Discovery of new Fe2Ni2CrAlx multi-principal element alloys with promising mechanical properties

Thermodynamic calculations were utilized to accelerate the pace of discovering promising composition combination by tailoring phase fraction. Then a family of Fe2Ni2CrAlx multi-principal element alloys (MPEAs) were synthesized to investigate the effect of Al on the crystal structure, microstructural evolution, and mechanical properties. A two-phase, face-centered cubic (FCC) and body-centered cubic (BCC), structure was identified in alloys with lower Al content (x = 0.9 and 1.1), the alloy consists of structure with stripe patterns. As the Al concentration increased, the FCC phases disappeared, the volume fraction of BCC and B2 phase increased. The morphology turned into polygonal grains in which the periodic maze-shaped microstructure can be identified. Higher Al content dramatically increased the nanohardness and strength of the Fe2Ni2CrAlx MPEAs, but reduced the plasticity. Among the developed alloys, the Fe2Ni2CrAl1.2 alloy displayed the best property combination, with yield stress, compressive strength, and plasticity of 1117.8 MPa, 2961 MPa and 42.3%. These values are superior to most reported as-cast MPEAs. Precipitation strengthening was found to be the main strengthening mechanism responsible for the enhanced mechanical properties of the Fe2Ni2CrAl1.2 alloy. The current work offers the systematic understanding of the strengthening.