Microstructures and Stability Origins of β-(Ti,Zr)-(Mo,Sn)-Nb Alloys with Low Young's Modulus

The present work investigates the microstructural evolution and beta-phase stability of a multi-component [(Mo,Sn)-(Ti,Zr)(14)]-Nb alloy series developed using the cluster-plus-glue-atom model. Low Young's modulus (E) can be reached, when both low-E elements, Sn and Zr, and beta-Ti stabilizers, Mo and Nb, are properly incorporated in the so-called cluster formulas. After the X-ray diffraction and transmission electron microscopy analysis, and in combination with the beta-Ti stability measured by the Mo equivalent, the Young's modulus of beta-Ti alloys is found to increase with increasing beta stabilities and is closely related to both the microstructures of the beta matrix and the precipitated phases. More importantly, the morphologies of the beta matrix change with beta stabilities apparently so that high-E (E > 70 GPa) and low-E (E a parts per thousand currency sign70 GPa) beta-Ti alloys can be distinguished with the microstructures of the beta matrix. The quinary alloy, formulated as [(Mo0.5Sn0.5)-(Ti13Zr1)]Nb-1, owns its lowest E of 48 GPa among the present alloy series to the mixed thin-lamellar and rod-shaped morphology of the beta structure with the lowest stability for the beta formation.