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对定向凝固DZ4合金进行扭转预变形和热处理后的高温低周疲劳寿命与断裂行为进行测试与研究,分析不同的扭转变形程度、变形速率等对低周疲劳寿命和再结晶的影响,研究沿晶特征区的形成机制。结果表明,定向凝固DZ4合金在扭转预变形和热处理后其低周疲劳寿命急剧下降,分析发现与塑性变形区产生的再结晶组织有关。再结晶区与基体变形不协调导致在再结晶与基体界面处出现损伤和裂纹,裂纹沿再结晶晶界扩展形成沿晶特征区,使高温低周疲劳寿命下降,且疲劳寿命随着再结晶深度的增大而急剧降低。扭转预变形程度较小时,低周疲劳断口上的沿晶特征区的深度与断面沿再结晶区扩展的深度一致;扭转预变形程度较大时,沿晶特征区的深度相对较小。另外,应变速率增大,加剧了不协调变形,再结晶具有局部化倾向,且再结晶程度增加,使高温低周疲劳寿命下降更严重。
The low-temperature fatigue life and fracture behavior of DZ4 alloy subjected to torsional pre-deformation and heat treatment were tested and studied. The effects of different torsional deformation and deformation rate on the low-cycle fatigue life and recrystallization were analyzed. Features of the formation mechanism. The results show that the low-cycle fatigue life of DZ4 alloy after steelage pre-deformation and heat treatment decreases sharply. It is found that the recrystallization microstructure of DZ4 alloy is related to the plastic deformation zone. The uncoordinated deformation of the recrystallized zone and the matrix leads to damage and cracks at the interface between the recrystallized and the matrix. The crack propagates along the recrystallized grain boundary to form the intergranular characteristic zone, which decreases the high temperature and low cycle fatigue life, and the fatigue life changes with the recrystallization depth The sharp decline in the increase. When the degree of pre-deformation is small, the depth of the intergranular zone along the low-cycle fatigue fracture coincides with the depth of the recrystallized zone along the fracture surface. When the degree of pre-deformation is large, the depth of the intergranular zone is relatively small. In addition, the strain rate increases, exacerbating the uncoordinated deformation, recrystallization has a localized tendency, and the degree of recrystallization increases, the high temperature low cycle fatigue life decline more serious.