AZ31 B镁合金电子束焊接接头显微组织及疲劳性能

摘要

为了改善镁合金焊接接头的微观组织及其力学性能，采用真空电子束焊接工艺对厚10 mm的AZ31B镁合金板材进行焊接，分析电子束对接接头的显微组织、元素分布和物相组成，检测了电子束对接接头静载拉伸性能和疲劳性能．试验结果表明AZ31B镁合金电子束焊接接头的微观组织和力学性能均得到了改善：焊缝区晶粒明显细化，焊缝区Mg、Zn元素的质量分数分别降低了0．12％和0．28％，Al、Mn元素的质量分数分别增加了0．24％、0．14％，焊缝区为单相α-Mg，无明显的低熔点β-Mg17Al12脆性；焊接接头的抗拉强度为242 MPa，能够达到母材的抗拉强度；在脉动载荷（R＝0．1）、2×106循环次数下，其接头的疲劳强度为91 MPa，能达到母材的78．4％．%In order to improve the microstructure and mechanical properties of magnesium alloy welded joints,a 10 mm thick AZ31B magnesium alloy plate was welded by the electron beam welding (EBW). The microstructure,element distribution,and phase composition of the EBW joints were then analyzed,and their static tensile properties and fatigue performance were measured. The results show that the microstructure and mechanical properties of the EBW butt joints all get improved. The crystal grains of the welding seam of are refined obviously. The mass fraction of Mg and Zn elements in the weld zone is decreased by 0 . 12% and 0 . 28%,respectively;while that of Al and Mn elements is increased by 0. 24% and 0. 14%,respectively. The fusion zone consists of single-phase α-Mg,and contains no obvious Mg17Al12 phase which has a low melting point and causes brittleness. The tensile strength of the EBW joints is 242 MPa,reaching the tensile strength of the base metals. Under 2 × 106 cycles and R=0. 1,the fatigue strength of the EBW joints is 91 MPa,nearly 78. 4% of the fatigue strength of the base metal.