Microstructure and oxidation behavior of the CrMoNbTaV high-entropy alloy
- PDF / 704,776 Bytes
- 8 Pages / 584.957 x 782.986 pts Page_size
- 7 Downloads / 226 Views
ARTICLE Microstructure and oxidation behavior of the CrMoNbTaV high-entropy alloy Yifeng Xiao, Wenhui Kuang, Yanfei Xu,a) Liang Wu, Wenjuan Gong, Jinwen Qian, and Qiankun Zhang School of Mechanical Engineering, Xiangtan University, Xiangtan 411105, People’s Republic of China; Key Laboratory of Welding Robot and Application Technology of Hunan Province, Xiangtan University, Xiangtan 411105, People’s Republic of China; and Engineering Research Center of Complex Tracks Processing Technology and Equipment of Ministry of Education, Xiangtan University, Xiangtan 411105, People’s Republic of China
Yuehui He State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, People’s Republic of China (Received 13 June 2018; accepted 21 August 2018)
The microstructure and oxidation behavior at high temperatures ranging from 900 °C to 1100 °C of equiatomic CrMoNbTaV high-entropy alloy produced by vacuum arc melting were investigated. The phase component, microstructure, and microhardness of the alloy were examined by using X-ray diffraction, scanning electron microscopy equipped with an energy-dispersive X-ray spectroscope, and Vickers hardness tests, respectively. The as-cast alloy consists of a single body-centered cubic (BCC) refractory metal solid solution due to the high mixing entropy effect and exhibits a dendritic microstructure. The alloy has a very high microhardness value of 923 HV due to the strong solid solution strengthening effect. The average microhardness in interdendrites (950 HV) was higher than that in dendrites (896 HV) because of composition segregation. The oxidation kinetic curves of the alloy after exposure to air at 900 and 1000 °C follow the pseudo-parabolic rate law, while the mass gain increases first and then decreases at 1100 °C. The thickness of the oxide layer increases with the increasing of oxidation time. The long rod-shaped oxidation products are composed of Nb2O5, NbO2, CrTaO4, CrNbO4, Ta9VO25, Nb9VO25, and TaO after oxidation at 900 and 1000 °C for 25 h. The oxides of CrTaO4 and CrNbO4 disappear as the oxidation temperature elevated to 1100 °C.
I. INTRODUCTION
High-entropy alloys (HEAs), a new alloying concept, which originally proposed by Yeh et al.1–4 According to this experimentally supported concept, the high entropy of mixed different metallic elements (generally $5) with near equimolar concentrations can considerably decrease the Gibbs free energy and stabilize disordered solid solution phases with relatively simple crystal structures rather than forming the conventionally expected complex intermetallic phases. Since proposed, a number of HEAs have attracted extensive research attention for both functional and structural applications due to the simple phase composition and excellent properties, which mainly consist of facecentered cubic (FCC) and/or body-centered cubic (BCC) crystal structures. So, HEAs have demonstrated favorable combinations of microhardness, strength, ductility, oxidation resistance, thermal stability, and corrosion resistance.5–11 Among a
Data Loading...
