their financial support
文摘Thixoforging is a type of semi-solid metal processing at high solid fraction (0.7<φs<1), which involves the processing of alloys in the semi-solid state.Tooling has to be adapted to this particular process to benefit shear thinning and thixotropic behaviour of such semi-solid material.Tooling parameters, such as the forming speed and tool temperature, have to be accurately controlled because of their influence on thermal exchanges between material flow and tool.These thermal exchanges influence the high-cracking tendency and the rheology of the semi-solid material during forming, which affects parts properties and therefore their quality.Extrusion tests show how thermal exchanges influence quality of thixoforged parts made of 7075 aluminium alloys at high solid fraction by modifying process parameters like forming speed, tool temperature and tool thermal protector.Thus an optimum in terms of thermal exchanges has to be found between surface quality and mechanical properties of the part.A direct application is the evaluation of surface quality of thixoforged thin wall parts made of 7075 aluminium alloy.
基金Project(50605015) supported by the National Natural Science Foundation of ChinaProject(HITQNJS.2008.012) supported by Development Program for Outstanding Young Teachers in Harbin Institute of Technology,China+1 种基金Projects(20090460884,20080440849) supported by China Postdoctoral Science FoundationProject(LBH-Q08104) supported by the Postdoctoral Foundation of Heilongjiang Province,China
文摘Semisolid billet of AZ80 magnesium alloy was prepared by new strain induced melt activated (new SIMA) process and thixoforging experiment was performed.The results show that after as-cast AZ80 magnesium alloy is processed by equal channel angular extrusion, microstructure is refined well due to heavy dynamic recrystallization occurring in severe plastic deformation.Compared with semisolid isothermal treatment and conventional SIMA, semisolid billet with fine and spheroidal grains are achieved in new SIMA.Thixoforging process of semisolid billet prepared by new SIMA has many advantages such as good surface quality of final component, high ability to fill cavity and net-shape.The fine and spheroidal grains and high mechanical properties such as tensile strength of 298 MPa and elongation of 28% can be developed in final part thixoforged.
基金financially supported by the National natural Science Foundation of China (Grant No.51761028)。
文摘A powder thixoforging route combined with slurry based mixing process was proposed to fabricate graphene nanoplatelets(GNPs) reinforced magnesium matrix composites(MgMCs). The originally spherical and ball-milled ZK60 powders were used as matrices, respectively.The mixing of 0.05 wt.% GNPs with the spherical powder led to GNPs clusters and degraded the mechanical properties of the composite.In contrast, with the addition of an optimal content(0.1 wt.%) of GNPs, the composite fabricated from ball-milled powder achieved a joint enhancement in tensile yield strength(52%) and fracture toughness(19%), demonstrating a pronounced strengthening efficiency of 650% and a good balance between strength and toughness. The ball-milled powder endowed the composite with a homogenous distribution of GNPs and a denser microstructure with reduced Mg-Zn eutectics, and the thixoforging process offered a well-bonded Mg/GNP interface, making full use of the strengthening and toughening potential of GNPs. Theoretical predication based on a modified shear-lag model suggested that load transfer dominated the strengthening mechanisms. In-situ tensile tests verified that crack deflection, secondary cracks and GNPs bridging mainly accounted for the toughening mechanisms. A numerical model with consideration of GNPs orientations was also established to understand the toughening effect from GNPs bridging.
文摘Cooling slope casting has been applied to aluminium casting alloys for producing ingots with non-dendritic microstructure.Semi-solid forming of the AA7075 was studied via cooling slope casting,reheating and thixoforging processes in order to determine the effect of semi-solid casting on the microstructure of the alloy.AA7075 ingots with non-dendritic microstructure were produced with cooling slope pouring.Castings were characterized by light microscopy,image analysis,scanning electron microscopy and EDS analysis.The resulting structures are promising in terms of grain size and sphericity.It was realized that grain coarsening may occur very suddenly in the reheating process.Cooling slope castings were obtained with 30°and 60°inclination angles,and in comparison,60°castings showed better results.Moreover,by using short reheating periods,semi-solid forging causes trace formation in the solid grains.
