Existing form and action mechanism of minor scandium and zirconium in Al-Cu-Mg alloy

Abstract

In order to investigate the existing form and action mechanism of minor scandium (Sc) and zirconium (Zr) in Al-Cu-Mg alloy, microstructures of Al-4Cu-1Mg-Sc-Zr alloy under different conditions, including states of as-cast, homogenized, hot-rolled, as-solution and natural aged, were observed by scanning electron microscopy (SEM), X-ray diffractometry (XRD) and transmission electron microscopy (TEM). It is revealed that Sc and Zr are completely dissolved into the supersaturated solid solution in as-cast ingot, but grain refinement is not observed. Coffee-bean-like Al₃(Sc, Zr) particles deposit during homogenization of ingot induce an increase in hardness. Al₃(Sc, Zr) particles are slightly coarsened in as-solution samples, but they still maintain coherent to matrix, which indicates a high thermal stability of these particles. Good coherency of Al₃(Sc, Zr) particles makes some benefits for inhibiting recrystallization and reserving work-hardening.

Keywords

Al-Cu-Mg-Sc-Zr alloy / Sc / Zr / existing form / action mechanism

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