Microstructural evolution and mechanical properties of CoCrFeNiMnTix high‐entropy alloys

Abstract This study was conducted to investigate the effect of titanium addition on the microstructure and properties of an equitaomic CoCrFeNiMn high‐entropy alloy. Homogenized microstructures of CoCrFeNiMnTi x (x = 0.1 and 0.3) alloys consist of face‐centered cubic phase; however, addition of more titanium led to formation of a (chromium, titanium)‐rich σ phase in CoCrFeNiMnTi 0.4 alloy. The average electron hole number calculations indicate the higher possibility of σ phase formation by adding more titanium. Furthermore, addition of an atom like titanium with a larger atomic radius in comparison with other elements can affect stability of face‐centered cubic structure. Chromium and manganese has a destabilizing influence on the single face‐centered cubic phase and manganese may reject chromium to facilitate the formation of a (chromium, titanium)‐rich phase in alloys containing more than 5.5 at.% titanium (x>0.3). The mechanical properties revealed an improvement in strength without losing the ductility drastically by adding titanium up to 5.5 at.% (x = 0.3). Nevertheless, the strength remarkably increased and ductility significantly decreased in CoCrFeNiMnTi 0.4 alloy due to formation of brittle σ phase in the microstructure.