A Comparative Study of Microstructure and Hot Deformability of a Fe–Al–Ta Iron Aluminide Prepared via Additive Manufacturing and Conventional Casting

Author:

Emdadi AliakbarORCID,Weiß SabineORCID

Abstract

In this work, the microstructure and hot deformation behavior of laser powder bed fusion (L-PBF) and conventionally cast Fe-25Al-1.5Ta (at.%) alloys were compared. The L-PBF builds recrystallized comparably to the as-cast samples during hot deformation. Nevertheless, distinct differences were observed in the flow behavior characteristics between the as-cast and L-PBF samples. The L-PBF builds exhibited lower flow stress than the as-cast material over the entire deformation conditions tested. The average activation energy of hot deformation (Q) of 344 kJ mol−1 was calculated for the L-PBF build and 385 kJ mol−1 for the cast material. The lower Q indicates lower deformation resistance of the L-PBF sample. The peak work hardening rate (θ) in the L-PBF sample (1.72 × 103 MPa) was significantly smaller than that of the as-cast sample (3.02 × 103 MPa), suggesting that the dislocation glide in the L-PBF sample is less hindered during deformation. Possible sources of the observed differences in the deformation behavior between the L-PBF and cast materials will be discussed. Initial and post-deformation microstructures were characterized using an X-ray diffractometer (XRD) and ultra-high-resolution scanning electron microscopy (SEM) equipped with energy-dispersive X-ray spectroscopy (EDX) detector. The C14-(Fe, Al)2Ta Laves phase (P63/mmc) was predominantly formed at the A2 α-(Fe, Al) matrix phase grain boundaries in both the as-cast and L-PBF materials. The XRD results suggest that the ordering transition from B2-FeAl to a D03-Fe3Al phase occurs during casting, but rarely during ultra-high-cooling L-PBF processing. In summary, the L-PBF creates samples that are subject to less work hardening and require less deformation resistance, and thus, can be formed by a lower deformation force. It, in turn, reduces the loads imposed on the tooling and dies during the deformation processing, contributing to less wear and the high durability of dies.

Publisher

MDPI AG

Subject

Inorganic Chemistry,Condensed Matter Physics,General Materials Science,General Chemical Engineering

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