Elastic and plastic anisotropy after straining of nanocrystalline palladium

Atomistic simulations of uniaxial straining of three-dimensional nanocrystalline palladium along different loading paths were performed at room temperature and at a constant strain rate of 10(8) s(-1). It is found that both the elastic behavior and plastic behavior of the specimen display a pronounced anisotropy after some deformation. Surprisingly, the Young's modulus can significantly change with the deformation history of the sample. Some of these changes are found to be reversible. They either relax or can be removed by applying the opposite deformation. A mechanism based on excess-free-volume migration in the grain boundaries is proposed to explain such behavior.