稀土La对含Cu马氏体不锈钢显微组织与力学性能的影响

Effect of rare earth La on microstructure and mechanical properties of Cu⁃bearing martensitic stainless steel

以不含La和含0.012%La的含Cu Cr13马氏体不锈钢为研究对象,对其进行980℃固溶油冷和500℃不同保温时间的时效处理,借助光学显微镜、扫描电镜、EBSD表征,结合力学性能测试,研究了稀土添加对试验钢显微组织和力学性能的影响。结果表明,稀土La可显著降低不锈钢中δ铁素体体积分数,使淬火马氏体增多,进而增加基体中的位错密度,从而提高油冷后试验钢的硬度和强度。在时效过程中,富Cu颗粒不断析出,在达到时效强化峰阶段可为不锈钢的屈服强度提供贡献约200 MPa,未发现稀土La对富Cu相析出动力学明显的作用行为。同时,由于时效过程中小角度晶界不断减少,大角度晶界增多,使试验钢的塑性显著改善。

Cu⁃bearing Cr13 martensitic stainless steels without La and with 0.012%La were taken as the test materials,which were subjected to solution treatment at 980℃,following by oil cooling,and aging at 500℃for different time.Effect of rare earth addition on microstructure and mechanical properties of the steel was studied by means of optical microscope,scanning electron microscope,EBSD,combined with mechanical property tests.The results show that rare earth La significantly reduces theδferrite volume fraction in the steel,leading to an increase of martensite after quenching,which in turn leads to the increase of dislocations in the matrix,and thus improves the hardness and strength of the tested steel.During the aging process,by the continuous precipitation of Cu⁃rich particles,about 200 MPa can be contributed to the yield strength of the tested steels at the peak stage of aging strengthening,but the rare earth La has no significant effect on the precipitation kinetics of Cu⁃rich phases.At the same time,the plasticity of the tested steels is significantly improved due to the continuous reduction of low⁃angle grain boundaries and the increase of high⁃angle grain boundaries during the aging process.