Effects of post-weld heat treatment on microstructure and mechanical properties of the welded joints by using multi-principal filler materials

Two types of multi-principal filler materials of FeCoCrNiMn and CrNi2MnTi0.5Al0.5 powders were used to butt weld the 304/Q235 stainless steel composite plate. The effects of post-weld heat treatment (PWHT) on the grain morphologies, phase structures, microhardness, and tensile properties of two welded joints were explored and discussed. An interesting finding was that the PWHT process had markedly different effects on the hardness, tensile properties, and fracture behavior of two welded joints. A simple phase structure, a face-centered cubic (FCC) phase, was achieved in the weld metal by using FeCoCrNiMn powders. The PWHT process had small effects on the microstructure, hardness value, tensile strength, and fracture position of the FeCoCrNiMn sample. However, the PWHT process could sharply increase the hardness and significantly decrease the tensile strength of the CrNi2MnTi0.5Al0.5 sample. Moreover, the grain morphologies in the weld zone were changed from columnar/equiaxed grains into structures with irregular morphologies for the CrNi2MnTi0.5Al0.5 sample after the PWHT process.