抽拉速率对 Co-Al-W 基单晶高温合金凝固行为的影响

The influences of withdrawal rate (50−300 μm/s) on dendrite arm spacing, microstructure, microsegregation behavior and solidification characteristic temperatures of Co-7Al-8W-1Ta-4Ti single crystal superalloy were systematically studied in this investigation. Meanwhile, the average liquid diffusion coefficient of single crystal superalloy was calculated based on Kurz-Fisher equation. The results indicate that the primary and secondary dendrite arm spacing is significantly refined with increasing withdrawal rate. And the average liquid diffusion coefficient of Co-7Al-8W-1TA-4Ti alloy is close to that of first-generation Ni based single crystal superalloy, and lower than that of CoNi based single crystal superalloy with high mole fraction ratio of Al and W, but higher than that of second-generation Ni based single crystal superalloy. Moreover, the microsegregation degree of Al, W, Ta and Ti elements and volume fraction of the interdendritic precipitations firstly increase (50−200 μm/s) and then decrease (200 − 300 μm/s) with increasing withdrawal rate. In addition, with increasing withdrawal rate, the liquidus temperature basically remains unchanged, while the solidus temperature firstly decreases (50−100 μm/s) and then remains unchanged (100−300 μm/s). In addition, the withdrawal rate does not change the solidification path of experimental alloy.