流变成形高强合金的成分设计与特征微结构调控

High strength aluminum alloys are key materials for rheoforming to realize “replacing forging by casting”. Rheoforming is an available processing technology for high strength aluminum alloys to produce complex shape components. However, high strength aluminum alloys used in rheoforming are standard alloys. For these alloys, there are high contradictions between rheoformability and potential of heat treatment, and between strength and ductility of rheoformed components. The present project will try to resolve the two contradictions by creative alloys design and adjusting characteristic microstructures by using of experiments, first principle calculation and CALPHAD approach. .The effects of main alloying elements and their matching and microalloying elements under rheoforming conditions will be deeply investigated. The design of main alloying elements will be implemented according to improving rheoformability and reducing amount of residual solidified phases, and the design of microalloying elements will be carried out by reducing high energy phase interface and modifying residual solidified phases. Based on those, critical criteria for designing high strength aluminum alloys used for rheoforming will be developed. .Formation and evolution mechanisms of residual solidified phases will be deeply investigated. The synergistic effects of residual solidified phases, precipitates and dispersoids on mechanical properties will be determined. Based on those, the adaptive microstructure model of multi-scale and multi-phase which can result in high strength and high toughness will be developed..Finally, Al-Cu-Mg-Mn-Si alloy designed for rheoforming withσb ≥450MPa、σs ≥350MPa、δ ≥12% will be developed. The present project will provide theoretical guidance for the design of alloys used for rheoforming with comprehensive mechanical properties that reach the level of forging.

高强铝合金是流变成形实现“以铸代锻”的关键材料，流变成形是高强铝合金实现复杂结构件近净成形的有效途径。但标准牌号高强铝合金的流变成形工艺性能与热处理强化潜力之间的矛盾突出，成形件强度和塑性之间的矛盾突出。本项目通过创新设计合金成分和调控特征微结构解决上述矛盾。.研究主合金元素总量及其匹配以及微合金化元素的作用规律，以提高工艺性能和减少残余结晶相为目标设计合金主成分，以降低高能界面和变质残余结晶相为目标设计微合金化成分，建立流变成形专用高强铝合金的成分设计准则；研究残余结晶相的形成机理和演变规律，探明残余结晶相、沉淀相、弥散相对综合力学性能的协同作用，确定流变成形条件下高强高韧的多尺度多相适配微结构模式；开发出σb ≥450MPa、σs ≥350MPa、δ ≥12%高综合性能的流变成形专用高强Al-Cu-Mg-Mn-Si合金原型，为流变成形材料的综合力学性能达到锻件水平提供理论指导。

高强铝合金是流变成形实现“以铸代锻”的关键材料，流变成形是高强铝合金实现复杂结构件近净成形的有效途径。但标准牌号高强铝合金的流变成形工艺性能与热处理强化潜力之间的矛盾突出，成形件强度和塑性之间的矛盾突出。本项目通过创新设计合金成分和调控特征微结构解决上述矛盾。.本项目基于轻量化领域的国家重大需求，主要研究内容包括：（1）合金元素对流变成形工艺性能的影响规律和机理；（2）合金元素对结晶相和铸态力学性能的影响规律和机理；（3）合金元素对残余结晶相、多元弥散相的影响规律和机理；（4）高强高韧的多尺度多相适配微结构模式设计。.采用物理实验、第一性原理和相图计算，结合DSC、XRD、SEM、TEM、HRTEM等特征微结构-综合性能关联表征方法开展研究内容，建立了流变成形专用高强铝合金的成分设计准则11项；探明了Al-Cu-Si高强高韧的多尺度多相适配微结构模式，7项多尺度微结构特征；有效的微合金化元素包括Mo、V、Er和Y等；建立了以第一性原理计算、相图计算、流变成形二步热力学计算方法为主体的材料计算模拟平台；开发出一种具有自主知识产权的水平转移式半固态浆料制备方法；开发出流变成形专用高强韧 Al-Cu-Si-Mg-Mn铸造铝合金原型，目前的力学性能可以达到σb ≥400MPa、σs ≥320MPa、δ≥10%。.流变成形专用高强铝合金的成分设计准则，综合解决了工艺性能和热处理强化能力间的矛盾、强度和塑性间的矛盾，是对现有成分设计准则的补充和提升，为开发新型的流变成形专用高强铝合金提供了重要的理论基础。高强高韧的多尺度多相适配微结构模式为解决流变成形材料强度和塑性间的突出矛盾提供重要的理论指导。Al-Cu-Si-Mg-Mn铸造铝合金具有尤其的综合力学性能，具有良好的铸造工艺性能，可应用于流变铸造、重力铸造、反重力铸造、挤压铸造生产高安全性高综合性能的结构类铸件。