(1. 桂林電子科技大學 材料科學與工程學院，桂林 541004；
2. 哈爾濱工業(yè)大學 材料科學與工程學院，哈爾濱 150001；
3. 三峽大學 機械與動力學院，宜昌 443002)
摘 要: 基于CALPHAD方法和Thermo-Calc軟件構(gòu)建了Nb-Ti-Co三元合金富Nb角相圖，而后結(jié)合微觀偏析統(tǒng)一模型研究58種合金的凝固路徑，探討固相反擴散系數(shù)和冷卻速率對凝固路徑的影響規(guī)律，并利用Bridgman定向凝固實驗對其驗證，最后通過SEM和XRD觀察上述合金的微觀結(jié)構(gòu)，并與數(shù)值模擬計算結(jié)果進行比較，建立了Nb-Ti-Co相圖中的滲氫成分區(qū)域。結(jié)果表明：1) Nb-Ti-Co三元合金相圖富Nb角存在兩個三元四相平衡反應(yīng)，分別為L+α-Nb→TiCo+Co6Nb7 (1225.35 ℃)和L+TiCo→α-Nb+Ti2Co (1099.06 ℃)；2) Nb相區(qū)中至少存在四種不同的凝固路徑，分別為(L+α-Nb)、(L+α-Nb)→(L+α-Nb+Co6Nb7)→(L+α-Nb+Co6Nb7+TiCo)、(L+α-Nb)→ (L+α-Nb+TiCo)和(L+α-Nb)→(L+α-Nb+TiCo)→(L+α-Nb+TiCo+Ti2Co)；3) 冷卻速率(Rf)對滲氫區(qū)域內(nèi)合金凝固路徑影響較小，相反，固相反擴散系數(shù)(Ф)對其凝固路徑影響較大；4) 滲氫區(qū)域內(nèi)合金顯微組織中初生α-Nb相體積分數(shù)隨著Nb含量和Ti/Co比率的增加而增加，相反，兩相共晶體積分數(shù)隨之而降低。
關(guān)鍵字: Nb-Ti-Co合金；CALPHAD；凝固路徑；滲氫區(qū)域
（1. School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, China;
2. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China;
3. College of Mechanical and Power Engineering, Three Gorges University, Yichang 443002, China）
Abstract:In the present work, Nb-Ti-Co phase diagram in the Nb-rich region was constructed by using CALPHAD method and Thermo-calc software, and then the solidification paths of 58 kinds of alloys were studied by using the uniform microsegregation model. The influences of solid back diffusion coefficient and solidification rate on their solidification path were discussed. The microstructure of these alloys was observed by SEM and XRD, which was compared with the numerical simulation results. Finally, the hydrogen permeable component region in the Nb-Ti-Co phase diagram was established. The results show that: (1) Two equilibrium reactions, i.e. L+α-Nb→TiCo+Co6Nb7 and L+TiCo→ α-Nb+Ti2Co, exist in the Nb-Ti-Co phase diagram. (2) There are at least four different solidification paths in the Nb-rich region, as follows, (L+α-Nb), (L+α-Nb)→(L+α-Nb+Co6Nb7)→(L+α-Nb+Co6Nb7+TiCo), (L+α-Nb)→(L+α-Nb+TiCo) and (L+α-Nb)→(L+α-Nb+TiCo)→(L+α-Nb+TiCo+Ti2Co), respectively. The cooling rates have no obvious effect on the solidification path whereas the solid back diffusion coefficient has a great effect on it. The volume fraction of primary phase increases with the increase of Nb content and Ti/Co ratio, whereas the volume fraction of eutectic phase decreases.
Key words: Nb-Ti-Co alloy; CALPHAD; solidification path; hydrogen permeable component region
