Increase in mechanical strength of Al-Y-Ni amorphous alloys by dispersion of nanoscale fcc-Al particles

Abstract

Al-base amorphous alloys in which nanoscale fcc-Al particles are uniformly dispersed have been produced over the composition range of 0 to 10% Y and 0 to 10% Ni. The alloys exhibit tensile fracture strength (σf) and hardness (Hv) higher than those of amorphous single phase alloys with the same compositions, retaining a good bending ductility. The particle size of the fcc-Al phase increases in the range of 3 to 50 nm with a decrease of cooling rate. The Hv and Young's modulus (E) increase monotonically with increasing volume fraction of the fcc phase (Vf) while the σf shows a maximum value in the Vf range of 10 to 20%. The increase of σf range below 20% is presumably due to an enhancement of the resistance to shear deformation caused by the nanoscale fcc particles which have higher mechanical strengths than the amorphous phase with the same compositions. On the other hand, the decrease of σf with further increasing Vf is due to an enhancement of embrittlement tendency. In addition, the increase of σf, Hv and E with a decrease of Y/(Y + Ni) in the mixed Al88Y12-xNix alloys with a constant Vf (≅ 10%) seems to originate from an increase in the attractive bonding force among the constituent atoms.