Effect of processing route on phase stability in equiatomic multicomponent Ti₂₀Fe₂₀Ni₂₀Co₂₀Cu₂₀ high entropy alloy

Abstract

The evolution of microstructure and phase formation in equiatomic Ti₂₀Fe₂₀Ni₂₀Co₂₀Cu₂₀ high entropy alloy synthesised by conventional arc melting followed with suction casting and ball milling with spark plasma sintering route is distinctly different. The cast microstructure exhibits one body centre cubic and two face centre cubic high entropy phases based on titanium, cobalt and copper respectively along with a eutectic containing Ti₂Ni type Laves phase. On the contrary, spinodal decomposed microstructure consisting of cobalt and copper solid solution is obtained in the sintered sample. However, long term annealing of cast sample at 950°C reveals a eutectoid transformation with different phases than the cast sample. The aforementioned observations are discussed using CALPHAD thermodynamical approach and available literature.

Keywords:

• HEA
• Suction casting
• Ball milling
• Stability
• Phase separation