Formation of multiple intermetallic phases in a hypereutectic Al–Fe binary alloy additively manufactured by laser powder bed fusion

• Published in: Intermetallics Vol. 125; p. 106892
• Main Authors: Wang, Wenyuan, Takata, Naoki, Suzuki, Asuka, Kobashi, Makoto, Kato, Masaki
• Format: Journal Article
• Language: English
• Published: Barking Elsevier Ltd 01.10.2020; Elsevier BV
• Subjects: Additive manufacturing; Alloying additive; Alloys; Aluminum base alloys; Binary alloys; Electron backscatter diffraction; Electron microscopy; Ferrous alloys; High temperature; Intermetallic phases; Intermetallics (aluminides, Silicides); Iron; Lasers; Melt pools; Melting; Metastable phases; Micrometers; Microstructure; Powder beds; Rapid solidification; Selective laser melting; Additive manufacturing; Selective laser melting; Electron backscatter diffraction; Microstructure; Electron microscopy; Intermetallics (aluminides, Silicides)
• ISSN: 0966-9795; 1879-0216
• DOI: 10.1016/j.intermet.2020.106892

An attempt was made to additively manufacture an Al–Fe binary alloy sample with a hypereutectic composition of 15 wt% Fe using a laser powder bed fusion (LPBF) process. The LPBF-built Al–15Fe alloy sample exhibited a microstructure consisting of a number of melt pools in which regions had locally melted and rapidly solidified due to scanning laser irradiation during the LPBF process. The α-Al (fcc) matrix consists of a number of elongated grains with a mean size of approximately 10 μm. These microstructural features correspond well to previous results of Al alloys additively manufactured by the LPBF process. It was found that relatively coarsened stable θ-Al13Fe4 phases with a length of a few micrometers were localized along the melt pool boundaries. Numerous spherical particles of a metastable Al–Fe intermetallic phase were finely distributed within the nanoscale eutectic microstructure consisting of α-Al and metastable Al6Fe phases inside the melt pools. The metastable phase formation corresponds well to the previous results on the rapidly solidified Al–Fe alloys. The refined multiple intermetallic phases produced by the LPBF process contribute to a high hardness of approximately 200 HV. The refined microstructure appeared stable at an elevated temperature of 300 °C. The high microstructural stability would sustain sufficient strength in a hostile environment for long-term periods of service at elevated temperatures above 200 °C. The present results were utilized to discuss the formation sequence of multiple Al–Fe intermetallic phases in rapid solidification by the LPBF process. •An Al–15 wt%Fe alloy was additively manufactured by laser powder bed fusion (LPBF).•Microstructure consists of melt pools in which regions locally melted and solidified.•Relatively coarsened Al13Fe4 phases were localized along the melt pool boundaries.•A nanoscale eutectic microstructure of α-Al and metastable Al6Fe phases was found.•Al–Fe intermetallic phases refined by LPBF exhibited high stability at 300°C.