三種鋯基非晶質合金在空氣中之氧化行為研究

The Oxidation Behavior of Zr-base BMGs in Air

本研究主要在討論三種鋯基非晶質合金（Zr-20Cu-12Ni-10Al-5Ti，Zr-30Cu-10Al-5Ni及Zr-15Cu-10Al-10Ni，均為at.%以下分別簡稱Zr53，Zr55及Zr65）在300-500℃空氣中的氧化行為。研究結果顯示三種非晶質合金在低溫（T ≦ 350℃）時，動力學趨於直線型定律；而當溫度超過350℃時，合金遵守單一式或兩段式之拋物線型定律，而Zr65為三種非晶質合金中最佳之抗氧化材料。由X光繞射儀分析氧化層發現三種合金在氧化後皆生成正方晶與單斜晶之ZrO2（以下簡稱t-和m-ZrO），而當溫度大於350℃時，亦有少量Cu0及NiO（僅在Zr53生成），而m-ZrO2之生成量與氧化時間及合金成份有關。此外TEM觀察Zr53在300℃下氧化73小時的結果可發現氧化層下生成許多奈米晶，顯示氧化的過程中亦伴隨著相變態的發生。觀察非晶質合金於高溫氧化後所產生之結晶相可發現Zr53只生成Zr2Cu，而Zr55與Zr65則生成Zr2Cu與ZrAl兩相。

The aim of this research is to study the oxidation behavior of three bulk amorphous glasses (BMGs), containing Zr-20Cu-12Ni-10Al-5Ti (Zr53), Zr-30Cu-10Al-5Ni (Zr55), and Zr-15Cu-10Al-10Ni (Zr65) in dry air at 300-500℃. The oxidation kinetics of all the alloys generally followed the single- or two-stage parabolic rate law at T > 350 , while the three BMGs followed a linear behavior at 300-350℃. The Zr65 alloy is the most oxidation-resistant alloy among the three BMGs studied. The scales formed on the alloys consist of a mixture of monoclinic- and tetragonal-ZrO2 ( m- and t-ZrO2 ), while CuO was also observed at higher temperatures ( T > 350℃), and NiO was exclusively detected in the Zr53 alloy. The amount of m-ZrO2 formed on all BMGs is time-dependent and strongly dependent on the alloy composition and oxidation temperature. Based upon TEM results, a plenty of nano-grained polycrystallines formed beneath the amorphous oxide scale for Zr53 at 300℃, indicating that phase transformation was taken place, in which Zr2Cu was exclusively detected, but both Zr2Cu and ZrAl were present in Zr55 and Zr65