SYNTHESIS AND HIGH MECHANICAL STRENGTH OF AL-BASED ALLOYS CONSISTING MAINLY OF NANOGRANULAR AMORPHOUS PARTICLES

A new nonequilibrium structure consisting of nanogranular amorphous an d fee-Al phases was found to form in the rapidly solidified Al(94)V(4) M(2) (M = Fe or Co) alloys. The deviation from the AI-V-M components c auses the formation of the nanoscale mixed structure of Al plus icosah edral (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 t he nanogranular amorphous phase in coexistence with the Al phase is pr esumably owing to the suppression of the transition from the supercool ed liquid to the I phase. The tensile fracture strength (sigma(f)) rea ches as high as 1390 MPa for the Al94V4Fe2 alloy and 1250 MPa for the Al94V4Co2 alloy and decreases significantly by the transition of I + A l phases. The high sigma(f) is presumed to result from the formation o f the nanoscale mixed structure consisting of amorphous + Al phases. T he first success of fabricating the nanogranular amorphous phase is pa rticularly important for the future development of nanophase materials .