Insights into laser powder bed fused Scalmalloy®: investigating the correlation between micromechanical and macroscale properties

Abstract

Additively manufactured Scalmalloy® using laser powder bed fusion (LPBF) has been showing increasing potential for industrial adoption. Its intended application in space, aerospace, and automotive industries requires extensive testing and characterization to produce parts with repeatable properties and safe operations. In the present paper, a thorough investigation of the association between small-scale (micro/nano-scale) and macro-scale (e.g., tensile) properties and microstructural features has been conducted. The prime novelty is the correlation of the small-scale hardness with the tensile properties, which is studied in both as-built and heat-treated conditions (325 °C/4 h) along parallel and perpendicular build directions of the samples. Advanced microstructural characterization including scanning and transmission electron microscopies (SEM/TEM), as well as electron backscatter diffraction (EBSD), was carried out on each condition to correlate microstructure and mechanical properties. While significant improvement in strength was found from as-built to heat-treated conditions, due to the precipitation of secondary Al3Sc and Al3(Sc, Zr), grain size or texture did not change considerably. The grain size analysis revealed a fine-grained zone (FGZ: mostly between 0.5 and 1 μm) next to the coarse-grained zone (CGZ: mostly between 2 and 15 μm). All samples show texture-free FGZ and textured CGZ with a predominance of <001> crystal directions parallel to the building direction.