The effect of forging on the microstructure and texture evolution of a high Nb containing Ti-45Al-7Nb-0.3W(at.%)alloy was investigated by X-ray diffractometer(XRD),scanning electron microscopy(SEM),and transmission el...The effect of forging on the microstructure and texture evolution of a high Nb containing Ti-45Al-7Nb-0.3W(at.%)alloy was investigated by X-ray diffractometer(XRD),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).The results show that the as-cast alloy is mainly composed of α_(2)/γ lamellar colonies with a mean size of 70μm,but the hot-forged pancake displays a near duplex microstructure(DP).Kinking and bending of lamellar colonies,deformation twinning and dynamic recrystallization(DRX)occur during hot forging.Meanwhile,dense dislocations in theβphase after forging suggest that the high-temperature β phase with a disordered structure is favorable for improving the hot-workability of the alloy.Unlike the common TiAl casting texture,the solidification process of the investigated as-cast alloy with high Nb content is completely via the β phase region,resulting in the formation of a<110>γ fiber texture where the<110>γ aligns parallel to the heat-flow direction.In comparison,the relatively strong<001>and weak<302>texture components in the as-forged alloy are attributed to the deformation twinning.After annealing,static recrystallization occurs at the twin boundary and intersections,which weakens the deformation texture.展开更多
In this work,a novel type of short-process deformation technology of Mg alloys,bifurcation-equal channel angular pressing(B-ECAP),was proposed to refine grain and improve the basal texture.The cylindrical billets were...In this work,a novel type of short-process deformation technology of Mg alloys,bifurcation-equal channel angular pressing(B-ECAP),was proposed to refine grain and improve the basal texture.The cylindrical billets were first compressed into the die cavity,then sequentially flowed downward through a 90°corner and two 120°shear steps.The total strain of B-ECAP process could reach 3.924 in a single pass.The results of microstructure observation showed that DRX occurred at upsetting process in the die cavity and completed at position D.The grains were refined to 6.3μm at being extruded at 300℃ and grew obviously with the extrusion temperature increase.The shear tress induced by 900 corner and two 120°shear steps resulted in the basal poles of most grains tilted to extrusion direction(ED)by±25°.Compared with the original billets,the extruded sheets exhibited higher yield strengths(YS),which was mainly attributed to the grain refinement.The higher Schmid factor caused by ED-tilt texture resulted in a fracture elongation(FE)more than that of the original bar in ED,while was equivalent to that in transverse direction(TD).As the extrusion temperature increased,the variation of UTS and YS in ED and TD decreased gradually without ductility obviously decrease.展开更多
In this study,specific warm rolling was carried out to process the Fe_(50)Mn_(30)Co_(10)Cr_(10) high-entropy alloy.The aim was to investigate the effect of warm rolling temperature on the microstructure and mechanical...In this study,specific warm rolling was carried out to process the Fe_(50)Mn_(30)Co_(10)Cr_(10) high-entropy alloy.The aim was to investigate the effect of warm rolling temperature on the microstructure and mechanical properties.The results indicated that serious transverse cracks appeared in the 25℃ rolled sheet with reduction of 60%,which was significantly improved through 100−300℃ warm rolling.In addition,the increase of rolling temperature promoted dislocation slip and inhibited martensitic transformation and twinning deformation.A single face centered cubic(FCC)matrix with abundant dislocations and stacking faults was developed in the 300℃rolled microstructure.Meanwhile,the deformation stored energy gradually increased,and the copper-type deformation texture was gradually enhanced.After annealing,the recrystallized microstructure of 25−200℃ rolled sheets was composed of FCC and a small amount of HCP phase.However,the hexagonal close packed(HCP)content in the annealed sheet rolled at 300℃ was as high as 20%−23% after annealing for 2−4 min and decreased to 4.5%after annealing for 8 min.All recrystallized microstructure contained a large number of annealing twins,and the average grain size increased with the increase of rolling temperature.Moreover,the mechanical properties of the annealed sheet were significantly improved after warm rolling.展开更多
The expanding of material library of laser powder bed fusion(L-PBF)is of great significance to the development of material science.In this study,the biomedical Ti-13Nb-13Zr powder was mixed with the tantalum particles...The expanding of material library of laser powder bed fusion(L-PBF)is of great significance to the development of material science.In this study,the biomedical Ti-13Nb-13Zr powder was mixed with the tantalum particles(2 wt%−8 wt%)and fabricated by L-PBF.The microstructure consists of aβmatrix with partially unmelted pure tantalum distributed along the boundaries of molten pool owing to the Marangoni convention.Because the melting process of Ta absorbs lots of energy,the size of molten pool becomes smaller with the increase of Ta content.The fine microstructure exists in the center of melt pool while coarse microstructure is on the boundaries of melt pool because of the existence of heat-affected zone.The columnar-to-equiaxed transitions(CETs)happen in the zones near the unmelted Ta,and the low lattice mismatch induced by solid Ta phase is responsible for this phenomenon.The recrystallization texture is strengthened while the fiber texture is weakened when the tantalum content is increased.Due to the formation of refined martensiteα′grains during L-PBF,the compressive strengths of L-PBF-processed samples are higher than those fabricated by traditional processing technologies.The present research will provide an important reference for biomedical alloy design via L-PBF process in the future.展开更多
基金Projects(52274402,52174381)supported by the National Natural Science Foundation of China。
文摘The effect of forging on the microstructure and texture evolution of a high Nb containing Ti-45Al-7Nb-0.3W(at.%)alloy was investigated by X-ray diffractometer(XRD),scanning electron microscopy(SEM),and transmission electron microscopy(TEM).The results show that the as-cast alloy is mainly composed of α_(2)/γ lamellar colonies with a mean size of 70μm,but the hot-forged pancake displays a near duplex microstructure(DP).Kinking and bending of lamellar colonies,deformation twinning and dynamic recrystallization(DRX)occur during hot forging.Meanwhile,dense dislocations in theβphase after forging suggest that the high-temperature β phase with a disordered structure is favorable for improving the hot-workability of the alloy.Unlike the common TiAl casting texture,the solidification process of the investigated as-cast alloy with high Nb content is completely via the β phase region,resulting in the formation of a<110>γ fiber texture where the<110>γ aligns parallel to the heat-flow direction.In comparison,the relatively strong<001>and weak<302>texture components in the as-forged alloy are attributed to the deformation twinning.After annealing,static recrystallization occurs at the twin boundary and intersections,which weakens the deformation texture.
