(1. 哈爾濱工業(yè)大學 金屬精密熱加工國家級重點實驗室，哈爾濱 150001；
2. 哈爾濱工業(yè)大學 材料科學與工程學院，哈爾濱 150001；
3. 山西機電職業(yè)技術學院 機械工程系，長治 046011)
摘 要: 通過XRD、OM、SEM和TEM分析鑄態(tài)合金組織，并進行800~850 ℃、250~325 MPa范圍內的高溫蠕變性能測試，以探究鑄態(tài)Ti-46Al-6Nb-2.5V-0.2B4C合金的顯微組織及高溫蠕變變形與斷裂行為。結果表明：該鑄態(tài)合金為全層片組織，多種形態(tài)的TiB于片層團內部及晶界處彌散析出，而C原子則固溶于基體中。根據(jù)蠕變性能數(shù)據(jù)計算， Ti-46Al-6Nb-2.5V-0.2B4C合金在測試范圍內的應力指數(shù)n和蠕變激活能QC分別為5.71和313.316 kJ/mol。該合金的蠕變變形主要由位錯攀移與孿生變形控制，并且蠕變誘導產生動態(tài)回復與動態(tài)再結晶，發(fā)揮軟化作用。同時，蠕變過程中Ti2AlC會在TiB與基體的界面處動態(tài)析出，并與TiB保持 和 位向關系。此外，該合金的蠕變斷裂機制主要為孔洞的萌生和聚合以及裂紋的擴展。
關鍵字: 高Nb-TiAl合金；顯微組織；蠕變；變形機制；斷裂機制
（1. National Key Laboratory for Precision Hot Processing of Metals, Harbin Institute of Technology, Harbin 150001, China;
2. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China;
3. Department of Mechanical Engineering, Shanxi Institute of Mechanical & Electrical Engineering, Changzhi 046011, China）
Abstract:In this paper, the microstructure of as-cast Ti-46Al-6Nb-2.5V-0.2B4C alloy was analyzed by using X-ray diffraction (XRD), optical microscope (OM), scanning electron microscope (SEM) and transmission electron microscope (TEM). And the elevated temperature creep tests at 800-850 ℃ under 250-325 MPa were conducted to investigate creep deformation and rupture mechanisms of as-cast high Nb-containing TiAl alloy. The results show that the as-cast alloy exhibits fully lamellar structure. Besides, TiB precipitates inside lamellar colony or at grain boundary and C atoms exist in the matrix in the form of solid solution. According to creep data, the stress exponent (n) at 800 ℃ and the apparent activation energy (QC) under 300 MPa of Ti-46Al-6Nb-2.5V-0.2B4C alloy are measured to be 5.71 and 313.316 kJ/mol, respectively. Combining microstructure observation by TEM, it is revealed that the creep deformation is controlled by dislocation climbing and mechanical twinning. And dynamic recovery and dynamic recrystallization induced by creep play a softening role. In addition, elements B and C play an important role in improving the creep resistance of high Nb containing TiAl alloys. Particularly, Ti2AlC precipitates dynamically at the interface between TiB and matrix during creep process. Moreover, TiB and Ti2AlC follow the well-established orientation relationship as , . Furthermore, the creep rupture is dominated by the initiation and coalescence of cavities as well as the propagation of cracks.
Key words: high Nb-containing TiAl alloy; microstructure; creep; deformation mechanism; rupture mechanism
