Processability and Optimization of Laser Parameters for Densification of Hypereutectic Al–Fe Binary Alloy Manufactured by Laser Powder Bed Fusion

Naoki Takata,Asuka Suzuki,Wenyuan Wang,Makoto Kobashi,Masaki Kato

doi:10.3390/cryst11030320

Abstract

Centimeter-sized samples of hypereutectic Al–15 mass% Fe alloy were manufactured by a laser powder bed fusion (L-PBF) process while systematically varying laser power (P) and scan speed (v). The effects on relative density and melt pool depth of L-PBF-manufactured samples were investigated. In comparison with other Al alloys, a small laser process window of P = 77–128 W and v = 0.4–0.8 ms−1 was found for manufacturing macroscopically crack-free samples. A higher v and P led to the creation of macroscopic cracks propagating parallel to the powder-bed plane. These cracks preferentially propagated along the melt pool boundaries decorated with brittle θ-Al13Fe4 phase, resulting in low L-PBF processability of Al–15%Fe alloy. The deposited energy density model (using P·v−1/2) would be useful for identifying the optimum L-PBF process conditions towards densification of Al–15%Fe alloy samples, in comparison with the volumetric energy density (using P·v−1), however, the validity of the model was reduced for this alloy in comparison with other alloys with high thermal conductivities. This is likely due to inhomogeneous microstructures having numerous coarsened θ–Al13Fe4 phases localized at melt pool boundaries. These results provide insights into achieving sufficient L-PBF processability for manufacturing dense Al–Fe binary alloy samples.

Highlights

Aluminum–iron alloys exhibit low density, superior thermal conductivity, and high recyclability
The present work seeks to systematically investigate the effects of two laser parameters (P and v) on the relative density of Al–15%Fe alloy samples manufactured by the LPBF process
The results provided a process window for manufacturing Al–15%Fe alloy samples (Figure 2a)

Summary

Introduction

Aluminum–iron alloys exhibit low density, superior thermal conductivity, and high recyclability. Al–Fe alloys are candidate materials for heat exchangers in air conditioning or refrigeration systems [1]. Al–Fe-based alloys are often designed for the strengthening by Al–Fe intermetallic phases at ambient and elevated temperatures. A high content of Fe alloy enhances the formation of Al–Fe intermetallic phases. The formed stable θ-Al13Fe4 phase [7] (in equilibrium with the α-Al (fcc) phase) often exhibits coarsened morphologies and very brittle properties at ambient temperature [8]. The θ intermetallic phase significantly reduces the ductility of Al–Fe alloys, contributing to a low formability and limiting the fabrication of mechanical components with complex geometries by conventional forming processes

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Conclusion