Microstructural and Orientation Dependence of the Plastic Deformation Behavior in β-type Ti-15Mo-5Zr-3Al Alloy Single Crystals

摘要

The plastic deformation behavior of a β-type Ti-15Mo-5Zr-3Al alloy with a body-centered cubic (bcc) structure, which is a promising material for biomedical applications, was investigated. The orientation dependence of the plastic deformation behavior was examined by using a single crystal. In addition, changes in the mechanical properties depending on the microstructure were examined. The β single phase was maintained even after short-time annealing below 673 K (400 °C). Thus, the variations in the mechanical properties were small. However, an ellipsoidal ω phase and a lath-like α phase were precipitated in long-time annealing at 573 K (300 °C) and 673 K (400 °C), leading to large increases in the yield stress. For the deformation behavior, a dislocation with a Burgers vector parallel to á 111 ñ leftlangle {111} rightrangle was observed irrespective of the heat-treatment conditions and loading orientations. However, the observed slip plane changed considerably depending on the loading axis, and the yield stress exhibited a strong orientation dependence because of the dislocation core structure effect in the bcc-structured crystals. The physical properties of Mo, which is the main constituent atom in the current alloy, may strongly affect the dislocation core structure and induce the characteristic orientation dependence of the plastic behavior.