Zong Cui, Liu Sujie, Ma Guangcai, Guo Yi, Huang Zhaohui
National Key Laboratory of Advanced High Temperature Structural Materials, Beijing Institute of Aeronautical Materials, Beijing 100095, China.
Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China.
Materials (Basel). 2024 Jun 10;17(12):2821. doi: 10.3390/ma17122821.
Ni-base superalloys operate in harsh service conditions where cyclic heating and cooling introduce deformation fields that need to be investigated in detail. We used the high-angular-resolution electron backscatter diffraction method to study the evolution of internal stress fields and dislocation density distributions in carbides, dendrites, and notch tips. The results indicate that the stress concentrations decay exponentially away from the notch, and this pattern of distribution was modified by the growth of cracks and the emission of dislocations from the crack tip. Crack initiation follows crystallographic traces and is weakly correlated with carbides and dendrites. Thermal cycles introduce local plasticity around carbides, the dendrite boundary, and cracks. The dislocations lead to higher local stored energy than the critical value that is often cited to induce recrystallization. No large-scale onset of recrystallization was detected, possibly due to the mild temperature (800 °C); however, numerous recrystallized grains were detected in carbides after 50 and 80 cycles. The results call for a detailed investigation of the microstructure-related, thermally assisted recrystallization phenomenon and may assist in the microstructure control and cooling channel design of turbine blades.
镍基高温合金在恶劣的服役条件下运行，循环加热和冷却会引入变形场，需要对其进行详细研究。我们使用高角分辨率电子背散射衍射方法来研究碳化物、枝晶和缺口尖端内部应力场和位错密度分布的演变。结果表明，应力集中从缺口处呈指数衰减，并且这种分布模式会因裂纹的扩展和裂纹尖端位错的发射而改变。裂纹萌生遵循晶体学迹线，与碳化物和枝晶的相关性较弱。热循环在碳化物、枝晶边界和裂纹周围引入局部塑性。位错导致的局部储能高于通常被认为会引发再结晶的临界值。未检测到大规模的再结晶开始，这可能是由于温度适中（800°C）；然而，在50次和80次循环后，在碳化物中检测到了大量再结晶晶粒。这些结果呼吁对与微观结构相关的热辅助再结晶现象进行详细研究，并可能有助于涡轮叶片的微观结构控制和冷却通道设计。
