Strengthening mechanism in ferrite and austenite of friction stir welded duplex stainless steel; neutron diffraction study

山下 享介*; 小山 元道*; Gong, W.   ; 川崎 卓郎   ; Harjo, S.   ; 潮田 浩作*; 藤井 英俊*

Yamashita, Takayuki*; Koyama, Motomichi*; Gong, W.; Kawasaki, Takuro; Harjo, S.; Ushioda, Kosaku*; Fujii, Hidetoshi*

This study investigated strengthening mechanisms in friction stir welded (FSW) duplex stainless steel (DSS) using in situ neutron diffraction during tensile testing. Two welding conditions, FSW300 and FSW600, produced significant grain refinement, with grains below 1 m in FSW300. Both conditions increased yield and tensile strength but reduced elongation compared with the base metal (BM), while FSW300 retained higher total elongation than FSW600. Neutron diffraction revealed that was the harder phase in the BM, whereas became the harder phase after FSW. Phase stress analysis showed that was more sensitive to grain refinement strengthening, shifting the dominant strengthening contribution from to . Although stacking faults in increased after FSW, work hardening of decreased, while showed enhanced texture development and dislocation accumulation.