Effect of Si on Fe-rich intermetallic formation and mechanical properties of heattreated Al-Cu-Mn-Fe alloys

TL;DR

This study investigates how silicon addition affects the formation of Fe-rich intermetallics and improves the mechanical properties of heat-treated Al-Cu-Mn-Fe alloys, showing significant strength enhancements with Si.

Contribution

It reveals that Si promotes finer intermetallics and dispersoid strengthening, leading to improved tensile and yield strengths in Al-Cu-Mn-Fe alloys.

Findings

Si increases the formation of Al15(FeMn)3(SiCu)2 and modifies T phase morphology.

Si addition results in higher tensile and yield strengths.

Alloy with 1.1% Si achieves tensile strength of 386 MPa and yield strength of 280 MPa.

Abstract

The effect of Si on Fe-rich intermetallics formation and mechanical properties of heat-treated squeeze cast Al-5.0Cu-0.6Mn-0.7Fe alloy was investigated. Our results show that increasing Si content promotes the formation of Al15(FeMn)3(SiCu)2 (${\alpha}$-Fe), and varying the morphology of T (Al20Cu3Mn2) where the size decreases and the amount increases. The major reason is that Si promotes heterogeneous nucleation of the intermetallics leading to finer precipitates. Si addition significantly enhances ultimate tensile strength and yield strength of the alloys. The strengthening effect is mainly owing to the dispersoid strengthening by increasing volume fraction of T phase and less harmful ${\alpha}$-Fe with a compact structure, which make the cracks more difficult to initiate and propagation during tensile test. The squeeze cast Al-5.0Cu-0.6Mn-0.7Fe alloy with 1.1% Si shows significantly improved mechanical properties than the alloy without Si addition, which has tensile strength of 386 MPa, yield strength of 280 MPa and elongation of 8.6%.