焊接热裂敏感性
(北京有色金属研究总院 国家有色金属复合材料工程技术研究中心，北京 100088)
摘 要: 采用鱼骨状试样裂纹试验、SEM和DSC等分析方法研究Sc、Zr和Er的复合添加对新型Al-5.6Mg-1.0Zn-0.6Mn基填充合金焊接热裂敏感性的影响。结果表明：Sc、Zr和Er(含Ti)参与形核核心Al3(Sc，X)的生成，Er(Ti)元素在晶界处形成富Er相，这对试验合金焊道熔池区域的晶粒度和晶间相富集状态影响显著；优化的Sc、Zr和Er成分配比能获得优异的晶粒细化效果，并抑制含Er相对晶界结合的恶化作用，使合金获得较高的焊接热裂抗力；焊接热裂敏感性降低的机理为合金偏析程度的降低、凝固终了温度的相对提高、细小晶粒的转动滑移和细晶晶界应力的分散。
关键字: Al-Mg合金；填充合金；微合金化；熔焊；热裂敏感性
Al-5Mg filler metals
（National Engineering and Technology Research Center for Non-ferrous Metal Matrix Composites,
General Research Institute for Non-ferrous Metals, Beijing 100088, China）
Abstract:The influence of Sc, Zr and Er additions on the welding hot-cracking susceptibility of Al-5.6Mg-1.0Zn-0.6Mn alloys was investigated by fishbone specimen hot-cracking test, SEM and DSC. The results show that Sc, Zr and Er including Ti participate from the melts in the Al3(Sc, X) nucleus, and Er (Ti) subsequently generates Er-riched phases at the grain boundaries. This significantly affects the grain size and phase enrichment state at the grain boundaries of the specimen molten pools. Optimized composition match of Sc, Zr and Er gives excellent grain-refining effect and suppresses the worsening effects of Er-bearing phases on the grain boundary binding, which endues the alloy with high hot-cracking resistance. The mechanism of lowering hot-cracking susceptibility is reduction of solute segregation, rise of finishing temperature, rotation and intergranular movement of refined grains and stress dispersion effect of large amounts of grains.
Key words: Al-Mg alloy; filler metal; microalloying; fusion welding; hot-cracking susceptibility
