17-4PH不锈钢长期时效对拉伸性能的影响

Effect of Long-Term Aging on Tensile Properties of 17-4PH Stainless Steel

通过拉伸实验研究了17-4PH马氏体不锈钢分别在温度350℃、400℃长期时效后的力学性能变化,并用扫描电镜(SEM)和透射显微镜(TEM)观察了不同时效时间的拉伸断口形貌和显微组织演化。结果表明:随着时效时间的延长,屈服强度和抗拉强度升高而断面收缩率和伸长率则相反;断口由细小韧窝向粗大韧窝转变,经过长期时效的试样断口上有二次裂纹。TEM分析表明,该钢在时效过程中发生spinodal分解,分解生成为富Cr的α’相和富Fe的α相是该钢强度逐渐升高,塑性逐渐下降的主要原因。

In this paper the effect of long-term aging on static tensile properties of 17-4 precipita- tion-hardening stainless steel was studied, and the fracture morphology and the microstructure evolution was observed mainly by scanning electron microscope （SEM） and transmission electron microscope （TEM）, respectively. The results showed that with the age time prolonging, yield strength and tensile strength increased, but contraction of area and elongation was decreased. Smaller ductile dimples on the fracture of the quenched and tempered steel became into lager ductile dimples on the fracture of the long-term aged steel, and there was secondary cracks on the fracture of the long-term aged steel. TEM observation showed that microstructure of the steel subjected to long-term aging took place spinodal decomposition, transforming to Cr-rich α＇ phase and Fe-rich α phase, which was principally responsible for strength increasing and ductility decreasing.