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 Y ) 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/m 2 , respectively. The highest value of the three point-bending flexural strength is 3900 MPa for Zr 55 Al 15 Ni 10 Cu 20 . 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.