Enhancement in mechanical properties and corrosion resistance of 2507 duplex stainless steel via friction stir processing

The mechanical properties and corrosion resistance of 2507 duplex stainless steel were improved by friction stir processing (FSP). Sound processed region was obtained with the traverse speed in the range of 50−200 mm/min and tool rotation speed of 400 rpm. The effect of traverse speed on the microstructure, mechanical properties and corrosion resistance of the processed area was analyzed. The grain size in the stir zone was obviously refined, and the minimum grain size was obtained at a traverse speed of 100 mm/min. The tensile strength and microhardness of the stir zone were higher than that of the base metal, while the elongation decreased to a certain extent. The traverse speed had little effect on the ratio of ferrite to austenite content in the processed zone. The refined grains in the stir zone promoted the diffusion of elements and enhanced the stability of the passivation film, which resulted in better corrosion resistance of the stir zone than that of the base metal.