Effect of σ phase on mechanical properties and corrosion resistance of S32205 duplex stainless steel
The precipitation behavior of σ phase in S32205 duplex stainless steel and its effect on mechanical properties and corrosion resistance of the steel were studied through a combination of JMatPro software simulation calculation and experiments.The results show that the precipitation nose temperature of the σ phase in the S32205 duplex stainless steel obtained through JMatPro software simulation calculation is 875 ℃.When S32205 duplex stainless steel is held at 875 ℃ for 0-90 min,the σ phase content increases rapidly.When the holding time increases to 90-120 min,the σ phase content slowly increases.When the holding time is 120-240 min,the σ phase content reaches saturation,with a maximum of 6.1％,which is basically consistent with the simulation calculation results.As the holding time gradually increases,the yield strength,tensile strength and microhardness of the S32205 duplex stainless steel first rapidly increase and then gradually maintain stability,while the elongation shows a decreasing trend.The strength and hardness are proportional to the volume content of the σ phase.The strengthening mechanism of the σ phase is transformed from the Orowan strengthening mechanism to the high elastic strain energy strengthening mechanism of the σ phase.The electrochemical test results of the S32205 duplex stainless steel with different u phase contents show that as the content of the σ phase gradually increases,the matrix is more prone to Cr-depleted,and the S32205 duplex stainless steel is more prone to corrosion,resulting in a gradual decrease in corrosion resistance.
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