(1. 兰州理工大学 省部共建有色金属先进加工与再利用国家重点实验室，兰州 730050；
2. 兰州理工大学 材料科学与工程学院，兰州 730050；
3. 兰州理工大学 白银新材料研究院，白银 730900)
摘 要: 利用场发射扫描电子显微镜(FESEM)研究了随时效时间和时效温度的改变，合金微观组织、γ′相的粗化行为和二次相析出的变化，分析合金元素对Co-8.8Al-9.8W-2X(X为Mo、Nb、Ta、Ti和Ni，摩尔分数，%)合金中γ′相粗化行为的影响。结果表明：5种合金γ′相尺寸均随时效温度的提高和时效时间的延长而长大，且γ′相尺寸的变化满足LSW粗化理论，但时效过程中γ′相的体积分数明显减少；时效过程中，2Mo和2Ni合金γ′相形貌出现球化现象，而2Nb、2Ta和2Ti合金仍保持较高的立方度；5种合金随时效温度的提高，粗化速率变化趋势不同，930 ℃时的粗化速率比870 ℃时的高很多；2Ni、2Ta和2Ti合金粗化速率常数在3种时效温度下均较低，但在930 ℃时，2Ta和2Ti合金粗化速率常数上升明显；合金二次相主要在晶界析出，且以DO19-Co3W相为主，2Ti合金晶界处析出链状的二次相，经EDS分析，该相为CoAl相，此相在晶界处形貌不规则，在晶内呈针状或不规则状。
关键字: 合金元素；Co-8.8Al-9.8W高温合金；γ′相；粗化行为；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
