大应变轧制AlMgSiCu合金小角度晶界、织构演变机理及其与成形性关系研究

AlMgSiCu alloy is an important material in automobile lightweight and energy conservation and emission reduction. However, how to improve the formability is one of the focus to be consideration. So, the present investigations will prepare ultrafine grained AlMgSiCu alloy sheet by a novel large strain rolling, and center on the problems of evolution of low angle grain boundaries and texture during rolling, and the relationship between these microstructures and mechanical properties, several important sites will be investigated such as the foemation and evolution mechanism of low angle grain boundaries and the second phases, evolution machanism of texture during rolling, the response of microstructures on temperature, and the effects of microstructures on mechanical properties. Based on these results, I believe it can provide more references on summarizing the deformation mechanism of large strain rolling and influence of deformation stress on shear deformation zone, grain boundary orientation, low angle grain boundary and texture. We can obtain the relationship between the mechanical properties, such as strength, toughness and fatigue, and formability for AlMgSiCu alloy sheet. Furthermore, it can help us to improve the toughening theory of AlMgSiCu alloy, and develop the forming technology of large strain rolling for AlMgSiCu alloy used in automotive field.

AlMgSiCu合金是汽车轻量化及实现节能减排的重要材料，但如何进一步提高其成形性能是当前学术界研究的重点之一。本项目拟采用自行开发的大应变轧制技术制备超细晶AlMgSiCu合金板材，并针对“大应变轧制变形过程中小角度晶界与织构演变规律、小角度晶界、织构与AlMgSiCu合金力学性能之间的关系”等科学问题，系统研究小角度晶界与第二相演变规律，AlMgSiCu合金形变织构演变机制，亚稳态组织对热场的响应行为，微观组织与力学、成形性能的耦合机制。探明AlMgSiCu合金大应变轧制变形机制，确定应力对AlMgSiCu合金剪切变形带、晶界取向、小角度晶界与织构等微观结构演变规律的影响机理，掌握具有普遍指导意义的微观结构与AlMgSiCu合金板材强度、韧性、疲劳等力学行为以及成形性的内在关系，完善AlMgSiCu合金强韧化理论，发展汽车车身用AlMgSiCu合金大应变轧制成形技术。

AlMgSiCu合金以其可快速强化、冲击韧性高、焊接性和耐蚀性优良、成形性较好等优点，成为汽车车身轻量化的首选材料，但如何进一步提高AlMgSiCu合金板材的成形性能是制约其应用的关键问题。本项目以汽车用AlMgSiCu合金为研究对象，发展了汽车车身用AlMgSiCu合金大应变轧制成形技术，开展了AlMgSiCu合金在大应变轧制变形过程中微观组织与力学性能演变规律、疲劳行为、蠕变时效成形等方面的研究，研究了Cu、Zr、Er、Mn等合金元素以及Mg/Si比等对Al-Mg-Si-Cu合金显微组织和力学性能的影响，制备出了抗拉强度达到493MPa的高强度AlMgSiCu合金薄板；探索了Al-Mg-Si-Cu合金疲劳裂纹萌生与扩展行为与疲劳特性；建立了Al-Mg-Si-Cu合金的蠕变时效成形的幂律本构方程、双曲正弦本构方程、基于晶粒尺寸的本构方程，描述了蠕变行为与温度、应力、晶粒尺寸之间的关系。本项研究工作对拓展汽车用AlMgSiCu合金塑性成形理论与成形机制具有重要的实际意义。