AZ31B镁合金TIG焊焊接接头的疲劳性能

FATIGUE BEHAVIOR OF AZ31B MAGNESIUM ALLOY JOINT WITH TIG-WELDING

对8mm厚AZ31B镁合金板及其三种TIG焊焊接接头的静载拉伸性能和疲劳性能进行试验研究。试验结果表明AZ31B镁合金母材的静载抗拉强度为245．50MPa，TIG焊对接接头、纵向角接接头和非承载十字接头的静载抗拉强度分别为193．55MPa、229．89MPa、227．39MPa。脉动循环（r=0）疲劳试验表明，在2×10^6循环次数下，AZ31B镁合金母材的疲劳强度为57．81MPa，为其静载抗拉强度的23．5％。相同循环次数下，AZ31B镁合金TIG焊对接接头、纵向角接接头和非承载十字接头的疲劳强度为24．60MPa、20．14MPa、17．25MPa，分别为母材疲劳强度的42．6％、34．8％和29．8％。按照国际焊接学会的规范，发现镁合金焊接接头的疲劳级别FAT仅为相应铝合金接头疲劳级别FAT的一半。由此看来，疲劳性能是影响镁合金在承受动态载荷结构中应用的主要因素之一。

The fatigue properties and the mechanical performance of AZ31B magnesium alloy with 8 mm thickness and its welded joint by TIG welding are studied. The results showed that the tensile strength of the base metal is 245.50 MPa and that of the butt joint, longitudinal fillet joint and transverse crossed joint are 193.55 MPa, 229.89 MPa and 227.39 MPa, respectively. The fatigue properties of AZ31B Magnesium alloy are evaluated, when the coefficient of stress cycle is zero. Under the condition of 2x106 cycles, the fatigue strength of the base metal is 57.81 MPa and that of the three types of joints are 24.60 MPa, 20.14 MPa and 17.25 MPa in turn. It is about 42.6%, 34.8% and 29.8% of that of the base metal, respectively. According to the standard of IIW, the FAT of the welded joint of magnesium alloy is about half of that of the aluminum alloy. So the fatigue properties are one of the key factors that obstructs the application of magnesium alloy for the structure suffered from the dynamic load.