Thermophysical properties of Al-Mg and Al-Cr based additive manufacturing alloys

Abstract

This study focuses on investigation the thermophysical properties of two aluminium additive manufacturing alloys, Al-Mg-based Scalmalloy (Al-Mg-3.18-Sc0.73-Mn0.39-Zr0.3) and Al-Cr based Scancromal (Al-Cr2.6-Sc0.72-Zr0.25). Viscosity and surface tension play critical roles in determining the performance of the welding process. Spatter formation and welding plumes cause defects like gas pores, process pores, lack of fusion etc. Of particular importance are understanding and controlling the formation of these manufacturing defects. Accurate measurement of the thermophysical properties is essential for optimization the manufacturing processes and imroving numerical simulations. The oscillating droplet method is employed to determine the thermophysical properties of the molten aluminium alloys. Ground-based experiments were conducted using the DLR electromagnetic levitator which showed contrasting behaviors between the two alloys. Scalmalloy demonstrated lower surface tension and significant magnesium evaporation; the additive manufacturing process using Laser Powder Bed Fusion showed unstable melt dynamics with significant spatter formation. In contrast Scancromal exhibited higher surface tension and stable melt behavior during the LPB-F process. Parabolic flight experiments using SUPOS EML were carried out to offer reduced gravity conditions. The influence of evaporation effects and composition changes on the thermophysical properties of the two aluminium alloys is adressed.