反应烧结Ti-22Al-25Nb合金的高温氧化行为

High temperature oxidation behaviors of Ti-22Al-25Nb Alloy Prepared by Reactive Sintering with Element Powders

摘要:

Ti-22Al-25Nb是一种高温结构材料，它的抗氧化性对今后的发展和应用具有重要意义。采用元素粉末和反应烧结法制备了Ti-22Al-25Nb烧结合金，研究了其在静态空气中的氧化行为(923~950℃温度范围内)。不同温度(650 °C, 750 °C, 850 °C, 950 °C)下的最大增重分别为0.15 mg﹒cm-2、0.41 mg·cm-2、1.68 mg·cm-2和6.9 mg·cm-2。研究发现Ti-22Al-25Nb烧结合金具有良好的抗氧化性，特别是在750°C以下（950°C时发生氧化分解）。根据氧化动力学分析，在750℃以下，氧化行为大致遵循抛物线规律，而在850℃以上，氧化行为符合线性规律。讨论了铌合金元素对氧化动力学的影响，通过对氧化形态和相的观察和分析，证明O相（有序Ti2AlNb相）的抗氧化性能优于其它相，其原因可以解释为不同相的Nb含量的差异导致抗氧化性的差异。

Abstract:

Ti-22Al-25Nb is a high-temperature structural material which oxidation resistance will be important for further developments and applications. The oxidation behaviors of sintered Ti-22Al-25Nb alloy which was prepared by reactive sintering with element powders were investigated at the temperature range of 650~950 °C in static air. The maxima of the mass gains at different temperatures (650 °C, 750 °C, 850 °C, 950 °C) were 0.15 mg·cm?2, 0.41 mg·cm?2, 1.68 mg·cm?2 and 6.9 mg·cm?2, respectively. The Ti-22Al-25Nb sintered alloy exhibited a good oxidation resistance, especially below 750 °C (with breakaway oxidation occurring at 950 °C). According to the oxidation kinetics analyses, the oxidation behaviors approximately followed parabolic law below 750 °C. Whereas, with temperatures rising above 850 °C, the oxidation behaviors fitted linear law. Oxidation kinetics were discussed with regard to the influence of the Nb alloying element. Based on the observations and analyses of the oxidation morphologies and phases, there were proven that the oxidation resistance of the O phase (orthorhombic Ti2AlNb) was superior to others. The reason for this phenomenon was the difference of Nb content in different phases could result in a difference of oxidation resistance.