高强铝合金大型薄壁件成形过程组织和应力演变模型及变形控制

High strength aluminum alloy has been widely used in manufacturing aerospace key components. The precision forming, toughening and deformation control of complex components made of such alloy is the key of the aerospace key components manufacturing. Based on these large thin wall complex high-strength aluminum alloy components, the applicant team carry out the integrated manufacturing theory and technology research in the casting, heat treatment and machining. Design idea of heat transfer and the control theory of interface heat transfer coefficient with equal Biot number are proposed in the condition of variable cross section. The quasi-synchronous solidification and the quasi-synchronous quenching technology of irregular body section are obtained. All these results ensure the uniformity of the microstructure and minimum residual stress during the process of casting and heat treatment. The profile simulation solution of partial differential equation is proposed, and the analytical model of internal and external heat transfer coefficient is derived. The basic database for ZL205A high strength aluminum alloy is constructed, and a multi-field coupling model for the evolution of structure and shape of the manufacturing process of large thin wall complex structures is built. Microstructure evolution simulation and deformation prediction in the manufacturing process of large thin wall complex ZL205A high strength aluminum alloy component can be achieved. The change rule of the shape and size and the deformation mechanism during the component manufacturing process are clarified. The corresponding relationship between microstructure and mechanical properties and toughening mechanisms are revealed. The control technology of performance and shape during the whole process of casting, heat treatment and machining of the above components can be achieved, which can guide the precision manufacturing of this kind of key components for aerospace and provide a way for the integration manufacturing of similar components in other fields. The obtained control theory of interface heat transfer coefficient with equal Biot number and its inverse problem analysis results have enriched the heat transfer theory.

高强铝合金广泛用于航空航天关键件制造，此类合金复杂构件成形、强韧化及变形控制是航天关键件制造瓶颈。申请团队以高强铝合金大型薄壁复杂构件为背景，开展铸造、热处理、机加一体化制造理论与技术研究：提出等Biot数下换热设计思想与界面换热系数调控理论，形成差异壁厚准同步凝固和准同步淬火技术，保证铸造和热处理过程构件内部组织均一和残余应力最小；提出仿型积分方法，导出构件内外传热系数解析模型；构建ZL205A高强铝合金基础数据库，建立多场下复杂构件制造过程组织与形状尺寸演变模型，实现ZL205A合金大型薄壁复杂构件制造过程组织演变与变形预报，阐明构件制造过程形状尺寸变化规律与变形机理，揭示组织与力学性能对应关系及强韧化机制，形成上述构件铸造、热处理和机加全过程控性与控形技术，指导此类关键件精确制造，亦为其它领域类似构件一体化制造提供思路；形成的等Biot数下换热系数调控及其反问题解析丰富了传热学理论。

高强铝合金大型薄壁件制造过程十分复杂，涉及铸造、固溶淬火、机加工、时效等步骤，制造过程容易发生变形而导致工件报废。针对高强铝合金大型薄壁件制造过程中变形超差的问题，开展高强铝合金薄壁件成形全流程变形控制研究。项目研究过程中，重点开展并完成了（1）ZL205A高强铝合金铸造凝固过程传热、流变特性、热处理本构方程及应力与组织演变方面的研究；（2）等Biot（简记为Bi）数下准同步凝固及淬火变形控制理论、数值模拟及试验验证；（3）ZL205A铝合金制造全流程组织与应力演变多尺度模拟；（4）ZL205A铝合金大型薄壁件制造全流程应力传递与一体化模拟。取得以下重要成果：（1）基于Bi数概念，提出了差异壁厚准同步凝固/准同步加热与冷却思想，创立差异壁厚/差异结构构件准同步凝固和淬火微变形控制的等Bi数理论，实现ZL205A高强铝合金大型薄壁件制造过程中变形控制；（2）基于等Bi数准同步凝固和淬火微变形控制理论，完成了差异壁厚试件淬火变形模拟及试验设计，形成基于等Bi数理论差异壁厚构件准同步凝固与淬火变形控制技术，变形减少50%以上，成功应用于高强铝合金薄壁件的制造中；（3）建立了ZL205A合金成型过程中组织与应力演变的多尺度模型，实现ZL205A合金从微观到宏观各尺度对组织演变与应力演变模拟；（4）提出ZL205A高强铝合金大型薄壁件全流程各步骤应力传递方法，实现构件制造全流程应力演变模拟。本项目研究找到了铝合金大型薄壁件成形过程变形的根本原因，基于传热学理论，创新地提出铝合金薄壁件变形控制方法，形成相应的工艺技术，成功实现铝合金大型薄壁构件微变形控制，具有重大的科学意义和工程应用价值。