High Strength Al–V–M (M=Fe, Co or Ni) Alloys Containing High Volume Fraction of Nanoscale Amorphous Precipitates

Publisher Website
Google Scholar
Abstract
A new nonequilibrium structure consisting of nanoscale amorphous particles surrounded by fcc-Al phase was found to form in the Al94V4M2 (M=Fe or Co) and Al93V5Ni2 alloys rapidly solidified at the circumferential velocity of 40 m/s. The deviation of the alloy component and the decrease in the circumferential velocity of the melt-spinning roll results in the formation of nanoscale mixed structures of fcc-Al plus icosahedral (I) phases or the fcc-Al plus I plus amorphous phases. The sizes of the amorphous and fcc-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 nanoscale amorphous particles in coexistence with the Al phase is presumably due to the suppression of the transition of supercooled liquid to I-phase resulting from the retardation of the diffusivity of the solute elements. The highest tensile strength reaches as high as 1390 MPa for the mixed phase Al94V4Fe2 alloy and decreases significantly by the transition to I plus fcc-Al phases. The high tensile strength is presumed to result from the formation of the nanoscale mixed structure consiting of nanoscale amorphous and Al phases in which the Al phase has enriched solute concentrations and contains a high density of interphase boundaries. The first success of fabricating the nanoamorphous structure is particularly important for the future development of nanophase materials.