纳米晶切屑的块体成型与纳米结构的协同生成与控制

The cooperative formation and control of nanostructure during the consolidation of nanostructured chips produced by large strain machining under heat and compression coupling mechanism is a novel method on preparation of nano bulk metal materials.It is pivotal to research the coupling relationship between grain growth under heat with grain refinement under compression and the contradiction between the inhibition of grain growth with the raise of density on consloidated bulk in consolidation of metastable nanocrystalline chips. In this project fractal model.on microstructure evolution of nanostructured chips under the heat is built based on fractal theory. Combining with the microstructure modeling techniques, the coupling relationship between grain growth model with grain refinement model and the contradiction between the inhibition of nanostructured grain growth and the raise of density on nanostructured bulk in consolidation of nanostructured chips are analysed.Mathematical model and parameter optimization model between heat , compression and microstructure of nanostructured chips with microstructure, mechanical properties and density of nanostructured bulk are established based on experiment.Evolution mechanism of microstructure and mechanical properties of nanostructured chips are revealed and thermal and compressional stability of nanostructured chips are ascertained with multi coupling mechanism in order to realize consolidation of nanostructured chips and coopersative generation and.control of nanostructure.

大应变切削制备的纳米晶切屑在热和高压耦合机制作用下块体成型和纳米结构的协同生成与控制是制备纳米块体金属材料的新方法，亚稳态纳米晶在热作用下晶粒生长和高压作用下晶粒细化的耦合关系，热作用下晶粒生长和纳米块体成型致密性的矛盾关系是该项研究的两个关键问题。本项目拟基于分形理论建立块体成型过程中纳米切屑微观组织演化的分形模型，结合微相结构建模技术分析热和高压协同作用下晶粒生长模型与晶粒细化模型的耦合关系及纳米晶粒生长的抑制与块体成型致密性的提高之间矛盾关系，以实验为依据建立热、高压、纳米晶切屑微结构和成型工艺等参数与纳米块体微观组织、力学性能和致密性之间递进影响的数学模型和参数优化模型，揭示纳米晶切屑在多场耦合机制作用下微观组织和力学性能的演化机理，探明热和高压协同作用下纳米晶切屑的热压稳定性能，从而实现纳米晶切屑块体成型和纳米结构的协同生成与控制。

大应变切削制备的纳米晶切屑在热和高压耦合机制作用下块体成型和纳米结构的协同生成与控制是制备纳米块体金属材料的新方法。本项目基于DEFORM模拟和SEM、EBSD等实验手段，采用纳米晶切屑大应变切削制备工艺和预挤压+压缩挤压+ECAP纳米晶切屑块体成型工艺，研究热、高压、纳米晶切屑微结构和成型工艺结构及参数与纳米块体微观组织、力学性能和致密性之间递进影响关系，建立亚稳态纳米晶在热作用下晶粒回复生长和高压作用下晶粒细化的耦合关系，探讨热和高压协同作用下纳米晶切屑的热压稳定性能，揭示纳米晶切屑在多场耦合机制作用下微观组织和力学性能的演化机理，分析纳米晶粒生长的抑制和块体成型致密性的提高之间的矛盾关系，优化ECAP工艺结构和参数，确定大应变切削工艺参数、温度、高压和成型工艺路线的最佳耦合值，实现纳米晶切屑的块体成型和纳米结构的协同生成与控制。研究表明：纳米晶铜切屑块体成型工艺中，高压作用下剪切应变对晶粒的细化作用强于热作用下晶粒的回复生长，纳米晶切屑成型块体致密性不高导致在显微组织细小的情况下硬度大幅下降，后期拟通过优化成型工艺结构增加成型过程中热和高压的协同作用，解决纳米晶切屑热压成型块体致密性与优异性能之间的矛盾。