INCREASE IN MECHANICAL STRENGTH OF AL-Y-NI AMORPHOUS-ALLOYS BY DISPERSION OF NANOSCALE FCC-AL PARTICLES

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 (sigma-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 colling rate. The H(v) and Young's modulus (E) increase monotonically with increasing volume fraction of the fcc phase (V(f)) while the sigma-f shows a maximum value in the V(f) range of 10 to 20%. The increase of sigma-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 sigma-f with further increasing V(f) is due to an enhancement of embrittlement tendency. In addition, the increase of sigma-f, H(v) and E with a decrease of Y/(Y + Ni) in the mixed Al88 Y(12-x)Ni(x) alloys with a constant V(f) (congruent-to 10%) seems to originate from an increase in the attractive bonding force among the constituent atoms.