基金the University of Liège,the First Europe Project,the COST541 action and the Walloon Region for their financial support
文摘Although thixoforming of low melting point alloys as aluminum or magnesium is now an industrial reality,thixoforming of high melting point alloys as steel is still at the research level.High working temperature,die wearing and production rate are problems that must be solved and are under investigation.The aim of this work is to evaluate the thermal and mechanical loadings applied to the tools during the steel thixoforging process in order to determine whether classical hot-work tool steel can be an appropriate tool material.This evaluation has been realized thanks to experimental trials and to simulations on the finite elements code Forge2008.The effect of the loadings on the tool's failure modes are highlighted and compared with the ones observed in classical hot forging.Beyond this,the failure modes of hot-work tool steel,the X38CrMoV5 or H11,were presented.
基金supported by the National Natural Science Foundation of China(No.51175036)
文摘A thixoforging process of the 9Cr18 steel was conducted in a designed setup, and a kind of multi-diameter component was fabricated. The effects of the forming temperature and the strain rate on the solid-/liquid-phase flow behavior were discussed. The results showed that functional gradient properties of the 9Cr18 steel could be obtained after thixoforging. Changes of microstructure along radial direction could be obtained. Solid austenite was retained after fast cooling, and the liquid film enriched in alloying elements was extruded outside to form a dendrite skin layer. As temperature increased, more molten liquid formed during thixoforging. A heterogeneous flow phenomenon was activated as free liquid channels were formed. The macro-separation of solid and liquid phases was critical for the formation of functional gradient properties. Above 1300 ℃, full dendrite skin layer could be formed. The strain rate affected the thixotropic property via influencing the deformation time of thixoforging. In the presence of lower strain rates, there was more time for the flow of liquid metal, which was the key to the extension of the thixotropic stage. High temperatures and low strain rates contributed to the formation of full skin layer for the designed specimen. The average thickness of skin layer for current specimen could be over 1000 ktm when thixoforged at 1340 ℃ and under a strain rate of 0.02 s^-1.
基金Projects(50875059,50774026) supported by the National Natural Science Foundation of ChinaProject(20070420023) supported by China Postdoctoral Science FoundationProject (2008AA03A239) supported by High-tech Research and Development Program of China
文摘The semi-solid filling-plastic flowing integrated forging process of semi-solid 6061 Al alloy was simulated by commercial finite element software DEFORM-3D.Temperature,fluid and stress-strain fields were considered in numerical simulation.The simulation results show that the plastic deformation of billet of the ends is higher than that of billet in the straight cylinder.The value of plastic deformation varies with loading mode and plastic deformation fields at the stage of increasing pressure to constant value.When the thixoforging experiments were performed at 590 ℃,15 mm/s of punch velocity and 46 MPa of pressure side urn,it gets the filling wholly and dense internal organization of semi-solid thixoforging parts is gotten.Finite element analysis results are compatible with experimental ones.
基金supported by the National Natural Science Foundation of China(No.51761028)the Natural Science Foundation of Gansu Province,China(No.21JR7RA232).
文摘Magnesium matrix composites(MgMCs)have always suffered low strengthening efficiency and poor ductility due to the difficulties in pursuing the well-bonded interface.Herein,graphene nanoplatelets(GNPs)were decorated with magnesium oxide nanoparticles(MgO NPs)through chemical co-precipitation and then incorporated into AZ91 alloy to fabricate MgMCs via powder thixoforging.The effect of MgO on the interface of the Mg/graphene system was investigated based on the first-principles calculations,and the result indicated that modifying GNPs with MgO NPs was helpful in improving the Mg-GNP interface bonding.The interface structural analysis revealed that the MgO NPs were firmly bonded with both GNPs andα-Mg through the distortion area bonding and semi-coherent interfacial bonding,severing as a bridge to fasten the interface bonding of composites.In addition,the MgO NPs on GNPs acted as a barrier to prevent GNPs from seriously reacting with the AZ91 alloy.As a result,the AZ91/MgO@GNPs composite was endowed with enhancements of 31%and 10%in the yield strength,and increments of 71%and 61%in elongation compared with the AZ91 alloy and AZ91/GNPs composite,respectively,exhibiting a more significant potential in optimizing the strength-toughness tradeoffcompared with the AZ91/GNPs.Moreover,the possible strengthening and toughening mechanisms were also discussed in detail.This work offers a relatively novel surface modification strategy to modulate the Mg-GNP interface for a simultane-ous improvement of strength and ductility.
基金supported by the National Key R&D Program of China(No.2022YFB3404204)the National Natural Science Foundation of China(No.U2241232)the Foundation of National Key Laboratory for Precision Hot Processing of Metals,China(No.6142909230203).
