Effect of Ti Content on Microstructure and Hardness of VCrFeTiTa High-entropy Alloy

Five VCrFeTi_xTa_0.2（x=0.2, 0.4, 0.6, 0.8, 1.0） series high-entropy alloys were designed and prepared by vacuum suspension melting technology. By X-ray diffract meter（XRD）, scanning electron microscope（SEM）, energy dispersive analyzer（EDS） and Vickers micro-hardness tester, the effects of different Ti contents on the microstructure and hardness of VCrFeTi_xTa_0.2series HEA were discussed. The results show that the five kinds of HEA contain BCC1 phase and BCC2 phase.The BCC1 phase contains more Cr and V, while the BCC2 phase contains more Fe, Ti and Ta. When the five kinds of HEA are kept at 1000 ℃ for 3 h, the grains are obviously refined after water-cooling and quenching. At the same time, the proportion of BCC1 phase increases significantly, the element distribution is more uniform, and it is more inclined to form a single solid solution structure. The atomic radius difference δ value of each sample increases gradually with the increase of Ti content, and the hardness also increases. After heat treatment, due to the formation of more single-phase solid solution and the occurrence of solid solution strengthening, the hardness of the high-entropy alloy is further improved.