ULTRAHIGH MECHANICAL STRENGTHS OF AL88Y2NI10-XMX (M = MN, FE OR CO) AMORPHOUS-ALLOYS CONTAINING NANOSCALE FCC-AL PARTICLES

Amorphous Al88Y2Ni10-xM(x) (M = Mn, Fe or Co) alloys containing nanoscale fcc-Al particles form in the composition ranges 0 to 2 at % Mn and 0 to 5% Fe or Co and exhibit tensile fracture strength (sigma-f) and hardness (H(v)) higher than those of amorphous single phase alloys with the same compositions, without detriment to good bending ductility. The particle size of the fcc-Al phase increases in the range of 2 to 30 nm with a decrease of cooling rate and decreases with an increase of M content. The H(v) and Young's modulus (E) for the mixed Al88Y2Ni10-xFe(x) alloys 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 5 to 25%. The increase of sigma-f in the V(f) range below about 25% is presumably due to an enhancement of the resistance to shear deformation caused by the nanoscale fcc particles which have higher mechanical strengths as compared with 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 increase in embrittlement tendency. The maximum sigma-f increases with increasing M content and the degree of the increase is greater in the order of Mn > Fe > Co. This order is presumed to result from the magnitude of attractive bonding force between M and the other constituent atoms.