Effects and quantitative analyses of mechanical properties on strain limit during plastic deformation of zirconium alloys

Zirconium alloys are widely used as structure materials in nuclear fuel assembly. However, the poor forming performance of zirconium alloy restricts its application and consequently hinders the development of nuclear industry. In this study, the concept of strain limit is defined, and the influencing mechanisms of different mechanical properties of zirconium alloys on the strain limit of tension-compression area and equi-biaxial area are revealed. The research shows that the variation of sheet thickness t and strength coefficient K has little impact on the strain limit of zirconium alloy. The increase of strain hardening exponent n will significantly raise the strain limit of zirconium alloys in both the tension-compression area and equi-biaxial area. the Lankford coefficient R can improve the strain limit of tension-compression area, but not the equi-biaxial area. Besides, the influencing mechanisms of R and n on the strain limit of zirconium alloy are different. The value of n mainly improves the strain limit by increasing the base point of forming limit curve while the value of R primarily increases the strain limit by changing the slopes of the strain paths in the tension-compression area. Therefore, the value increase of R and n can be considered as an effective way to improve the forming performance of zirconium alloys.