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以Ti-42.5Al-8Nb-0.2W-0.2B-0.1Y(原子分数,%)合金为研究对象,通过热处理获得不同大小片层团的2种全片层显微组织,并在900℃空气条件下,进行了100 h的抗氧化性实验。利用OM、SEM、TEM、XRD和EDS对试样的微观结构、相组成及微区成分进行了分析。恒温氧化动力学结果表明:在900℃空气条件下,具有2种不同大小全片层组织的Ti Al合金,其恒温氧化动力学曲线符合近抛物线规律,且大片层组织合金的抗氧化性能优于小片层组织。氧化100 h后,大片层组织的合金其氧化增重为6.45 g/m~2,小片层组织的合金的氧化增重为7.62 g/cm~2。对合金截面进行观察后发现,具有大小片层团2种合金表面氧化物的厚度分别为5和7μm。通过对氧化动力学曲线、组织结构、氧化膜结构、氧化表面形貌进行综合分析,2种合金组织结构的不同影响了O元素在基体中的扩散,而扩散速率的不同最终导致2种Ti Al合金表现出不同的氧化行为。
Two full-scale microstructures of Ti-42.5Al-8Nb-0.2W-0.2B-0.1Y (atomic fraction,%) alloy were obtained by heat treatment. Under the conditions of 100 h antioxidant test. The microstructure, phase composition and micro-zone composition of the samples were analyzed by OM, SEM, TEM, XRD and EDS. The results of isothermal oxidation kinetics show that the kinetic curves of isothermal oxidation kinetics of Ti Al alloy with two different sizes of whole lamellae at 900 ℃ are close to the law of near parabola and the oxidation resistance of the lamellar layer is better than Small piece of tissue. After oxidation for 100 h, the oxidation weight gain of the alloy in large lamellae was 6.45 g / m ~ 2, and the oxidation weight gain of the alloy in small lamellae was 7.62 g / cm ~ 2. After observing the cross section of the alloy, it was found that the thickness of the oxide on the surface of the alloy with the size of the lamellar group was 5 and 7 μm, respectively. Through the comprehensive analysis of the oxidation kinetics curve, structure, oxide film structure and oxidation surface morphology, the difference of the two kinds of alloy structure influences the diffusion of O element in the matrix, and the different diffusion rate finally leads to two kinds of TiAl The alloys show different oxidation behavior.