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利用外约束型模拟空间热循环温度场试验设备对1420Al-Li合金焊缝进行了热循环(77~393 K)试验,测量了热循环前后焊缝的拉伸性能,并观察了热循环前后焊缝的显微组织,讨论了热循环对焊缝组织和拉伸性能的影响。试验结果表明,经1000次或3000次热循环后,焊缝的强度和延伸率显著降低。热应力使焊缝显微组织产生损伤,主要表现为从晶界处向晶内发射位错,在晶界处形成位错塞积群,晶粒内位错密度逐渐升高。随着热循环次数的增加,组织损伤的不断累积导致在晶界处产生的应力集中程度增大,这是导致合金焊缝强度和延伸率下降的主要原因。
The thermal cycling (77 ~ 393 K) test of 1420Al-Li alloy weld was carried out by using the outer constraint beam simulated thermal cycling temperature field test equipment. The tensile properties of the weld before and after thermal cycling were measured. The microstructure of the joint was discussed and the effect of thermal cycling on the microstructure and tensile properties of the weld was also discussed. The test results show that after 1000 or 3000 thermal cycles, the weld strength and elongation significantly reduced. The thermal stress causes the microstructure of the weld to be damaged, which is mainly caused by the emission of dislocations from the grain boundaries into the grains and the formation of dislocation buildup groups at the grain boundaries, and the gradual increase in dislocation density within the grains. With the increase of the number of thermal cycles, the continuous accumulation of tissue damage led to the increase of stress concentration at the grain boundaries, which is the main reason for the decrease of strength and elongation of the alloy weld.