(1. 長安大學 材料科學與工程學院，西安 710064；
2. 中國石油管材研究院，西安 710077)
摘 要: 采用定向凝固技術制備CoCrCuFeNiTi0.8高熵合金，研究不同抽拉速率(5 μm/s、10 μm/s、25 μm/s)對合金微觀組織及力學性能的影響。使用光學顯微鏡(OM)對其微觀組織進行分析，并用X射線衍射儀(XRD)和透射電子顯微鏡(TEM)確定合金的相組成。結果表明：在所有的抽拉速率下，合金的微觀組織均為樹枝狀，隨著凝固過程的進行，枝晶取向趨于一致。當抽拉速率從5 μm/s增加到25 μm/s時，枝晶直徑從469.70 μm減小到355.48 μm，枝晶組織明顯細化，分形維數(shù)從1.5981增加到1.6158，枝晶生長更加規(guī)律，說明抽拉速率的增加使合金獲得了細密的枝晶陣列。此外，在抽拉速率為25 μm/s時，定向凝固CoCrCuFeNiTi0.8高熵合金達到了最大壓縮應變11.98%和最大抗壓強度1440.19 MPa，證明定向凝固技術能有效地改善CoCrCuFeNiTi0.8高熵合金的力學性能。
關鍵字: 高熵合金；定向凝固；一次枝晶間距；力學行為
（1. School of Material Science and Engineering, Chang’an University, Xi’an 710064, China;
2. CNPC Tubular Goods Research Institute, Xi’an 710077, China）
Abstract:The CoCrCuFeNiTi0.8 high-entropy alloy was prepared by directional solidification technology. The effects of different withdrawal rates (5？μm/s, 10？μm/s, 25？μm/s) on the microstructure and mechanical properties of the alloy were studied. The microstructures of the alloy were analyzed by optical microscope, and the phase composition of the alloy was determined by X-ray diffraction and transmission electron microscope. The results show that the microstructure of the alloy is dendritic at all withdrawal rates, the dendrite orientation tends to be uniform as the solidification process goes on. When the withdrawal rates increase from 5 μm/s to 25 μm/s, the dendrite diameter decrease from 469.70 μm to 355.48 μm, and the fractal dimension increases from 1.5981 to 1.6158. The dendrite structure is obviously refined with the increase of withdrawal rate to 25 μm/s. Moreover, the maximum compressive strength reaches 1440.19 MPa and the maximum plastic strain is 11.98%, which prove that the directional solidification technology can effectively improve the mechanical properties of the CoCrCuFeNiTi0.8 high-entropy alloy.
Key words: high-entropy alloy; directional solidification; primary dendrite arm spacing; mechanical behavior
