Oxygen embrittlement in a Cu-Hf-Al bulk metallic glass

Compression testing shows that at low-oxygen levels (240 ppm) the Cu₄₉Hf₄₂Al₉ glass deforms predominantly by shear and is quite tough. Specimens with higher oxygen levels (1700 ppm) have oxygen-containing dendrites in an amorphous matrix and show no plasticity. Importantly, the dominant fracture mode is not shear but local tensile failure. Although there is a slight reduction in the toughness of the glassy matrix, the severe embrittlement is primarily because of the brittle dendrites that facilitate crack initiation and propagation.