Unveiling the growth mechanism of Fe-containing intermetallics in Al–Si alloy in the perspective of surface stability and atom adsorption

Abstract

Three-dimensional (3D) morphology and growth mechanism of β-AlFeSi, α-Al(FeMn)Si and α-Al(FeMnCr)Si phases were investigated by phase extraction and first-principles calculations. Experimental results showed that the 3D morphology of Fe-containing intermetallics change from plate-like to rhombic dodecahedron and regular hexahedron under the modification of Mn and Mn + Cr synergistic addition. First principles calculation results showed that the final 3D morphology of α-Al(FeMn)Si and α-Al(FeMnCr)Si phase are determined by the surface stability and growth competition of (100), (110) and (111) surface. The α-Al(FeMnCr)Si (100) surface exhibit a larger probability to be exposed due to the lower surface energy than that of (110) and (111) surface. The rhombic dodecahedron equilibrium morphology of α-Al(FeMn)Si phase is attribute to the lower surface energy of (110) surface than that of (100) and (111) surface and the plate-like morphology of β-AlFeSi stems from the lowest surface energy of (001) surfaces. Further adsorption energy calculation results showed that Mn shows lower adsorption capacity on the α-Al(FeMn)Si (110) surfaces, then inhibits the preferential growth of (110) surface. While Cr atom shows lower adsorption capacity on α-Al(FeMnCr)Si (100) surfaces, thus leading to the slower growth rate of (100) surface. The calculation results reasonably explained the modification mechanism of the Mn and Cr elements on the 3D morphology and growth behavior of Fe-containing intermetallics. This study provide new insights for understanding the morphological evolution of Fe-containing intermetallics induced by the incorporation of modifying elements, which contributes to guiding the development of high performance recycled Al–Si alloys.