This study investigates the differences in microstructural control between cryogenic forging combined with pre-deformation(PCF)and traditional thermal forging(TTF)for 7050 aluminum forgings intended for aerospace appl...This study investigates the differences in microstructural control between cryogenic forging combined with pre-deformation(PCF)and traditional thermal forging(TTF)for 7050 aluminum forgings intended for aerospace applications.The PCF process,utilizing cryogenic deformation,significantly refines the coarse grains at the surface of the forgings,resulting in a finer and more uniform microstructure,thereby effectively addressing the issue of surface coarse grains associated with traditional methods.The findings indicate that the PCF process can accumulate higher stored energy,facilitating static recrystallization(SRX)during subsequent heat treatment and enhancing the microstructural uniformity.Utilizing various analytical techniques,including optical microscopy(OM),electron backscatter diffraction(EBSD),and transmission electron microscopy(TEM).This study reveals the superiority of the PCF process in terms of strain accumulation,dislocation density,and grain refinement.In conclusion,this method offers advantages in enhancing the performance and microstructural uniformity of 7050 aluminum forgings,presenting new opportunities for applications in the aluminum forging industry.展开更多
The mechanical properties and microstructural evolution of zircaloy-4 subjected to cumulative strains of 1.48,2.96,4.44 and 5.91 through multiaxial forging（MAF） at cryogenic temperature（77 K） were investigated.The...The mechanical properties and microstructural evolution of zircaloy-4 subjected to cumulative strains of 1.48,2.96,4.44 and 5.91 through multiaxial forging（MAF） at cryogenic temperature（77 K） were investigated.The mechanical properties of the MAF treated alloy were measured through universal tensile testing and Vickers hardness testing equipment.The zircaloy-4 deformed up to a cumulative strain of 5.91 showed improvement in both ultimate tensile strength and hardness from 474 MPa to 717 MPa and from HV 190 to HV 238,respectively,as compared with the as-received alloy.However,there was a noticeable decrement in ductility（from 18%to 3.5%） due to the low strain hardening ability of deformed zircaloy-4.The improvement in strength and hardness of the deformed alloy is attributed to the grain size effect and higher dislocation density generated during multiaxial forging.The microstructural evolutions of deformed samples were characterized by optical microscopy and transmission electron microscopy（TEM）.The evolved microstructure at a cumulative strain of 5.91 obtained after MAF up to 12 cycles depicted the formation of ultrafine grains with an average size of 150-250 nm.展开更多
Microstructure and mechanical properties of AZ61 Mg alloy during isothermal multi-axial forging （MAF） were studied. The mechanisms of grain refinement and relationship between the microstructures and mechanical prop...Microstructure and mechanical properties of AZ61 Mg alloy during isothermal multi-axial forging （MAF） were studied. The mechanisms of grain refinement and relationship between the microstructures and mechanical properties were discussed. The results show that the average grain size decreases with increasing the number of MAF passes. The grains are significantly refined at the 1st and 2nd MAF passes, and gradually refined at higher MAF passes. The initial grain size of 148 lam decreases to about 14 gm after 6 MAF passes. The grain refinement occurs mainly by continuous dynamic recrystallization. With increasing the MAF passes, both the tensile strength and the elongation to failure of the alloy are significantly enhanced.展开更多
The dynamic precipitation behavior during multi-axial forging in an Mg-7Gd-5Y-1Nd-0.5Zr alloy has been investigated and compared with that in static precipitation treatment. The results indicated that dynamic precipit...The dynamic precipitation behavior during multi-axial forging in an Mg-7Gd-5Y-1Nd-0.5Zr alloy has been investigated and compared with that in static precipitation treatment. The results indicated that dynamic precipitation does occur during multi-axial forging. The dynamic precipitate can be deduced as β phase with face-centered cubic crystal structure (a = 2.22 nm). Most of the β precipitates locate at the dynamic recrystallization grain boundaries. The morphology and orientation relationship is different from that of the β phase formed in the static precipitation treated alloys, although the crystal structure is the same. The precipitation temperature of β phase during MAF is higher than that in the static precipitation treatment.展开更多
