Mechanical and thermal behaviors of Ti36-Al16-V16-Fe16-Cr16 high entropy alloys fabricated by spark plasma sintering: An advanced material for high temperature/strength applications

Abstract

Conventional superalloys possess high strength, high oxidation resistance and high creep resistance. Nonetheless, some lose strength at elevated temperatures, while others suffer high temperature oxidation and creep. This work was aimed at developing high entropy alloy (HEA) of Ti36-Al16-V16-Fe16-Cr16 at near equi molar configuration using spark plasma sintering technique which would be able to address the challenges of conventional superalloys. The powders were mixed with Turbular mixer at 69 rpm for 10 h. The sintering was carried out with the same sintering pressure of 40 MPa, time of 10 min, heating rate of 100°C/mins on all the samples. Only the sintering temperature was varied. The temperatures used included 700°C, 800°C, 900°C, 1000°C and 1100°C, respectively. The powders and sintered samples were characterized with Scanning electron microscopy connected to Energy Dispersive Spectroscopy and X-ray diffractometer. The mechanical properties were tested with Nano indenter using ASTM D785 standard; while the thermal stability was investigated with thermogravimetric analyzer. Results showed that HEA sintered at 1000°C possessed the best nanomechanical, thermal and microstructural properties while that sintered at 700°C had the weakest properties. The best developed alloy had an improved elastic modulus of 671.17 ± 50 GPa and 930.12 ± 38 GPa at darker flakey phase and white phase, respectively. It had creep resistance of 1.82%, densification of 98.96% and porosity of 1.04%. It was concluded that the developed alloy can perform much better than most superalloys in high temperature and high strength and applications.