Laves Phase in 22Cr-27Ni-2Ti-Al Austenitic Valve Steel

The Thermo Calc software was employed to calculate the equilibrium phase of 22Cr-27Ni-2Ti-Al austenitic valve steel, and the Laves phase in this steel was investigated after solid solution and aging by means of scanning electron microscopy （SEM）, transmission electron microscopy （TEM） and X- ray diffraction （XRD）. Results show that the microstructure of the experimental steel consists of γ, γ′, Laves and NbC. I.aves phases mainly precipitate on grain boundaries, with granular and fibrous morphologies. The size of the granular Laves phase is about 50-600 nm, and the fihrous Laves phase is composed of short strip Laves phases which are 300-600 nm in length and 50 150 nm in width. These two morphologies of Laves phase coarsen with increasing aging temperature, and this steel possesses the highest strength and hardness at aging temperature of 760 ℃.

57Ni-22Cr-14W-2Mo高温合金的高温本构模型及微观组织演化

利用Gleeble-3500热模拟试验机,结合光学显微镜和电子背向散射衍射等表征手段系统研究了57Ni-22Cr-14W-2Mo高温合金在变形温度为900~1100℃、应变速率为0.01~5 s^-1条件下的塑性变形行为。考虑应变量对57Ni-22Cr-14W-2Mo合金流动应力的影响,构建出耦合应变量的改进型本构模型,预测材料在变形过程中的流动应力,其预测值与实际值平均相对误差为6.9976%。基于动态材料模型推导出57Ni-22Cr-14W-2Mo合金的热加工图,并确定功率耗散峰值区域为:变形温度为1050~1100℃、应变速率为0.05~0.3 s^-1。结合该变形参数下的微观组织特征,可知等轴状的再结晶晶粒和极细的新生再结晶晶粒完全吞噬了原始晶粒,晶粒呈现随机取向。建议将功率耗散峰值区域作为57Ni-22Cr-14W-2Mo合金的最佳热加工区间。

精密仪器用合金的耐腐蚀性能分析

开发具有工程应用价值的Fe-Cr-Ni-Mo系精密仪器用新型合金并制备新型Fe-25Cr-22Ni-3.5Mo-3Ti合金,对合金的物相组成进行分析,进行电化学腐蚀和乙酸盐雾腐蚀试验。结果表明:新型合金由σ相(即(FeNi)x(CrMo)y相)、Ti Ni相组成。与常规Fe-25Cr-22Ni-3.5Mo合金相比,该新型合金的腐蚀电位正移194mV,乙酸盐雾腐蚀10天后的质量损失率减小77%,耐腐蚀性能得到显著改善。