Design of oxygen-doped TiZrHfNbTa refractory high entropy alloys with enhanced strength and ductility. (November 2022)

• Record Type: Journal Article
• Authors: Iroc, L.K.; Tukac, O.U.; Tanrisevdi, B.B.; El-Atwani, O.; Tunes, M.A.; Kalay, Y.E.; Aydogan, E.
• Is Part Of: Materials & design. Volume 223(2022)
• Publication Date: 2022-11
• Subjects: Refractory High Entropy Alloys (RHEAs) -- CALPHAD -- Nano-lamellar structures -- Nanotwins -- In-situ TEM; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2022.111239
• Languages: English
• ISSNs: 0264-1275

Abstract

Graphical abstract: Highlights: A novel light-weight (Ti25 Zr35 Nb20 Hf5 Ta15 )95 O5 RHEA with superior properties has been designed using CALPHAD modelling. During in-situ heating tests, formation of a secondary BCC phase besides an HCP phase occurs between 600 and 1000 °C. Oxygen doping and high temperature annealing improve the strength and ductility of the alloy. Enhanced high-temperature strength result from nano-lamellar structure of BCC+HCP phases as well as nano-twins. CALPHAD calculations match well with the experiments to predict the phase diagrams and microstructure of the RHEAs. Abstract: Refractory high entropy alloys (RHEAs) are considered promising materials for high-temperature applications due to their thermal stability and high-temperature mechanical properties. However, most RHEAs have high density (>10 g/cm 3 ) and exhibit limited ductility at low temperatures and softening at high temperatures. In this study, we show that oxygen-doping can be used as a new alloy design strategy for tailoring the mechanical behavior of the TiZrHfNbTa alloy: a novel low-density (7.98 g/cm 3 ) ductile RHEA. Even though the material is a single-phase BCC with some oxides at room temperature, secondary BCC and HCP nano-lamellar structures start to form above 600 °C in addition to the nano-twins which are shown to be stable up to 1000 °C. This alloy shows superior strength and compressive ductility due to the nanoengineered microstructure. The present study sheds light on tailoring the strength-ductility balance in RHEAs by controlling the microstructure of novel RHEAs at the nanoscale via oxygen-doping.