Change in Microstructure and Mechanical Properties by Friction Stir Processing in Zr-Cu-Al-Ni Bulk Metallic Glass

Abstract

Change in microstructure and mechanical properties by friction stir processing (FSP) is investigated in Zr-Cu-Al-Ni bulk metallic glass. The microstructure exhibits an amorphous band-like structure with widths of 10∼45nm and nanoscale crystalline particles of 5∼20nm. The contrast in amorphous band-like structure arises as the result of the difference of the thickness, which should be introduced by the difference of the density. The hardness increases by FSP. In compression tests, the increment of stress with strain decreases by FSP. Since the increment of hardness by FSP is larger than that by crystallization by annealing and the density seems to be different in amorphous band-like structure, the change in mechanical properties must be originated from the change in local structure such as free volume by FSP.