Microstructure and mechanical property of Zr₆₅Al_7.5Ni₁₀Cu_12.5Ag₅ bulk metallic glass subjected to rolling

The as-cast and the pre-annealed Zr₆₅Al_7.5Ni₁₀Cu_12.5Ag₅ bulk metallic glasses were rolled at room temperature to different deformation degrees, and the microstructure and microhardness were examined. It is revealed that no phase transformation occurs in the as-cast/rolled specimen except for localized shear bands, indicating that the material has a good structural stability against plastic deformation. When the glass is pre-annealed in the supercooled liquid region for a short time, however, the stability deteriorates significantly. In this case, rolling deformation results in nanocrystallization in the specimen. The pre-annealed glass has less free volume than the as-cast glass, but it does not exhibit a quicker increase in free volume content during the rolling, suggesting that free volume is prone to annihilate at the crystal/glass interfaces. With nanocrystallization occurred, the microhardness of the pre-annealed specimen decreases at a slower rate than that of the as-cast one during rolling deformation.