In the present study,different structured,Mg-7Gd-4Y-1Zn-0.2Zr(GWZ)and Mg-3Zn-1Al-1Ca-0.5Mn(ZA)alloys based bi-metal composites were fabricated through extrusion.In particular,we reported that the strong and large diff...In the present study,different structured,Mg-7Gd-4Y-1Zn-0.2Zr(GWZ)and Mg-3Zn-1Al-1Ca-0.5Mn(ZA)alloys based bi-metal composites were fabricated through extrusion.In particular,we reported that the strong and large diffusional interfacial thickness comprised of fine grains along with the segregation of the different elements at the interfacial region transferred the load to the base of the composite,and hence acted like a bonder and increased the stability of the interfaces.Most specifically,the rare“composite texture”having c-axes//radial direction(RD)and tilted c-axes//extruded direction(ED)with very low texture intensities was developed in all composites,which is the key requirement for retaining high strength and high ductility.The microstructure of GWZ Mg alloy consists of dense lamellar LPSO_(s),blocky LPSO_(s),rod-shaped LPSO_(s),Mg-enriched rare earth(RE)precipitates,and broken square-shaped RE-enriched precipitates.In contrast,the microstructure of ZA Mg alloy is comprised of MgAl_(2)Ca laves,different-shaped Al_(8)Mn_(5),and nano-sized Mg_(17)Al_(12) precipitates.Particularly,after extrusion,the strongly bonded interfacial region was decorated by Al,Ca,Gd,Y,and Zr elements.The WAW bi-metal composite showed a wavy interfacial morphology compared to the AWA and AW bi-metal composites and the diffusional thickness for all composites was quite large(>20μm).Therefore,based on the above brief discussion,the AWA bi-metal composite(having HAGBs>93%),exhibited exceptionally high performance.The elongation to fracture and strength under compression was significantly higher(EF∼50%,UCS∼17.70%)compared to the GWZ Mg alloy.Likewise,the bendability of the AWA bi-metal composite was much higher(∼103.2%)than the GWZ Mg alloy and higher than other composites.Therefore,the fabrication of bi-metal composites is a practical approach in achieving strength and ductility.展开更多
Reducing the yield asymmetry is very important concern for wrought Mg-Li alloys.In this study,Mg-5Li-3Al-2 Zn(LAZ532)alloy was successfully produced by hot-extrusion followed by multi-pass rolling at 573 K.Microstruct...Reducing the yield asymmetry is very important concern for wrought Mg-Li alloys.In this study,Mg-5Li-3Al-2 Zn(LAZ532)alloy was successfully produced by hot-extrusion followed by multi-pass rolling at 573 K.Microstructure evolution,mechanical properties and yield asymmetry reducing of LAZ532 alloys at different rolling passes were studied.By observing microstructure using transmission electron microscopy showed that a small amount of ultra-fine Al Mg_(4)Zn_(11)and nano Li_(3)Al_(2) phases existed in the alloy.With the increasing of rolling passes,the grains of the alloys were obviously refined,and comprehensive mechanical properties were dramatically improved.Meanwhile,it also showed an excellent tension and compression yield symmetry(TYS/CYS was about 1).The results showed that the combined action of the weak{0001}basal lamellar texture,grain refinement and addition of Li element could effectively improve the yield symmetry.Furthermore,based on theoretical analysis,the yield strength in the alloys mainly depended on the strengthening contributions of LAGBs and HAGBs,and strengthening effect of HAGBs most(~50%)to the yield strength improvement.展开更多
The oxidation behaviors of AZ80,AZ8O-0.32 Y and AZ8O-0.38 Nd(wt.%)alloys were researched at 413℃,420℃,427v and 433℃for up to 6 h in air environment via a high precision analytical balance,a laser confocal microscop...The oxidation behaviors of AZ80,AZ8O-0.32 Y and AZ8O-0.38 Nd(wt.%)alloys were researched at 413℃,420℃,427v and 433℃for up to 6 h in air environment via a high precision analytical balance,a laser confocal microscope,differential scanning calorimeter(DSC)analysis,X-ray diffraction(XRD)analysis,scanning electron microscope(SEM)observation,and X-ray photoelectron spectroscopy(XPS)analysis.The results show that the weight gain and oxidation rate of AZ80 are reduced significantly,the initiation form and propagation of cracks in oxide layer are changed.Compact and protective oxide layer forms on alloy surface with Y or Nd addition.And the activation energies of AZ80,AZ80-0.32Y and AZ8O-0.38Nd alloys calculated via Arrhenius equation are 82.556 kJ/mol,177.148kJ/mol and 136.738 kJ/mol,respectively.展开更多
