New Al-based amorphous alloys with high mechanical strength in the AlNiM and AlCoM (M = Mn, Fe, Co, Ni) systems

Abstract

It has been found that new amorphous alloys with high strength and good bending ductility are formed in the AlNiM 1 (M 1 = Mn, Fe, Co) and AlCoM 2 (M 2 = Mn, Fe) systems by the melt spinning technique. The comparison ranges in which the amorphous single phase and the coexistent amorphous and Al phases form extends from 87 to 94 at.% Al. The highest values of tensile fracture strength σ f and Vickers hardness H v for the amorphous single phase are 1070 MPa and 320 respectively for AlNiCo alloys. As the cooling rate decreases, the structure changes to mixed Al and amorphous phases, and σ f and H v increase to 1270 MPa and 360 respectively without detriment to ductility in the mixed state where the volume fraction of Al phase is about 20%. The highest σ f value in the mixed state was 1340 MPa for the AlCoFe system. These high σ f values are presumably due to the high strength of Al particles resulting from the absence of internal defects as well as of the effective barrier of the Al particles against shear deformation of the amorphous matrix.