Influence of heat treatment on microstructure and mechanical properties of spray formed 7xxx series aluminum alloy TIG weld joint

Tungsten inert gas welding of spray formed 7xxx serial aluminum alloy was conducted with 7055 aluminum alloy as the filler wire.The resultant joints were solid solution treated at 450℃×1 h+475℃×1 h,and then water quenched and finally aged at 120℃×24 h.After solution,the microstructure of the weld was homogenous without overburning and the grain size slightly increased.The double-stage solution treatment dissolved the alloying elements in the base metal sufficiently,therefore the content of alloying elements increased in base metal but decreased in grain boundaries.Consequently,the alloying elements distributed more uniformly after the solid solution.In the subsequent aging treatment,strengthening phases precipitated from the oversaturated solid solutions,which improved the joint strength remarkably.The joint strength of 7055 and 7475 aluminum alloy reached 65% and 91% of the base metal,respectively,which indicated that the proposed heat treatment in this paper was suitable.