中文摘要：

借助扫描电子显微镜、透射电子显微镜以及高温、室温拉伸和硬度测试研究了实验室研发的改进310奥氏体不锈钢在700℃长期时效后的组织与性能.700℃时效1000 h后,实验钢在晶界和晶内析出了大量（Cr,Fe,Mo）23C6、（Cr,Fe）23C6、σ相和少量的χ相.析出相对实验钢的室温力学性能有明显的强化作用.强度增加,硬度升高20 Hv,同时延伸率仍保持在30%以上.高温下,析出强化效应减弱,延伸率轻微下降.通过断口表面和剖面观察发现,时效1000 h后,实验钢的高温拉伸断口为韧性断裂,未观察到裂纹和孔洞;而室温拉伸断口为脆性断裂,断口附近则观察到σ相中出现裂纹和孔洞.从σ相的脆-韧转变和实验钢基体的室温和高温强度的不同,讨论了在室温拉伸过程中产生裂纹和孔洞的原因,以及时效对室温和高温力学行为的不同影响.

英文摘要：

The microstructures and mechanical properties of a modified 310 austenitic stainless steel during isothermal aging at700℃ were investigated by using scanning electron microscopy（ SEM） and transmission electron microscopy（ TEM）,tensile testing at ambient temperature and 700℃,and micro-hardness testing. It was found that massive block（ Cr,Fe,Mo）23C6,（ Cr,Fe）23C6carbides,σ-phase and a small quantity of χ-phase formed on grain boundaries and within grains in the tested steel after aging at 700℃ for1000 h. Precipitates significantly strengthened the mechanical properties of the tested steel at room temperature. The strength increased and the hardness raised by 20 Hv,while the elongation still remained above 30%. However,at high temperature,the effect of precipitation strengthening was weakened,and the ductility slightly decreased. Fracture surface and cross-sectional microstructural analysis after tensile testing showed that the high temperature tensile fracture mode after aging for 1000 h was ductile fracture; neither cracks nor holes were observed; but the room temperature tensile fracture was brittle,and there were some cracks and holes in σ-phase near the fracture. Finally,from the ductile-brittle transition of σ-phase and the difference in strength between room temperature and 700 ℃,this article discussed the reason for crack and hole forming in the stretching process at room temperature as well as the different effects of aging on the mechanical properties at room temperature and high temperature.