ELECTRODEPOSITION MECHANISM OF ALUMINUM-MANGANESE ALLOYS WITH AMORPHOUS AND QUASI-CRYSTAL PHASES

研究了氯化物熔盐电沉积Al-Mn合金的机理。研究了电流密度对合金成分和阴极电流效率的影响。结果表明，在较低的电流密度下，镀层中Mn含量基本保持不变。在较高的电流密度下，沉积层中的Mn含量会转移到另一个恒定值，该恒定值取决于熔池成分，并由Al和Mn的极限电流密度决定。然后，测量了Al和Al- mn沉积的极化曲线。合金镀液中Al和Mn的沉积都发生在相同的电位下，没有观察到单独沉积Mn或Al的电位区。Al沉积的部分极化曲线表明，由于与Mn共沉积，Al沉积电位向低贵金属方向偏移了70mV。采用扫描电镜、x射线衍射等方法对Al-Mn合金的形貌和组织进行了研究。随着Mn含量的增加，合金变得有光泽。合金的x射线衍射图表明，低锰含量合金由a-Al晶相组成。随着Mn含量的增加，晶相的衍射峰强度减小，出现宽峰。ca.7质量%Mn合金的电子衍射图显示为α - al多晶相。随着镀层中Mn含量的增加。合金相由α - al变为非晶相。这些相呈平行于衬底的层状结构。在质量为ca.30 %Mn的Al-Mn合金的电子衍射图像中，观察到晶粒尺寸为3 ~ 5 nm的金属间化合物Al_6Mn微晶反射出四个宽环。

The electrodeposition of Al-Mn alloys from the molten chlorides salts was carried out to investigate the codeposition mechanism.The effect of a current density on the alloy composition and on the cathode current efficiency was investigated. The result shows characteristic feature that the Mn content in the deposits is kept almost constant at relatively lower current densities. At higher current densities, the Mn content in the deposits shifts to reach another constant values which are depended on the bath composition and determined by the limiting aurrent densities of Al and Mn. Then, the polarization curves were measured for Al and Al-Mn deposition. Both depositions of Al and Mn from the alloy plating baths occur at the same potential and no potential region where Mn or Al deposited individually is observed. The partial polarization curves for Al deposition show that the potential of Al deposition shifts to less noble direction by 70mV due to the codeposition with Mn.The morphology and the structure of the Al-Mn alloys were investigated using scanning electron microscope, X-ray diffraction.The alloys became lustrous with an increase in Mn content. X-ray diffraction patterns of these alloys showed that the alloys of lower Mn content consisted of a-Al crystalline phase. With an increase in Mn content, the intensities of the diffraction peaks from the crystalline phase decreased while a broad peak appeared. The electron diffraction pattern of ca.7mass%Mn alloy showed alpha-Al polycrystalline phase. With an increasing Mn content in deposit.the alloy phases changed from alpha-Al to amorphous phase. These phases showed lamellar structure which was parallel to the substrate. In electron diffraction images of Al-Mn alloy of ca.30mass%Mn, four broad rings were observed and they were reflected from microcrystalline intermetallic compound Al_6Mn with the grain size of 3 to 5 nm.