镍基单晶高温合金DD11杂晶形成的过冷度时间判定

发布时间：2018-03-07 00:28

本文选题：单晶高温合金　切入点：定向凝固　出处：《航空材料学报》2015年04期 　论文类型：期刊论文

【摘要】：以第二代镍基单晶高温合金DD11为研究对象,参照工程单晶铸件横向突变结构设计平台试样进行浇注及定向凝固实验。采用光学显微镜(OM)观察平台晶体组成及其形貌特征,并借助差热分析法(DSC)研究DD11合金的过冷效应。以过冷度时间(ΔT/v)判定杂晶形成条件,探讨平台尺寸、空间位置及抽拉速率对杂晶形成倾向性的影响机制,并研究定向凝固过程中的杂晶形成规律。结果表明,当抽拉速率为2mm/min时,外侧平台长度从8mm到26mm均未形成杂晶,而内侧平台尺寸超过18mm时开始形成杂晶,表明较大的平台试样长度和内侧位置会增加杂晶形成的倾向性。随着抽拉速率提高到6mm/min,不同尺寸的外侧平台均形成杂晶,内侧平台则在尺寸大于12mm后出现杂晶,表明增加抽拉速率均提高内外侧平台试样的杂晶形成倾向。与内侧平台试样相比,抽拉速率对外侧平台试样形成杂晶的影响更显著。平台尺寸、空间位置及抽拉速率影响了定向凝固过程中的环境温度和冷却速率,其通过产生较小过冷度时间(ΔT/v)从而增加了杂晶形成的倾向性。
[Abstract]:Taking the second generation nickel base single crystal superalloy DD11 as the research object, the casting and directional solidification experiments were carried out with reference to the engineering single crystal castings' transverse abrupt structure design platform specimen. The crystal composition and morphology of the platform were observed by optical microscope. The supercooling effect of DD11 alloy was studied by differential thermal analysis method. The formation conditions of heterocrystals were determined by the time of undercooling (螖 T / v), and the influence mechanism of platform size, space position and pull-out rate on the tendency of heterocrystalline formation was discussed. The formation of heterocrystals in the process of directional solidification is studied. The results show that when the drawing rate is 2 mm / min, no heterocrystals are formed from 8 mm to 26 mm in length of the outer platform, but the heterocrystals begin to form when the inner platform size is more than 18 mm. The results show that the larger specimen length and the inner position increase the tendency of heterocrystalline formation. With the increase of drawing rate to 6 mm / min, the heterocrystals are formed on the outer platform with different sizes, and the heterocrystals appear on the inner platform when the size is larger than 12 mm. The results show that the heterocrystalline formation tendency of the inner and outer platform samples is increased by increasing the pulling rate, and the influence of the pulling rate on the heterocrystalline formation of the outer platform specimen is more significant than that of the inner platform specimen. The space position and the pulling rate affect the ambient temperature and cooling rate during directional solidification, which increase the tendency of heterocrystalline formation by producing a small undercooling time (螖 T / v).
【作者单位】：北京航空材料研究院先进高温结构材料重点实验室;中航工业南方航空工业(集团)有限公司;北京科技大学新金属材料国家重点实验室;北京科技大学材料科学与工程学院;
【分类号】：TG132.3;TG24

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