Effects of Fe on microstructure and mechanical properties of CoCrNiFeAl multi-principle elements alloys

Precipitation and twinning strengthening mechanisms have been extensively investigated to improve the yield strength and ductility of face-centered cubic (FCC) multi-principle elements alloys (MPEAs). Compared with well-studied Al_0.3CoCrFeNi in CoCrFeNi system, the microstructure and mechanical properties of a new designed CoCrNiFe_0.62Al_0.38 MPEA with lower Fe content were evaluated by transmission electron microscopy and tensile tests, respectively. Higher volume fraction of B2 nanoprecipitates and early deformation twining within FCC matrix were proposed to play key roles in improving the synergy strength and ductility of the AlCoCrFeNi system. The experimental results presented herein not only provide insight into how transition metal element affect precipitation and twining process of B2 phase reinforced FCC MPEAs, but also demonstrate useful guidance for the development of precipitation hardened CoCrFeNi system other than adjusting conventional elements such as Al, Ti, Ta, etc.