In this study, AA2519 alloy was initially processed by multi axial forging (MAF) at room and cryogenic temperatures. Subsequently, the microstructure and the mechanical behavior of the processed samples under quasi-st...In this study, AA2519 alloy was initially processed by multi axial forging (MAF) at room and cryogenic temperatures. Subsequently, the microstructure and the mechanical behavior of the processed samples under quasi-static loading were investigated to determine the influence of cryogenic forging on alloys’ subgrains dimensions, grain boundaries interactions, strength, ductility and toughness. In addition, the failure mechanisms at the tensile rupture surfaces were characterized using scanning electron micro-scope (SEM). The results show significant improvements in the strength, ductility and toughness of the alloy as a result of the cryogenic MAF process. The formation of nanoscale crystallite microstructure, heavily deformed grains with high density of grain boundaries and second phase breakage to finer particles were characterized as the main reasons for the increase in the mechanical properties of the cryogenic forged samples. The cryogenic processing of the alloy resulted in the formation of an ultrafine grained material with tensile strength and toughness that are ~41% and ~80% higher respectively after 2 cycles MAF when compared with the materials processed at ambient temperature. The fractography analysis on the tested materials shows a substantial ductility improvement in the cryoforged (CF) samples when compared to the room temperature forged (RTF) samples which is in alignment with their stress-strain profiles. However, extended forging at higher cycles than 2 cycles led only to increase in strength at the expense of ductility for both the CF and RTF samples.展开更多
针对08Ni3D锻钢,采用HS09Mn Ni D焊丝,W107,W107Ni,W107DR焊条等4种焊材进行了焊接工艺试验,对其母材、焊缝、热影响区进行了-100℃的低温吸收能量试验,对焊缝、热影响区进行了板式拉伸以及180°侧弯试验,并应用光学显微镜(OM)、扫...针对08Ni3D锻钢,采用HS09Mn Ni D焊丝,W107,W107Ni,W107DR焊条等4种焊材进行了焊接工艺试验,对其母材、焊缝、热影响区进行了-100℃的低温吸收能量试验,对焊缝、热影响区进行了板式拉伸以及180°侧弯试验,并应用光学显微镜(OM)、扫描电子显微镜(SEM)等检验仪器进行了显微组织、断口形貌、高倍显微组织等相关理论的检验分析。结果表明:08Ni3D锻钢采用W107Ni焊条的低温力学性能、显微组织、断口形貌最佳,满足相关标准和产品的设计要求,完全可以应用在-100℃的风机定子上。展开更多
基金Project(2021GK1040) supported by the Major Projects of Scientific and Technology Innovation of Hunan Province,ChinaProjects(52375398,52171018) supported by the National Natural Science Foundation of China+1 种基金Project(Kfkt2023-09) supported by the Open Research Fund of State Key Laboratory of Precision Manufacturing for Extreme Service Performance,Central South University,ChinaProject(E2021203059) supported by the Natural Science Foundation of Hebei Province,China。
文摘This study investigates the differences in microstructural control between cryogenic forging combined with pre-deformation(PCF)and traditional thermal forging(TTF)for 7050 aluminum forgings intended for aerospace applications.The PCF process,utilizing cryogenic deformation,significantly refines the coarse grains at the surface of the forgings,resulting in a finer and more uniform microstructure,thereby effectively addressing the issue of surface coarse grains associated with traditional methods.The findings indicate that the PCF process can accumulate higher stored energy,facilitating static recrystallization(SRX)during subsequent heat treatment and enhancing the microstructural uniformity.Utilizing various analytical techniques,including optical microscopy(OM),electron backscatter diffraction(EBSD),and transmission electron microscopy(TEM).This study reveals the superiority of the PCF process in terms of strain accumulation,dislocation density,and grain refinement.In conclusion,this method offers advantages in enhancing the performance and microstructural uniformity of 7050 aluminum forgings,presenting new opportunities for applications in the aluminum forging industry.
