(1. 蘭州理工大學 省部共建有色金屬先進加工與再利用國家重點實驗室，蘭州 730050；
2. 蘭州理工大學 材料科學與工程學院，蘭州 730050；
3. 蘭州理工大學 白銀新材料研究院，白銀 730900)
摘 要: 利用場發(fā)射掃描電子顯微鏡(FESEM)研究了隨時效時間和時效溫度的改變，合金微觀組織、γ′相的粗化行為和二次相析出的變化，分析合金元素對Co-8.8Al-9.8W-2X(X為Mo、Nb、Ta、Ti和Ni，摩爾分數(shù)，%)合金中γ′相粗化行為的影響。結(jié)果表明：5種合金γ′相尺寸均隨時效溫度的提高和時效時間的延長而長大，且γ′相尺寸的變化滿足LSW粗化理論，但時效過程中γ′相的體積分數(shù)明顯減少；時效過程中，2Mo和2Ni合金γ′相形貌出現(xiàn)球化現(xiàn)象，而2Nb、2Ta和2Ti合金仍保持較高的立方度；5種合金隨時效溫度的提高，粗化速率變化趨勢不同，930 ℃時的粗化速率比870 ℃時的高很多；2Ni、2Ta和2Ti合金粗化速率常數(shù)在3種時效溫度下均較低，但在930 ℃時，2Ta和2Ti合金粗化速率常數(shù)上升明顯；合金二次相主要在晶界析出，且以DO19-Co3W相為主，2Ti合金晶界處析出鏈狀的二次相，經(jīng)EDS分析，該相為CoAl相，此相在晶界處形貌不規(guī)則，在晶內(nèi)呈針狀或不規(guī)則狀。
關(guān)鍵字: 合金元素；Co-8.8Al-9.8W高溫合金；γ′相；粗化行為；二次相
（1. State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals, Lanzhou University of Technology, Lanzhou 730050, China;
2. School of Materials Science and Engineering, Lanzhou University of Technology, Lanzhou 730050, China;
3. Baiyin Research Institute of Novel Materials, Lanzhou University of Technology, Baiyin 730900, China）
Abstract:With the changing of aging time and temperature, the microstructure, coarsening behavior of γ′ phase and secondary phase precipitation of Co-8.8Al-9.8W-2X (X is Mo, Nb, Ta, Ti and Ni, mole fraction, %) superalloys were investigated by EFSEM. The effect of alloying elements on the coarsening behavior of γ′ phase in the superalloys was analyzed. The result shows that the size of γ′ phase increases with the increase of aging temperature and aging time in five alloys, and size of γ′ phase follows LSW theory, but the volume fraction of γ′ phase decreases obviously during aging process. The spheroidization of the γ′ phase morphology of 2Mo and 2Ni alloys is observed during aging, while the cubic degrees of 2Nb, 2Ta and 2Ti alloys remain high. The coarsening rate curves of the five alloys are valley-shaped with increasing aging temperature, the coarsening rate is much higher at 930 ℃ than that at 870 ℃. The coarsening rate constants of 2Ni, 2Ta and 2Ti alloys are lower at three aging temperatures, but at 930 ℃, the coarsening rate constants of 2Ta and 2Ti alloys increase significantly. The secondary phase mainly precipitates at grain boundary, and DO19-Co3W phase is dominant, 2Ti alloy precipitates chained-like CoAl phase at grain boundary determined by EDS, which is irregular at grain boundary and needle like or irregular inside grain.
Key words: alloying elements; Co-8.8Al-9.8W superalloy; γ′ phase; coarsening behavior; secondary phase
