对2种不同成分的高锰TRIP钢(15Mn-4Si-2Al和20Mn-4Si-2Al)热轧后进行热处理实验.结果表明, 增加固溶处理的保温时间, 可以获得不同的显微组织并提高高锰TRIP钢的强塑积. 分析了不同的热处理条件下, 2种高Mn钢在拉伸变形过程中加工硬化速率随真应变的变化关系. 利用TEM技术研究了高锰TRIP钢中马氏体相变的特点, 确定相变途径为γ→ε→α'和γ→α', 鉴别出ε-M和α'-M 2种马氏体的组织及形貌特点, 确定γ与α'马氏体之间存在K-S取向关系; γ和ε马氏体之间存在S-N(Shoji-Nishiyama)取向关系; ε马氏体与α'马氏体之间存在Burgers取向关系.
High manganese steels containing 15%—30% (mass fractions) Mn and additions of (2%—4%)Si and (2%—4%)Al exhibit superior ductility and extraordinary strengthening behavior during plastic deformation, due to extensive twin formation under mechanical load (the so–called TWIP effect–twinning induced plasticity effect) or the ε–martensite and α′–martensite transformation (the so–called TRIP effect–transformation induced plasticity effect). In this paper, different heat treatments were carried out for high–manganese TRIP steels of Fe–15Mn–4Si–2Al and Fe–20Mn–4Si–2Al, and the uniaxial tensile tests were performed. The results show that increase of holding time at 1373 K can increase elongation and strength. Through the analysis of stress–strain curves, the relationship between mechanical properties and deformation mechanism was established. The dependence of phase compositions in high manganese TRIP steels on the heat treatment parameters has been studied by metallographic characterization and XRD pattern. The transformation routes of γ→ ε→ α′ and γ → α′ were observed by TEM, which dominates the TRIP effects. Microstructural characterization of ε–martensite and α′–martensite indicated that α′–martensite held the K–S orientation relationship with austenite, and the S–N (Shoji–Nishiyama) orientation relationship was observed between austenite and ε–martensite, whereas ε–martensite and α′–martensite held the Burgers orientation relationship. Deformation behavior of the two kinds of high Mn steels has been clarified through the relationship between work hardening rate of dσ/dε and true strain based on the true stress–true stain curves. It has been found that continuous transformation from austenite or ε–martensite to α′–martensite can take place during deformation, which increases the work–hardening rate to improve the TRIP effect.
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