Structure of nanocomposites of Al-Fe alloys prepared by mechanical alloying and rapid solidification processing

摘要

Structures of Al-based nanocomposites of Al-Fe alloys prepared by mechanical alloying (MA) and subsequent annealing are compared with those obtained by rapid solidification processing (RSP). MA produced only supersaturated solid solution of Fe in Al up to 10 at. percent Fe, while for higher Fe content up to 20 at. percent the nonequilibrium intermetallic Al_5Fe_2 appeared. Subsequent annealing at 673 K resulted in more Al_5Fe_2 formation with very little coarsening. The equilibrium intermetallics, Al_3Fe (Al_(13)Fe_4, was not observed even at this temperature. In contrast, ribbons of similar composition produced by RSP formed fine cellular or dendritic structure with nanosized dispersoids of possibly a nano-quasicrystalline phase and amorphous phase along with alpha-Al depending on the Fe content in the alloys. This difference in the product structure can be attributed to the difference in alloying mechanisms in MA and RSP.