低作用应力引起的溶质在晶界非平衡偏聚或贫化

提出了关于应力时效（高温及作用应力）引起溶质原子的晶界非平衡偏聚或贫化机理的一个新模型。此模型基于如下假设：晶界相对于完整晶体而言在强度上是弱化区。当多晶体受到一个在弹性范围内的作用应力时，晶界优先变形。若压应力作用时，晶界作为激发射空位；若拉应力作用时，晶界作为阱吸收空位，应力引起的过饱和空位与溶质原子形成复合体，此复合体在基体中的扩散速率远高于溶质原子。作用应力对晶界溶质偏聚或贫化的影响，是由复合体的扩散和溶质原子的反向扩散之间的平衡所决定。根据此模型，应力时效过程中存在一个临界时间，在此时间，应力引起的晶界偏聚或贫化程度将达到一个极大值。此模型已由ShinodaT等所作的磷在钢中的应力时效实验和MisraR D K所作的硫在钢中的应力时效实验结果所证实。

Intergranular Segregation/Dilution Induced by Ap plied Stress

A model for the effect of low applied stress on grain boundary segregation/dilution of solutes has been suggested in the present paper. This model is based on the following assumptions. The grain boundary is a region which strength is less than that of perfect crystal and is preferentialy deformed under stress. The grain boundaries emit vacancies when a compression stress is exerted on them and absorb vacancies when a tension stress is exerted. Oversaturated vacancies induced by the stress are combined with the solute atoms to form vacancy solute atom complexes. The effect of stress on grain boundary segregation/dilution of solute depends on the balance between the complex diffusion and reverse solute atom diffusion. According to this model, there is a critical time during stress aging, at which a maximum level of grain boundary segregation/dilution is occurred. This model is corroborated by Shinoda T et al for P and Misra R D K for S behavior in steels.