Effects of Niobium addition on dynamic mechanical behavior and fracture properties of iron-aluminide-based alloys

The compressive mechanical behavior and fracture characteristics of FeAl intermetallic alloys containing 0–9 at.% Nb were investigated over a wide strain rate range of 10−3 s−1 to 5 × 103 s−1. For all of the alloys, the flow stress and strain rate sensitivity increased with increasing strain rate; however, the fracture strain decreased. The addition of Nb improved both the compressive strength and the ductility of the alloys. Among the various alloys, the alloy containing 6 at.% Nb showed the highest yield stress and fracture strain. The optical microscopy observations and X-ray diffraction results showed that the change in mechanical behavior of the various FeAl–Nb alloys was due mainly to differences in the precipitation of (Fe,Al)2Nb Laves phase. Moreover, a higher level of Nb addition prompted a change in the fracture morphology from a brittle fracture mode to a ductile fracture mode.