Cu43Zr43Al7Ag7非晶合金在375~500℃之空氣氧化行為

Air-Oxidation Behavior of Cu43Zr43Al7Ag7 Bulk Metallic Glass at 375 ~ 500 ℃

本研究探討Cu43Zr43Al7Ag7非晶合金在375 ~ 500℃空氣下的氧化行為。研究結果顯示，銅鋯基非晶合金的氧化反應速率常數（kp）與溫度呈現不規則之變化；當氧化溫度低於425℃時，kp值隨溫度上升而加快，但在450℃以上時，卻有相反的趨勢。氧化後的氧化生成物以正方晶體的ZrO2(t-ZrO2)和CuO為主，另外，有少量的單斜及斜方的ZrO2（m-和o-ZrO2）以及α-Al2O3（只有在500℃生成）。此外，少量Ag的添加可增加非晶在375 ~ 425℃的抗氧化能力，但高溫時（溫度大於450℃）並無此種的效果產生。當溫度低於玻璃轉換溫度（Tg）下時，基材仍保有非晶狀態；但當溫度升高時，非晶合金會先氧化後結晶的相變化發生，基材轉變為Cu10Zr7和ZrAl兩種結晶相。

Air-oxidation behavior of the Cu43Zr43Al7Ag7 bulk metallic glass was studied over the temperature range of 375 ~ 500 ℃. The oxidation rate constants (kp values) of the glassy alloy fluctuated with temperature. The kp values increased with increasing temperature when the oxidation temperature (Toxid) was below 425 ℃, but these values instead decreased with increasing temperature at Toxid > 450 ℃. The scales formed on the Cu43Zr43Al7Ag7 consisted mostly of tetragonal-ZrO2 (t-ZrO2 ), CuO, minor amounts of monoclinic- and orthorhombic-ZrO2, (m- and o- ZrO2), and α-Al2O3 (only detected at 500 ℃). In the meantime, small amounts of Ag addition provided a better oxidation resistance at the temperature range of 375 ~ 425 ℃, but no improvement was obtained at higher temperatures. In addition, the glassy substrate remained unchanged at temperatures below the glass-transition temperature (Tg), yet it underwent a preoxidation process and a phase transformation after the oxidation at Toxid > 425 ℃, causing the substrate to transform from an amorphous state to crystallized Cu10Zr7 and ZrAl.