【作者】 芮玉龙；

【导师】 张益华；

【作者基本信息】 南京航空航天大学 ， 航空宇航制造工程， 2006， 硕士

【摘要】 Al-Mg-Sc合金有较高的强度和韧性,优良的耐蚀性和可焊性,有极好的超塑性,在汽车和航空工业有很好的应用前景。常温下该合金延伸率低,塑性加工困难。在超塑性状态下有很高的延伸率,Al-Mg-Sc合金超塑性研究成为当前研究的一个热点。本文完成的是北京航空材料研究所的一项研究课题,研究Al-6Mg-0.2Sc合金的超塑性能和胀形工艺。首先进行单向拉伸试验并进行有限元模拟,得到在450℃,以2×10-3s-1等应变速率变形,有超过300%的最大延伸率。建立半球形和盒形件的有限元模型,进行等应变速率胀形的模拟,得到压力-时间曲线。并按照仿真结果进行等应变速率胀形实验,得到的厚度分布结果与模拟值非常吻合。超塑性胀形存在厚度分布不均和空洞等缺点。本文通过正反向超塑性胀形的有限元模拟,改善半球形件的厚度分布,模拟结果显示正反胀形半球形件,球顶点处厚度减薄率降低约10%,并进行了实验验证。通过增加胀形背压,降低成形件的空洞率,结果显示背压对于空洞率的降低有比较明显的作用,适当的背压甚至可以基本消除应变不是特别大时的空洞。更多还原

【Abstract】 Al-Mg-Sc alloy has high strength, corrosion-resistance, very good welding property, especial superplasticity. In the auto and aerospace industry, there is increasing interest in fabricating complex part by superplastic forming process. The alloy exhibits small elongation on normal temperature and is hard to deform. While on superplastic condition it has large elongation and its superplasticity is a research focus.It is a subject for Beijing Aero Material Institute. In this thesis superplasticity and bulging process are researched on Al-6Mg-0.2Sc alloy. Firstly uniaxial tensile tests were carried out on dog bone specimen of the alloy. At 450℃, it exhibits more than 300% of elongation prior to fracture under const strain rate of 2×10-3s-1. Then the bulging model of hemisphere and rectangular box were built and simulated on const strain forming to research the thickness distribution. A pressure-time curve was gotten through the simulation by using the software MARC. The results of experiment which followed the curve agreed well with that of the simulation.The non-uniform thickness distribution and cavity have negative influence on the formability. Direct-reverse superplastic bulging can improve the thickness distribution greatly. The simulation of hemisphere bulging shows that the thin rate decreases about 10% with direct-reverse process. Cavity rate is decreased evidently in the bulging if back pressure is provided. Experiment shows that proper back pressure can eliminate big cavity on the condition that strain is not very high.更多还原