Enhancement of ductility and plasticity of Zr55Cu30Al10Ni5 bulk glassy alloy by cold rolling

With the aim of improving ductility and plasticity of a Zr55Cu30Al10Ni5 bulk glassy alloy, a cold rolling treatment leading to the rolled structure with high-density slip bands was performed. A number of slip bands were introduced along the maximum shear stress plane by cold rolling, and the first slip bands were found to slant significantly with increasing reduction ratio in thickness. At the critical reduction ratios, the second slip bands were introduced at a reduction ratio of 30%, followed by the third slip bands at a reduction ratio of 60%. Mechanical properties of the rolled samples were examined by bending test and Charpy impact test. The maximum bend deflection value before failure increased with an increase of reduction ratio, indicating that the cold rolling improves the plasticity of the bulk glassy alloy. Since the Charpy impact value depends on the rolling direction, we selected an optimum rolling direction in which the maximum Charpy impact value is obtained. The control of the rolling direction causes an increase in the Charpy impact value by 36% as compared with the unrolled alloy. Consequently, the cold rolling process is concluded to be a valuable method for improving the ductility and plasticity of the bulk glassy alloy.