Pre-yield serrations in a Mg-based bulk metallic glass during compression

Bulk metallic glasses based on magnesium are brittle, which limits their widespread use for light-weight application. Many Mg-based bulk metallic glasses failed catastrophically with wavy fracture surfaces and split into fragments, in contrast to other bulk metallic glasses that fractured on a plane oriented at the highest shear stress. Under monotonic compression, a brittle Mg68Cu23Gd9 bulk metallic glass is examined here. In its elastic regime, there are a lot of pre-yield stress serrations, and after yielding, the results are zero plastic-strain and a wavy fracture with vein-like patterns and microcracks. Pre-yield serrations statistically follow a truncated power-law relationship with a power exponent that is nearly identical to the post-yield serrations of other bulk metallic glasses, suggesting microplastic events. Microcracking, on the other hand, prevents the formation of macro-plasticity, leading to a ductile-to-brittle transition that is brought on by compression. A high-pressure quenching technique that uses high pressure at a higher temperature can be used to suppress the pre-yield serrations. Statistical-distribution changes in the pre-yield serrations reveal how various thermo-mechanical processes alter the interior structures of brittle metallic glasses. The present work offers insights of the microstructural changes at the elastic regime, which may be useful for making plastic Mg-based metallic glass.