Microstructure and mechanical properties in friction stir welded nanostructured oxide dispersion strengthened steel joint

The oxide dispersion strengthened (ODS) steel was joined by friction stir welding (FSW) technique and the optimum friction welding parameter was determined. High quality of welded joints can be obtained when the traverse speed and rotation speed are 150 rpm and 30 mm/min, respectively. Microstructure observation results show that remarkable onion structure appeared in thermo-mechanically affected zone of the advanced side (AS-TMAZ). Equiaxed grain structure was achieved in stir zone. The grains in heat affected zone are quite different from that of the base material. High temperature tensile properties of FSW ODS steel were compared to those of as-received ODS steel and the results indicate that FSW process resulted in a large degradation of the joint strength, while the strength of the joint increases followed by post weld heat treatment at 1 150 ℃ for 1 hour.