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 (σ_f) and hardness (H_v) 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 H_v and Young’s modulus (E) increase monotonically with increasing volume fraction of the fcc phase (V_f) while the σ_f shows a maximum value in the V_f range of 10 to 20%. The increase of σ_f in the V_f 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 σ_f with further increasing V_f is due to an enhancement of embrittlement tendency. In addtion, the increase of σ_f, H_v and E with a decrease of Y/(Y+Ni) in the mixed Al₈₈Y_12−xNi_x alloys with a constant V_f (\simeq10%) seems to originate from an increase in the attractive bonding force among the constituent atoms.