Mechanical properties of Zr-Ti-Al-Ni-Cu bulk amorphous sheets prepared by squeeze casting

Tensile fracture strength (sigma(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 sigma(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 (sigma(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 Zr55Al15Ni10Cu20. The high impact fracture energy indicates that the cast amorphous alloy sheets have good ductility. Furthermore, the improvement of sigma(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 Kith 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-AI-Ni-Cu amorphous alloys with the 10 at%Al concentration have already been used as new engineering materials.