热处理对一种新型析出强化型奥氏体不锈钢显微组织与性能的影响

The effect of heat treatment on microstructure and mechanical properties of a precipitation⁃strengthened austenitic stainless steel

新型析出强化型奥氏体不锈钢Fe⁃(26⁃29)Ni⁃(13⁃19)Cr⁃(2.8⁃3.0)Al⁃(1.8⁃2.4)Ti(wt.%)具有优异的高温强度和抗氧化性能。为了揭示热处理工艺与力学性能间关联关系,本文利用先进扫描/透射电子显微技术系统地研究了再结晶和时效温度对Fe⁃29Ni⁃18Cr⁃3Al⁃2.35Ti(wt.%)合金显微结构的影响,利用拉伸试验测试了热处理工艺不同合金的力学性能。试验结果表明不同温度时效处理后,钢中均析出大量与基体共格的L12结构纳米级球形析出相Ni_(3)(Al,Ti),但再结晶温度低于1040℃或时效温度高于720℃时,合金中将析出有害相{Ni2AlTi和Fe(Cr,Mo)},这些有害相虽然能够提高合金室温强度,但会消耗Al、Ti和Mo元素,降低纳米Ni3(Al,Ti)体积分数,损害合金的高温强度。

The newly⁃developed precipitation⁃strengthened austenitic stainless steels Fe⁃(26-29)Ni⁃(13-19)Cr⁃(2.8-3.0)Al⁃(1.8-2.4)Ti(wt.%)exhibit excellent high⁃temperature strength and oxidation resistance.To elucidate the relationship between heat treatment and mechanical properties,the effects of recrystallization and aging temperatures on the microstructure of Fe⁃29Ni⁃18Cr⁃3Al⁃2.35Ti(wt.%)steel were systematically investigated using advanced scanning/transmission electron microscopy.The mechanical properties of steels subjected to different heat treatments were measured via tensile tests.Results showed that after aging treatment at different temperatures,a large number of spherical Ni_(3)(Al,Ti)nanoprecipitates with an L12 structure formed in the steels.However,when the recrystallization temperature was lower than 1040℃or the aging temperature was higher than 720℃,harmful phases[Ni2AlTi and Fe(Cr,Mo)]precipitated.Although those harmful phases appeared to improve the strength at room temperature,they consumed Al and Ti and Mo elements,reducing the volume fraction of nano⁃Ni3(Al,Ti)and consequently decreasing the high⁃temperature strength of the steels.