Decrement in Dislocation Density in Cu-0.1 at%Ni Alloy Crystals by Thermal Cyclic Annealing

Czochralski-grown Cu-0.1 at%Ni alloy crystals were annealed in a stream of purified argon gas under thermal cycle conditions by varying the heating temperature sinusoidally between 1123 K and 1323 K with a period of 1.8 ks. Changes in dislocation distribution and density as a function of annealing time were investigated by an etch pit technique with two specimen crystals which had different initial dislocation structures.Many subboundaries, mostly of the 〈211〉 type, were formed at the beginning of cyclic annealing, though they vanished during an early stage of annealing. Overall dislocation densities of 5×109 m−2∼8×109 m−2 in as-grown crystals decreased to 2×107 m−2∼3×107 m−2 after cyclic annealing for 172.8∼345.6 ks. It was observed that an elimination of edge dislocations was more remerkable than that of screw dislocations, especially in the early annealing stage. The decrement in dislocation density in Cu-0.1 at%Ni alloy crystal with an increase of annealing time was found to be comparable to that in pure copper crystal reported so far, showing that a small addition of Ni in Cu has little effect on the annihilation process of dislocations.