【作者】 王东辉；

【导师】 王向杰；

【作者基本信息】 东北大学 ， 材料工程（专业学位）， 2023， 硕士

【摘要】 2024铝合金具有密度低、强度高、耐腐蚀性强等特点,在航空航天领域得到广泛应用。段环产品作为客机的重要结构件,对产品精度以及强度都有着极高的要求,且该产品工艺路线复杂,国内尚无批产能力。为此本文采用仿真模拟、现场实验相结合的方法研究了 2024铝合金铸造、反向挤压、拉弯成型过程中的组织及性能,通过调控合金成分、均匀化退火、反向挤压、固溶处理以及拉弯成型工艺,提高了 2024铝合金材料的成型性能和零部件的尺寸精度,满足了大型高精度段环对铝合金材料及成型工艺的迫切需求。论文的主要研究内容如下:研究了不同Mn含量条件下2024铝合金铸态微观组织演变,基于晶粒尺寸及第二相分布特征,确定最优Mn元素添加质量分数为0.5%。结合热力学计算及差热分析,明确低熔点共晶相溶解温度,通过观测不同保温时间下非平衡相溶解情况,获得最佳均匀化退火工艺为495℃×16 h。基于动态材料模型,绘制了 2024铝合金热加工图,明确了 2024铝合金形变温度以及应变速率的最佳耦合区间为420～450℃和0.01～0.08 s-1。构建了 2024铝合金高温形变本构方程,并以此建立了 2024铝合金热变形响应曲面。创建了 2024铝合金反向挤压仿真模拟模型,分析了反向挤压工艺参数对型材温度以及应变速率分布的影响规律,获得了 2024铝合金最佳反向挤压工艺为铸锭温度420℃,挤压筒温度420℃,模具温度420℃,挤压杆速0.5 mm/s。系统研究了不同固溶处理工艺对2024铝合金型材显微组织和性能的影响规律,最佳固溶工艺为495℃×1.5 h,此时,型材弯曲性能最优,屈服强度和抗拉强度分别为151.9 MPa和376.4 MPa,断后延伸率为20.0%,屈强比为0.4。创建了 2024铝合金零部件拉弯仿真模拟模型,结合正交试验研究了预拉伸量、补拉伸量以及摩擦系数三个工艺参数对拉弯回弹率的影响。结果表明:随着预拉伸量和补拉伸量的增加以及摩擦系数的减小,拉弯回弹率减少,据此获得了最佳拉弯工艺为预拉伸量2%,补拉伸量2.6%,润滑介质采用摩擦系数为0.2的MoS2,回弹率为0.13。综上,本文制定了 2024铝合金大型高精度段环的成型工艺,并阐明了其对组织演变和成型性能的影响机理,对于提高2024铝合金成型性能具有一定的理论价值创建了高精准度的拉弯模拟模型,对指导段环的批量生产及应用具有重要意义。更多还原

【Abstract】 The 2024 aluminum alloy has the characteristics of low density,high strength and strong corrosion resistance,and is widely used in the aerospace field.As an important structural component of passenger aircraft,frame chord products have extremely high requirements for product accuracy and strength,and the process of this product is complex,so there is no batch production capacity in China.This paper adopts the combination of simulation and on-site tests to research the microstructure and properties of 2024 aluminum alloy during the process of casting,backward extrusion,tensile bending and forming.By adjusting the process parameters of alloy composition,homogenization annealing,backward extrusion,solid solution and tensile bending,the forming performance of 2024 aluminum alloy material and the dimensional accuracy of the components have been improved,satisfied the urgent demand for aluminum alloy material and forming processes of large high-precision frame chord.Main research contents of the paper are as follows:The microstructure evolution of as-cast 2024 aluminum alloy under different Mn content was studied.Based on grain size and distribution characteristics of the second phase,the optimal Mn addition amount was determined to be 0.5%.Combined with thermodynamic calculations and differential thermal analysis,the dissolution temperature of low melting point eutectic phases was determined and the optimal homogenizing annealing process of 495℃ × 16 h was obtained by observing non equilibrium phase dissolution under different holding times.Based on the dynamic material model,the hot working diagram of 2024 aluminum alloy was drawn,and the optimal coupling range of temperature field and strain rate field of 2024 aluminum alloy is 420～450℃ and 0.01～0.08 s-1.The high temperature deformation constitutive equation of 2024 aluminum alloy was constructed and the response surface of 2024 aluminum alloy was established.The simulation model of 2024 aluminum alloy backward extrusion was established,and the influence of the process parameters on the temperature distribution and strain rate distribution was analyzed.The optimal backward extrusion process for 2024 aluminum alloy was obtained as follows:ingot temperature 420℃,extrusion cylinder temperature 420℃,die temperature 420℃and extrusion ram speed 0.5mm/s.The influence of different solid solution treatment processes on the microstructure and properties of 2024 aluminum alloy profiles was systematically studied,and the optimal solid solution process was 495℃×1.5 h,the bending performance of the profile is optimal,with yield strength and tensile strength of 151.9 MPa and 376.4 MPa,respectively.The elongation after fracture is 20.0%,and the yield strength ratio is 0.4.A simulation model for tensile bending of 2024 aluminum alloy components was established,and the effects of three process parameters,including pre stretching,supplementary stretching,and friction coefficient on the tensile bending rebound rate of components were studied through orthogonal experiments.The result shows that:With the increase of pretension and supplementary tension and the decrease of friction coefficient,the rebound rate of bending components decreases.Therefore,the optimal stretching and bending process of 2024 aluminum alloy frame chord is obtained as pre stretching 2%,supplementary stretching 2.6%,lubrication medium adopting MoS2 with friction coefficient of 0.2,and rebound rate of 0.13.In summary,the forming process of 2024 aluminum alloy large and high precision frame chord is formulated in this paper,and its influence mechanism on the microstructure evolution and forming performance is expounded,which has certain theoretical value for improving the forming performance of 2024 aluminum alloy.A high-precision tensile bending simulation was established which is of great significance for guiding the application and mass production of 2024 aluminum alloy frame chord.更多还原