Internal friction in directed-crystallization (Cu-Sn)-Nb alloys
Abstract
The distinctive features of the low-frequency internal friction Q −1(T) of (Cu-Sn)-Nb composites at high temperatures (up to 400°C) are investigated for strains in the range 10−5–10−4. Considerable hysteresis of Q −1(T) in the heating-cooling cycle is recorded, including the presence of a minimum at ∼175°C when the sample is heated to 400°C and two peaks P 2 (at 280°C) and P 1 (at ∼100°C) when the sample is cooled from 400°C. The activation energy of the anomalous internal friction background (up to 175°C), the oxygen diffusion parameters, and the oxygen concentration in the niobium fibers (all of which govern the peak P 2) are calculated, and the value and temperature dependence of the yield point of the bronze matrix (which govern the peak P 1) are estimated.