Synthesis and high mechanical strength of Al-based alloys consisting mainly of nanogranular amorphous particles

A new nonequilibrium structure consisting of nanogranular amorphous and fcc-Al phases was found to form in the rapidly solidified Al94V4M2 (M = Fe or Co) alloys. The deviation from the Al-V-M components causes the formation of the nanoscale mixed structure of Al plus icosahedral (I) phases. The sizes of the amorphous and Al phase regions are about 10 nm and 7 nm, respectively, for the Al-V-Fe alloy and about 25 nm and 20 nm, respectively, for the Al-V-Co alloy. The formation of the nanogranular amorphous phase in coexistence with the Al phase is presumably owing to the suppression of the transition from the supercooled liquid to the I phase. The tensile fracture strength (σf) reaches as high as 1390 MPa for the Al94V4Fe2 alloy and 1250 MPa for the Al94V4Co2 alloy and decreases significantly by the transition of I + Al phases. The high σf is presumed to result from the formation of the nanoscale mixed structure consisting of amorphous + Al phases. The first success of fabricating the nanogranular amorphous phase is particularly important for the future development of nanophase materials.