材料期刊网

在等原子比的TiAl基化合物的基础上添加不同量的Nb元素，获得了4种含不同组成相和微观组织的合金。用氧化增重法研究了这4种含Nb合金和二元TiAl合金在1000℃静止空气中的断续氧化行为。采用XRD、SEM和EPMA分析了氧化膜的结构和组成。结果表明，Nb的加入能够提高合金的高温抗氧化性。以γ+α2为主相的合金Ti-42.8Al-14.2Nb形成了有效的保护性抗氧化膜。过量Nb的加入促使合金中富Nb相增多，氧化膜中出现Nb2O3使氧化膜的结构疏松，同时氧化膜出现分层，氧化层剥落加速。

Four alloys with different morphology and microstructure were prepared by adding different amount of niobium to equal atom-ratio TiAl-based intermetallic compound. Interrupted oxidation behavior of the four as-cast high-Nb TiAl alloys and binary TiAl alloy at 1000℃ in static air was studied using oxidation mass gain analysis. The structure and component of the oxide scales were analyzed by XRD\SEM and EPMA. Results indicate that Nb enhances oxidation resistance of the alloy. The alloy Ti-42.8Al-14.2Nb consisting of main phase of γand α2 forms the protective oxide scale. However, excessive addition of Nb results the existence of Nb-enriched phase in the alloy and the formation of Nb2O3 in oxide scale, simultaneously the oxide scale structure becomes porous. It leads to the multi-layered scale, accelerating the spallation of the oxide.