Fe-12Mn-7Al-0.2C-0.6Si双相钢拉伸变形行为

Tensile deformation behavior of Fe-12Mn-7Al-0.2C-0.6Si dual-phase steel

设计制备了一种新型Fe-12Mn-7Al-0.2C-0.6Si双相钢,通过拉伸性能测试对比了固溶处理及冷轧退火处理对试验钢拉伸性能的影响,利用光学显微镜(OM)、背散射电子衍射(EBSD)和扫描电镜(SEM)等手段对试验钢原始及变形组织进行分析。结果表明:组织中含有粗大δ-铁素体和奥氏体相,经冷轧退火处理后得到具有带状δ-铁素体和等轴状奥氏体的双相组织,且组织显著细化;冷轧退火态试样的屈服强度、抗拉强度及伸长率均高于锻造态试样;冷轧退火态试样变形过程中未有孪晶诱发塑性(TWIP)和相变诱发塑性(TRIP)效应发生。综合考虑元素偏聚以及两相比例分数,对试验钢中奥氏体层错能的计算方法进行优化。据此计算出奥氏体层错能为38.7 mJ·m^(-2),产生孪晶所需要的临界应力超过试样所能达到的最大流变应力,因此难以触发TWIP效应。

A new type of Fe-12 Mn-7 Al-0.2 C-0.6 Si dual-phase steel was prepared. The effect of solution treatment and cold rolling and annealing treatment on tensile properties of the test steel was compared by tensile properties test. The original and deformation microstructures of the test steel were analyzed by optical microscope(OM), electron back-scattered diffraction(EBSD) and scanning electron microscope(SEM) techniques. The results show that there are two phases of coarse δ-ferrite and austenite in the microstructure. Biphase microstructure with banded δ-ferrite and equiaxed austenite are obtained and the microstructure is significantly refined after cold rolling and annealing treatment. The yield strength, tensile strength and elongation of cold rolled and annealed samples are higher than those of forged samples. No twinning induced plasticity(TWIP) or transformation induced plasticity(TRIP) effect trigger during the deformation of cold rolled and annealed samples. The calculation method of austenite stacking fault energy(SFE) in test steel was optimized considering element segregation and two-phase proportion. The SFE of austenite is calculated to be 38.7 mJ·m^(-2), and the critical stress required for twin generation exceeds the maximum flow stress of the sample. Therefore, it is difficult to trigger TWIP effect.