Study of Annealing Effect of Cold-Worked αCu-Al Alloys

Abstract

The annealing behavior of Cu-14.2 at% Al alloys was investigated by means of X-ray diffraction, supplemented with micro-Vickers hardness and specific heat measurements. Samples filed at room temperature were step-annealed from room temperature up to 500°C. Effective domain sizes and rms microstrains were determined from diffraction line profiles by Fourier analysis. Stacking fault probabilities and lattice parameters were calculated from shifts in the peak maximum position by the least squares analysis.
The experimental results are interpreted as follows:
(1) The increase of the lattice parameter on deformation of αCu-Al alloys might be due to the destruction of short range order (SRO).
(2) Filing is more efficient in producing a disordered state in αCu-Al alloys at room temperature than quenching from a high temperature.
(3) Step-annealing treatment shows that the recovery of SRO, the annihilation of stacking faults and the growth of domains take place in turn with increasing temperature.
(4) The increase of the asymmetry of the diffraction line profile in filed αCu-Al alloys on annealing might involve the effect of the local ordered segregation of solute atoms which is considered as the origin of anneal-hardening.
(5) Kinetic study shows that the effective order and activation energy for the reaction which describe the variation in stacking fault probability in the second stage of annealing process are approximately 2 and 43 kcal/g·atom, respectively.