Effect of Dimensions on Martensitic Formation of Quenched Ti-Nb Alloys

Abstract

Although certain quenched titanium alloy sheets exhibit excellent damping properties, the effect of dimensions has not been clarified. In this study, the cooling rate, microstructure, phase constitutions, lattice parameters, and hardness distribution of cylindrical specimens of Ti-(15, 18, 20) mass%Nb alloys were investigated in order to examine the effect of dimensions. The difference in the phase constitutions of cylindrical specimens could arise from slower cooling rates than those for the sheet samples, even though the same lattice constant, axial ratio, and unit volume are to be achieved in both cases. The hardness change occurs in the distribution regions such as Ti15Nb or Ti18Nb, and is caused due to different distribution patterns between ' and " martensite phases. The residual phase in Ti20Nb seems to be affected by the faster cooling rate, as it migrates to the outer edge regions. These results imply the cylindrical specimens can exhibit damping properties equivalent to those of the sheet samples.