The metallurgical bonding and high temperature tensile behaviors of 9Cr-1W steel and 316L steel dissimilar joint by friction stir welding

摘要

Dissimilar welded joints of 9Cr-1W reduced activation ferritic/martensitic (RAFM) steel and 316 L austenitic stainless steel were made by friction stir welding (FSW) with optimized welding parameters. In stir zone (SZ), mechanically mixing and metallurgical bonding of the two materials are observed. A alpha + gamma two-phase microstructure is observed nearby the bonding interface characterized by diffusion of Cr and Ni from 316 L steel side to RAFM steel side during FSW process. The grain size and dislocation density of the SZ 316 L in are critical for high temperature tensile behavior of the joint. Reducing the rotational speed or placing 316 L at AS could enhance the grain refining, but lead to the increase of the dislocation density of SZ 316 L. The tensile properties of the joint at 550 degrees C are 297.5 MPa yield strength, 546.5 MPa ultimate tensile strength and 17.5% elongation.