Role of crystalline precipitates on the mechanical properties of (Cu0.50Zr0.50)100−xAlx (x = 4, 5, 7) bulk metallic glasses

The mechanical behaviour upon compression of (Cu0.50Zr0.50)100−xAlx (x = 4, 5, 7) rods with 2 and 3 mm diameter was systematically studied and compared with the literature data. Fully amorphous bulk metallic glasses (x = 5, 7) show little permanent deformation and reproducible yield stress values. The remarkable fracture strain, observed for some apparently X-ray diffraction amorphous samples (x = 4), was found to be due to significant amounts (at least 20%) of the B2-CuZr crystalline phase. The effect of possible flaws on the external surface of the rods was evaluated by mechanical testing of either as cast and machined samples.

Research highlights
► The glass formation reproducibility of (Cu0.50Zr0.50)100−xAlx (x = 4,5,7) was investigated.
► X-ray amorphous Cu48Zr48Al4 samples contain up to 20% of B2-CuZr crystals.
► Fracture strain scales directly with the amount of the B2-CuZr crystalline phase.
► Spread in literature values of fracture strain for these alloys is likely due to the presence of undetected crystals.
► Mechanical properties reliability can be improved by sample surface finishing.