Densification mechanism and microstructure development of Fe-Ni alloys consolidated by field assisted sintering

Abstract

Fe-xNi alloys (x = 0–5.0 in wt%) were consolidated by conventional sintering (CS), hot pressing (HP), and field assisted (activated) sintering technique (FAS or FAST), and their densification, microstructure, mechanical properties were comparatively investigated, particularly focusing on the field or current effects of FAS technique. The Ni addition promoted the densification and suppressed the grain growth in Fe-Ni alloys consolidated by both CS and FAS, and the FAS produced the Fe-Ni alloys with higher apparent density and smaller grain size. Consequently, the Fe-Ni alloys fabricated by FAS exhibited a significant improvement in the bulk hardness compared to those consolidated by CS and HP. The element distribution mapping by energy dispersive spectroscopy (EDS) indicated that Ni was mainly present along the grain boundaries in the FAS specimen. Furthermore, the diffusion couple experiment showed that the FAS enhanced the Ni diffusion along the grain boundaries. The obtained results indicated that the electric current together with mechanical pressure in FAS promoted the Ni diffusion along the grain boundaries, which resulted in the enhanced densification with suppressed grain growth.