Deformation mechanisms of Mo alloyed FeCoCrNi high entropy alloy: In situ neutron diffraction

A FeCoCrNiMo0.23 high entropy alloy was processed by powder metallurgy with two conditions: hot extruded and annealed. In situ neutron diffraction, together with electron microscopy, was used to study the deformation mechanisms and concomitant microstructural evolution for both conditions. The as extruded alloy has a single face-centered-cubic structure with a calculated stacking fault energy of similar to 19 mJ/m(2). When the alloy is tensile deformed, nano-twins and microbands are induced, resulting in an excellent combination of strength and ductility (784 MPa ultimate tensile strength and over 50% elongation). Annealing at 800 degrees C for 72 h increases the strength of the alloy but decreases its ductility. This is due to the decomposition of the alloy after annealing, causing the formation of Mo-rich intermetallic particles and a decrease of the stacking fault probability. These results highlight that combined mechanisms (i.e. solute strengthening and twinimicroband induced plasticity) can effectively improve both the strength and ductility of high entropy alloys. Crown Copyright (C) 2017 Published by Elsevier Ltd on behalf of Acta Materialia Inc. All rights reserved.