Effect of Thermal Cycling on Transformation Behavior of Ti-24Nb-1Mo Alloy (at.%)

Abstract

The effect of thermal cycling on the transformation behavior of a Ti-24Nb-1Mo alloy was investigated by means of electrical resistivity measurement, transmission electron microscopy (TEM), X-ray diffraction (XRD), tensile test and Vickers hardness tests. Electrical resistivity changes were not observed in all alloys. It indicates that thermally induced martensitic transformation does not take place in the alloys. After thermal cycling between 298 K and 77 K, clear X-ray diffraction peaks corresponding to omega(ath) phase, which did not exist before thermal cycling, were observed. Volume fraction of omega(ath) phase increased as increasing the number of thermal cycling. omega(ath) phase formed during thermal cycling increased hardness of the alloy. Although thermally induced martensitic transformation did not occur in the alloys, superelastic deformation behavior was observed in the alloys. The superelastic recovery ratio decreased from 81% to 41% by increasing the number of thermal cycling, which came from the increase in the volume fraction of omega(ath) phase.