稀土钇、钪及时效工艺对A357合金组织与性能的影响

发布时间：2017-12-27 17:10

本文关键词：稀土钇、钪及时效工艺对A357合金组织与性能的影响　出处：《南昌大学》2015年硕士论文　论文类型：学位论文

【摘要】：A357合金是一种典型的亚共晶Al-Si-Mg合金,由于它有优良的铸造性能和力学性能,被广泛应用于航空航天、汽车等工业领域。本文以A357合金为研究对象,利用金相显微镜、布氏硬度机、万能电子拉伸机、XRD和扫描电镜等分析测试仪器,通过在熔体中添加Al-5Ti-B、Al-10Sr、微量Sc和Y,研究细化变质剂对合金组织性能的影响,以期通过优化熔体细化变质工艺,改善合金组织与力学性能。研究表明:0.3%Y、0.3%Sc均能明显细化合金的α-Al晶粒,并改善共晶硅的形态,但Y的细化效果不及等量Sc;0.3%Y、0.2%Sc能够明显改变共晶硅的形貌,具一定的变质效果,但Y对共晶硅的变质效果强于Sc。Y提高合金铸态力学性能幅度也要大于Sc。将Y与传统Al-5Ti-B+Al-10Sr细化变质联合添加,三者之间未见相互干扰作用。与传统Al-5Ti-B+Al-10Sr细化变质效果相比,添加稀土Y使α-Al二次枝晶间距从15.4 um变成14.1 um,小幅增加细化效果;添加稀土Y明显强化对共晶硅的变质效果;在传统Al-5Ti-B+Al-10Sr细化变质处理的基础上添加稀土Y,合金抗拉强度和延伸率分别提升了4.5%和0.5%。在添加Al-5Ti-B和Sr的基础上,添加稀土Y后,并未明显改变合金的最佳固溶温度和时效温度,其最佳的时效工艺为548oC固溶处理12 h+175oC时效6 h。与经传统Al-5Ti-B+Al-10Sr细化变质处理的合金相比,再添加稀土Y使合金热处理后的抗拉强度提升2.1%、延伸率提升29%。
[Abstract]:A357 alloy is a typical hypoeutectic Al-Si-Mg alloy. Because of its excellent casting and mechanical properties, it is widely used in aerospace, automobile and other industrial fields. In this paper, A357 alloy as the research object, by using metallurgical microscope and Brinell hardness tester, universal electronic tensile machine, XRD and scanning electron microscopy analysis test instrument, by adding Al-5Ti-B, Al-10Sr, Sc and Y trace in the melt, of refinement modifier on Microstructure and properties of the influence, in order to optimize the melt modification process to improve the microstructure and mechanical properties of the alloy. The results show that 0.3%Y and 0.3%Sc can significantly refine the grain of alpha -Al and improve the morphology of eutectic silicon, but the refinement effect of Y is not equal to that of Sc. 0.3%Y and 0.2%Sc can obviously change the morphology of eutectic silicon and have certain modification effect, but Y has greater modification effect on eutectic silicon than Sc. The increase of the mechanical properties of the cast alloy by Y is greater than that of Sc. The combination of Y and traditional Al-5Ti-B+Al-10Sr was added, and there was no mutual interference between the three. Compared with the traditional Al-5Ti-B+Al-10Sr modification effect of refinement, adding Y to a -Al two primary dendrite spacing from 15.4 um to 14.1 um, a small increase in refining effect; adding Y significantly enhanced modification effect on eutectic silicon; adding Y based on traditional Al-5Ti-B+Al-10Sr grain refinement and modification on the tensile strength and elongation of the alloy. Up to 4.5% and 0.5%. On the basis of adding Al-5Ti-B and Sr, adding rare earth Y did not significantly change the best solution temperature and aging temperature of the alloy. The best aging process was 548oC solid solution treatment 12 h+175oC aging 6 h. With the addition of rare earth Y, the tensile strength of the alloy after heat treatment is increased by 2.1% and the elongation increase by 29%, compared with the alloy refined by the traditional Al-5Ti-B+Al-10Sr.
【学位授予单位】：南昌大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG146.21;TG166.3

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