2195铝锂合金热加工力学行为及微观组织演变规律研究

发布时间：2017-12-28 07:16

本文关键词：2195铝锂合金热加工力学行为及微观组织演变规律研究　出处：《重庆大学》2015年硕士论文　论文类型：学位论文

【摘要】：2195铝锂合金是1989年开发的第三代新型铝锂合金。该合金具有密度低、高强度、比刚度高以及良好的耐热性和抗腐蚀性能等特点,被认为是航空航天工业中的理想结构材料。本文通过在Gleeble-3500热模拟机上对均匀化后的2195铝锂合金试样进行单道次变形量为60%的圆柱体单向压缩与平面应变压缩实验,其热变形温度为400℃,420℃,440℃,460℃,480℃,500℃,应变速率为0.01s-1,0.1s-1,1s-1,10s-1。研究了该合金在两种压缩方式下的高温流变行为,包括流变应力、本构关系、微观组织演变和加工图,并对比分析了它们在两种压缩方式下的差异,为工厂的实际生产工艺提供了一定的理论指导意义。主要研究结果如下:2195铝锂合金在圆柱体单向压缩与平面应变压缩过程中均具有稳态流变特征和动态软化趋势。且当应变速率不变时,随着温度的升高,材料的峰值应力和峰值应变均变小。建立了该合金在两种压缩方式下的流变应力本本构方程,得出了2195铝锂合金两种压缩方式下的热激活能,其分别为圆柱体单向压缩条件下为190.27KJ/mol,平面应变压缩条件下为216.56 KJ/mol,简要分析了其激活能差异的原因。2195铝锂合金两种压缩方式下热变形过程中的金相微观组织观察表明在420℃以下呈现动态回复特征,在440℃以上则以动态再结晶为主要特征;EBSD分析结果表明随着Z参数的降低(即温度升高或应变速率降低),合金内部小角度晶界逐渐减少,大角度晶界逐渐增加,软化机制由动态回复向动态再结晶转变。获得了2195铝锂合金两种压缩方式下不同应变的热加工图与整体加工图。热加工图表明应变对2195铝锂合金两种压缩方式下的流变失稳区都有较大影响,随着应变的增加,流变失稳区逐渐明显增大,而安全加工区域逐渐减小,功率耗散系数变化不大,即应变对功率耗散系数的影响较小。对整体加工图的差异区域进行微观组织进行对比分析,表明平面应变压缩相比圆柱体单向压缩的组织更能准确的反应实验室条件下真实的加工过程。综合考虑两种压缩方式下的各变形条件的影响,并结合两种压缩方式下加工图的特点,得出2195铝锂合金的安全加工区域为:温度范围在440℃-500℃之间,应变速率范围在0.01s-1-0.1s-1之间。
[Abstract]:2195 Al Li alloy is the third generation of new type Al Li alloy developed in 1989. The alloy is characterized by low density, high strength, high specific stiffness, good heat resistance and corrosion resistance. It is considered as an ideal structural material in aerospace industry. Based on Gleeble-3500 hot simulator for single pass deformation of 60% cylinder compression and plane strain compression tests of 2195 aluminum lithium alloy samples after homogenization, the thermal deformation temperature of 400 DEG C, 420 C, 440 C, 460 C, 480 C, 500 C, the strain rate of 0.01s-1,0.1s-1,1s-1,10s-1. Study on the alloy in two kinds of compression under high temperature rheological behavior, including rheological stress, constitutive relation, microstructure evolution and processing map, and analyzed them in two compression mode difference, provides certain theoretical guidance for the actual production process of the factory. The main results are as follows: 2195 Al Li alloy has steady state rheological characteristics and Dynamic Softening Trend during the unidirectional compression and plane strain compression of the cylinder. When the strain rate is constant, the peak stress and peak strain of the material become smaller with the increase of temperature. Founded by the alloy in the two kinds of compression stress under this constitutive equation, obtained 2195 aluminum lithium alloy two kinds of compression of the thermal activation energy, which are respectively a cylinder one-way compression under the condition of 190.27KJ/mol, the plane strain compression under the condition of 216.56 KJ/mol, a brief analysis of the causes of the differences in the activation energy. The deformation microstructure of 2195 aluminum lithium alloy two kinds of compression heat present observation shows that dynamic recovery at 420 Deg. C, at 440 DEG by dynamic recrystallization is the main characteristic; EBSD analysis results show that with decreasing Z parameters (i.e., temperature or strain rate), alloy internal small angle the grain boundary decreases gradually, high angle grain boundary increases gradually, the softening mechanism of dynamic recrystallization by dynamic recovery to change. The thermal processing diagram and whole processing diagram of different strain of 2195 aluminum lithium alloy under two compression methods were obtained. Thermal processing shows that the strain on the rheology of 2195 aluminum lithium alloy two kinds of compression under the unstable region have a greater impact, with the increase of the strain, flow instability region gradually increased, and the safe processing region gradually decreases and the power dissipation coefficient changes little, the strain has little effect on power consumption dispersion coefficient. The microstructure of the difference area of the whole processing map is compared and analyzed. It shows that the plane strain compression is more accurate than the cylinder unidirectional compression structure to react to the real machining process under laboratory conditions. Considering the influence of all the deformation conditions under the two compression modes, and combining the characteristics of the two processing methods, it is concluded that the safe processing area of the 2195 aluminum lithium alloy is: the temperature range is between 440 -500 and the strain rate range is between 0.01s-1-0.1s-1.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG146.21

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