微量Sc对Al-Zn-Mg合金焊接接头组织和性能的影响

使用光学显微镜、扫描电镜和透射电镜分析了Al-Zn-Mg合金和含微量钪的Al-Zn-Mg合金钨极氩弧焊接头的微观组织，并对其力学性能和耐应力腐蚀性能进行了对比。结果表明：在传统Al-Zn-Mg合金板材熔合线附近的热影响区出现再结晶和晶粒异常长大，而含钪Al-Zn-Mg合金基体中热稳定性优良的纳米Al₃(Sc, Zr, Ti)相在焊接过程中能阻碍晶界迁移，抑制再结晶晶粒的形核和长大，进而细化熔合线附近的组织。同时，含微量钪的Al-Zn-Mg合金焊接接头的强度明显比传统合金的高，其强化效果主要来源于熔合线附近区域的细晶强化和二次Al₃(Sc, Zr, Ti)相的弥散强化。

Effect of Minor Sc on Microstructure and Properties of Al-Zn-Mg Alloy Weld Joint

The microstructures, tensile properties and stress corrosion cracking resistance of tungsten inert gas weld joints of Al-Zn-Mg alloy and Al-Zn-Mg alloy with 0.06% (mass fraction) Sc were comparatively investigated by means of optical microscope, scanning electron microscope, transmission electron microscopy, electronic universal testing machine and slow strain rate test. The results show that recrystallization with abnormal grain growth occurred in heat affected zone near the fusion line of the traditional Al-Zn-Mg alloy, while the excellent thermal stability of secondary Al₃(Sc, Zr, Ti) phase existed in the Al-Zn-Mg alloy with 0.06% Sc, which could hinder the grain boundary migration during the welding process, thereby inhibit the nucleation and growth of recrystallized grains and then refine the grain size in the matrix near the fusion line. At the same time, the strength of the weld joint for Al-Zn-Mg alloy with 0.06% Sc is obviously higher than that for Al-Zn-Mg alloy, which is mainly related to the grain-boundary strengthening and dispersion strengthening caused by secondary Al₃(Sc, Zr, Ti) phase.