An investigation of mechanical, corrosion and high-temperature oxidation behaviors on designed Ti-based entropic alloys
Wei Wang, Qian Chen, Chunyun Zhou, Zhou Li, Nan Wang, Zhankun Weng, Wenda Zhang, Wangzhong Mu
Abstract
To satisfy the high performance requirements of new generation materials in application of aerospace and automotive industries, a series of TiZrHf-based entropic (i.e., entropy-stabilized) alloys with α+β dual-phase microstructure were designed using the CALPHAD (CALculation of PHAse Diagram) methodology. The present work aimed to achieve an balanced performance between mechanical properties, corrosion resistance, and high-temperature oxidation stability by tailoring Zr/Hf ratios. The alloys were comprehensively characterized using X-ray diffraction (XRD), electron channeling contrast imaging (ECCI), and and high angle annular dark field scanning transmission electron microscope (HAADF-STEM). Due to the effect of transformation-induced plasticity (TRIP), the homogenized and cryogenic alloys exhibit balanced mechanical properties (i.e., high strength and ductility). Electrochemical tests in 3.5 wt.% NaCl solution demonstrated good corrosion resistance, and the stability of the passive film was slightly compromised by both cryogenic treatment and Zr/Hf additions. Moderate high-temperature oxidation tests at 500 and 600 °C showed that the alloys have good oxidation resistance result from the formation of protective scales dominated by TiO 2 and Al 2 O 3 . However, the formation of less-protective Zr/Hf-oxides at higher temperatures (700 °C) was found to be detrimental. This work provide a CALPHAD-guided design strategy for developing Ti-based entropic alloys with a well-balanced properties for applying in different severe environments.