Micro- and Macromechanical Properties of Fully Densified Nanocrystalline Metals

我们建议研究全致密体纳米晶（nc）金属塑性变形的基本原理，这些金属的平均晶粒尺寸在10到30 nm之间，是通过惰性气体冷凝（IGC）和随后的严重塑性变形（SPD）或轧制的致密化的创新组合制备的。所研究的模型体系是钯（fcc）和几种单相钯合金。实验将重点进行以应力状态条件、应变速率和温度为变量，采用新型试验设备对小型化试样进行力学试验。目的是获得这些合金在这种非常小的晶粒尺寸下的材料行为的显著改进的数据库，因为这之前只是零星地进行了探索，并以以晶粒尺寸，应变速率和温度为参数的变形机制图的形式阐明和描述-调解变形的微观机制。特别强调的是纳米晶材料塑性流动中的细观效应的原位研究，如剪切带和/或晶界协同滑动的形成，以及定量和定性断口学研究。所获得的结果不仅对基础材料科学很重要，而且将允许详细阐述技术上可行的纳米结构材料的发展原则，提供这些材料的最高强度和延展性。

We propose to study the fundamentals of plastic deformation in fully dense bulk nanocrystalline (nc) metals with a mean grain size between 10 and 30 nm prepared by an innovative and new combination of Inert Gas Condensation (IGC) and subsequent densification by Severe Plastic Deformation (SPD) or rolling. The model system to be investigated is Pd (fcc) and several single-phase Pd alloys. The experiments will focus on mechanical tests using new testing equipment for miniaturized specimens with stress state conditions, strain rate and temperature as the variables. The aim is to obtain a significantly improved database of materials behaviour for these alloys at this very small grain size, since this has previously been explored only sporadically, and to elucidate and describe - in the form of a deformation mechanism map with the grain size, strain rate, and temperature as the parameters - the microscopic mechanisms that mediate the deformation. Special emphasis will be addressed to in situ investigation of mesoscopic effects in plastic flow of nanocrystalline materials, such as formation of shear bands and/or cooperative grain boundary sliding, and quantitative and qualitative fractography investigations. The obtained results will be important not only for fundamental material science, but also will allow to elaborate the principles of development of technically feasible nanostructured materials providing the highest level of strength and ductility of these materials.