铝合金氧化膜厚度对搅拌摩擦焊接接头组织和性能的影响

Effect of the Thickness of Aluminum Alloy Oxide Film on the Microstructure and Properties of Friction Stir Welded Joint

对表面氧化膜厚度不同的6005A-T4铝合金挤压板材进行搅拌摩擦焊接,观察接头宏观形貌、显微组织,并测试拉伸力学性能,研究氧化膜厚度对焊接后接头组织和力学性能的影响。试验结果表明:在搅拌头转速1 200 r·min-1和焊速750 mm·min-1时,可获得质量良好的接头;通过表面处理改变母材焊接前氧化膜厚度,由自然状态下5μm增至30μm,可使焊接接头抗拉强度由194.9 MPa下降至177.1 MPa,接头强度系数由82.56%下降到72.38%,说明氧化膜厚度对接头强度有极大影响;通过对接头处断口进行扫描电子显微镜和能谱分析,确定S曲线中"黑色物质"主要成分为Al2O3,而且大量氧化物颗粒形成的弱连接是导致接头抗拉强度下降的主要原因。

Friction stir welding(FSW) was carried out on 6005 A-T4 aluminum alloy extruded plates with different surface oxide thickness. The macro-morphology and microstructure of the joint were observed, the tensile mechanical properties were tested, and the effect of oxide layer thickness on the microstructure and mechanical properties of the welded joint was studied. The test results show that the joint with good quality is obtained when the speed of stirring head is 1 200 rpm and welding speed is750 mm·min-1. By surface treatment, the thickness of oxide layer before welding is increased from5 μm to 30 μm, the tensile strength of welded joint is decreased from 194.9 MPa to 177.1 MPa, and the strength coefficient of joint is reduced from 82.56% to 72.38%, which indicates that the thickness of oxide layer shows great influence on the strength of joint. The main component of "black substance" in S curve is determined to be Al2 O3 by the scanning electron microscopy observation and energy spectrum analysis on the fracture surface. The main reason for the decrease of tensile strength is the weak connection caused by many oxide particles.