Combined First-Principles and Experimental Study on the Microstructure and Mechanical Characteristics of the Multicomponent Additive-Manufactured Ti-35Nb-7Zr-5Ta Alloy.

New ß-stabilized Ti-based alloys are highly promising for bone implants, thanks in part to their low elasticity. The nature of this elasticity, however, is as yet unknown. We here present combined first-principles DFT calculations and experiments on the microstructure, structural stability, mechanical characteristics, and electronic structure to elucidate this origin. Our results suggest that the studied ß Ti-35Nb-7Zr-5Ta wt % (TNZT) alloy manufactured by the electron-beam powder bed fusion (E-PBF) method has homogeneous mechanical properties (H = 2.01 ± 0.22 GPa and E = 69.48 ± 0.03 GPa) along the building direction, which is dictated by the crystallographic texture and microstructure morphologies. The analysis of the structural and electronic properties, as the main factors dominating the chemical bonding mechanism, indicates that TNZT has a mixture of strong metallic and weak covalent bonding. Our calculations demonstrate that the softening in the Cauchy pressure (C' = 98.00 GPa) and elastic constant C̅44 = 23.84 GPa is the origin of the low elasticity of TNZT. Moreover, the nature of this softening phenomenon can be related to the weakness of the second and third neighbor bonds in comparison with the first neighbor bonds in the TNZT. Thus, the obtained results indicate that a carefully designed TNZT alloy can be an excellent candidate for the manufacturing of orthopedic internal fixation devices. In addition, the current findings can be used as guidance not only for predicting the mechanical properties but also the nature of elastic characteristics of the newly developed alloys with yet unknown properties.