AL-NI-Y-CO AMORPHOUS-ALLOYS WITH HIGH MECHANICAL STRENGTHS, WIDE SUPERCOOLED LIQUID REGION AND LARGE GLASS-FORMING CAPACITY

The effect of additional elements on the formation, thermal stability and mechanical properties of Al-Ni-Y and Al-Ni-Ce amorphous alloys was examined with the aim of obtaining Al-based amorphous alloys exhibiting simultaneously high strengths, large glass-forming capacity and wide supercooled liquid region. The replacement of Y by 2 at% Co for Al85Ni5Y10 was found to result in an increase of the critical ribbon thickness for formation of an amorphous phase (tc) from 120 to 900 μm, the heat of endothermic reaction due to glass transition (ΔHg) from 143 to 393 J/mol and the tensile strength (σf) from 920 to 1250 MPa. In addition, the heat of crystallization (Δx) increases from 3.37 kJ/mol for Al85Ni5Y10 to 3.60 kJ/mol for Al85Ni5Y8Co2. The simultaneous increase in the tc, ΔHg and σf is presumably due to the change to the amorphous structure with a more dense random packing and a larger bonding energy among the constituent atoms because the Hx is thought to reflect the integral of the atomic forces over the interatomic distance change in collapse from the amorphous to the crystalline phase. The finding of the Al85Ni5Y8Co2 alloy is important for subsequent development of Al-based amorphous alloys as a new type of high strength materials with low density. © 1990, The Japan Institute of Metals. All rights reserved.