Thin Film Martensites

[321185] wutig本研究项目研究薄膜中的马氏体相变，重点研究衬底上奥氏体的相变。本研究着重研究了薄膜奥氏体/马氏体/基体复合材料的弹性和非弹性特性，并用非弹性特性来表征复合材料的金相变化和内应力。该方法的主要优点是可以实时监测组织和微观组织的变化、附着力和应力，并研究它们对相变的影响。目的是了解衬底约束和薄膜厚度的影响，以及“奥氏体”的结晶度和微观结构状态对相变的影响。鉴于形状记忆合金（SMA）具有潜在的应用价值，本文研究了镍/钛基、铜基、铁/锰基、铁/铂/钯基这四大形状记忆合金家族及其混合合金。表征技术包括x射线衍射、扫描和透射电子显微镜以及卢瑟福背散射。强调的是热弹性马氏体。由于具有微机械器件集成的潜力，衬底包括具有不同缓冲层的硅以及碳化硅，碳化硅正迅速成为更重要的微机械材料之一。＊＊＊

9321185 Wuttig This research project examines martensitic transformation in thin films, concentrating on the transformation of austenite on a substrate. This study emphasizes the elastic and anelastic properties of thin film austenite/martensite/substrate composites and use the anelastic properties to characterize the metallurgical changes in the composite as well as the internal stresses. This approach has the major advantage that the structural and microstructural changes, the adhesion and stresses can be monitored and their effect on the transformation investigated, all in-situ and simultaneously. The goal is to learn the effects of substrate constraint and film thickness, and the state of crystallinity and microstructure of the "austenite" on the transformation. In view of their potential practical importance, alloys from the four major shape memory alloy (SMA) families, nickel/titanium-based, copper- based, iron/manganese-based, and iron/platinum/palladium-based, as well as hybrids thereof, are investigated. Characterization techniques include X-ray diffraction, scanning and transmission electron microscopy, and Rutherford back scattering. %%% Emphasized are thermoelastic martensites. The substrates include silicon with different buffer layers because of the potential for micro-mechanical device integration as well as silicon-carbide which is fast becoming one of the more important micro-mechanical materials. ***