纳米化3J33钢低温渗氮生成相性能第一性原理表征

First-principles characterization on mechanical properties of phases produced during lower temperature nitriding for nanocrystallized 3J33 steel

采用固溶处理、热轧、冷拔变形和电加热的复合技术实现了3J33马氏体时效钢纳米化,平均晶粒尺寸约为70nm。对纳米化的马氏体时效钢分别在390℃和360℃进行8h脉冲等离子体渗氮,利用XRD、显微硬度计和纳米硬度计对渗氮层生成相和性能进行了测试,并且基于第一性原理对渗氮相的性能进行了表征。结果表明,两个温度下渗层中生成的氮化相分别为γ′-Fe4N和FeN0.076,二者均具有较高的硬度和良好的塑性。计算结果表明,γ′-Fe4N和FeN0.076相中N与Fe原子的成键作用较强,且两相都具有延性。

Steel 3J33 has been entirely nanocrystallized by a complex processing including solution-treatment, hot-rolling, hard-drawn deformation and electric heating. Plasma nitriding of nanocrystallized maraging steel with an average grain size about 70nm was carried out at 390℃ and 360℃ for 8h. The structure and mechanical properties of phases in surface layers plasmas nitrided at the two temperatures were measured and characterized by XRD, nano indentation technique, microhardness tester and first-principles calculations. The experimental results show that the nitride phases formed at 390℃ and 360℃ are γ′-Fe4 N and FeN0.076, respectively, and the nitride phases possess higher hardness and better plasticity. The calculated results indicate that the bonding between N and Fe atoms in γ′-Fe4 N and FeN0.076 phases is very strong, and the two phases are ductile.