Electrochemical micromachining of high-strength metallic glasses

高强度块体金属玻璃在高机械载荷下的微器件或具有限定功能表面微结构的器件中的应用是非常有吸引力的。对于这些玻璃在微米和亚微米尺度上的表面结构化，先进的电化学技术被认为是非常有前景的。拟议项目的目的是进行基础研究的潜在的微电化学加工方法的评估使用金属尖端电极选择Zr和Fe基玻璃。对合金在水溶液和甲醇工作电解质中的电极行为的基础研究使复杂的阳极反应过程的分析成为可能。锆基玻璃表现出特征的过钝化击穿行为，并逐渐再钝化。合金成分和结构状态（非晶与结晶）没有显著影响。利用超短脉冲超钝电压进行微细加工的可能性得到了证实，但目前只能得到不规则的孔结构。通过鉴定更合适的电解质，旨在达到更好地控制过钝化局部溶解。软磁铁基合金的电极行为主要由单相非晶结构和高磷含量决定，这两者都能实现均匀的强钝化。它的特点是一个渐进的被动-过被动的过渡和快速再钝化。特别是在甲醇硫酸中，通过微加工可以实现非常均匀的光滑表面微结构、孔和线模型。因此，无定形结构被揭示为有利于均匀溶解和再钝化。计划通过高分辨率方法进行研究，以更详细地分析机加工边缘区域可能的选择性溶解现象和相关的局部结晶。 在应用项目的最后一年，重点将放在迄今为止获得的知识的基础上产生复杂的非晶微结构/微部件。水平底切是电化学加工方法的一种独特的可能性，将用于生产独立的微型薄片和微型零件，用于具有非常高的精度的磁致动器应用。多组分玻璃合金的复杂电化学加工过程将被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.