In order to compare the workability of AZ110 alloy with and without addition of La-rich Mish Metal(MM), hot compression tests were performed on a Gleeble-3500 D thermo-mechanical simulator at the deformation temperatu...In order to compare the workability of AZ110 alloy with and without addition of La-rich Mish Metal(MM), hot compression tests were performed on a Gleeble-3500 D thermo-mechanical simulator at the deformation temperature range of 473-623 K and strain rate range of 0.001-1 s-1. The flow stress, constitutive relation, DRX kinetic model, processing map and microstructure characterization of the alloys were investigated. The results show that the flow stress is very sensitive to deformation temperature and strain rate, and the peak stress of AZ110 LC(LC = La-rich MM) alloy is higher than that of AZ110 alloy.The hot deformation behavior of the alloys can be accurately predicted by the constitutive relations. The derived constitutive equations show that the calculated activation energy Q and stress exponent n for AZ110 alloy are higher than the calculated values of AZ110 LC alloy. The analysis of DRX kinetic models show that the development of DRX in AZ110 LC alloy is earlier than AZ110 alloy at the same deformation condition. The processing maps show that the workability of AZ110 LC alloy is significantly more excellent than AZ110 alloy and the microstructures are in good agreement with the calculated results.The AZ110 LC alloys can obtain complete DRX microstructure at high strain rate due to its higher stored energy and weak basal texture.展开更多
Avoiding the Portevin-Le Chatelier(PLC)effect is very important concern for wrought Mg-Li alloys.In this study,the special PLC effect was found in rolled Mg-5Li-3Al-2Zn(LAZ532)alloy during tensile and compressive defo...Avoiding the Portevin-Le Chatelier(PLC)effect is very important concern for wrought Mg-Li alloys.In this study,the special PLC effect was found in rolled Mg-5Li-3Al-2Zn(LAZ532)alloy during tensile and compressive deformation.By observing microstructure evolution of the alloy during tensile and compressive deformation,it was found that prismaticand pyramidalslips were activated during tensile deformation,resulting in plenty of dislocation accumulation.In the deformation process after compressive yielding,the deformations in coarse grains and fine grains were dominated by{1012}extension twinning and grain boundary slip,respectively.Based on experimental result analysis,the sudden appearance of PLC effect in the later stage of axial tensile deformation(along rolled direction)was caused by interaction between solute atoms and dislocations.In the process of axial compressive deformation(along rolled direction),PLC effect presented the complex and changeable phenomenon of appeared-disappeared-appeared,which was mainly caused by the continuous nucleation of twin in the material,the activation of grain boundary slip and the shear deformation of twin,respectively.展开更多
Magnesium alloys are more widely used at higher temperatures.However,it is not well known whether oxide layer,produced at high temperature,could show corrosion protection.Thus,the corrosion behaviors of oxidized AZW80...Magnesium alloys are more widely used at higher temperatures.However,it is not well known whether oxide layer,produced at high temperature,could show corrosion protection.Thus,the corrosion behaviors of oxidized AZW800 alloy were investigated by hydrogen evolution and electrochemical measurements to evaluate effect of oxide layer on corrosion resistance.The results showed that corrosion of removed oxide layer AZW800 alloy showed characteristic of localized corrosion,leaving randomly bulky pits.While reserved oxide layer AZW800 alloy exhibited a relatively uniform corrosion.The results indicated that oxide layer could hinder corrosion of oxidized AZW800 alloy in the initial period of immersion.While subsequently,aggravated corrosion would occur owing to defects of oxide layer and less protective products film.Besides,present of oxide layer eliminated micro-galvanic couple on alloy surface.The synergistic effect of elimination of micro-galvanic couple on alloy surface and alkalization effect transforms localized corrosion into relatively uniform corrosion of alloys.展开更多
A high-ductility Mg-8.10Al-0.42Zn-0.51Mn-1.52La-1.10Gd-0.86 Y(wt%)alloy was developed by hot extrusion and multi-rolling processes.Relationships between microstructure,mechanical properties and texture evolution of th...A high-ductility Mg-8.10Al-0.42Zn-0.51Mn-1.52La-1.10Gd-0.86 Y(wt%)alloy was developed by hot extrusion and multi-rolling processes.Relationships between microstructure,mechanical properties and texture evolution of the extruded and rolled alloy were investigated.The rolling process had significant effect on grain refinement of the extruded plate.The grain size reduced from 12.3 to 4.9μm with the increasing rolling pass.With the increase in rolling pass,the proportion of dynamic recrystallized(DRXed)grains increases due to particle-stimulated nucleation,grain boundary nucleation and twin induced nucleation.In the process of multiple rolling,the basal pole gradually tilted from normal direction to transverse direction due to the asymmetric deformation and irregular grain deformation,resulting in the weakening of the base texture.The results showed that grain refinement and texture weakening were the main reasons for the good ductility of the alloy.展开更多
基金fully supported by the National Natural Science Foundation of China RFIS-1(52250410344 and 52250410343)the Deanship of Research and Graduate Studies at King Khalid University for funding this work through Large Research Project under grant number RGP2/277/45.
