Microstructure, indentation and first principles study of AlCuFeMn alloy

Abstract

Equi-atomic AlCuFeMn alloy with yield strength of ∼1000 MPa and elastic modulus of ∼175 GPa was synthesized using arc-melting. The cast alloy possesses a cellular microstructure with cells exhibiting segregation into Copper and Iron rich regions. Room temperature characterization reveals that the principal phase in Copper rich region is a disordered Body Centered Cubic phase ( 𝐼𝑚 ̄3 𝑚 ) of threaded morphology in a disordered body centered cubic matrix. The phase morphology is typical of spinodal decomposition with additional ordered face centered cubic nano-precipitates observed. Conversely, the Iron rich region consists of a partially ordered oval Face Centered Cubic phase ( 𝐹 𝑚 ̄3 𝑚 ) in a disordered Body Centered Cubic matrix. The distribution is typical of first order chemical ordering with negligible amount of disordered Face Centered Cubic phase observed. The formation energy of the 𝐹 𝑚 ̄3 𝑚 phase is lower than that of 𝐼𝑚 ̄3 𝑚 phase and varies with change in atomic position. The overall valence electron concentration of the alloy is 7.25 which results in a combination of body and face centered cubic phases. Such multiple phase formation is an outcome of significant electronic contribution to entropy of mixing for the two principal phases as is reflected from their density of states distribution.