本文選題：單晶高溫合金　切入點：定向凝固　出處：《航空材料學報》2015年04期 　論文類型：期刊論文

【摘要】：以第二代鎳基單晶高溫合金DD11為研究對象,參照工程單晶鑄件橫向突變結(jié)構(gòu)設計平臺試樣進行澆注及定向凝固實驗。采用光學顯微鏡(OM)觀察平臺晶體組成及其形貌特征,并借助差熱分析法(DSC)研究DD11合金的過冷效應。以過冷度時間(ΔT/v)判定雜晶形成條件,探討平臺尺寸、空間位置及抽拉速率對雜晶形成傾向性的影響機制,并研究定向凝固過程中的雜晶形成規(guī)律。結(jié)果表明,當抽拉速率為2mm/min時,外側(cè)平臺長度從8mm到26mm均未形成雜晶,而內(nèi)側(cè)平臺尺寸超過18mm時開始形成雜晶,表明較大的平臺試樣長度和內(nèi)側(cè)位置會增加雜晶形成的傾向性。隨著抽拉速率提高到6mm/min,不同尺寸的外側(cè)平臺均形成雜晶,內(nèi)側(cè)平臺則在尺寸大于12mm后出現(xiàn)雜晶,表明增加抽拉速率均提高內(nèi)外側(cè)平臺試樣的雜晶形成傾向。與內(nèi)側(cè)平臺試樣相比,抽拉速率對外側(cè)平臺試樣形成雜晶的影響更顯著。平臺尺寸、空間位置及抽拉速率影響了定向凝固過程中的環(huán)境溫度和冷卻速率,其通過產(chǎn)生較小過冷度時間(ΔT/v)從而增加了雜晶形成的傾向性。
[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).
【作者單位】： 北京航空材料研究院先進高溫結(jié)構(gòu)材料重點實驗室;中航工業(yè)南方航空工業(yè)(集團)有限公司;北京科技大學新金屬材料國家重點實驗室;北京科技大學材料科學與工程學院;
【分類號】：TG132.3;TG24

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本文編號：1577187