文摘In the present study,different structured,Mg-7Gd-4Y-1Zn-0.2Zr(GWZ)and Mg-3Zn-1Al-1Ca-0.5Mn(ZA)alloys based bi-metal composites were fabricated through extrusion.In particular,we reported that the strong and large diffusional interfacial thickness comprised of fine grains along with the segregation of the different elements at the interfacial region transferred the load to the base of the composite,and hence acted like a bonder and increased the stability of the interfaces.Most specifically,the rare“composite texture”having c-axes//radial direction(RD)and tilted c-axes//extruded direction(ED)with very low texture intensities was developed in all composites,which is the key requirement for retaining high strength and high ductility.The microstructure of GWZ Mg alloy consists of dense lamellar LPSO_(s),blocky LPSO_(s),rod-shaped LPSO_(s),Mg-enriched rare earth(RE)precipitates,and broken square-shaped RE-enriched precipitates.In contrast,the microstructure of ZA Mg alloy is comprised of MgAl_(2)Ca laves,different-shaped Al_(8)Mn_(5),and nano-sized Mg_(17)Al_(12) precipitates.Particularly,after extrusion,the strongly bonded interfacial region was decorated by Al,Ca,Gd,Y,and Zr elements.The WAW bi-metal composite showed a wavy interfacial morphology compared to the AWA and AW bi-metal composites and the diffusional thickness for all composites was quite large(>20μm).Therefore,based on the above brief discussion,the AWA bi-metal composite(having HAGBs>93%),exhibited exceptionally high performance.The elongation to fracture and strength under compression was significantly higher(EF∼50%,UCS∼17.70%)compared to the GWZ Mg alloy.Likewise,the bendability of the AWA bi-metal composite was much higher(∼103.2%)than the GWZ Mg alloy and higher than other composites.Therefore,the fabrication of bi-metal composites is a practical approach in achieving strength and ductility.
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0301104)National Natural Science Foundation of China(No.51771043)Programme of Introducing Talents of Discipline Innovation to Universities 2.0(the 111 Project 2.0 of China,No.BP0719037)。
文摘Reducing the yield asymmetry is very important concern for wrought Mg-Li alloys.In this study,Mg-5Li-3Al-2 Zn(LAZ532)alloy was successfully produced by hot-extrusion followed by multi-pass rolling at 573 K.Microstructure evolution,mechanical properties and yield asymmetry reducing of LAZ532 alloys at different rolling passes were studied.By observing microstructure using transmission electron microscopy showed that a small amount of ultra-fine Al Mg_(4)Zn_(11)and nano Li_(3)Al_(2) phases existed in the alloy.With the increasing of rolling passes,the grains of the alloys were obviously refined,and comprehensive mechanical properties were dramatically improved.Meanwhile,it also showed an excellent tension and compression yield symmetry(TYS/CYS was about 1).The results showed that the combined action of the weak{0001}basal lamellar texture,grain refinement and addition of Li element could effectively improve the yield symmetry.Furthermore,based on theoretical analysis,the yield strength in the alloys mainly depended on the strengthening contributions of LAGBs and HAGBs,and strengthening effect of HAGBs most(~50%)to the yield strength improvement.
基金the National Key Research and Development Program of China(No.2016YFB0301104)Nation Natural Science Foundation of China(No.51771043)Foundation of State Key Laboratory of Baiyunobo Rare Earth researches and Comprehensive Utilization,and Programme of Introducing Talents of Discipline Innovation to Universities 2.0(the 111 Project 2.0 of China,No.BP0719037).
文摘The oxidation behaviors of AZ80,AZ8O-0.32 Y and AZ8O-0.38 Nd(wt.%)alloys were researched at 413℃,420℃,427v and 433℃for up to 6 h in air environment via a high precision analytical balance,a laser confocal microscope,differential scanning calorimeter(DSC)analysis,X-ray diffraction(XRD)analysis,scanning electron microscope(SEM)observation,and X-ray photoelectron spectroscopy(XPS)analysis.The results show that the weight gain and oxidation rate of AZ80 are reduced significantly,the initiation form and propagation of cracks in oxide layer are changed.Compact and protective oxide layer forms on alloy surface with Y or Nd addition.And the activation energies of AZ80,AZ80-0.32Y and AZ8O-0.38Nd alloys calculated via Arrhenius equation are 82.556 kJ/mol,177.148kJ/mol and 136.738 kJ/mol,respectively.
