Properties of Consolidated Nanocrystalline Metals and Composites

本研究的主要目的是了解全密度纳米晶金属合金的固有机械性能。继续我们最近在将机械研磨的纳米金属和合金粉末固结成全密度样品的过程中取得的进展，这项工作将基本性质的研究扩展到一些元素和两相材料。为了系统地研究固有的机械响应，纳米相和超细晶粒的金属和合金将特别小心地制备，以尽量减少孔隙率和颗粒脱粘问题。将在压缩和拉伸条件下进行试验。研究了基本的变形行为和变形机理。特别是，在变形之前和之后，在晶粒内部和界面附近（晶粒与相边界）的单相和两相合金中的位错结构和行为，将在一定范围的晶粒尺寸上进行表征和监测。应变硬化和剪切带的行为和它们的成分和晶粒尺寸的依赖性将被调查，并与传统材料中发现的那些进行比较。多相合金中相间边界的强化效应将被表征和模拟。纳米晶金属和多相合金与一个有用的机械性能的组合将被证明。*

The main objective of this research is to understand the inherent mechanical properties of full-density nanocrystalline metallic alloys. Continuing on with our recent progress in devloping procedures to consolidate mechanicallu milled nanophase metal and alloy powders into full-density samples, this work expands the investigation on basic properties to a number of elemental and two phase materials. To systematically investigate the intrinsic mechanical response, nanophase and ultrafine-grained metals and alloys will be prepared with special care taken to minimize porosity and particle debonding problems. Testing will be conducted in compression and tension. Fundamental deformation behavior and mechanisms will be studies. In particular, dislocation structure and behavior in single-and two-phase alloys, before and after deformation, inside grains and near interfaces (grain vs. phase boundaries), will be characterized and monitored over a range of grain sizes. The strain hardening and shear banding behavior and their dependence on composition and grain size will be investigated and compared with those found in conventional materials. The strengthening effects of interphase boundaries in multi-phase alloys will be characterized and modeled. Nanocrystalline metals and multi-phase alloys with a useful combination of mechanical properties will be demonstrated.***