Thermal stability and thermal expansion behavior of FeCoCrNi2Al high entropy alloy

Present work reports the thermal stability and thermal expansion behavior of dual-phase FeCoCrNi2Al HEA prepared by Mechanical Activated Synthesis and consolidated by hot pressing. The thermal stability of the phases present in FeCoCrNi2Al HEA has been extensively studied using in-situ high-temperature Xray diffraction (HT-XRD) in conjunction with dilatometry and differential scanning calorimetry (DSC). The DSC thermogram shows a single endothermic peak at 1430 degrees C (1703 K) which belongs to the melting point of the alloy. HT-XRD and dilatometry experiments were carried out from room temperature to 1000 degrees C (1273 K). HT-XRD study has shown that the room temperature FCC + BCC (face-centred cubic + body-centred cubic) phases remains stable up to 1000 degrees C (1273 K). Although the amount of BCC phase has increased above 800 degrees C (1073 K), no additional phase formation was observed in HTXRD. The coefficient of thermal expansion (CTE) curve shows linear increment up to 1000 degrees C (1273 K) with a slight change in slope beyond 800 degrees C (1073 K). Theoretical CTE was computed using the lattice parameter of the FCC phase, obtained from HT-XRD, as a function of temperature and compared with experimental CTE. Third-order polynomial equation was fitted to the experimental CTE data and the constants were evaluated which can be used to predict the coefficient of thermal expansion of the alloy. (c) 2020 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.