测量了铸造Ti-47Al-2Cr-2Nb-0.15B(原子分数,%)合金的高温疲劳强度以及 650℃/100 h和800℃/100 h热暴露后的拉伸性能和疲劳强度, 采用X射线衍射和扫描电镜等方法分析了经热暴 露后合金基体组织的变化和表面层的结构. 随暴露温度的提高, 合金的室温塑性和疲劳强度 降低, 650℃附近有一转折点, 大于650℃时上述性能加速下降; 合金高温疲劳性能具有相似 的变化规律. 显微分析表明, 在热暴露或高温疲劳实验时, \表面形成的脆性层是导致合金性能降低的直接原因; 而随温度的提高, 表面层由渗氧层转变为氧化层是导致合金性能随温度变 化出现转折的原因.
The elevated temperature fatigue strength and room temperature tensile properties and fatigue strength of cast Ti-47Al-2Cr-2Nb-0.15B(atomic fraction, %) alloy after thermal exposure were investigated. The microstructural change of the bulk alloy and the microstructure of surface layer after 650℃/100 h and 800℃/100 h exposures were analyzed by means of XRD and SEM. The room temperature tensile ductility and fatigue strength decreased slowly with increasing exposure temperature when it is below 650℃, and then rapidly decreased above this temperature. Dependence of fatigue strength for the unexposed alloy with test temperature exhibits the same trend. The surface layer formed after 650℃/100 h exposure is an oxygen-enriched layer, while that after 800℃/100 h exposure is an oxide layer consisting of TiO2 and Al2O3. Such a change in the nature of the surface layer corresponds to the onset of rapid drop in mechanical proerties and fatigue strength of the alloy with increasing exposure temperature.
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