基金BRNS,Bombay for their financial grant to this work through grant No.BRN-577-MMD
文摘The mechanical properties and microstructural evolution of zircaloy-4 subjected to cumulative strains of 1.48,2.96,4.44 and 5.91 through multiaxial forging（MAF） at cryogenic temperature（77 K） were investigated.The mechanical properties of the MAF treated alloy were measured through universal tensile testing and Vickers hardness testing equipment.The zircaloy-4 deformed up to a cumulative strain of 5.91 showed improvement in both ultimate tensile strength and hardness from 474 MPa to 717 MPa and from HV 190 to HV 238,respectively,as compared with the as-received alloy.However,there was a noticeable decrement in ductility（from 18%to 3.5%） due to the low strain hardening ability of deformed zircaloy-4.The improvement in strength and hardness of the deformed alloy is attributed to the grain size effect and higher dislocation density generated during multiaxial forging.The microstructural evolutions of deformed samples were characterized by optical microscopy and transmission electron microscopy（TEM）.The evolved microstructure at a cumulative strain of 5.91 obtained after MAF up to 12 cycles depicted the formation of ultrafine grains with an average size of 150-250 nm.
文摘Microstructure and mechanical properties of AZ61 Mg alloy during isothermal multi-axial forging （MAF） were studied. The mechanisms of grain refinement and relationship between the microstructures and mechanical properties were discussed. The results show that the average grain size decreases with increasing the number of MAF passes. The grains are significantly refined at the 1st and 2nd MAF passes, and gradually refined at higher MAF passes. The initial grain size of 148 lam decreases to about 14 gm after 6 MAF passes. The grain refinement occurs mainly by continuous dynamic recrystallization. With increasing the MAF passes, both the tensile strength and the elongation to failure of the alloy are significantly enhanced.
基金National Basic Research Program of China(No.2013CB632202)Key Projects in the National Science&Technology Pillar Program during the twelfth Five-year Plan Period through project(No.2011BAE22B01)for financial support.
文摘The dynamic precipitation behavior during multi-axial forging in an Mg-7Gd-5Y-1Nd-0.5Zr alloy has been investigated and compared with that in static precipitation treatment. The results indicated that dynamic precipitation does occur during multi-axial forging. The dynamic precipitate can be deduced as β phase with face-centered cubic crystal structure (a = 2.22 nm). Most of the β precipitates locate at the dynamic recrystallization grain boundaries. The morphology and orientation relationship is different from that of the β phase formed in the static precipitation treated alloys, although the crystal structure is the same. The precipitation temperature of β phase during MAF is higher than that in the static precipitation treatment.
文摘In this study, AA2519 alloy was initially processed by multi axial forging (MAF) at room and cryogenic temperatures. Subsequently, the microstructure and the mechanical behavior of the processed samples under quasi-static loading were investigated to determine the influence of cryogenic forging on alloys’ subgrains dimensions, grain boundaries interactions, strength, ductility and toughness. In addition, the failure mechanisms at the tensile rupture surfaces were characterized using scanning electron micro-scope (SEM). The results show significant improvements in the strength, ductility and toughness of the alloy as a result of the cryogenic MAF process. The formation of nanoscale crystallite microstructure, heavily deformed grains with high density of grain boundaries and second phase breakage to finer particles were characterized as the main reasons for the increase in the mechanical properties of the cryogenic forged samples. The cryogenic processing of the alloy resulted in the formation of an ultrafine grained material with tensile strength and toughness that are ~41% and ~80% higher respectively after 2 cycles MAF when compared with the materials processed at ambient temperature. The fractography analysis on the tested materials shows a substantial ductility improvement in the cryoforged (CF) samples when compared to the room temperature forged (RTF) samples which is in alignment with their stress-strain profiles. However, extended forging at higher cycles than 2 cycles led only to increase in strength at the expense of ductility for both the CF and RTF samples.
文摘针对08Ni3D锻钢,采用HS09Mn Ni D焊丝,W107,W107Ni,W107DR焊条等4种焊材进行了焊接工艺试验,对其母材、焊缝、热影响区进行了-100℃的低温吸收能量试验,对焊缝、热影响区进行了板式拉伸以及180°侧弯试验,并应用光学显微镜(OM)、扫描电子显微镜(SEM)等检验仪器进行了显微组织、断口形貌、高倍显微组织等相关理论的检验分析。结果表明:08Ni3D锻钢采用W107Ni焊条的低温力学性能、显微组织、断口形貌最佳,满足相关标准和产品的设计要求,完全可以应用在-100℃的风机定子上。
