材料期刊网

用原子吸收光谱测定了在慢应变速率的应力腐蚀试验条件下,70/30黄铜在1当量亚硝酸钠水溶液中,电位范围—0.1～+0.1V(SCE)内的脱锌系数。结果表明,所有试验都发生严重脱锌,但是,电位对脱锌系数和应力腐蚀开裂敏感性的作用影响相反:提高电位加速裂纹扩展,却降低了脱锌系数。应变速率的加快对增加脱锌系数的作用也随电位提高而减弱。在阳极溶解模型的基础上,采用快速应变电极测试的数据,理论计算得出的脱锌系数随电位和应变速率变化的趋势与实验结果相似。从而说明,尽管黄铜总的溶解速率随电位提高而增加(黄铜中的锌亦如此),加剧了开裂敏性,但是锌、铜溶解相对比率中铜溶解部份的递增造成脱锌系数下降。 文章进一步讨论了与黄铜应力腐蚀机理有关的本结果涵义。

Atomic absorption spectroscopy was used to determine the dezincification coefficient of 70/30 brass subjected to slow-strain rate stress corrosion tests in 1 normal aqueous sodium nitrite solution over the potential range from -0.1～+0.1V(SCE). The results showed that extensive dezincification occurred in all the tests but potential had opposite effects on the dezincification coefficient and susceptibility to stress corrosion cracking; an increase in potential accelerated crack velocity but depressed the dezincification coefficient. The effect of increasing sttrain rate on the increase of dezincification coefficient was diminished with increase in potential. Similar tendencies of dezincification coefficient as functions of potential and strain rate were obtained by theoretical calculations based on anodic dinsolution model using available date measured by rapid straining electrode. The indication is that the increase of proportion of copper dissolution in the dissolution ratio of zinc to copper was responsible for the drop of dezincification coefficient, even though the total dissolution rate increased with increasing potential, so was zinc in the brass, to enhance the susceptibility to cracking. The implication of the pressent results relevant to the cracking mechanism is further discussed.