A novel equiatomic TiNbTaZrMo high-entropy alloy (HEA) was developed as a new metallic biomaterial. The constituent elements of the HEA were biocomparable, and the HEA was designed based on parameters such as the mixing enthalpy (ΔHmix), the omega parameter (Ω), the delta parameter (δ), and the valence electron concentration (VEC) theory. The bcc solid solution phases with the different lattice constants were obtained in as-cast and annealed states. The HEA showed considerable strength with deformability and superior biocompatibility comparable to pure Ti. This study demonstrated the possibility of using HEAs as a new class of metallic biomaterials

This paper clarified a novel strategy to improve the tensile properties of the Ti-48Al-2Cr-2Nb alloys fabricated by electron beam melting (EBM), via the finding of the development of unique layered microstructure composed of duplex-like fine grains layers and coarser γ grains layers. It was clarified that the mechanical properties of the alloy fabricated by EBM can be controlled by varying an angle θ between EBM-building directions and stress loading direction. At room temperature, the yield strength exhibits high values more than 550MPa at all the loading orientations investigated (θ=0, 45 and 90°). In addition, the elongation at θ=45° was surprisingly larger than 2%, owing to the development of this unique layered microstructure. The anisotropy of the yield strength decreased with increasing temperature. All the examined alloys exhibited a brittle-ductile transition temperature of approximately 750°C and the yield strength and tensile elongation at 800°C were over 350MPa and 40%, respectively.By the detailed observation of the microstructure, the formation mechanism of the unique layered microstructure was found to be closely related to the repeated local heat treatment effect during the EBM process, and thus its control is further possible by the tuning-up of the process parameters. The results demonstrate that the EBM process enables not only the fabrication of TiAl products with complex shape but also the control of the tensile properties associated with the peculiar microstructure formed during the process