航空铝厚板梯温强剪切轧制多尺度宏微结构与性能演变机理研究

Aluminium alloy thick plates with light weight, high strength, good corrosion resistance and formability, as key material for integrated-structure parts, are widely used in field of aerospace. Hot rolling is the key process of preparation for thick plates, however, the conventional symmetrical rolling process causes large deformation on the surface and small deformation in the central portion of the thick plate, resulting in inhomogeneous deformation, microstructure and properties distribution through the thickness direction of the plate, which has become a barrier to the development of aerospace. Therefore, the velocity ratio and offset distance of two work rolls and temerature difference distribution of the plates are adjusted, gradient temperature shear rolling is adopted in this project to study the effects of movement asymmetry, geometry asymmetry and temperature gradient on the deformation characteristics and microstructure evolution of the plates. Combined with material properties testing experiments, the mapping relations between microstructure and mechanical properties are systemically studied for the rolling process and the following heat treatment process of the plates. On this basis, the internal relation of “deformation-microstructure-properties” for plates preparation process can be acquired. Model of properties prediction of the plate is established to study the regulatory mechanism for macro/microstructure characteristics of getting good performance. The forming/properties collaborative manufacture mechanism of the plates during rolling process and the following heat treatment process will be explored in this project. The research achievements in this project can provide theoretical guidance for the study of new technologies of rolling as well as preparation of high performance aluminium alloy thick plates.

铝合金厚板具有轻质、高强、耐腐蚀、易成形等优点，作为整体结构件关键材料，广泛应用于航空航天领域。热轧是厚板制备关键工艺过程，然而，传统对称轧制厚板表层变形大，难以渗透进心部，容易造成厚板厚度方向变形、微观组织及性能不均匀，这已经成为制约我国航空航天领域发展的瓶颈。因此，本项目拟采用梯温强剪切轧制方法，通过调整上下轧辊速度比和错位量及厚板表面和中心的温度分布，研究运动与几何双重非对称性及温度梯度对多尺度、多场耦合轧制过程厚板流变特征和微观组织演变的影响规律；结合材料性能实验，从热轧成形及热处理全过程系统研究厚板微结构与力学性能的映射规律，探明厚板制备过程“流变场-微观组织-力学性能”内在联系；建立厚板性能预测模型，探明获得优异性能的特征宏/微结构的调控机制，探索厚板在轧制成形-热处理过程形/性协同制造机理。研究成果可为该新轧制方式研究及高性能铝合金厚板制备提供理论指导。

随着航空航天工业的发展，对铝合金厚板的性能提出了更苛刻的要求（如对铝板的强度要求甚至达到700MPa以上，厚度要求甚至达到250mm以上）。然而，传统对称轧制造成轧板表面变形大和中心变形小的不均匀分布，会引起微观组织及性能不均匀。. 本项目提出了一种新型的梯温强剪切轧制技术，该技术可以有效地促进厚板心部变形，同时，解决异步轧制中厚板弯曲严重的问题，主要研究工作如下：（1）建立喷淋淬火模型，获得不同冷却方式下厚板梯度温度分布规律；研究了梯温强剪切轧制下轧板的变形特性，探究了梯度温度、异速比等工艺参数对厚板应变分布及其均匀性的影响规律，并拟合回归获得等效应变和剪切应变的灵敏度方程。（2）定义轧板的变形不对称系数和弯曲值，定量分析不同工艺参数对轧板表面变形不对称性和轧板弯曲程度的影响规律；拟合获得轧板弯曲调控方程，能有效地调控轧板的弯曲程度。（3）建立了基于元胞自动机法的微观组织演变模型，定量研究了轧制工艺参数对微观组织晶粒度及再结晶百分数的作用规律；在此基础上建立了轧制宏微观多尺度仿真模型，分析了轧制变形区微观组织分布特征。（4）开展对称轧制和梯温强剪切轧制实验，采用“网格法”对轧板变形进行测量，计算获得轧板厚向各处变形特征。通过金相实验、硬度实验，研究了对称轧制和梯温强剪切轧制对轧板微观组织和性能的影响。结果表明，上下表面的温度差和异速比都能够引入强剪切作用，多道次梯温强剪切轧制下轧板中心层的晶粒比对称轧制细化了33.5%。本项目的研究可为航空高性能铝合金厚板轧制过程中力学性能及其均匀性调控提供理论指导，对推动高性能铝合金厚板的制备技术的发展具有重要意义。