TIG熔修对7N01铝合金焊接接头疲劳性能的影响

Effect of TIG-dressing on fatigue properties of 7N01 aluminium alloy welded joint

采用焊条电弧焊的方法对7N01铝合金焊接试板进行TIG熔修,对熔修前后的试件进行疲劳寿命测试,并对焊接接头的显微硬度变化进行测试,采用扫描电镜对疲劳断口进行显微形貌分析,并对疲劳源区缺陷进行XRD成分检测.结果表明,TIG熔修对焊趾应力集中的降低有限,还可能引入新的焊接缺陷成为疲劳裂纹源;同时TIG熔修使得焊接区域经受二次加热,沉淀强化相的形态和重新分布造成接头组织弱化,降低了焊接接头抵抗疲劳裂纹扩展的能力,多方面作用的结果是:经TIG熔修后铝合金焊接接头疲劳寿命略有降低,所以对于7N01高强铝合金对接接头单纯采用焊趾TIG熔修的方法提高疲劳性能不具备可行性.

TIG-dressing of 7N01 aluminium alloy welded joint was carried out by shielded metal arc welding. The fatigue properties and microhardness of specimens were tested before and after TIG-dressing, and the fractography was analyzed with SEM and the composition in defect zone was examined with XRD. Experimental results show that TIG-dressing slightly reduced the stress concentration on the weld toe, however, TIG-dressing could also bring additional weld defects which would initiate fatigue crack. The reheating by TIG-dressing could soften the welded joint and degrade the resistance to fatigue crack propagation. Consequently, the fatigue life of welded joint after TIGdressing slightly decreased. Therefore, it had no feasibility to improve the fatigue properties of 7N01 high strength aluminium alloy welded joint by TIG-dressing.