Effect of Thermo-Mechanical Processing on Microstructure and Elastic Modulus of Metastable Ti-Nb-Si Alloys for Biomedical Application

Abstract

This work describes the effect of microstructures on elastic modulus in Ti-26Nb-xSi alloy (x=0.5~1.5at.%) prepared by arc melting, cold rolling and recrystallization heat treatment. OM observation and x-ray diffraction analysis revealed that the microstructure of as-quenched sample appeared to mixture appearance consisting of mostly bcc-structured β phase and small amount of orthorhombic-structured α″ phase. After cold rolling, elongated structure parallel to the rolling direction was observed, and equiaxed structure with the average grain size of about 20~30μm was developed for the sample after recrystallization heat treatment. In as-quenched sample randomly distributed feature of pole figure was characterized without showing a specific texture component. In cold-rolled sample α-fiber, γ-fiber and rotated cube texture components were detected. After recrystallization heat treatment the intensity of α-fiber texture component was markedly decreased, while the rotated cube component becomes sharpened and γ-fiber component remains relatively unchanged. The elastic modulus increased by cold rolling and then decreased by recrystallization over the entire chemical composition range investigated. The variation of elastic modulus values was interpreted in terms of changes in texture components depending on thermomechanical processing.