大型飞机轮毂用铝合金热变形及模锻强韧化机制研究

The proposed research is based on the demanding needs of the C919 commercial aircraft which focuses on the hot-deformation behavior and strengthening-toughening mechanism of Al alloy for commercial aircraft wheel by die-forging thermalmechanical treatment. Firstly, based on the related stress-strain-temperature change of 2A14 Al alloy under hot simulation, the thermal deformation constitutive relationship model and thermal deformation operation map can be developed. Secondly, through the hot-deformation of reduced ratio sample of the 2A14 Al alloy, the hot-deformation behavior and microstructure evolution during hot-deformation process can be understood; the deformation strain and flow of the material can be observed; the process parameter for different deformation stages of the reduced ratio sample can be determined; the theory of multi-field cooperating control during hot-deformation can be established; the method for formation and property control of 2A14 Al alloy can be defined. Then, through the die-forging thermalmechanical treatment of the 2A14 Al alloy, the precipitating process during the aging of the treatment can be understood; the model of precipitation and strengthening-toughening mechanism of the alloy can be built. All of the above research provides a theoretical base for the optimization of forming process and microstructure-property control of the 2A14 Al alloy, through which eventually, a technical prototype of hot-deformation and thermalmechanical treatment multi-field cooperating strengthening and toughening mechanism of Al alloy for commercial aircraft wheel can be formed.

本项目依据C919大飞机的需求，研究大型飞机轮毂用铝合金的热变形行为及模锻形变热处理强韧化机制。首先采用热压缩实验研究2A14铝合金热变形时的应力-应变-温度的关系，建立热变形本构关系数学模型和热变形加工图。其次对大型飞机轮毂的缩比件进行热变形实验研究，探明缩比件的热变形行为及热变形过程中的组织演化规律，及变形过程中材料的流动规律和流线分布特征,确定大型飞机轮毂用2A14铝合金缩比件在不同变形阶段的具体工艺参数，建立铝合金热变形多场协作控制理论，确定轮毂用铝合金的成型与控制方法。然后采用模锻形变热处理的方法对2A14铝合金进行热处理，研究形变热处理过程中沉淀相的析出过程，建立时效析出相与合金的强韧化关系模型。从而为优化轮毂用铝合金成形工艺以及调控其组织与性能提供理论依据，最终形成大型飞机轮毂用铝合金热变形及热处理多场协作强韧化的技术原型。

起落架轮毂作为飞机起落架和制动系统间的桥梁，属于机轮刹车制动系统的关键部件，承载飞机起飞、着陆、地面滑行和停放过程中较大的载荷，并承受飞机制动过程带来的巨大冲击，它的强度和刚度直接影响到飞机的起落安全，是飞机重要的安全功能部件。对大飞机轮毂，不仅要有优异的力学性能、耐疲劳和抗冲击性能，还需要有较好的高温蠕变强度，以满足高速制动时所产生热量对轮毂性能的影响，本研究以大飞机轮毂用2A14铝合金为研究对象，对该合金的热塑性成型特点及热处理强化机理进行了研究。结果表明：2A14铝合金在热变形过程中，合金主要的软化机制是动态回复。随着变形条件由350~430℃/0.005~0.1s-1过渡到450~480℃，0.001~0.05s-1，动态回复的程度增大；晶粒由均匀的动态回复晶粒结构转变为连续动态再结晶晶粒。2A14铝合金机轮轮毂锻造成形的适宜工艺为：恒应变速率0.01s-1，坯料温度为420℃，摩擦系数为0.5，采用该工艺可有效降低材料变形抗力，获得流线分布合理，变形组织均匀，成形完好的机轮轮毂。2A14铝合金经50%变形量锻造后的最佳T8形变热处理制度为：经10%预变形后在170℃温度下保温14h，此时，合金抗拉强度、屈服强度和延伸率分别为537MPa、500MPa和9.67%。