用测试~(64)Cu和~(65)Zn同位素γ射线的放射性示踪技术研究了在慢应变速率动态拉伸条件下70/30黄铜在室温1M NaNO_2溶液中,-0.1V(SCE)下的应力腐蚀开裂(SCC)和脱锌行为。结果说明,包含铜在内的局部阳极溶解是该体系SCC的根本原因,而大量的脱锌则加剧了开裂敏感性。在应力达到最高拉伸应力(σ_(UTS))之前的裂纹稳态扩展阶段,脱锌系数最大,此阶段之后由于铜的溶解比例增大,脱锌系数相对较低。在稳态扩展阶段,裂纹尖端导致最大脱锌系数的应变速率估计约为初始应变速率的4倍左右。按择优溶解的体扩散模型算得SCC过程中锌的扩散系数可达10~(-11)cm~2/s数量级以上。文中还讨论了黄铜在亚硝酸盐溶液中SCC过程的脱锌机理。
Radiotracer technique was used to study the dezincifieation behaviour of 70/30 brass subjected to stress corrosion cracking (SCC) in 1M NaNO_2, at —0.1V (SCE) under dynamic slow strain-test condition. The results showed that localized anodic dissolution is the essential cause of SCC, while considerable dezincification enhanced the suseptibility to cracking. The maximum dezincification coefficient was obtained during the stage of steady crack propagation before the stress reached the ultimate tensile level (σ_(uts)). After that, the relative increase of dissolved copper gave rise to correspondingly lower dezincification coefficient. The strain rate at the crack tip for the maximum dezincification coefficient was approximately 4 times as high as initially applied strain rate. Calculation based on a volume diffusion model for preferential dissolution indicated that zinc diffusion coefficient in the SCC processes could reach more that 10~(-11)cm~2/s. Finally, the mechanism of dezincification related to the SCC of brass in nitrate solution is discussed.
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