铝合金扁宽薄壁型材蝶形模挤压变形行为与模具优化设计方法研究

Butterfly die extrusion technology is a recently developed and advanced extrusion forming technology for hollow aluminum profiles, which has the advantages of improving the metal flow and reducing the breakthrough pressure during the extrusion, so this technology has great potentials in the production of flat-wide and thin-walled aluminum alloy profiles. However, due to the severe lack of of systematic research on butterfly die design methods and rules, extrusion deformation behavior, etc., the application of butterfly die has been always limited in the production of the aluminum alloy profiles with complex cross-sections. Therefore, focusing on 3-5 typical flat-wide and thin-walled aluminum alloy profiles, the metal flow rules and material volume distribution, extrusion temperature rise, etc. will be investigated during the butterfly die extrusion in this proposal, and the influences of die structures (e.g. arched shape bridge, multiple feeder, etc.) and process parameters (e.g. billet temperature taper, extrusion speed, etc.) on extrusion process will be obtained. The experimental setup will be designed to study the welding behavior and the formation mechanism of welding lines will be revealed during butterfly die extrusion, and finally the relationship between of welding quality and key die structures and process parameters will be built. The die optimization method based on mesh deformation technology will be used to optimize the butterfly dies. Consequently, this proposal will provide theoretical and technical supports for the determination of process parameters, the design of extrusion dies, and the control of the product quality during butterfly die extrusion for the flat-wide and thin-walled aluminum alloy profiles. Therefore, the proposal has important theoretical significance and engineering application values.

蝶形模挤压技术是一种新型的空心铝型材挤压成形技术，具有改善材料流动性和降低突破压力的优点，在扁宽薄壁铝型材挤压生产中具有很大的潜在技术优势。但目前蝶形模的设计方法与规范、挤压变形行为等方面研究的缺乏，制约了该技术在复杂截面铝型材挤压中的应用。以3-5种具有典型断面形状的扁宽薄壁铝型材为例，通过研究其蝶形模挤压全过程中的材料流动规律与体积分配原理、挤压温升规律等基础理论问题，揭示拱形分流桥、分层导流等蝶形模结构参数和铸锭梯温、挤压速度等工艺参数对挤压过程的影响规律；构建铝型材蝶形模挤压焊合机理实验研究平台，建立焊合质量与关键工艺参数和模具结构参数之间的关系模型，揭示蝶形模挤压焊合线的形成机理；研究基于网格变形技术的模具结构优化设计方法，实现蝶形模具结构的多目标优化设计，为扁宽薄壁铝型材蝶形模挤压工艺制定、模具结构设计和型材质量控制提供理论支撑和技术支持，具有重要的理论意义和工程应用价值。

蝶形模挤压技术是一种新型的空心铝型材挤压成形技术，具有改善材料流动性和降低突破压力的优点，在扁宽薄壁铝型材挤压生产中具有很大的潜在技术优势。但目前蝶形模的设计方法与规范、挤压变形行为等方面研究的缺乏，制约了该技术在复杂截面铝型材挤压中的应用。为此，本项目开展了铝合金扁宽薄壁型材蝶形模挤压变形行为与模具优化设计方法研究，其主要研究内容和重要成果为：.（1）研究了高速列车用6N01、7N01等铝合金材料的热流变行为，得到了考虑应变补偿的双曲正弦本构模型的材料参数。在此基础上，建立了6N01和7N01等铝合金材料的热加工图，为型材挤压工艺和模具结构设计提供了重要基础数据。.（2）阐明了铝合金材料的固态焊合机制，发现并解释了晶粒跨越焊合界面生长的现象，并提出了一种具有普适性的三维挤压过程焊合质量的评价方法。.（3）确定了高强韧铝合金材料发生动态再结晶的类型，阐明了晶粒异常长大及表层粗晶环的发生机理，建立了考虑动态再结晶、静态再结晶及晶粒长大行为的热变形过程再结晶组织演变模型。.（4）发展了蝶形模挤压、扁挤压筒挤压以及宽展挤压等新型挤压技术及其模具设计理论与方法，优化设计并研制出系列大型精密挤压模具及其铝型材，提高了复杂断面铝合金型材成品率。.研究成果对于扁宽薄壁铝型材蝶形模挤压工艺制定、模具结构设计和型材质量控制提供理论支撑和技术支持，具有重要的理论意义和工程应用价值。