Powder-based porous materials for additive manufacturing: alloy design and custom atomization process

Abstract

Metal foams offer attractive properties for lightweight structures. This study presents the development of a powder metallurgical aluminum alloy intended for foamable wires that can be used in additive manufacturing processes such as wire and arc additive manufacturing (WAAM). Unlike established aluminum wrought alloys, whose melting range is not well suited for foaming, or cast alloys which are not easily extruded into thin wires, the custom AlMg2Si1.2 alloy developed in this study combines a melting interval matched to the decomposition of pre-oxidized blowing agent (TiH 2 ) with a low alloying content suitable for high extrusion ratios. For this, the alloy composition was determined using thermodynamic calculations. The material was then cast into billets, which were extruded into rod electrodes. Pre-alloyed metal powder was produced from these electrodes using electrode induction melting inert gas atomization (EIGA), and the influence of atomization gas parameters on powder properties was investigated. Increasing the gas pressure from 16.8 bar to 23.0 bar reduced the median particle size from 51 to 40 µm. The best flowability was observed for the fraction 63–90 µm. A solidus temperature of 560 °C and a liquidus of 646 °C were determined by differential scanning calorimetry, aligning with the principal hydrogen-release peak of the blowing agent. Foam samples produced from the powder confirmed the material’s foamability, reaching porosities of 64–68%, as determined by X-ray microscopy. These results indicate that AlMg2Si1.2 processed via EIGA yields reproducible, highly porous foams, and is a suitable basis for foamable wires in WAAM.