Electrochemical micromachining of high-strength metallic glasses

高强度大块金属玻璃在高机械载荷下的微器件或具有明确功能表面微结构的器件中具有广泛的应用前景。在微观和亚微观尺度上，先进的电化学技术被认为是非常有前途的。该项目的目的是开展基础研究，以评估使用金属尖端电极对选定的锆基和铁基玻璃进行微电化学加工的潜力。对合金在水溶液和甲醇电解液中电极行为的基础研究使复杂阳极反应过程的分析成为可能。zr基玻璃表现出特有的透射击穿行为，并逐渐重钝化。合金成分和结构状态（非晶与结晶）没有明显的影响。论证了超短透射电压脉冲微加工的可能性，但目前只能得到不规则的孔结构。通过确定更合适的电解质，旨在更好地控制通过局部溶解。软磁性铁基合金的电极行为主要由单相非晶结构和高P含量决定，两者都能实现均匀的强钝化。它的特点是逐渐的被动过渡和快速的再钝化。特别是在甲醇硫酸中通过微加工，可以实现非常均匀光滑的表面微结构、孔洞和线条模型。因此，非晶结构有利于均匀溶解和再钝化。计划采用高分辨率方法对加工边缘区域进行更详细的分析，以了解可能的选择性溶解现象和相关的局部结晶。在申请的最后一个项目年度，重点将放在基于迄今为止获得的知识生成复杂的非晶微结构/微部件上。水平下切是电化学加工方法的一种独特的可能性，将用于生产高精度的独立微片和微部件。多组分玻璃合金的复杂电化学加工过程将描述与结构和成分相关的材料特性。

High strength bulk metallic glasses are very attractive for applications in micro-devices under high mechanical load or devices with defined functional surface microstructures. For surface structuring of those glasses on the micro- and submicro-scale advanced electrochemical techniques are regarded as very perspective. Aim of the proposed project is to conduct fundamental studies for the evaluation of the potential of micro-electrochemical machining methods using metal tip electrodes for selected Zr- and Fe-based glasses. Fundamental studies of the electrode behaviour of the alloys in aqueous and methanolic working electrolytes enabled the analysis of the complex anodic reaction processes. Zr-based glasses showed characteristic transpassive breakdown behaviour and repassivated gradually. There was no significant effect of the alloy composition and of the structural state (amorphous vs. crystalline) detectable. The possibility of micro-machining with ultra-short transpassive voltage pulses was demonstrated, but so far only irregular hole structures could obtained. By the identification of a more suitable electrolyte a better control of the transpassive local dissolution is aimed to be reached. The electrode behaviour of the softmagnetic Fe-based alloy is principally determined by the single phase amorphous structure and the high P content which both enable a homogeneous strong passivation. It is characterized by a gradual passive-transpassive transition and by a fast repassivation. In particular in methanolic sulphuric acid by micro-machining very homogeneous smooth surface microstructures, hole and line models, could be realized. Thereby, the amorphous structure was revealed to be advantageous for homogeneous dissolution and repassivation. Studies by means of high resolution method are planned to analyze the machined rim areas in more detail regarding possible selective dissolution phenomena and related local crystallization. In the applied last project year the focus will be set on the generation of complex amorphous microstructures/microparts based on the knowledge gained so far. Horizontal undercutting is a unique possibility of the electrochemical machining method and will be used to produce free-standing micro-lamellas and microparts for magnetic actuator applications with very high precision. The complex electrochemical machining processes of multi-component glassy alloys will be described in relation to structural and composition-dependent materials characteristics.