Fe-25Mn-3Si-3Al TWIP钢凝固特性研究

Study on solidification characteristic of Fe-25Mn-3Si-3Al TWIP steel

某厂试制的Fe-25Mn-3Si-3AlTWIP钢电渣重熔锭在高温锻压过程中出现开裂。利用Gleeble3500热模拟试验机研究了Fe-25Mn-3Si-3AlTWIP钢的高温力学性能，得出第工脆性区间为1250℃到熔点，第Ⅲ脆性区间为650~800℃。利用扫描电镜（SEM）观察不同拉伸温度下断口的宏观形貌，光学显微镜观察断口附近的组织形貌，电子探针（EPMA）测定拉伸试样的偏析状态，电子背散射衍射（EBSD）试验分析研究试样中的相组成，以此来确定Fe-25Mn-3Si-3AlTWP钢的断裂机制。研究表明，在第Ⅲ脆性区间，TWIP钢的断裂形式为沿晶和穿晶的混合断裂，其脆性断裂的主要原因为铁素体的析出和晶界偏析。动态再结晶对提高TWIP钢的高温塑性具有决定性的影响。在今后的生产中应优化电渣重熔和热加工的工艺参数以避免裂纹的产生。

The as-cast Fe-25Mn-3Si-3Al TWIP steel produced by electroslag remelting has cracked in the process of forging at high temperature. The high temperature mechanical properties of Fe-25Mn-3Si-3Al TWIP steel have been investigated using the Gleeble 3500 machine. The results show that the brittleness temperature interval I is from 1 250 ℃ to the melting point and the brittleness temperature interval Ⅲ is from 650 ℃ to 800 ℃. By means of the scanning electron microscope, the types of fractures under different tensile temperatures have been analyzed, and the structure morphologies have been observed by optical microscope. The microsegregation of specimens was investigated using electron probe micro analyser, and the phase composition was examined using electron backscatter diffraction detector to determine the fracture mechanisms. The results show that the ferrite eduction and microsgregation make the specimens brittle fracture in brittleness temperature interval Ⅲ. The determining fator is dynamic recrystallization to improve the high temperature plasticity of TWIP steel. The processes of electroslag remelting and hot working should be optimized to avoid cracks in the future.