高氧TC4/TC17钛合金线性摩擦焊接头组织特征及力学性能

对高氧TC4/TC17异质钛合金进行线性摩擦焊试验，研究了焊接接头各区域组织特征、焊接界面合金元素扩散行为及力学性能. 结果表明，焊接过程中焊缝区发生了相变及动态再结晶，形成细小的等轴晶粒. 高氧TC4侧焊缝区形成针状马氏体，TC17侧形成亚稳定β相；两侧热力影响区晶粒均发生了破碎，沿着振动方向拉长. 焊后冷却阶段在焊合线附近出现合金元素扩散现象，扩散区域狭窄. 焊缝中心处显微硬度值最高达到420 HV，高氧TC4侧显微硬度随着靠近母材而逐渐降低；TC17侧显微硬度随着远离焊缝中心迅速升高. 拉伸性能测试结果表明，接头抗拉强度与高氧TC4母材相当.

Microstructure and properties of linear friction welded joint of hyperoxia TC4/TC17 dissimilar titanium alloys

The linear friction welding test was carried out on the hyperoxic TC4/TC17 dissimilar titanium alloys, the analysis of the microstructure evolution of different areas of joint, the diffusion behavior of the alloying elements at the weld line interface and the properties of joint were analyzed. As shown in the results of the test, the phase transformation and dynamic recrystallization occurred in the weld zone during the process of linear friction welding, and eventually forming fine equiaxed grains. The needle-shaped martensite is formed in the weld zone of the hyperoxic TC4 side, while the TC17 side is mainly composed of the metastable β phase. The grains in both sides of the thermos-mechanically affected zone are broken, and elongated along the oscillation direction. During the cooling process of welding, the diffusion behavior of alloy elements appeared near the weld line, and the diffusion area is narrow. The micro-hardness at the center of the weld is up to 420 HV, while decreased gradually as approaching to the base material in the side of TC4. On the contrary micro-hardness of the TC17 side increased rapidly as moving away from the weld center. The tensile test results showed that the tensile strength of the joint is equal to that of the hyperoxic TC4 parent.