3A21铝合金厚板搅拌摩擦焊组织及性能研究

Analysis of microstructure and properties in friction-stir welding of 3A21 aluminum alloy plate

对18mm厚的3A21铝合金板进行搅拌摩擦焊单道对接,焊后通过分层切片拉伸试验、显微硬度试验以及微观组织、断口形貌观察来分析接头的组织和性能。试验结果表明,在焊速为30mm/min,转速为1500r/min时,接头的抗拉强度为122N/mm^2,达到了母材强度的87%。显微硬度分布趋势为,热力影响区的硬度比热影响区的高;前进侧热力影响区的硬度比后退侧热力影响区的高;显微硬度沿焊缝中心呈不对称分布,沿焊缝中心厚度方向硬度的最高值出现在焊缝下部。焊缝四个区域的晶粒组织有明显差异。热影响区组织最为粗大,性能较差,是拉伸试验时均断裂在前进侧热影响区处的原因。

Friction-stir welding of 3A21 aluminum plate with 18 mm thickness were completed in a single pass.The microstructure and properties of the joints were analyzed through the overall and slicing tensile tests,microhardness test,microstructure observation and fracture morphology observation.The results show that the strength reaches 122 N/mm^2 which is 87% of the base material when the rotating speed is 1 500 r/min and the welding speed is 30 mm/min.The microhardness of the heat-mechanical affected zone is higher than that of the heat affected zone,while the microhardness of forward edge of the heat-mechanical affected zone is higher than that of the backward edge.The microhardness is asymmetrically distributed along the weld center,and the highest microhardness is the bottom of the weld.The microstructure of each part of the weld is obviously different and the coarsest grains and worse properties exist in the heat affected zone,which is the reason of fracture in the forward edge of the heat affected zone.