2198铝锂合金板材温热成形极限试验研究

发布时间：2018-06-23 08:48

  本文选题：2198铝锂合金板材 + 成形极限图(FLD)　； 参考：《南昌航空大学》2015年硕士论文

【摘要】：2198铝锂合金作为第三代铝锂合金,具有很高的比强度、比刚度和质量轻,同时具有较好的抗腐蚀性和抗疲劳性以及适宜的延展性,受到了航空工业的广泛关注。然而,该合金板材在变形过程中,变形抗力对变形温度和变形速率很敏感,室温成形性能差,导致成形困难。研究2198铝锂合金板材在温热态的成形性能,并建立其成形极限图,对我国新型航空材料板材的研究和应用都有重要意义。成形极限图(Forming Limit Diagram)也称成形极限曲线(Forming Limit Curves),通常用FLD或FLC表示。FLD或FLC是评判板材成形性能最为简便和直观的方法,可以用来预测和判断板材冲压工艺的成败,协助制定冲压工艺的参数,是有效解决冲压工艺问题的一种工具。成形极限曲线位置的高低反映了材料在各种应力状态下局部极限变形能力的大小,其位置越高则材料的成形性能越好。最近几年,FLD被国内外学者广泛应用于第一代和第二代铝锂合金板材综合成形性能评价。而对第三代铝锂合金板材FLD研究还较少。因此本文通过FLD试验的方法研究第三代铝锂合金2198铝锂合金在温热状态下的成形极限。采用北航研制的板料热成形机BCS-50AR以及网格应变自动测量系统VIALUX Guto Grid,在25℃~350℃温度范围内进行2198铝锂合金板材的成形极限试验,研究成形温度、凸模速度、应力状态对2198铝锂合金板材的成形性能的影响;借助OM、SEM、TEM等微观手段对分析2198铝锂合金板材在相应温度下的成形后的微观组织形态和变化进行了表述。研究表明成形温度对2198铝锂合金板材成形极限图影响很大,成形极限曲线的高度随成形温度的升高而提高,板材的塑性显著提高。在25℃时,凸模速度对2198铝锂合金板材成形性能影响很小,但受应力状态的影响很大;然而在300℃~350℃温度和凸模速度对2198铝锂合金板材成形性能影响增大,而受应力状态影响减小。微观组织分析表明,2198铝锂合金板材在25℃下成形时断口有明显的分层断裂的特征,并带有少量韧窝。在350℃下成形时2198铝锂合金板材断口有大量孔洞,孔洞随着变形时间的延长不断增大,同时在高温下2198铝锂合金板材会出现动态再结晶。基于成形极限试验,以M-K理论为基础,结合Swift和Hill两种屈服准则成功预测了2198铝锂合金板材在温热环境中的成形极限图,通过对比得到不同温度下基于这两种屈服准则进行的2198铝锂合金板材成形极限图预测较为理想的屈服参数,获得2198铝锂合金板材在不同温度下较为理想的成形极限图理论计算模型,对促进2198铝锂合金板材在实际生产工艺规范的制定提供理论支持。
[Abstract]:As the third generation Al-Li alloy, 2198 Al-Li alloy has high specific strength, light specific stiffness and mass, good corrosion resistance, fatigue resistance and suitable ductility. However, during deformation, the deformation resistance of the alloy sheet is sensitive to the deformation temperature and the deformation rate, and the forming performance is poor at room temperature, which leads to the difficulty of forming. It is of great significance for the research and application of new aeronautical material sheet in China to study the formability of 2198 Al-Li alloy sheet in warm state and to establish its forming limit diagram. Forming limit Diagram is also called forming limit Curves. It is usually expressed by FLD or FLC. FLD or FLC is the most convenient and intuitionistic method to evaluate sheet metal formability, which can be used to predict and judge the success or failure of sheet metal stamping process. To assist in the development of stamping process parameters, is an effective solution to stamping process problems. The position of the forming limit curve reflects the local ultimate deformation ability of the material under various stress conditions, and the higher the position, the better the formability of the material. In recent years, FLD has been widely used by scholars at home and abroad to evaluate the comprehensive forming properties of the first and second generation Al-Li alloy sheet. But the third generation aluminum lithium alloy sheet FLD research is still less. In this paper, the forming limit of the third generation Al-Li alloy 2198 is studied by means of FLD test. Using BCS-50AR and VIALUX Guto griddle, the forming limit test of 2198 Al-Li alloy sheet was carried out in the temperature range of 25 鈩，

本文编号：2056560