Fe--22Mn--0.7CTWIP钢的热塑性与断裂机制

基于Gleeble-1500热力模拟试验机测定了Fe-22Mn-0.7C TWIP钢和Q235钢700~1300益范围内的静态拉伸行为.采用光学显微镜、扫描电子显微镜、能谱仪、电子探针微区分析等技术表征两钢种不同温度下的变形特征和断口形貌.通过分析基体化学成分、相体积分数、晶粒尺寸、凝固缺陷等因素探讨TWIP钢铸态热塑性的变化规律及其影响机制.研究结果表明,Fe-22Mn-0.7C TWIP钢700~1250益范围内的铸态抗拉强度高于Q235,而其断面收缩率低于40%,且断口均以沿枝晶间断裂方式为主.晶粒细化和控制溶质显微偏析有利于提高TWIP钢热塑性,与基体均质性改善有关.此外,增加应变速率TWIP钢拉伸强度和断面收缩率同时增大.

Hot ductility and fracture mechanism of Fe--22 Mn--0. 7 C TWIP steel

The static tensile behaviors of Fe-22Mn-0. 7C TWIP steel and Q235 steel between 700℃ and 1300℃ were investiga-ted by Gleeble-1500 thermo-mechanical simulator. The microstructure characteristic and fracture morphology were observed by optical microscopy, scanning electron microscopy, energy dispersive spectrometry and electron probe micro-analysis. The hot ductility and influenced mechanism were revealed based on the discussion of chemical composition, matrix phase volume fraction, grain size and solidification defects. It is found that the TWIP steel has a reduction in area lower than 40% in the temperature range of 700℃ to 1250℃, but its tensile strength is higher than that of Q235 steel. Fractographic results manifest intergranular fracture for the TWIP steel. Grain refinement and microsegregation descending in the TWIP steel are beneficial to increasing the hot ductility due to the improvement of matrix homogeneity. Besides, the tensile strength and reduction in area of the TWIP steel increase with increasing strain rate.