Al（l）/NiO（s）/Ni（s）液固介面反應機制之研究

Abstract

本研究係以擠壓鑄造法製作Ni(s)-NiO(s)-Al(l)介面，在低氧分壓的狀態下，進行不同溫度之熱處理，鑑定不同溫度之熱處理後的生成相，並以熱力學計算探討實驗結果，藉以研究NimAln/Al2O3(α)金屬基複合材料。 根據熱力學計算Al形成Al2O3的氧分壓1.05×10-56atm，Ni形成NiO的平衡氧分壓7.08×10-20 atm，於本實驗的固態反應中觀察到介面上3NiO(s)＋2Al(s)→3Ni(s)＋Al2O3(s)的反應，與計算結果相符合。 溫度高於純鋁熔點的熱處理，3NiO（s）＋2Al（l）→3Ni（s）＋Al2O3(s)，所形成之Al2O3為顆粒狀非連續之α－Al2O3，產生之後並不會影響後續的反應。 Ni Al2O4在Ni-Al-O三元系統是常見的穩定相，但是在固固態反應與液固態熱處理的反應前後皆無觀察到Ni Al2O4，此為Ni Al2O4 受到NiO的活性與氧分壓影響，本實驗反應在氬氣氣氛中，因此Ni Al2O4不產生。 熱處理溫度為NimAln形成的主要因素，600˚C固態反應無觀察到NimAln產生，670˚C熱處理反應初期 NiO（s）＋Al（l）→Ni Al3（s）＋Al2O3（α），待NiO消耗完全，Ni和Al直接反應，Ni和Al介面上則有NiAl3＋Ni2Al3兩層。於1000˚C在鋁基材開始析出Ni2Al3，在Ni和Ni2Al3之間形成Ni3Al 。達1200˚C時，在鋁基材開始析出NiAl，在介面形成 NiAl。

In this study, Al（l）/NiO（s）/ Ni（s） interface was produced by squeeze casting. Under low oxygen pressure, heat treatments which were employed at different temperatures induced various intermetallic compound. The experimental results were studies by thermodynamic calculation to investigate the reacting mechanism of Al/NiO/Ni interface. According to thermodynamics, Al forms Al2O3 under the oxygen partial pressure of 1.05×10-56 atm, and, Ni forms NiO at 7.08×10-20 atm. The NiO would decomposed at very low oxygen pressure. In this research oxygen pressure was very low, therefore 3NiO（S）+2Al（s）→3Ni（S）+ Al2O3 （s） was observed in solid state. The result is identical with the thermodynamic consequence. When the temperature is higher than the melting point of the pure Al, the reaction of 3NiO（S）+2Al（s）→3Ni（S）+ Al2O3 （s） formed α-Al2O3 particles which didn’t block the liquid Al to pass through the reaction zone. NiAl2O4 is the common stable phase in Ni-Al-O system. However in this study, Ar atmosphere is applied owning heat treatments, NiAl2O4 which is affected by the activity of NiO and O2 pressure cannot be formed during this study. Temperature is the main factor of obtaining NimAln, At 600℃, NimAln can not be observed .During the initial period, the reaction followed .After NiO is depleted, Ni reacted with Al, forming NiAl3 and Ni2Al3.At 1000℃, Ni2Al3 is eutectic from the Al substrate, and NiAl is eutectic to produce NiAl as the temperature up to 1200℃.