铝锌镁钪锆合金搅拌摩擦焊接头组织与性能

Microstructure and mechanical properties of friction stir welding joints of AlZn-Mg-Sc-Zr Alloy

通过对铝锌镁钪锆合金热轧板进行搅拌摩擦焊接试验，对合金焊接接头的力学性能和焊接接头各个区域的微观组织进行了分析．结果表明，沿焊接接头焊缝横截面的显微硬度呈W形分布，硬度最高处位于焊核区，硬度最低处位于距焊缝中心12mm的热影响区，焊接接头焊接系数达到0．90；焊核区大小为1～2μm的再结晶等轴晶粒，基材中的析出相被破碎和部分溶解为细小的圆颗粒；热机影响区的晶粒发生了强烈的弯曲变形，晶内析出相由片状转变为短棒状；热影响区的晶粒发生了明显长大，析出相也明显粗化；焊接接头拉伸断口都发生在热影响区内．

The joints of friction stir welding of Al-Zn-Mg-Sc-Zr alloy were investigated,and the mechanical properties and microstructures of the joint were analysed.The results show that the distribution of micro-hardness in the cross-section presents a trend of high-low-high-low-high,the maximal hardness appears in the region of the weld nugget and the lowest hardness in head-affected zone(HAZ), and the welding coefficient reaches 0.90.The weld nugget has a dynamic recrystallized,fine isometric crystal structure with the size of 1-2 μm,and the precipitation phases in the base metal are melted and broken up to small round particles;the thermo-mechanically affected zone has a highly curved structure,and the precipitation phases transform to club-shaped;the size of grains in HAZ is larger than that in the base metal.The tensile samples of welding joint break in the HAZ.