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针对铸态690合金,利用单向热压缩实验研究了外力与柱状晶垂直时材料的热变形行为,并对流变曲线进行了本构分析,对变形显微组织进行观察。结果表明:在工程应变量50%范围内,铸态690合金的变形抗力随着应变量的增大而持续增长,变形结束时仍没有达到峰值应力。硬化率曲线存在3个线性区域,而动态再结晶区域只在应变速率为0.01 s-1时出现。变形温度的升高和应变速率的降低均会使流变应力减小。组织分析表明,柱状晶条件下材料的动态再结晶主要有3种形核方式:应变诱发晶界迁移、碳化物颗粒诱发形核和形变带亚晶转化形核。再结晶软化作用的弱化和亚晶的形成是导致铸态690合金变形抗力持续增加的主要原因。
Aiming at the as - cast 690 alloy, the thermal deformation behavior of the material was studied by means of unidirectional hot compression experiment. The deformation of the material was analyzed and the deformation microstructure was observed. The results show that the deformation resistance of as-cast 690 alloy increases continuously with the increase of strain amount within 50% of the engineering strain, and the peak stress does not reach the end of deformation. There are three linear regions in the hardening rate curve, while the dynamic recrystallization region appears only at a strain rate of 0.01 s-1. Deformation temperature and strain rate decreases will reduce the flow stress. Tissue analysis shows that there are mainly three kinds of nucleation modes in the dynamic recrystallization of materials under columnar crystal conditions: strain-induced grain boundary migration, nucleation induced by carbide particles and subgrain nucleation. The weakening of recrystallization softening and the formation of subgrains are the main reasons that lead to the increasing deformation resistance of as-cast 690 alloy.