Mechanical Properties of Zr–Ti–Al–Ni–Cu Bulk Amorphous Sheets Prepared by Squeeze Casting

Abstract

Tensile fracture strength (σ_f) and Vickers hardness (H_v) of Zr–Al–Ni–Cu amorphous sheets with a thickness of 2.5 mm prepared by squeeze casting were found to increase by the addition of 2.5–5 at%Ti and the increase of Al content to 12.5–15 at%. The σ_f and H_v of the amorphous alloy sheets with the new compositions are 1800 to 1850 MPa and 500 to 520, respectively, which are higher than those (σ_f=1650 to 1790 MPa and H_v=470 to 480) for the Zr-10%Al–Ni–Cu amorphous cylinders prepared by copper mold casting. The Young’s modulus, elastic elongation and Charpy impact fracture energy are 86 to 92 GPa, 2.0 to 2.2% and 90 to 160 kJ/m², respectively. The highest value of the three point-bending flexural strength is 3900 MPa for Zr₅₅Al₁₅Ni₁₀Cu₂₀. The high impact fracture energy indicates that the cast amorphous alloy sheets have good ductility. Furthermore, the improvement of σ_f and H_v by the simultaneous addition of Ti and Al is presumably due to the increase of the bonding force of the constituent elements resulting from the increase of Zr–Al and Ti–Al pairs with larger negative heats of mixing. The synthesis of the high Al concentration Zr–Al–Ni–Cu and Zr–Ti–Al–Ni–Cu amorphous alloys with higher mechanical strength, higher impact fracture energy and lower density is important for the future progress of high-strength bulk amorphous alloys because the Zr–Al–Ni–Cu amorphous alloys with the 10 at%Al concentration have already been used as new engineering materials.