文摘To form complex box-shape parts with large wall-thickness difference,a directly thixoforged technology of 2A14 alloy with low-cost and short-process was proposed and verified.The results showed that complex components were successfully thixoforged.Solid grains in the microstructure of the thixoforged parts exhibited a large deformation degree.This led to an obvious improvement in the mechanical properties of the thixoforged parts.No obvious liquid segregation was found in the microstructure.High mechanical properties were obtained in the thixoforged 2A14 alloy components.The yield strength varied from 157.1 to 187.3 MPa,the ultimate tensile strength varied from 268.2 to 316.6 MPa,and the elongation varied from 7.8%to 24.9%.Increase in plastic deformation degree caused by larger size and less round grains is beneficial to the mechanical properties of the thixoforged components.
基金Project(2014-07)supported by the Basic Scientific Fund of Gansu University,ChinaProject(NCET-10-0023)supported by the Program for New Century Excellent Talents in University of ChinaProject supported by the Program for Hongliu Outstanding Talents of Lanzhou University of Technology,China
文摘A new processing technology,powder thixoforming,for preparation of particle reinforced metal matrix composites was proposed and 6061 aluminum alloy was prepared by powder thixoforging.6061 ingots were first prepared by cold-pressing the atomized 6061 alloy powders,and then the ingots were partially remelted followed by thixoforging.The effects of reheating time,mould temperature and reheating temperature on microstructure and mechanical properties of the thixoforged alloys were investigated.The results indicate that all of the three parameters have large effects on the microstructure and mechanical properties.Owing to the microstructure changes,the fracture regime varies with the processing parameters.Furthermore,cracks always initiate from shrinkage porosities and inclusions,and then propagate either along the secondarily solidified structures or primary particles.The ultimate tensile strength,elongation and hardness of the resulting alloy are up to 196 MPa,11.0%and HV 55.7 respectively.
文摘Tensile properties of a thixoforged A356 alloy were measured and compared with those of rheocast and gravity cast alloys with the same composition.In the thixoforging process,A356 rheocast alloy produced by stirring method was reheated to 600 °C or 610 °C,held for 10 min,and then 50% deformation was applied.Microstructure,tensile properties and fracture surfaces of produced specimens were then investigated.Results obtained show that tensile strength,yield strength and elongation-to-failure of thixoforged samples formed at lower temperature are higher than those of samples formed at higher temperature.By increasing temperature,in the case of thixoforged samples,tensile fracture path is changed from trans-primary alpha phase to inter-primary alpha phase.Differences observed in the tensile fracture path and improvement in the mechanical properties due to thixoforging process is attributed to microstructural changes as well as morphological aspects of silicon phase.
基金Project(51804190)supported by the National Natural Science Foundation of ChinaProject(ZR2017LEM001)supported by Shandong Provincial Natural Science Foundation,China+1 种基金Project(2017CXGC0404)supported by Shandong Province Key Research and Development Plan,ChinaProject(2019QN0022)supported by the Youth Science Funds of Shandong Academy of Sciences,China.
文摘The effects of punch velocity on the microstructures and tensile properties of Mg2 Sip/AM60 B composite were investigated.In comparison,the tensile properties of the permanent mold casting of this composite were also analyzed.The results indicate that the punch velocity obviously influences the microstructure through changing the secondary solidification behaviors and semisolid deformation mechanisms.The variations of the microstructures and deformation mechanisms are responsible for the changes in tensile properties and fracture modes of the composites.The best comprehensive tensile properties of this composite are obtained under the punch velocity of 60 mm/s.The resulting ultimate tensile strength and elongation of the composite are found to be 198 MPa and 10.2%,respectively.The excellent tensile properties of the thixoforged composite are ascribed to the elimination of porosities and the work hardening.
基金the German Research Foundation for the financial support within the project T01 of the TFB 289 ‘Forming of metals in the semi-solid state and their properties’
文摘Thixoforging of steels is a potential forming technology,which aims at producing near-net-shaped components with good quality from high strength steels in one forging step.The thixoforging process parameters such as billet temperature,temperature distribution after reheating,argon gas pressure,transportation time and forging load were investigated on the thixoforging of non axis-symmetric parts of steel grade X210CrW12.The experimental and numerical study of the material flow and tool temperature load reveal the areas of intensive tool wear,thus being useful for further tool design.Hardened hot working steel X38CrMoV5-1 as a tool bulk material with protecting thin films of TiAlN/γ-Al2O3 shows good experimental results at 170 forging cycles.
