Fundamental Understanding of Deformation Mechanisms in Nanocrystalline Superplasticity

纳米晶超塑性变形机制的基本理解

• 批准号: 0240144
• 负责人: Amiya Mukherjee
• 金额: --
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-02-15 至 2008-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0240144&HistoricalAwards=false
• 关键词: Fundamental; Understanding; Deformation; Mechanisms; Nanocrystalline

This proposal is designed to gain a fundamental understanding of the deformation mechanisms of plasticity in nanocrystalline materials. The nanostructured metallic materials will be produced by several processing methods that include high-pressure torsion of cast material, pulsed electrodeposition, and crystallization from metallic glass. The phenomenon of sliding along the grain interfaces is one of the dominant rheological characteristics in elevated temperature plasticity. The ultrafine-grained nanocrystalline materials contain a very large density of interfaces and they offer a unique opportunity to study the structural state of grain boundary and its role on grain boundary sliding in elevated temperature plasticity. The intellectual merit lies in attempting to correlate the microstructural information with the mechanical data obtained from such nanoscale materials in the context of plasticity in really diminished length scales. Special emphasis will be given to the difficulty of intragranular dislocation generation inside the matrix in truly nanoscale structure and its implication to slip accommodation processes in current models of nanocrystalline plasticity at elevated temperatures.The grant explores whether the observed increase in superplasticity with decreasing grain size is a general phenomenon or not. Increasing superplastic strain rate will decrease forming time and will make it an economically viable process. Lowering superplastic forming temperature will allow utilization of some of the existing forming technology for shop-floor practice in industrially significant intermetallic structural materials. The results are expected to be technologically significant in forming of sensors and devices with complex shapes that can benefit from the nanocrystalline matrix with large ambient temperature strength and hardness.

该建议旨在获得对纳米晶材料可塑性变形机制的基本理解。纳米结构的金属材料将通过多种加工方法产生，包括高压铸造材料，脉冲电沉积和金属玻璃的结晶。沿谷物界面滑动的现象是温度可塑性升高的主要流变特征之一。超铁粒纳米晶体材料包含非常大的界面密度，它们提供了一个独特的机会来研究晶界的结构状态及其在晶界在升高温度可塑性中的作用。 智力优点在于试图将微观结构信息与从这种纳米级材料获得的机械数据相关联，而在可塑性的背景下，长度尺度确实减少。 特别重点将给予真正的纳米级结构内部矩阵内部脱位产生的难度及其对在升高温度下纳米晶体可塑性模型中滑移适应过程的影响。该赠款探讨了观察到的超塑性随着晶粒尺寸的降低而增加是否普遍现象。增强应变率的提高将减少形成时间，并将其成为经济上可行的过程。降低超代化的形成温度将允许在工业意义上的金属间结构材料中利用一些现有的成型技术来用于售货机练习。预计该结果在形成具有复杂形状的传感器和设备方面具有技术意义，这些传感器和设备可以从纳米晶体基质中受益，并具有较大的环境温度强度和硬度。