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采用不同去应力退火工艺(T=250、350、400℃,t=1~4 h)对AZ31镁合金焊接接头进行真空热压去应力退火处理,采用盲孔法研究镁合金焊接接头退火前后的残余应力变化规律,利用金相显微镜观察接头显微组织。结果表明:经真空热压去应力退火后,镁合金焊接接头残余应力消除效果显著,且退火温度越高,残余应力越低,应力松弛效果越好,350℃时,接头应力松弛率达到85%以上;保温时间对接头残余应力的松弛影响并不显著;随着退火温度的升高,接头显微组织呈现规律性变化,当温度在350℃以上时,晶粒显著长大,且β-Mg17Al12相显著增加;保温时间越长,晶粒平均尺寸越大;最后得到AZ31镁合金焊接接头的真空热压去应力退火最佳工艺为350℃×1 h。
The AZ31 magnesium alloy welded joints were subjected to hot pressing and stress relief annealing under different stress relief annealing (T = 250, 350, 400 ℃, t = 1 ~ 4 h). The blind hole method was used to study the mechanical properties of AZ31 magnesium alloy before and after annealing Residual stress changes, the use of metallographic microscope to observe the joint microstructure. The results show that the residual stress of magnesium alloy welding joint is remarkably eliminated after vacuum hot-pressing and stress-relief annealing. The higher the annealing temperature is, the lower the residual stress is and the better the stress relaxation effect is. When 350 ℃, the stress relaxation rate of the joint reaches 85% , And the holding time has no significant effect on the relaxation of the residual stress. The microstructure of the joint exhibits a regular change with the increase of the annealing temperature. When the temperature is above 350 ℃, the grains grow significantly, and the β-Mg17Al12 And the average grain size of the AZ31 magnesium alloy welded joints is the best. The best annealing temperature is 350 ℃ × 1 h.