Tensile fracture behavior of a Zr-based bulk metallic glass subjected to HPT

The microstructure and mechanical properties of the Zr62Cu22Al10Fe5Dy1 bulk metallic glass (BMG) processed by high pressure torsion (HPT) at temperatures of 20 degrees and 150 degrees C were investigated. Transmission electron microscopy and XRD studies did not reveal any structural transformations. The material in both initial amorphous state and after HPT processing demonstrates brittle fracture under uniaxial tensile testing at temperatures in the range of 20-300 degrees C. The maximum fracture stress of the material in the initial state is 1410 MPa. Fracture stress of the HPT-processed states is lower in comparison with that of the initial state due to the presence of microcracks in the HPT-processed samples. The values of the maximum fracture stress are 250 and 1240 MPa for the samples processed by HPT at 20 degrees and 150 degrees C, respectively. Fracture surfaces of the material in the initial state and after HPT processing have different morphologies due to structural transformations induced by HPT processing. Annealing of the samples in the initial state and after HPT processing results in smaller grain size in the HPT-processed samples in comparison with the initial samples. However, microindentation reveals that hardness of the material in the initial state after annealing is noticeably higher than hardness of the HPT processed alloy after the same annealing. Thus, it can be outlined that HPT processing affects the microstructure evolution in the material during further annealing.