NEW AMORPHOUS AL-NI-FE AND AL-NI-CO ALLOYS

New amorphous alloys were found to form by melt spinning in Al-Ni-Fe and Al-Ni-Co systems without lanthanide (Ln), Zr and Nb, which are known to be glass-forming elements for Al-based alloys. Coexistent amorphous and Al phases, and the amorphous phase also formed in the ranges of 0 to 14 at% Ni and 0 to 10%Fe or 0 to 14%Co. The mixed phase alloys containing more than 87%Al as well as the amorphous single phase alloys have good bending ductility. Tensile fracture strength (sigma(f)) and Vickers hardness (H(v)) for the amorphous single phase are in the range 870 to 1070 MPa and 280 to 320, respectively. With decreasing cooling rate, the structure changes to Al and amorphous phases. Sigma(f) and H(v) increase to 1270 MPa and 360 without losing ductility in the mixed state where the volume fraction of the Al phase is about 20% and the particle size and interparticle spacing are about 10 nm and 30 nm, respectively. From the similarity in the mixed structure between the present alloys and the previously reported Al-Ni-Ln alloys, it is presumed that the increase in sigma(f) for the mixed phase alloys is due to the increase in strength of the Al particles resulting from the absence of internal defects as well as to the effective barrier of the Al particles against shear deformation of the amorphous matrix.