Grain growth in copper and alpha-brasses

Abstract

The wires of 99.999% copper and alpha-brasses containing 12, 20, 30 and 35 at % Zn have been annealed in vacuum for 30 to 240 min at 873, 923, 973 and 1023 K. The grain-growth data obtained are well encompassed by the relationD ², —D ²₀ , =Kt exp(-H/kT), whereD is the instantaneous mean grain diameter at the time,t, of isothermal anneal andD ₀ refers to the initial mean grain diameter. In alpha-brasses the activation energy for grain-boundary self-diffusion,H, and the pre-exponential factor,K, depends on the zinc concentration,c, asH = (H ₀ — 1.1c) eV andK =K ₀ exp(-10.7c) cm² sec⁻¹. The values ofH ₀ andK ₀, referred to the base metal are respectively 0.87 eV and 3.0 × 10⁻⁴ cm² sec⁻¹, which are in good agreement with those (0.85 eV and 3.6 × 10⁻⁴ cm² sec⁻¹) found for copper.