Thermal and mechanical properties of an Al-Mg-Sc-Zr high strength alloy fabricated by selective laser melting

Thermal management is one of the most promising applications of Al parts fabricated by additive manufacturing, primarily due to the drastically expanded design space enabled by the latter. The thermal properties of additively manufactured Al alloys are crucial for this application but remain poorly understood. The present study focuses on a high-strength Al-Mg-Sc-Zr alloy fabricated by Selective Laser Melting (SLM). The microstructure of the alloy is characterized by optical and electron microscopy, hardness and tensile testing are conducted, and the thermal conductivity and thermal dilatation behavior are tested. The fabricated samples exhibit strong age hardenability and yield strengths reaching ~460 MPa. The thermal conductivity in the as-built condition is found to be rather low mainly because of the high solute concentration in the Al matrix as well as the fine grain size, and is improved by 33% after 10 h aging due to precipitation of particles. Meanwhile, abnormal non-linear thermal dilatation behavior is observed in the samples above 400 °C, probably related to the expansion of pores. Lastly, orientation dependency with respect to the building direction is found in both thermal conductivity and dilatation, which is associated with the grain alignment and melt pool structures. The above results provide critical knowledge to the process design toward co-optimization of mechanical and thermal properties of Al alloys fabricated by SLM.