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业已证实,淬火硼钢中硼向奥氏体晶界的偏聚,是在冷却过程中发生的一种非平衡的晶界偏聚。本文通过解变温扩散方程,导出了非平衡晶界偏聚的理论公式,建立了晶界贫硼区宽度与淬火加热温度、冷却速度以及非平衡晶界偏聚扩散激活能与扩散常数之间的关系,理论预言与实验结果较好地吻合。根据实验结果和理论分析,提出这种非平衡晶界偏聚的机制,是在冷却过程中,过饱和空位或双空位带着硼原子向晶界(空位阱)迁移的结果。基于这种非平衡晶界偏聚的新概念,可以较完满地说明影响硼钢淬透性的众多复杂因素。
It has been confirmed that the segregation of boron into the austenite grain boundaries in the quenched boron steel is an unbalanced grain boundary segregation that occurs during cooling. In this paper, the theoretical equation for the segregation of non-equilibrium grain boundaries is deduced by solving the temperature-dependent diffusion equation. The relationship between the width of the boron-depleted region and the quenching temperature, the cooling rate and the activation energy and the diffusion constant of the unbalanced grain boundary are established Relations, theoretical predictions and experimental results fit well. According to the experimental results and theoretical analysis, the mechanism of this non-equilibrium grain boundary segregation is proposed as the result of supersaturated vacancies or double vacancies carrying boron atoms to the grain boundary (vacancy trap) during the cooling process. Based on this new concept of segregation of non-equilibrium grain boundaries, many complicated factors that affect the hardenability of boron steel can be explained more satisfactorily.