(Cr2O3+Al)粉末铝热剂对6061铝合金电阻点焊熔核的影响

通过添加Cr₂O₃+Al粉末铝热剂介入6061铝合金电阻点焊,研究Cr₂O₃+Al粉末铝热剂介入对电阻点焊熔核成形、显微组织、力学性能等质量因素的影响.研究结果表明,在Cr₂O₃+Al粉末铝热剂冶金反应提供的铝热反应热的辅助作用下,可以有效增大6061铝合金的熔核尺寸.由于反应热的释放使熔核中心周围区域温度梯度降低;Cr₂O₃+Al粉末铝热剂的添加,使熔核中心区域分布了更多的异质形核晶核,并促使凝固进程中的固-液界面前沿出现大范围成分过冷,从而更有利于等轴晶的形核.熔核中心等轴晶的分布更为均匀,枝晶束更为细小,并强化熔核胞状晶区,从而使焊点强韧性得到提高.

Influence of (Cr2O3+Al) powder thermite on nugget in resistance spot welding of 6061 aluminum alloy

The resistance spot welding of 6061 aluminum alloy with addition of Cr₂O₃+Al powder thermite was conducted. With the assistance of reaction heat released by the metallurgical reaction of powder thermite,the quality factors,including the nugget formation,microstructure and mechanical property, were affected by the Cr₂O₃+Al powder thermite during the welding. The experimental results show that the nugget dimensions of 6061 aluminum alloy spot weld was improved effectively as the reaction heat was released. Because the reaction heat lowered the temperature gradient and more heterogeneous nucleation distributed in the central zone of nugget with the addition of Cr₂O₃+Al powder thermite,the large-scale composition supercooling was enlarged in front of the solid-liquid interface upon solidification. This was beneficial to the nucleation of isometric dentrite which was distributed more uniformly. The grain bundles were refined and the cellular crystal region was strengthened, which improved the strength of the spot weld.