The tensile mechanical properties and fracture behaviors of Ti 22Al 20Nb 7Ta alloys were studied at room temperature. Three typical microstructures of Ti 2AlNb based alloys were obtained by combination of thermal mech...The tensile mechanical properties and fracture behaviors of Ti 22Al 20Nb 7Ta alloys were studied at room temperature. Three typical microstructures of Ti 2AlNb based alloys were obtained by combination of thermal mechanical processing and heat treat ment. They are: 1) lath mixture of O + B 2 with remaining β grain boundaries and α 2 phase; 2) equiaxed O phase in B 2 matrix; 3) fine lath mixture of O + B 2 without remaining β grain boundaries. It is shown that the microstructure obviously affects the tensile properties of Ti 2AlNb based alloys. The microstructure of fine lath mixture of O + B 2 without remaining β grain boundaries has good combination of yield stress and ductility, while the microstructure with lath mixture of O + B 2 with remaining β grain boundaries and α 2 phase has low yield stress and elongation. The fracture mode was also controlled by the microstructure of Ti 2AlNb based alloys. By means of SEM, it was found that the dominated fracture mode of microstructure with lath mixture of O + B 2 with remained β grain boundary and α 2 phase was intergranular, and the fracture mode of the other two microstructures was mainly transgranular.展开更多
采用电子束选区熔化(selective electron beam melting,SEBM)成形技术制备了高致密的Ti_(2)AlNb合金试样,并以此Ti_(2)AlNb合金试样为对象,系统研究了它在不同热处理制度下的显微组织及物相组成,并对其硬度、室温及650℃拉伸性能以及断...采用电子束选区熔化(selective electron beam melting,SEBM)成形技术制备了高致密的Ti_(2)AlNb合金试样,并以此Ti_(2)AlNb合金试样为对象,系统研究了它在不同热处理制度下的显微组织及物相组成,并对其硬度、室温及650℃拉伸性能以及断口形貌进行了分析表征。结果表明,电子束选区熔化成形Ti_(2)AlNb合金热处理态试样的微观组织主要由B2基体相、晶粒尺寸较大的板条状初生O/α_(2)相和细小的次生针状O相组成,950℃固溶+700℃时效试样的次生针状O相和α_(2)相含量较高,950℃固溶+800℃时效试样的初生O/α_(2)板条更为粗大。700和800℃时效热处理制度下Ti_(2)AlNb合金试样的显微硬度值接近,为3190~3210 MPa。950℃固溶+700℃时效处理试样的室温和650℃抗拉强度最高,分别为(1068±12.22)MPa和(843±39.72)MPa;而950℃固溶+800℃时效处理试样的室温和650℃下的延伸率更高,分别为(7.30±0.58)%和(8.50±0.50)%。950℃固溶+700℃时效试样的室温拉伸断口观察到较大尺寸的裂纹,时效温度提高到800℃后,裂纹消失,高温拉伸断口呈现出韧性断裂特征。展开更多
The Ti_(2)AlNb alloy was joined with TC4 alloy by vacuum diffusion bonding.The relationship between bonding parameters,and joint microstructure and shear strength was investigated.The results indicated that the diffus...The Ti_(2)AlNb alloy was joined with TC4 alloy by vacuum diffusion bonding.The relationship between bonding parameters,and joint microstructure and shear strength was investigated.The results indicated that the diffusion of Al,Ti,Nb and V elements across bonding interface led to the formation of three reaction layers:B2/βlayer andα2 layer on the TC4 side,andα2+B2/βlayer on the Ti_(2)AlNb side.The bonding temperature determined the atomic activity,thus controlling the growth of reaction layers and influencing the shear strength of the joint.When the Ti_(2)AlNb alloy and TC4 alloy were bonded at 950℃for 30 min under 10 MPa,the shear strength of the joint reached the maximum of 467 MPa.The analysis on the fracture morphology showed that the fracture occurred within the B2/βlayer and the fracture model was ductile rupture.Meanwhile,the formation mechanism of the Ti_(2)AlNb/TC4 joint was discussed in depth.展开更多
文摘The tensile mechanical properties and fracture behaviors of Ti 22Al 20Nb 7Ta alloys were studied at room temperature. Three typical microstructures of Ti 2AlNb based alloys were obtained by combination of thermal mechanical processing and heat treat ment. They are: 1) lath mixture of O + B 2 with remaining β grain boundaries and α 2 phase; 2) equiaxed O phase in B 2 matrix; 3) fine lath mixture of O + B 2 without remaining β grain boundaries. It is shown that the microstructure obviously affects the tensile properties of Ti 2AlNb based alloys. The microstructure of fine lath mixture of O + B 2 without remaining β grain boundaries has good combination of yield stress and ductility, while the microstructure with lath mixture of O + B 2 with remaining β grain boundaries and α 2 phase has low yield stress and elongation. The fracture mode was also controlled by the microstructure of Ti 2AlNb based alloys. By means of SEM, it was found that the dominated fracture mode of microstructure with lath mixture of O + B 2 with remained β grain boundary and α 2 phase was intergranular, and the fracture mode of the other two microstructures was mainly transgranular.
文摘采用电子束选区熔化(selective electron beam melting,SEBM)成形技术制备了高致密的Ti_(2)AlNb合金试样,并以此Ti_(2)AlNb合金试样为对象,系统研究了它在不同热处理制度下的显微组织及物相组成,并对其硬度、室温及650℃拉伸性能以及断口形貌进行了分析表征。结果表明,电子束选区熔化成形Ti_(2)AlNb合金热处理态试样的微观组织主要由B2基体相、晶粒尺寸较大的板条状初生O/α_(2)相和细小的次生针状O相组成,950℃固溶+700℃时效试样的次生针状O相和α_(2)相含量较高,950℃固溶+800℃时效试样的初生O/α_(2)板条更为粗大。700和800℃时效热处理制度下Ti_(2)AlNb合金试样的显微硬度值接近,为3190~3210 MPa。950℃固溶+700℃时效处理试样的室温和650℃抗拉强度最高,分别为(1068±12.22)MPa和(843±39.72)MPa;而950℃固溶+800℃时效处理试样的室温和650℃下的延伸率更高,分别为(7.30±0.58)%和(8.50±0.50)%。950℃固溶+700℃时效试样的室温拉伸断口观察到较大尺寸的裂纹,时效温度提高到800℃后,裂纹消失,高温拉伸断口呈现出韧性断裂特征。
基金This work was supported by the National Natural Science Foundation of China(No.51905055)the Natural Science Foundation of Chongqing,China(No.cstc2020jcyj-msxmX0115)the Fundamental Research Funds for the Central Universities,China(No.2020CDJ-LHZZ-086).
文摘The Ti_(2)AlNb alloy was joined with TC4 alloy by vacuum diffusion bonding.The relationship between bonding parameters,and joint microstructure and shear strength was investigated.The results indicated that the diffusion of Al,Ti,Nb and V elements across bonding interface led to the formation of three reaction layers:B2/βlayer andα2 layer on the TC4 side,andα2+B2/βlayer on the Ti_(2)AlNb side.The bonding temperature determined the atomic activity,thus controlling the growth of reaction layers and influencing the shear strength of the joint.When the Ti_(2)AlNb alloy and TC4 alloy were bonded at 950℃for 30 min under 10 MPa,the shear strength of the joint reached the maximum of 467 MPa.The analysis on the fracture morphology showed that the fracture occurred within the B2/βlayer and the fracture model was ductile rupture.Meanwhile,the formation mechanism of the Ti_(2)AlNb/TC4 joint was discussed in depth.
