**Principles of Brass Bar Manufacturing**
**(1) Conductivity and Alloying Principles**
All alloying elements invariably reduce the electrical and thermal conductivity of copper bars. Elements that form solid solutions in copper induce lattice distortion, causing electron scattering during directional flow and increasing resistivity. Conversely, elements with negligible solubility in copper have minimal impact on conductivity. Notably, certain elements exhibit drastically reduced solubility at lower temperatures, precipitating as pure metals or intermetallic compounds. This enables solid-solution and dispersion strengthening without significantly compromising conductivity—a key principle in developing high-strength, high-conductivity alloys. Particularly important are alloys combining copper with iron, silicon, zirconium, and chromium. The cumulative effects of alloying elements make the Co-Cr-Zr system a renowned high-strength, high-conductivity alloy.
**(2) Corrosion-Resistant Alloy Design**
Copper-based corrosion-resistant alloys should maintain a single-phase microstructure to prevent electrochemical corrosion from secondary phases. Thus, alloying elements must exhibit high or even unlimited solubility in copper. Single-phase brass, bronze, and cupronickel bars demonstrate excellent corrosion resistance, making them vital heat-exchange materials.
**(3) Wear-Resistant Alloy Design**
Wear-resistant copper alloys require a dual-phase structure of soft and hard phases. Alloying must ensure elements not only dissolve in copper but also precipitate hard phases (e.g., Ni₃Si, FeAlSi). In modern automotive synchronizer gear alloys, the soft α-phase should not exceed 10%, while the hard β-phase provides durability.
**(4) Functional Alloys**
- **Damping alloys**: Copper alloys with solid-state polymorphic transformations (e.g., Cu-Mn).
- **Shape-memory alloys**: Systems undergoing thermoelastic martensitic transformations (e.g., Cu-Zn-Al, Cu-Al-Mn).
**(5) Color Control**
Alloying elements (zinc, aluminum, tin, nickel, etc.) enable color modulation from red → cyan → yellow → white. Precise composition control yields gold-like or silver-like aesthetic materials.
**(6) Eco-Conscious Alloying**
Preferred elements should be economical, abundant, and environmentally benign. Follow a "multi-component, low-concentration" approach to ensure:
- Resource efficiency in raw material utilization
- Superior workability for diverse semi-finished/finished products
- Minimal environmental impact
黄铜棒制造的原则
（1）所有元素都无一例外地降低铜棒的电导率和热导率，凡元素固溶于铜棒中，造成铜棒的晶格畸变，使自由电子定向流动时产生波散射，使电阻率增加，相反在铜棒中没有固溶度或很少固溶的元素，对铜棒的导电和导热影响很少，特别应注意的是有些元素在铜棒中固溶度随着温度降低而激烈地降低，以单质和金属化合物析出，既可固溶和弥散强化铜棒合金，又对电导率降低不多，这对研究高强高导合金来说，是重要的合金化原则，这里应特别指出的是铁、硅、错、铬四元素与铜棒组成的合金是极为重要的高强高导合金；由于合金元素对铜棒性能影响是叠加的，其中CoCr —Zr 系合金是著名的高强高导合金；
（2）铜基耐蚀合金的组织都应该是单相，避免在合金中出现第二相引起电化学腐蚀。为此加人的合金元素在铜棒中都应该有很大的固溶度，甚至是无限互溶的元素，在工程应用的单相黄铜棒、青铜棒、白铜棒都具有优良的耐蚀性能，是重要的热交换材料。
（3）铜基耐磨合金组织中均存在软相和硬相，因此在合金化时必须确保所加人的元素除固溶于铜棒之外，还应该有硬相析出，铜棒合金中典型的硬相有Ni3Si 、FeALSi 化合物等。近年来开发的汽车同步器齿轮合金中a 相为软相，负相为硬相，a 相不宜大于10 %。
（4）固态有多晶转变的铜棒合金具有阻尼性能，如Cu 一Mn 系合金，固态下有热弹性马氏体转变过程的合金具有记忆性能，如Cu 一Zn 一Al 、Cu 一Al 一Mn 系合金。
（5）铜棒的颜色可以通过加人合金元素的办法来改变，比如加人锌、铝、锡、镍等元素，随着含量的变化，颜色也发生红一青一黄一白的变化，合理地控制含量会获得仿金材料和仿银合金。
（6）铜棒及合金的合金化所选择的元素应该是常用、廉价和无污染的，所加元素应该本着多元少量的原则，合金原料能够综合利用，合金应具有优良的工艺性能，适于加工成各种成品和半成品。
