【摘要】 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℃/100h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.更多还原

【Abstract】 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.更多还原