论文标题
伽马钛铝制的疲劳破裂
Fatigue cracking in gamma titanium aluminide
论文作者
论文摘要
铸造和HIP'ED \ Textgamma-Tial 4522XD正在开发用于喷气发动机低压涡轮叶片，其中温度变化在飞行周期中发生。因此，在本研究中检查了温度变化对疲劳裂纹的影响。发现在750c时，疲劳裂纹的增长率高于400c，但是$ΔK_\ mathrm {th} $也更高。在疲劳裂纹生长期间，温度偏移在400至750°C之间导致裂纹生长速度在加热和冷却时延迟。还发现，对于缩小$ 0.6 $ 〜mm的长度和较小的档次，可以在类似于材料故障应力的应力下观察到来自微观结构的启动；存在一个微观结构启动场地。可以观察到从反式，跨层间和层内裂纹的变化，而裂纹尖端塑料区域的估计尺寸超过了菌落的大小。
Cast and HIP'ed \textgamma-TiAl 4522XD is being developed for use in jet engine low pressure turbine blades, where temperature variations occur through the flight cycle. The effects of temperature variations on fatigue cracking were therefore examined in this study. It was found that fatigue crack growth rates were higher at 750C than 400C, but that $ΔK_\mathrm{th}$ was also higher. Temperature excursions between 400 and 750C during fatigue crack growth resulted in retardation of the crack growth rate, both on heating and cooling. It was also found that for notches $0.6$~mm in length and smaller, initiation from the microstructure could instead be observed at stresses similar to the material failure stress; a microstructural initiation site exists. A change from trans- to mixed trans-, inter- and intra-lamellar cracking could be observed where the estimated size of the crack tip plastic zone exceeded the colony size.