基金Projects(52274397,52275382)supported by the National Natural Science Foundation of ChinaProject(tsqn202211115)supported by the Taishan Scholars Program of Shandong Province,China+2 种基金Project supported by the Yantai High-end Talent Introduction“Double Hundred Plan”(2021),ChinaProject(ZR2024JQ020)supported by the Shandong Provincial Natural Science Foundation of ChinaProjects(CZ20210034,CM20223013)supported by the Changzhou Sci&Tech Program,China。
文摘In this work,a novel type of short-process deformation technology of Mg alloys,bifurcation-equal channel angular pressing(B-ECAP),was proposed to refine grain and improve the basal texture.The cylindrical billets were first compressed into the die cavity,then sequentially flowed downward through a 90°corner and two 120°shear steps.The total strain of B-ECAP process could reach 3.924 in a single pass.The results of microstructure observation showed that DRX occurred at upsetting process in the die cavity and completed at position D.The grains were refined to 6.3μm at being extruded at 300℃ and grew obviously with the extrusion temperature increase.The shear tress induced by 900 corner and two 120°shear steps resulted in the basal poles of most grains tilted to extrusion direction(ED)by±25°.Compared with the original billets,the extruded sheets exhibited higher yield strengths(YS),which was mainly attributed to the grain refinement.The higher Schmid factor caused by ED-tilt texture resulted in a fracture elongation(FE)more than that of the original bar in ED,while was equivalent to that in transverse direction(TD).As the extrusion temperature increased,the variation of UTS and YS in ED and TD decreased gradually without ductility obviously decrease.
基金Project(2022RALKFKT003)supported by the Open Research Fund from the State Key Laboratory of Rolling and Automation of Northeastern University,ChinaProjects(20232BAB204053,20202ACBL214015)supported by the Natural Science Foundation of Jiangxi Province,China。
文摘In this study,specific warm rolling was carried out to process the Fe_(50)Mn_(30)Co_(10)Cr_(10) high-entropy alloy.The aim was to investigate the effect of warm rolling temperature on the microstructure and mechanical properties.The results indicated that serious transverse cracks appeared in the 25℃ rolled sheet with reduction of 60%,which was significantly improved through 100−300℃ warm rolling.In addition,the increase of rolling temperature promoted dislocation slip and inhibited martensitic transformation and twinning deformation.A single face centered cubic(FCC)matrix with abundant dislocations and stacking faults was developed in the 300℃rolled microstructure.Meanwhile,the deformation stored energy gradually increased,and the copper-type deformation texture was gradually enhanced.After annealing,the recrystallized microstructure of 25−200℃ rolled sheets was composed of FCC and a small amount of HCP phase.However,the hexagonal close packed(HCP)content in the annealed sheet rolled at 300℃ was as high as 20%−23% after annealing for 2−4 min and decreased to 4.5%after annealing for 8 min.All recrystallized microstructure contained a large number of annealing twins,and the average grain size increased with the increase of rolling temperature.Moreover,the mechanical properties of the annealed sheet were significantly improved after warm rolling.
基金Projects(51975061,51775055)supported by the National Natural Science Foundation of ChinaProject(2020JJ5599)supported by the Natural Science Foundation of Hunan Province,ChinaProjects(19C0032,19B033)supported by the Research Foundation of Education Bureau of Hunan Province,China。
文摘The expanding of material library of laser powder bed fusion(L-PBF)is of great significance to the development of material science.In this study,the biomedical Ti-13Nb-13Zr powder was mixed with the tantalum particles(2 wt%−8 wt%)and fabricated by L-PBF.The microstructure consists of aβmatrix with partially unmelted pure tantalum distributed along the boundaries of molten pool owing to the Marangoni convention.Because the melting process of Ta absorbs lots of energy,the size of molten pool becomes smaller with the increase of Ta content.The fine microstructure exists in the center of melt pool while coarse microstructure is on the boundaries of melt pool because of the existence of heat-affected zone.The columnar-to-equiaxed transitions(CETs)happen in the zones near the unmelted Ta,and the low lattice mismatch induced by solid Ta phase is responsible for this phenomenon.The recrystallization texture is strengthened while the fiber texture is weakened when the tantalum content is increased.Due to the formation of refined martensiteα′grains during L-PBF,the compressive strengths of L-PBF-processed samples are higher than those fabricated by traditional processing technologies.The present research will provide an important reference for biomedical alloy design via L-PBF process in the future.
