时效超低碳低密度钢中碳化物的形成与控制

Formation and control of carbide in aged low-density untra-low carbon steel

采用SEM、EBSD、TEM等试验方法对时效超低碳低密度钢中碳化物的形成机制与控制进行了研究。结果表明,试验钢在热处理后存在粗大的碳化物析出相(Fe_(3)C、TiC)。试验钢中Fe_(3)C碳化物随时效温度提高发生长大,Fe_(3)C析出相与位错的作用为绕过机制,其与时效后细晶强化的共同作用使得试验钢强度大幅增加。试验钢中TiC为微米级析出相,呈方形或三角片状分布,其直径随时效温度的升高而减少,形状由不规则趋向球形。TiC与基体间存在高密度位错使得试验钢在变形过程中形成位错堆积,从而增加了基体变形的难度,导致试验钢塑性降低。

SEM, EBSD, TEM and other experimental methods were used to study the formation mechanism and control of carbides in aged low density ultra-low carbon steel. The results show that the experimental steel has coarse carbide precipitates(Fe_(3)C, TiC) after heat treatment. The Fe_(3)C carbide in the experimental steel grows with the increase of the aging temperature. The role of the Fe_(3)C precipitated phase and dislocation is the bypass mechanism. This combined with the fine-grain strengthening after aging has greatly increased the strength of the test steel. The TiC in the experimental steel is a micron-level precipitate phase, which is distributed in the shape of a square or triangle. Its diameter decreases with the increase of the aging temperature, and the shape changes from irregular to spherical. The existence of high-density dislocations between TiC and the matrix results in the formation of dislocation accumulation during the deformation of the test steel, which increases the difficulty of deformation of the matrix and leads to a decrease in the toughness of the experimental steel.