摘要
DP780 steel sheets consisting of ferrite and martensite were successfully friction stir spot welded （FSSW） at the rotation rates of 500 to 1500 r/min using a W-Re alloy tool, The effect of rotation rate on micro- structure and mechanical properties of the FSSW DP780 was investigated. The peak temperatures in the welds at various rotation rates were identified to be above A3 temperature. FSSW caused the dynamic recrystallization in the stir zone （SZ）, thereby producing the fine equiaxed grain structures. At the higher rotation rates of≥1000 r/min, a full martensitic structure was observed throughout the SZs, whereas at the lower rotation rate of 500 r/min, the SZ consisted of a fine dual phase structure of ferrite and mar- tensite due to the action of deformation induced ferrite transformation. The maximum average failure load as high as 18.2 kN was obtained at the rotation rate of 1000 r/min and the fracture occurred at the thinned upper sheet.
DP780 steel sheets consisting of ferrite and martensite were successfully friction stir spot welded （FSSW） at the rotation rates of 500 to 1500 r/min using a W-Re alloy tool, The effect of rotation rate on micro- structure and mechanical properties of the FSSW DP780 was investigated. The peak temperatures in the welds at various rotation rates were identified to be above A3 temperature. FSSW caused the dynamic recrystallization in the stir zone （SZ）, thereby producing the fine equiaxed grain structures. At the higher rotation rates of≥1000 r/min, a full martensitic structure was observed throughout the SZs, whereas at the lower rotation rate of 500 r/min, the SZ consisted of a fine dual phase structure of ferrite and mar- tensite due to the action of deformation induced ferrite transformation. The maximum average failure load as high as 18.2 kN was obtained at the rotation rate of 1000 r/min and the fracture occurred at the thinned upper sheet.
基金
supported by the National Natural Science Foundation of China (No. 51001023)
the Fundamental Research for the Chinese Central Universities (No. N120407004)
the National High Technology Research and Development Program of China (No. 2015AA03A501)
