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研究了微合金化对AZ31B镁合金点焊接头组织和耐蚀性能的影响。结果表明:微合金化不改变AZ31B镁合金点焊接头相组成,但有细化晶粒作用,从而提高镁合金接头性能。Cu因能提供高熔点的非自发形核质点细化晶粒效果显著;Al促进胞状晶结晶的同时导致晶界上硬脆沉淀相Mg_(17)Al_(12)的生成。Cu抑制柱状晶的外延生长,促进等轴晶的生长;熔核区形成Cu_2MgO_3脆相。微合金化有利于提高AZ31B镁合金点焊接头的抗腐蚀性能。Cu、Al、Zn三种合金元素中,Al对接头抗腐蚀性能的提高较显著。
The effect of microalloying on microstructure and corrosion resistance of AZ31B magnesium alloy spot welded joints was studied. The results show that: micro-alloying does not change the phase composition of AZ31B magnesium alloy spot welding joints, but the role of grain refinement, thereby improving the performance of magnesium alloy joints. The effect of Cu on grain refinement of non-spontaneous nucleation sites with high melting point was remarkable. Al promoted the formation of cellular crystallization and the formation of hard-brittle precipitation phase Mg_ (17) Al_ (12) at the grain boundary. Cu inhibits the epitaxial growth of columnar grains and promotes the growth of equiaxed grains; the Cu2MgO3 brittle phase forms in the nugget zone. Micro-alloying helps to improve the corrosion resistance of AZ31B magnesium alloy spot welding joints. Cu, Al, Zn three alloying elements, Al on the joint corrosion resistance improvement is more significant.