含稀土的23Cr型双相不锈钢的高温变形行为

利用Gleeble-3500热力模拟试验机在950-1200℃,应变速率为0.1-10s-1条件下进行了含稀土的23Cr型双相不锈钢的热压缩变形,获得了流变曲线,建立了热变形方程,分析了变形组织。结果表明：在流变曲线上既存在峰值应力也有稳态应力;在高温低应变速率条件下,峰值应变减小。上述变形条件下,试验钢的热变形激活能Q=436kJ/mol,表观应力指数n=3.91,热变形方程为：ε=2.41×1016[sinh（0.012σs）]3.91exp （-436000/RT）。奥氏体的动态再结晶在试验钢的动态软化机制中起主导作用且随着温度的升高和应变速率的降低越来越充分;而大应变下,铁素体的软化主要表现为较充分的动态回复。稀土元素影响了热变形时两相中Mo元素的再分配是稀土改善双相不锈钢高温塑性的重要原因之一。稀土使Mo在铁素体中浓度较低温度下降低,高温下升高;而奥氏体相中,使得Mo浓度在较低温度下升高而高温下降低。

Hot deformation behavior of a 23Cr type duplex stainless steel containing rare earth

The hot deformation behavior of a 23Cr type duplex stainless steel （DSS） has been investigated by Gleeble-3500 thermal-mechanical simulator within the temperature range of 950-1 200 ℃ and the strain rate range of 0.1-10 s-1. The flow curves and the constitutive equation have been obtained and the microstructure has been analyzed. The results show that there is not only peak stress but also steady stre.ss on the flow curves, and the peak strain decreases with increasing temperature and decreasing strain rate. The annarent activation energy （O） and the aDoarent stress exoonent （n） of the test steel are obtained to be about 436 kJ/mol and 3.91, respectively, and the constitutive equation can be described as ε=2.41×1016[sinh（0.012σs）]3.91exp （-436000/RT）.The dynamic recrystallization （DRX） ofaustenite which can develop more easily with increasing temperature and decreasing strain rate, plays a dominant role in dynamic softening, while the ferrite phase mainly continues to exhibit relatively well-developed dynamic recovery （DRV） at large strain. The effect of RE on the redistribution of Mo between austenite and ferrite is believed to be an important cause for improvement on hot ductility. At lower temperature, the concentration of Mo in ferrite of DSS with RE is higher than that of DSS without RE, while at higher temperature, the concentration of Mo in ferrite of DSS with RE is lower than that of DSS without RE. However, the distribution of Mo in austenite is adverse to that in ferrite during the whole hot working temperature range.