Laser-scanning of induction-melted Al alloys: are they representative of additively manufactured ones?

TL;DR

This study evaluates whether laser scanning of induction-melted Al alloys can effectively mimic additively manufactured alloys, potentially accelerating alloy development without the need for custom powder production.

Contribution

It demonstrates that multipath laser scanning of induction-melted samples produces microstructures similar to LPBF, offering a faster alternative for alloy screening in AM.

Findings

Microstructures are highly similar between laser-scanned and LPBF samples.

Laser-scanned samples show a 20% reduction in microhardness compared to LPBF.

The workflow can accelerate alloy design by avoiding custom powder production.

Abstract

The bottleneck of alloy design for powder-based additive manufacturing (AM) resides in customized powder production - an expensive and time-consuming process hindering the rapid closed-loop design iterations. This study analyzed an expedited experimental workflow, i.e., multipath laser scanning of induction-melted samples, to mimic rapid solidification of AM to serve as an alternative approach to down-select from the design space. Using Al-Ni-Zr-Er model alloy, comprehensive multi-scale characterizations were performed to compare microstructural features between laser-scanned and laser powder bed fusion (LPBF) samples. Although demonstrating a difference in melt pool geometries, the microstructures in scanning electron microscopy (SEM)- and transmission electron microscopy (TEM)- scale demonstrate a high degree of similarity, in terms of microstructure morphology, grain size, presence of precipitates, and phase distribution. The mechanical performance was evaluated by microhardness tests. The results revealed a 20% reduction in laser-scanned samples compared to LPBF samples, attributed to the thermal history and potential differences in phase fractions. The decreasing trend was also observed in the benchmark alloy showing a 10% absolute error with respect to the model alloy. This study underscores the potential of this workflow to accelerate alloy design in AM by circumventing customized powder production and encourages further exploration across diverse materials and processing parameters.