【作者】 张建益；

【导师】 董晟全；

【作者基本信息】 西安工业大学 ， 材料物理与化学， 2011， 硕士

【摘要】 铅黄铜以其优异的成型性能、易切削性能和耐腐蚀性能而广泛应用在各个制造领域。但是铅元素在环境中是极其有害的物质,因而本文的研究目的在于开发出一种环境友好无铅易切削黄铜用来代替传统的铅黄铜。本文在了解铅黄铜易切削原理的基础上,用铝硅镁元素替代有毒的铅元素,采用普通铸造工艺得到金相组织为(β+γ)的合金,通过变质处理使第二相γ变细小且弥散分布,起到类似铅的断屑作用,同时所添加的镁与铜硅形成化合物,使合金的断屑质点增加。针对本文所开发的无铅易切削黄铜60Cu-Zn-1Si-2.4Al-xMg-0.1Ti,利用金相显微镜、扫描电镜、能谱分析仪研究了Ti和Mg对高锌黄铜显微组织和耐蚀性的影响,通过力学性能测试、脱锌腐蚀、车切测试等手段考察了所研制黄铜的力学性能、腐蚀性能和切削性能,分析了合金腐蚀过程和切削机理。该黄铜的显微组织主要由基体p相、细小的变质γ相和含镁化合物颗粒构成。经钛元素变质处理后,γ相由原来大的星花状转变为细小的点状,均匀弥散分布于基体p相颗粒内部,提高合金的综合性能；随镁含量增加,化合物数量增多,当镁含量小余2%时,含镁化合物颗粒弥散分布基体内部,强化合金。变质处理和热处理降低了合金的内应力使黄铜中锌的流失减少,脱锌层变小,镁含量的增加促进了锌的流失,脱锌层变厚。无铅黄铜具有良好的耐脱锌腐蚀性能,其在CuCl2溶液中腐蚀24小时后脱锌层厚度仅为131μm,扩散系数的数量级为10-11,失重方程符合指数衰减方程。变质处理和镁元素使合金断屑变细小,切削力减小,切削性能提高。合金切削力受切削深度的影响最大,其次为进给量,切削速度影响最小。根据Griffith脆性断裂理论计算得第二相颗粒临界尺寸为0.88 um。更多还原

【Abstract】 The Lead brass is used in various fields of machinery manufacturing widely because of its superior performance, easy molding cutting and ability corrosion resistance. However the lead is extremely harmful in the environment. The purpose of this research is to produce a kind of unleaded free-cutting brass, which can used to instead of the traditional lead brass.The experiment is based on the theory of lead brass cut ability, considering using Si, Al and Mg to replace Pb, and using common casting to get brass alloy which microstructure is (β+γ). The second phase y becomes small and mass by modification to play the role of lead to broken crumbs. The number of particle to broken crumbs is added by compound composed of Mg, Cu and Si in the alloy.The effect of adding Ti and Mg on the microstructure and corrosive properties of the alloy were study by optical microscope, SEM, energy spectrum analyzer. The mechanical properties, corrosion resistance and cutting performance are reviewed by the tests of mechanical, dezincification and cutting. The corrosion process and mechanism of cutting process are analyzed.The microstructure of the brass consists of matrix P, tiny metamorphic y and particle composition of Mg. The y is changed from the large flower-like into a small dot and distribution diffuse in theβby modification of Ti, and the mechanical properties of the alloy is improved. The number of compound increase as the content of Mg adds. The performance of alloy strengthened as compound particle disperse in matrix distribution when the content of Mg less than 2%.The depth of dezincification and the weightlessness are decreased after modification and heat treatment. However, Mg promotes dezincification. The corrosion resistance performance of this unleaded brass is excellented. The depth of dezincification is 131μm, the order of magnitude of diffusion coefficient of Zn is 1011～1012, and the weightlessness of alloy conforms to index regression.The scraps become smaller, cutting force decreases and cutting performance improved by adding Ti and Mg in the alloy. The factors effecting force are in the order of depth of cut, feed rate and cut speeding. According to the fracture theory of Griffith, the critical dimension of particle was calculated, which is 0.88μm.更多还原