Nb-20Si和(Nb-20Si)90Al10合金在700~1000℃之空氣氧化行為研究

Air-oxidation Behavior of Nb-20Si and (Nb-20Si)90Al10 Alloys at 700 ~ 1000 ℃

本研究探討Nb-20Si和（Nb-20Si）90Al10合金在700 ~ 1000℃之空氣氧化行為。研究結果顯示，Nb-20Si為NbSi2及Nb5Si3之兩相合金；(Nb-20Si)90Al10則為包括Nb5Si3、NbAl3及Nb3Si5Al2相之三相合金。此外Nb-20Si合金在700 ~ 800℃之氧化動力學遵守多段式拋物線率；而900 ~ 1000℃之氧化動力學則因完全氧化而呈現無增重的持平反應。(Nb-20Si)90Al10合金在700 ~ 1000℃之氧化動力學皆遵守拋物線率，試片氧化後皆呈現粉末狀。添加Al並無法防止Nb-Si合金發生pest現象。

The oxidation behavior of Nb-20Si and (Nb-20Si)90Al10 alloys was studied over the temperature range of 700 ~ 1000 ℃ in dry air. The Nb-20Si alloy consisted of a two-phase structure of Nb5Si3 and NbSi2, while the (Nb-20Si)90Al10 alloy consisted of a three-phase structure of Nb5Si3, NbAl3, and Nb3Si5Al2. The oxidation kinetics of the Nb-20Si alloy followed a parabolicrate law at 700 ~ 800 ℃, while no-mass-gain kinetics were observed at 900-1000 ℃. On the other hand, the oxidation kinetics of the (Nb-20Si)90Al10 alloy also followed a parabolic-rate law at 700 ~ 1000 ℃. The scales formed on the two alloys exhibited a powder-like structure, which suggested that the addition of Al was not able to effectively prevent the pest phenomenon for the ternary alloy.