异质界面调控的密排六方系超细尺度金属层状复合体塑性变形机制和织构演化的研究

Ultrafine-scaled multilayered metallic composites are attracting much attention because of the high strength/hardness as well as the excellent performance of anti-radiation damage of the materials. With the submicron or nano scaled layer thickness, hetero-interface between the constituent phases play an important role in both plastic deformation and texture evolution of the composites. In this project, the micromechanical behavior of ultrafine-scaled multilayered composites incorporating hcp/fcc, hcp/bcc and hcp/hcp hetero-interfaces are investigated, respectively (hcp: hexagonal close packing). Based on the atomic-scale studies via both experimental characterization and molecular dynamics simulation, the micromechanisms of dislocation slip, twinning and shear banding at the interface area together with the impact of hetero-interphase on micromechanisms and lattice rotations are explored. Subsequently, by introducing the dynamics of each microscopic deformation mechanism at the interface into the crystal plasticity theory, the relationship between macroscopic mechanical properties of the composite materials and mechanical properties of the constituent metals, the thickness of single layers, as well as the mechanical properties of hetero-interface is established quantitatively. The developed numerical model is capable of precisely predicting and controlling deformation microstructures, textures and mechanical behaviors of ultrafine-scaled multilayered hcp composites. The model is also helpful for the design and development of hexagonal composite materials with a combination of high strength and good ductility, the application of severe plastic deformation (SPD) technique for preparing such materials, and the security service of the materials.

超细尺度金属层状复合材料因其高强度/硬度、优异的抗辐照损伤等力学特性而受到广泛关注。在微纳米尺度下，异质界面对超细尺度层状复合体的塑性变形和织构演化具有重要影响。本项目以包含hcp/fcc、hcp/bcc和hcp/hcp异质界面的密排六方系微纳米金属多层复合材料为研究对象，通过对异质界面处位错、孪晶和剪切带的原子尺度表征和分子动力学模拟，研究各微观形变组态开动与扩展的物理机制以及晶体取向转动的过程，阐明异质界面对组元金属微观变形机制和织构演化的影响；进而将滑移、孪生和剪切带在界面处的动力学特性引入晶体塑性理论，建立宏观性能与金属的力学性能、尺度以及界面属性之间的定量关系，开发可准确预测和控制包含hcp金属的超细尺度层状复合体形变微结构、织构和力学行为的介观尺度有限元模型，从而为设计开发高强韧性六方系复合材料、利用严重塑性变形技术制备材料以及材料的安全服役提供理论指导。

依托本项目，采用累积叠轧工艺成功制备了Cu/Ti、Nb/Ti和Zr/Ti等多种密排六方系金属层状复合体。以包含hcp/fcc、hcp/bcc和hcp/hcp异质界面的密排六方系金属多层复合材料为模型材料，通过对异质界面处位错、孪晶和剪切带的原子尺度精细表征和分子动力学模拟，研究了各微观形变组态开动与扩展的物理机制以及晶体取向转动的过程，阐明了异质界面对组元金属微观变形机制和织构演化的影响，构建了六方系多层复合材料塑性变形和织构演化的微观物理模型。进而将滑移、孪生和剪切带在界面处的动力学特性引入晶体塑性理论，开发了可准确预测和控制包含hcp金属的超细尺度层状复合体形变微结构、织构和力学行为的介观尺度有限元模型，建立了材料宏观性能与组元金属的力学性能、尺度以及界面属性之间的定量关系。项目研究成果能够为设计开发高强韧性六方系复合材料、利用严重塑性变形技术制备材料以及工程部件的安全服役提供理论指导。