Relationship between stress—corrosion cracking and strain rate in alpha brass

Abstract

Stress—corrosion cracking of Cu—30%Zn alloy under the constant strain rate in the range of 6·6 × 10 −6 s −1 to 1·1 × 10 −2 s −1 was investigated in Mattsson's solution (pH 7·2) (for inter-granular cracking) and in 1 M/L NH 4OH + 0·25 M/L CuCl 2 aqueous solution (pH 11·0) (for transgranular cracking). Within strain rates of 6·6 × 10 −6 s −1 for intergranular cracking and of 1·1 × 10 −5 s −1 for transgranular cracking, the rate-controlling step of stress—corrosion cracking corresponds to the slip step formation. Exceeding the above strain rates the s c c is controlled by the corrosion, where the rate-controlling mechanism requires the activation energy of about 18·7 Kcal/mol. When the strain rate exceeds 1·1 × 10 −3 s −1, intergranular s c c never occurs at room temperature. Width of crack tip increases with increase of strain rate for intergranular cracking, while decreases for transgranular cracking.