Mechanical properties and microstructure of cold-rolled Scalmalloy® (Al-4.5Mg-0.6Sc-0.3Zr alloy) at a low reduction in thickness

Abstract

A selective laser melted Al-4.5Mg-0.6Sc-0.3Zr alloy, also known as Scalmalloy®, was cold-rolled at two different reductions in thickness to observe the effect on microstructure and mechanical properties. Optical microscopy, scanning electron microscopy, tensile testing with digital image correlation, surface roughness testing and microhardness testing was used to examine samples. Hardness increased significantly in the 30% cold-rolled condition - 20.2% in the horizontal plane, 12.5% in the transverse plane, and 18.2% in the longitudinal plane. Surface roughness was reduced to as low as 1.2µm for cold-rolled conditions compared to >15µm for as-built conditions. Yield strengths were less for cold-rolled conditions compared to as-built and ultimate tensile strengths were similar for as-built and 10% cold rolled conditions. However, 30% cold-rolled condition saw a 10.8% increase compared to as built. Strain distribution among samples was uniform for as-built conditions but concentrated in certain areas for cold-rolled conditions. SEM micrographs of fracture surfaces showed some very ductile fractures evident from dimpling. The microstructure was heavily deformed for all cold-rolled conditions in all build directions showing flattened, elongated grains and grain refinement in both the coarse grain and fine grain regions present in Scalmalloy, especially for the 30% cold-rolled condition.