Cracking in Brittle Films on Ductile Substrates

延性基材上脆性薄膜的开裂

• 批准号: 0103385
• 负责人: Ivar Reimanis
• 金额: $ 22.7万
• 依托单位: Colorado School of Mines
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-06-15 至 2004-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0103385&HistoricalAwards=false
• 关键词: Cracking; Brittle; Films; Ductile; Substrates

0103385ReimanisOur current understanding of surface cracking phenomena is too limited to adequately predict conditions for fracture in sophisticated, inhomogeneous structures. Recent advances in mechanics modeling of graded structures, as well as advances in the micro- and nano-scale control over the fabrication of specific film structures have opened new doors for developing a better understanding of the connection between crack growth and performance in brittle films. Work proposed here will examine how surface cracking depends on 1) surface architectural characteristics, including the gradation architecture, and the associated residual stress distributions, 2) the elastic and plastic properties of the substrate, 3) the strength of the film/substrate interface, and 4) microstructural features of the film. Surfaces will be prepared by depositing films of chromium nitride (CrN and Cr2N), which have been extensively studied at Colorado School of Mines, as well as CrxCy, TixN, and TixC. Cartridge brass (Cu-30wt. % Zn), and Ni alloys will be utilized as model substrate systems, while steel substrates will provide a connection to technological systems, offering comparison to data in the literature. Conventional layered and novel architectures will be fabricated, and their mechanical behavior will be characterized using fundamental fracture experiments. A comprehensive set of experiments will elucidate the generic behavior among the different films, and this behavior will be compared to existing theoretical models for the purpose of extracting mechanics effects from material behavior effects. The inherent complexity in these systems dictates the need for numerical methods to model the mechanical response. Thus, finite element analysis will be employed to evaluate residual stress states and crack tip stress fields. %%%Brittle films serve a wide variety of purposes: corrosion, radiation and thermal protection, and wear resistance. In applications such as high temperature superconductors and for many microelectronic components, the film is the device, engineered to conduct current or respond to photons, electrons or ions. The performance of a film depends in large part on its structural integrity. In the case of high temperature superconductor tape, a surface crack dramatically reduces the current density; in the case of turbine engine components, cracking may result in enhanced oxidation; in the case of tools and dies, surface cracking decreases the wear resistance. In some applications, such as turbine engines for land based power generation, a limited amount of cracking may actually be desired in order to increase the film compliance. Clearly, it is technologically extremely important to understand how cracking occurs in engineered surfaces. The proposed work is designed to advance understanding in the fracture behavior of hard, brittle films with complex structures so that it may ultimately be applied to design new, high performance surfaces.

0103385Reimanis 我们目前对表面裂纹现象的理解过于有限，无法充分预测复杂、不均匀结构中的断裂条件。 分级结构力学建模的最新进展，以及对特定薄膜结构制造的微米和纳米尺度控制的进展，为更好地理解脆性薄膜裂纹扩展和性能之间的联系打开了新的大门。 这里提出的工作将检查表面裂纹如何取决于 1) 表面结构特征，包括级配结构和相关的残余应力分布，2) 基材的弹性和塑性特性，3) 薄膜/基材界面的强度， 4）薄膜的微观结构特征。 表面将通过沉积氮化铬（CrN 和 Cr2N）薄膜来制备，这些氮化铬薄膜以及 CrxCy、TixN 和 TixC 已在科罗拉多矿业学院进行了广泛研究。 筒状黄铜（Cu-30wt.% Zn）和镍合金将用作模型基材系统，而钢基材将提供与技术系统的连接，提供与文献中数据的比较。 将制造传统的层状和新颖的结构，并使用基本断裂实验来表征它们的机械行为。 一组全面的实验将阐明不同薄膜之间的一般行为，并将这种行为与现有的理论模型进行比较，以便从材料行为效应中提取力学效应。 这些系统固有的复杂性决定了需要采用数值方法来模拟机械响应。 因此，将采用有限元分析来评估残余应力状态和裂纹尖端应力场。 %%%脆性薄膜具有多种用途：腐蚀、辐射和热防护以及耐磨性。 在高温超导体和许多微电子元件等应用中，薄膜是一种设计用于传导电流或响应光子、电子或离子的器件。 薄膜的性能在很大程度上取决于其结构完整性。 对于高温超导带，表面裂纹会显着降低电流密度；对于涡轮发动机部件，裂纹可能会导致氧化加剧；对于工具和模具，表面裂纹会降低耐磨性。 在一些应用中，例如用于陆基发电的涡轮发动机，实际上可能需要有限量的裂纹，以增加薄膜柔量。 显然，了解工程表面如何发生裂纹在技术上极其重要。 拟议的工作旨在增进对具有复杂结构的硬脆薄膜断裂行为的理解，以便最终将其应用于设计新的高性能表面。