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0301104)the National Natural Science Foundation of China(No.51771043)support by State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization。
文摘In order to compare the workability of AZ110 alloy with and without addition of La-rich Mish Metal(MM), hot compression tests were performed on a Gleeble-3500 D thermo-mechanical simulator at the deformation temperature range of 473-623 K and strain rate range of 0.001-1 s-1. The flow stress, constitutive relation, DRX kinetic model, processing map and microstructure characterization of the alloys were investigated. The results show that the flow stress is very sensitive to deformation temperature and strain rate, and the peak stress of AZ110 LC(LC = La-rich MM) alloy is higher than that of AZ110 alloy.The hot deformation behavior of the alloys can be accurately predicted by the constitutive relations. The derived constitutive equations show that the calculated activation energy Q and stress exponent n for AZ110 alloy are higher than the calculated values of AZ110 LC alloy. The analysis of DRX kinetic models show that the development of DRX in AZ110 LC alloy is earlier than AZ110 alloy at the same deformation condition. The processing maps show that the workability of AZ110 LC alloy is significantly more excellent than AZ110 alloy and the microstructures are in good agreement with the calculated results.The AZ110 LC alloys can obtain complete DRX microstructure at high strain rate due to its higher stored energy and weak basal texture.
基金financially supported by the National Key Research and Development Program of China(No.2016YFB0301104)the National Natural Science Foundation of China(No.51771043)。
文摘Avoiding the Portevin-Le Chatelier(PLC)effect is very important concern for wrought Mg-Li alloys.In this study,the special PLC effect was found in rolled Mg-5Li-3Al-2Zn(LAZ532)alloy during tensile and compressive deformation.By observing microstructure evolution of the alloy during tensile and compressive deformation,it was found that prismaticand pyramidalslips were activated during tensile deformation,resulting in plenty of dislocation accumulation.In the deformation process after compressive yielding,the deformations in coarse grains and fine grains were dominated by{1012}extension twinning and grain boundary slip,respectively.Based on experimental result analysis,the sudden appearance of PLC effect in the later stage of axial tensile deformation(along rolled direction)was caused by interaction between solute atoms and dislocations.In the process of axial compressive deformation(along rolled direction),PLC effect presented the complex and changeable phenomenon of appeared-disappeared-appeared,which was mainly caused by the continuous nucleation of twin in the material,the activation of grain boundary slip and the shear deformation of twin,respectively.
基金The authors are very grateful to the Nation Natural Science Foundation of China(No.51974082,No.51901037)the Natural Science Foundation of Liaoning Province,China(No.2019-BS-083)State Key Laboratory of Baiyunobo Rare Earth Resource Researched and Comprehensive Utilization(No.2021H2279)。
文摘Magnesium alloys are more widely used at higher temperatures.However,it is not well known whether oxide layer,produced at high temperature,could show corrosion protection.Thus,the corrosion behaviors of oxidized AZW800 alloy were investigated by hydrogen evolution and electrochemical measurements to evaluate effect of oxide layer on corrosion resistance.The results showed that corrosion of removed oxide layer AZW800 alloy showed characteristic of localized corrosion,leaving randomly bulky pits.While reserved oxide layer AZW800 alloy exhibited a relatively uniform corrosion.The results indicated that oxide layer could hinder corrosion of oxidized AZW800 alloy in the initial period of immersion.While subsequently,aggravated corrosion would occur owing to defects of oxide layer and less protective products film.Besides,present of oxide layer eliminated micro-galvanic couple on alloy surface.The synergistic effect of elimination of micro-galvanic couple on alloy surface and alkalization effect transforms localized corrosion into relatively uniform corrosion of alloys.
基金financially supported by the National Key Research and Development Program of China(Grant No.2016YFB0301104)the National Natural Science Foundation of China(Grant No.51771043)the State Key Laboratory of Baiyunobo Rare Earth Resource Researches and Comprehensive Utilization。
文摘A high-ductility Mg-8.10Al-0.42Zn-0.51Mn-1.52La-1.10Gd-0.86 Y(wt%)alloy was developed by hot extrusion and multi-rolling processes.Relationships between microstructure,mechanical properties and texture evolution of the extruded and rolled alloy were investigated.The rolling process had significant effect on grain refinement of the extruded plate.The grain size reduced from 12.3 to 4.9μm with the increasing rolling pass.With the increase in rolling pass,the proportion of dynamic recrystallized(DRXed)grains increases due to particle-stimulated nucleation,grain boundary nucleation and twin induced nucleation.In the process of multiple rolling,the basal pole gradually tilted from normal direction to transverse direction due to the asymmetric deformation and irregular grain deformation,resulting in the weakening of the base texture.The results showed that grain refinement and texture weakening were the main reasons for the good ductility of the alloy.
