焊后热处理对铝锂合金电子束焊接头组织与性能的影响

Influence of Post-Weld Heat Treatment on Microstructure and Mechanical Properties of Al-Li Alloy Electron Beam Welding Joint

摘要:

对2090铝锂合金电子束焊接头进行焊后热处理，热处理工艺为530 ℃固溶0.5 h +190 ℃时效12 h。结果发现，焊接接头的抗拉强度由焊态下的331 MPa提高到热处理后的415 MPa，焊后热处理使接头的强度大大提高。金相组织观察表明，铝锂合金电子束焊接头经过热处理后焊缝晶粒形貌由焊态下的等轴树枝晶转变成等轴晶，并且在晶粒内部和晶界处析出细小的强化相。XRD相结构分析显示接头焊缝中的强化相主要为δ′(Al3Li)、T1(Al2CuLi)、β′(Al3Zr)等。TEM观察证实，热处理后2090铝锂合金接头焊缝中析出了多量的球状δ′相和针状T1相。拉伸断口分析表明，铝锂合金电子束焊接头在焊态下为带韧窝的穿晶断裂，经过热处理后接头断裂模式转变为沿晶断裂。

Abstract:

2090 Al-Li alloy electron beam welding joints were heat treated after welding, and the heat treatment scheme was 530 °C quenching for 0.5 h + 190 °C artificial aging for 12 h. Results show that the strength of 2090 Al-Li alloy joint is from 331 MPa in the as-welded state to 415 MPa under the condition of post-weld heat treatment. Therefore, the post-weld heat treatment can increase the strength of Al-Li alloy joints greatly. The observation of joint microstructure demonstrates that the grain morphology of the weldment varies form equiaxed dendrites in as-welded state into equiaxed grains after heat treatment, and the fine strengthening phases precipitate within the grain and along the grain boundary. The XRD analysis of phase constituent indicates that the main strengthening phases in Al-Li weldment are δ′(Al3Li), T1(Al2CuLi) and β′(Al3Zr), etc. The TEM observation shows that after heat treatment, many strengthening phases of spheroidal δ′ and needle-like T1 precipitate in weld metal of 2090 Al-Li alloy joint, which contribute to the joint strength. The observation of joint tensile fracture shows that the Al-Li alloy electron beam welding joint presents the characteristic of transgranular ductile fracture in the as-welded state. After post-weld heat treatment, the Al-Li alloy welded joint presents the pattern of intergranular fracture