Al–Ni–Y–Co Amorphous Alloys with High Mechanical Strengths, Wide Supercooled Liquid Region and Large Glass-Forming Capacity

抄録

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 (t_c) from 120 to 900 μm, the heat of endothermic reaction due to glass transition (ΔH_g) from 143 to 393 J/mol and the tensile strength (σ_f) from 920 to 1250 MPa. In addition, the heat of crystallization (ΔH_x) increases from 3.37 kJ/mol for Al₈₅Ni₅Y₁₀ to 3.60 kJ/mol for Al₈₅Ni₅Y₈Co₂. The simultaneous increase in the t_c, ΔH_g and σ_f 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 H_x 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.