7075铝合金搅拌摩擦焊接头组织及性能

文摘对航空用5 mm厚的7075铝合金搅拌摩擦焊试样热处理前后的焊缝微观组织及性能进行了研究。结果表明:当搅拌头旋转速度400 r/m in、焊接速度40 mm/m in时,接头拉伸强度达到353 MPa,是母材强度的78.5%;焊核区为等轴晶;经热处理后接头拉伸强度值达到母材强度的83.0%;硬度的最低处在前进侧热机影响区;断口的微观形貌表现为具有强化相的韧窝特征,且断裂几乎发生在前进侧的热机影响区。由此认为,7075铝合金搅拌摩擦焊接头的薄弱点在热机影响区。

Microstructure and Properties of Friction Stir Welding Joints for 7075 Aluminum Alloy

Microstructure and properties before and after heat treatment of friction stir welded 5 mm aero aluminum alloy 7075 were investigated.The results show that with the rotating speed of stirring joint at 400 r/min and welding speed at 40 mm/min,tensile strength can reach to 353 MPa which is 78.5% of base metals;Weld nugget is composed of equiaxed grains;After heat treatment the tensile strength can reach to 83.0% of base metals;The lowest hardness appears in thermomechanically affected zone(TMAZ) of advancing side.The fractography possesses a climple characteristics of strengthening phases and the strain fracture appears in TMAZ of advancing side of joints.From this view,the weak points of friction stir welding aluminum alloy 7075 accur in the TMAZ.