Fundamental Understanding of Superplasticity in Nanocrystalline Metals

9630881慕克吉这项资助提供了对纳米晶体材料超塑性行为的基本了解。超细晶纳米晶材料含有非常大的界面密度，为研究超塑性过程中晶界的结构状态及其对晶界滑移的作用提供了独特的机会。结合纳米粉末的合成和固结方法，该实验程序检查了纳米金属、纳米金属间化合物和纳米复合材料的超塑性变形行为，其中纳米氧化物分散在纳米金属基质中。科学目标是在超塑性理论模型的背景下，将新的微结构信息与从纳米材料获得的力学数据相关联。特别强调了在目前的超塑性模型中，在真正的纳米结构中在基质内产生晶内位错的困难及其对滑移调节的影响。用透射电子显微镜、X射线衍射仪和内耗法研究了变形前后的纳米结构。%这项研究可能为纳米晶材料的变形加工带来新的加工技术，并可能对金属成形行业未来的金属合金加工产生影响。***

9630881 Mukherjee This grant provides fundamental understanding of superplastic behavior in nanocrystalline materials. Ultrafine-grained nanocrystalline materials contain a very large density of interfaces and, therefore, offer unique opportunities for studying the structural state of grain boundaries and their role on grain boundary sliding during superplasticity. Combining methods for synthesis as well as consolidation of nanopowders, the experimental program examines superplastic deformation behavior of nanometals, nanointermetallics, and nanocomposites with nanoscale oxides dispersed in the nanoscale metallic matrix. The scientific goal is to correlate in the context of theoretical models of superplasticity new microstructural information with mechanical data obtained from nanoscale materials. Special emphasis is given to the difficulty of intragranular dislocation generation inside the matrix in truly nanoscale structure and its consequences to slip accommodation in current models of superplasticity. The nanostructure before and after deformation is investigated using transmission electron microscopy, X-ray diffraction and internal friction methods. %%% The research could lead to new processing techniques for deformation processing of nanocrystalline materials and could impact future metal alloy processing in the metal forming industries. ***