GH4169合金晶粒尺寸与持久性能的关联性

以GH4169合金大规格棒材为研究对象,结合棒材的加工过程,利用OM、FE-SEM、EBSD和TEM等手段分析了该合金不同晶粒尺寸试样的持久性能。结果表明:在长时高温应力作用下,不同晶粒尺寸试样呈现不同的持久性能和不同的晶粒取向演变规律。发生变形至断裂的位置,晶粒尺寸较小时,部分〈101〉取向明显转向〈001〉或〈111〉取向,加上宏观变形协调性较好,促使应力集中得到有效释放,表现出较好的塑性;但细晶试样中更多晶界带来的扩散蠕变对高温强度不利,裂纹也容易在与〈111〉硬取向晶粒接邻的晶界处形核并扩展,降低持久寿命;此外,细晶试样的变形程度较大,应变主要集中于晶界处,且大角度取向差的含量较多,这些位置容易萌生裂纹而使寿命降低。

Investigations on correlation between grain size and stress rupture property of GH4169 alloy

Taking GH4169 alloy large-size bar as research object, combined with the manufacturing process of the bar, the stress rupture properties of the specimens with different grain sizes were analyzed by means of OM, FE-SEM, EBSD and TEM. The results show that under the high temperature and stress of the long-lasting test, various grain size samples exhibit different stress rupture properties and grain orientation evolution. When the grain size is small, some orientation of〈101〉obviously rotates to 〈001〉or〈111〉orientation where deformation and fracture occur. Besides, the coordination of macroscopic deformation of fine grain is better. These promote the effective release of stress concentration and then better plasticity. But the diffusion creep caused by more grain boundaries in the fine grain sample is unfavorable to the high temperature strength and cracks are prone to nucleate and expand at the grain boundary adjacent to the hard orientation of 〈111〉, thus the rupture life is reduced. In addition, the deformation of the fine grain sample is larger, mainly concentrated at grain boundaries, and the number fraction of large angle misorientation is more,which is easy to crack and reduce the life.