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对718镍基合金的激光焊接接头微观组织进行了研究。结果表明:焊接接头的焊缝组织呈“钉头”状,结晶方向由熔合线指向焊缝中心,焊缝中心组织主要是等轴晶,焊缝熔合区出现了大量黑色沉淀相,是Nb在晶界的析出物和碳化物,热影响区也存在部分黑色沉淀相。在热影响区有大量的不连续裂纹,在钉头中间缩颈部位的裂纹最为明显。裂纹的出现与树枝晶间析出较多的Nb低熔点共晶相有关。焊缝区的显微硬度明显低于母材,在熔合线附近出现了软化区。
The microstructure of laser welded joints of 718 Ni-based alloy was studied. The results show that the microstructure of the welded joint is “pinnacle”, the crystal orientation is from the fusion line to the center of the weld, and the center of the weld is mainly equiaxed. There are a lot of black precipitates in the weld zone Nb precipitates and carbides in the grain boundary, heat-affected zone also exists in part of the black precipitate phase. In the heat affected zone there are a large number of discontinuous cracks in the middle of the nail head neck crack the most obvious. The appearance of cracks is related to the precipitation of more Nb low-melting eutectic phases among the dendrites. The microhardness of the weld zone is obviously lower than that of the base metal, and the softening zone appears near the fusion line.