Toward the superior high-temperature strength of Al-5Fe alloy for powder bed fusion-laser beam: Stabilizing Al6Fe nanoprecipitate by Sc and Zr elements

Abstract

Existing additively manufactured aluminum alloys exhibit unfavorable tensile strength above 200 °C due to the strengthening phase coarsening, microstructure instability and cracking. This paper designed a novel Al-5Fe-1Mg-0.6Sc-0.3Zr alloy for powder bed fusion using laser beam (PBF-LB) with tensile strength of 189 MPa at 400 °C, which is the highest value reported. The main strengthening phases of the alloy were Al6Fe particle and nano-scaled L12-Al3(Sc, Zr) precipitates. The exceptional high-temperature performance is attributed to high volume fraction (∼35%) of nanoprecipitates Al6Fe modified by Sc and Zr elements, showing enhanced thermal stability and refined particle dimension. The addition of Sc and Zr elements also significantly retards the phase transformation from Al6Fe to θ-Al13Fe4 and inhibits brittle θ phase growth during thermal exposure.