Ti6Al7Nb和Ti6Al4V合金的热氧化行为

Thermal oxidation behaviour of Ti6Al7Nb and Ti6Al4V alloys

在600～900℃温度下,0.5～72 h时间范围内空气气氛下对Ti6Al7Nb进行热氧化,根据增重曲线计算其氧化动力学规律,利用XRD、XPS分析表面氧化层的相组成、成分和价态,并以Ti6Al4V合金做为比照。结果表明,Ti6Al7Nb合金较Ti6Al4V合金抗氧化能力更强。同等氧化条件下,Ti6Al7Nb合金的氧化速率常数(k)更小。对短时间(1 h)氧化的样品的表面分析显示:各合金元素均以最高价态或稳定价态存在,其中Al和V被富集,而Nb则贫化;另外,Ti6Al7Nb合金和Ti6Al4V合金氧化层主要由金红石型TiO2(R-TiO2)组成,Al2O3相仅出现在900℃Ti6Al4V合金样品中。

Themal oxidation behaviour of Ti6Al7Nb and Ti6Al4V alloys in air at 600-900 ℃ for 0.5-72 h was investigated.The oxidation kinetics of the alloys was examined by weight gain curves.Composition and valence state of the surface oxide film were investigated by means of XRD and XPS.The results show that Ti6Al7Nb alloy exhibits higher resistance to thermal oxidation as compared to Ti6Al4V alloy.The value of oxidation rate constant for Ti6Al7Nb alloy is lower under the same oxidation conditions.The surface oxide film of specimens oxidized for 1 h only contains cations with the highest or most stable valences,and Al and V elements are enriched in the oxide film,while Nb element is deficient.The surfaces of both Ti6Al7Nb and Ti6Al4V alloys are mainly covered by R-TiO2.Al2 O3 is only detected in the surface oxide film of Ti6Al4V alloy oxidized at 900 ℃.