Microstructural Characterization and Phase Diagram Calculation of a Less Known Al-Fe-Mn-Si Phase in a SiCp/2014Al Composite.

A systematic characterization of a less known Al, Fe, Mn, and Si phase in a SiC particulate-reinforced 2014Al composite (SiCp/2014Al) was performed. In addition to the expected CuAl2 phase, the Al, Fe, Mn, and Si phase was formed as either an adhesion (>1 µm) onto SiC in the as-cast composite, or as a precipitate (<100 nm) in the matrix after hot extrusion. The structure of the phase was identified as cubic by both X-ray diffraction and selected area electron diffraction (SAED). The SAED pattern also indicated that the structure belongs to the Pm space group instead of Im. The thermodynamic phase diagram was calculated, confirming the presence of an α-AlFeMn or α-AlFeSi phase in the Al-Fe-Mn and Al-Fe-Si ternary systems, respectively, within the Fe, Mn, and Si content range corresponding to 2014Al. Wavelength-dispersive spectroscopy analysis indicated that the composition of the phase is close to Al12(Fe, Mn)3Si2, in which the Mn/Fe ratio is in the range of 0.6-1.4. The determined Mn/Fe ratio corresponds to the nominal composition of Mn and Fe in the alloy.