Effect of Annealing Temperature and External Tensile Stress on Negative Thermal Expansion to Cold Rolled Ti-23Nb-0.7Ta-2Zr Alloy

Abstract

The effect of annealing temperature and external stress on the thermal expansion of a Ti-23Nb-0.7Ta-2Zr alloy were investigated by means of thermal expansion tests under constant load and X-ray diffraction (XRD). Negative thermal expansion (NTE), which is a shrinkage during heating, was observed in both a cold rolled and annealed specimens. The intensity of (200)(beta) peak decreased while that of (211)(beta) peak increased as the annealing temperature increased. The difference in expansion rate between 50 degrees C and 250 degrees C is found to decrease with an increasing annealing temperature from 600 degrees C to 800 degrees C, above which it kept almost constant. The expansion rate decreased as the applied stress increased.