Abstract
To evaluate formability, deformation behavior can be examined under biaxial stress by using a biaxial tensile testing machine in combination with a cruciform specimen. Application of continuous biaxial stresses in the same plane makes it easier to correlate the mechanical properties and the structural changes that occur with increasing deformation than by using conventional methods. When an equivalent strain of 60% was applied at a temperature of 673K, the grain size was refined from 9.8μm to 5.0μm before and after tensioning. In this case, voids were connected in 45°directions to each tensile axis, and grain boundary separations were observed in the vicinity of the voids. Under the biaxial stress state, refining of grains, together with grain rotation and slip, occurs more readily than under a uniaxial stress state.
