THE EFFECT OF CU ADDITION ON THE STRUCTURE AND MECHANICAL-PROPERTIES OF AL-NI-M (M-EQUIVALENT-TO-CE OR ND) AMORPHOUS-ALLOYS CONTAINING NANOSCALE FCC-AL PARTICLES

The crystallized structure and mechanical strength of amorphous Al87Ni7CuCe3 and Al87Ni7Cu3Nd3 alloys were examined with the aim of clarifying the effect of the replacement of Ni by Cu. These amorphous alloys crystallize via a two-stage process: Al + amorphous phase and Al + compounds. The replacement extends the temperature region in which the Al phase precipitates, causing a decrease in particle size from 10 to 3 nm. These changes are presumably due to the following two factors: (1) the difficulty of growth of Al particles resulting from the necessity of redistribution of Cu at the amorphous-Al interface, and (2) an increase in the nucleation sites of the Al phase resulting from the apparent increase in Al content due to the decrease in Ni content as well as to the addition of Cu which is soluble in the Al phase. The homogeneous dispersion of the smaller Al particles causes a more significant increase in sigma(f) and H(v) compared with the amorphous single phase, and the highest sigma(f) and H(v) are 1460 MPa and 480 respectively, for the Al-Ni-Cu-Nd alloy annealed for 60 s at 436 K. It is thus concluded that the replacement of Ni by Cu in Al-Ni-Ln (Ln = Ce or Nd) alloys is effective in increasing sigma(f) through refinement of the Al particle size.