Cu-3%Ti合金の復元現象について

Abstract

On the reversion phenomena of Cu-3%Ti alloys were investigated by measurements of electrical resistivity, hardness, 0.2% proof stress and tensile strength and the X-ray method.Some results obtained are as follows: (1) The reversion process investigated by the electrical resistivity change is described as a first order reaction up to f=0.6∼0.7. (2) The activation energy for the reversion process obtained from the initial tangents of resistivity reversion curves is nearly equal to 2.3 eV. (3) Under constant ageing conditions, the amount of reversion increases, and the time required for the max. increment of electrical resistivity becomes shorter as the reversion temperature rises. Also, under the condition of a constant reversion temperature and a constant decrement of electrical resistivity due to ageing treatment, the amount of reversion is greater as the difference between ageing and reversion temperatures increases. (4) In the case of short time ageing, the reversion phenomena are apparently undetectable, but the amount of reversion increases with ageing time up to the max. value, and thereafter decreases gradually. (5) Reversion phenomena of this alloy can be repeated many times almost completely when they are investigated by electrical resistivity, 0.2% proof stress and tensile strength. However, this reversible behavior is not complete in the case of hardness measurement. (6) The profile of side bands in the Debye film from a specimen aged for 1 hr at 450°C disappears almost completely after reversion treatment for 10 sec at 700°C. When this specimen is reverted at 550°C, the spacing (Δθ) between the side bands and the relative intensity between the side bands and the main diffraction line seem to decrease as the reversion proceeds. (7) If the decomposition process of this alloy follows the nucleation and growth mechanism, the reversion mechanism of its modulated structure may be explained by the conventional (critical size or G-P solvus) theories. If it follows the spinodal decomposition, this reversion phenomena may be explained qualitatively by the temperature depondence of the critical wave length λc in the spinodal decomposition theory proposed by Cahn et al.