Ti-Cr合金的非等温氧化及着火预测

摘要

The non-isothermal oxidation behavior and oxide scale microstructure of Ti-Cr alloy (0≤w(Cr)≤25％) were studied from room temperature to 1723 K by thermogravimetric analysis (TGA),X-ray diffraction (XRD) and scanning electron microscopy (SEM).The influencing mechanism of chromium on the oxidation resistance ofTi-Cr alloys was discussed.The results show that the oxidation resistance of the alloys decreases with Cr below a critical chromium content wc and increases above wc; above 1000 K,the oxidation kinetics obeys parabolic rule and titanium dominates the oxidation process; after oxidation,the oxygen-diffusing layer is present in the alloy matrix,the oxide scale is mainly composed of rutile whose internal layer is rich in chromium,and chromium oxides separated out from TiO2 near the alloy-oxide interface improve the oxidation resistance.Ignition of metals and alloys is a fast non-isothermal oxidation process and the oxidation mechanism ofTi-Cr alloys during ignition is predicted.%采用热重分析、XRD和SEM等方法研究Ti-Cr合金(0≤w(Cr)≤5％)从室温至1723 K的非等温氧化行为及氧化膜的微观结构,探讨Cr元素对Ti-Cr合金抗氧化能力的影响机制.结果表明:当Cr含量小于某一临界值wC时,随着Cr含量的增加合金的抗氧化能力降低；当Cr含量高于wC时,随着Cr含量的增加合金的抗氧化能力提高；当温度高到1000 K时,Ti-Cr合金的氧化仍符合抛物线规律,且主要发生钛的氧化；Ti-Cr合金氧化后基体中存在氧扩散层,氧化膜主要为金红石型TiO2,内层氧化膜出现富Cr现象,Cr氧化物的析出提高了Ti-Cr合金的抗氧化能力.金属和合金的着火是一个快速非等温氧化的过程,预测了Ti-Cr合金着火阶段的氧化机制.