双辊铸轧6xxx系铝合金层状偏析控制与增强增塑机理研究

In this project, 6xxx series aluminum alloy plate is prepared by twin-roll casting technology to solve the problems like inhomogeneous structure, layered segregation and poor strength and plasticity in cast-rolled plate for high-quality forming. After production of the twin-roll casting 6xxx series aluminum alloy plate by means of the microalloying element addition, controlled rolling and cooling methods, heat treatment, it will be systematically investigated with finite element simulation, microstructure characterization and mechanical property tests. We will study the crystallization principle and rheological properties during the solidification process and the effects of adding microalloying elements, controlled rolling and cooling and heat treatment process on the microstructure and properties of 6xxx series aluminum alloy cast-rolled slab. The results reveal the constitutive relationship of the cast solidification shell between the growth and layered segregation and the role of adding microalloy elements, residual heat rolling and controlled cooling technology on the segregation and mcirostructure modulation of casting slab as well as the mechanism of enhanced strength and plasticity of the sheet. After the above research, the 6xxx series aluminum alloy cast-rolled sheet with higher strength and plasticity is finally developed to meet the needs of the automobile industry and civil sheeting..The process for preparation of 6xxx series aluminum alloy sheet can be simplifed and shortened with twin-roll casting technology. On the other hand, it holds a great significance on the fields such as energy conservation, environmental protection and lightweight. Currently, there is no domestic reports about the application of twin-roll casting 6xxx series aluminum alloy sheet.

本项目以双辊铸轧技术制备6xxx系铝合金板材，解决铸轧板组织不均、层状偏析及强塑性差等难题，实现6xxx系铝合金铸轧板材的优质成形。利用微合金元素添加、控轧控冷和热处理等技术，结合有限元模拟、微观组织检验及力学性能测试等手段研究6xxx系铝合金铸轧凝固结晶规律及流变特性、添加微合金元素对6xxx系铝合金铸轧板坯的组织结构与层状偏析的影响、控轧控冷及热处理工艺对6xxx系铝合金铸轧板坯组织与性能的影响，明确铸轧凝固坯壳生长与层状偏析的本构关系、添加微合金元素及余热轧制与控冷技术对铸轧板坯偏析及组织调控的作用、铸轧板材的增强增塑机理，最终研制开发出具有较高强塑性的6xxx系铝合金铸轧板材，满足汽车工业和民用板材的需要。.利用铸轧技术制备6xxx系铝合金板材，不仅缩短了工艺流程，而且对节能减排、环境友好和轻量化等方面具有重要的意义。目前国内未发现有关于铸轧6xxx系铝合金板材的应用报道。

本项目以双辊铸轧技术制备6xxx系铝合金板材，解决了铸轧板组织不均、层状偏析及强塑性差等难题，实现了6xxx系铝合金铸轧板材的优质成形。从多角度对多元高合金含量6000系铸轧铝合金增强增塑机理进行了系统分析，通过分析工艺参数对铸轧熔池内流场、温度场和速度场影响，明确了流场、温度场与速度场的相互关系，揭示了工艺参数、微合金化、控制控冷、热处理等对稳定铸轧6000系铝合金流变特性及组织性能影响规律，最终研制开发出了具有较高强塑性的6xxx系铝合金铸轧板材，满足汽车工业和民用板材的需要。研究发现：当浇注温度为690℃-710℃时，铸轧速度13m/in-15m/min时，为最佳的6061铝合金铸轧浇注温度和铸轧速度范围；当Mn/Fe质量比为2.0时，6061铝合金铸轧板中针片状β-Fe基本全部转变为颗粒状，铸轧板的力学性能显著提升；Er元素对6061铝合金铸轧板材晶粒尺寸具有显著的细化效果，随着Er添加量的增加，铸轧板晶粒尺寸呈现出先减小后增大的变化规律，当Er含量达到0.4wt%时，晶粒细化效果最佳；Mg/Si比对Al-Mg-Si铸轧板材成形性与表面质量有着重要影响，当Mg/Si比为1.45时，热裂敏感系数相对较小，铸轧板成形性较好；随着余热轧制道次的增多及压下量的增加，铸轧板材的表面更加光亮，内部组织更加致密，硬度逐渐增加，拉伸强度逐渐增大；随着铸轧二次轧制变形量及压下率的增大，晶粒变得细小，纵断面晶粒被拉长，沿轧制方向呈长条状，铸轧板性能大幅度改善。