Materials World Network: Mechanisms leading to nanometer-sized materials

通过常温和低温轧制及低温退火热处理，发现纯铜中存在形变诱导的晶粒细化现象。此外，锌还使合金的层错能从78(纯铜)降低到14mJ/m2(铜-30wt.%锌)，并促进了晶粒的细化。在本项目中，将通过轧制和低温退火法合成纳米/超细晶铜/铜-锌合金，以克服专门的强度和塑性临界力学测试的尺寸限制，这些限制对此类NC/UFG材料了解较少。通过彻底和系统的分析，将对微观结构进行深入和系统的分析，并将研究这些材料在拉伸、压缩和扭转下的力学性能。在扫描和透射电子显微镜观察下进行原位变形研究，以揭示不同长度尺度下的变形机制。为了揭示加工诱发结构缺陷对具有不同SFE和变形机制的铜/铜锌合金的细化效果的影响，比较了不同加工方法(IFW制备的轧制/退火态样品和球磨(NCSU)和等通道转角挤压/高压扭转(UV)制备的样品)所获得的纳米/超细结构。比较了合金成分和工艺条件，即轧制温度、变形严重程度对不同SFE的铜/铜-锌合金纳米组织发展和最终晶粒度的影响。

Deformation induced grain refinement has been revealed in pure Cu by rolling at ambient and cryogenic temperature and low temperature annealing. In addition, Zn decreases the stacking fault energy (SFE) from 78 (for pure Cu) to 14 mJ/m2 (Cu-30 wt.% Zn) and enhances the grain refinement. In this project, nano-/ultrafine grained Cu-/Cu-Zn alloys will be synthesized by rolling and low temperature annealing, in order to overcome dimension limitations of specialized critical mechanical tests for strength and ductility, which are poorly understood for such NC/UFG materials. Characterization of the microstructure will be performed down to the atomic level by thorough and systematic analysis; and mechanical properties of these materials will be studied under tension, compression and torsion. In-situ deformation studies under scanning and transmission electron microscopic observation will be performed to reveal the deformation mechanisms at different length-scales. The nano-/ultrafine structures obtained by various processing routes (rolled/annealed samples prepared at IFW and specimens produced by ball milling (NCSU) and equal channel angular pressing/ high pressure torsion (UV)) will be compared in order to reveal the influence of processing induced structural defects on the ease of grain refinement in Cu-/Cu-Zn alloys with different SFE and deformation mechanisms as a function of grain size and SFE. The influence of alloy composition and processing conditions, i.e., rolling temperature, severity of deformation, on nanostructure development, and final grain size will be compared in these Cu/Cu-Zn alloys with different SFE.