黄铜静态腐蚀脱Zn层引起拉应力的研究

STUDY OF TENSILE STRESS GENERATED BY DEZINC LAYER DURING CORROSION FOR BRASS

研究了黄铜在静态腐蚀过程中表面疏松层的应力状态．通过测量自由端挠度的变化及用 Ｓ Ｅ Ｍ 技术测量脱 Ｚｎ 层的厚度，计算了在脱 Ｚｎ 层和基体界面处产生的拉应力，其稳定值约等于黄铜屈服强度的 １／５．在 Ｓ Ｃ Ｃ 过程中这个附加的拉应力将协助外应力促进位错发射和运动，从而 Ｓ Ｃ

The stress state in the dezinc layer for brass due to free corrosion was investigated. The top end of foil brass sample with one side protected, was fixed. The free end bent towards corrosion surface gradually during corrosion in 1 mol/L NH 4OH+5g/L CuCl 2 solution, when the dezinc layer was formed. The deflection of the free end was measured. The loose dezinc layer was studied by SEM, and its thickness was measured. The stress state at the interface of dezinc layer/substrate was calculated. The results showed that a tensile stress was developed at the alloy/dezinc layer interface, which was 23.4 MPa, about 1/5 of yield strength for brass. It is possible that this additional tensile stress will assist the applied stress to facilitate dislocation emission and motion, and enhance micro\|crack nucleation for stress corrosion cracking.