Cryogenic behaviour of the Al5Ti5Co35Ni35Fe20 multi-principal component alloy

The microstructure and properties of cast and hot-rolled Al5Ti5Co35Ni35Fe20 High-Entropy Alloy were studied. Presented alloy after initial homogenization for 20 h at 1100 °C is characterised by γ/γ’structure. After solid solution annealing at 1200 °C γ’ precipitates were dissolved that allowed further hot plastic deformation. Heat treatment performed after hot-rolling were used to increase the strength by γ’ precipitation strengthening. Tensile testing was performed at 20 °C, −120 °C and −196 °C. Deformation mechanisms observation was conducted by means of SEM-EBSD and TEM. To evaluate the mechanical properties after solid solution treatment the σy0.2 and σu at 20 °C were measured approx. 775 MPa and 1045 MPa, respectively. The decrease in temperature to −196 °C increase mentioned above parameters of about 20%. Precipitation strengthening enhances the σy0.2 and σu up to 900 MPa and 1200 MPa at room temperature and to 1020 MPa and 1460 MPa at −196 °C, respectively. Investigated alloy exhibits a high elongation to failure over 18% regardless of heat treatment and deformation temperature. Despite the face-centers cubic crystal structure and high Co, Fe and Ni content the twinning were not observed. Deformation behaviour at all testing temperature was the same, the main deformation mechanism was dislocation slip.