Study on softening behavior of laser welded joint in GH909 alloy

Laser beam welding was conducted on GH909 alloy in a solution treatment and aging conditions. The microstructure, mechanical properties, and softening behavior of welded joints were carefully studied using scanning electron microscopy, energy diffraction spectroscopy, and other techniques. Results indicated that gamma'-Ni-3(TiAl)-precipitated phases were produced inside the matrix, and the presence of Laves at grain boundaries restricted grain growth. A sharp reduction in gamma'-precipitated phases evidently weakened the average tensile strength and microhardness of the welded joints. Moreover, fractures occurred in the weld zone. Microcracks in the fracture of the joint mainly depended on the competition result between thermal stress and cohesion forces among the grains.