析出相特征对GH4720Li合金疲劳性能的影响

Effect of precipitates characteristics on fatigue properties of GH4720Li alloy

摘要:

本文对不同温度固溶热处理的GH4720Li合金进行系列疲劳实验，研究合金析出相特征与疲劳性能的关联性。结果表明：固溶温度在1080℃~1120℃，合金中一次γ′相体积分数高，近球形的三次γ′相尺寸逐渐长大，晶粒组织细小、均匀，位错滑移主要是切过和绕过球形的γ′相并留下细小的滑移带，说明γ′析出相可以有效阻碍滑移带的扩展，合金疲劳性能较好；在1140℃，一次γ′相不均匀回溶，合金出现明显的混晶组织，三次γ′相形貌逐渐转变为方形，相互平行的滑移带尺寸明显增大，此时材料内部已发生较大程度的变形，材料的抗疲劳性能降低；在1180℃，一次γ′相完全回溶，合金产生粗大的晶粒组织，滑移带相互交叉，并且穿过晶界，严重降低合金的疲劳抗性。

Abstract:

In this paper, series experiments were carried under different fatigue load spectrum for different solution annealing treated GH4720Li alloy. The results show that when the solution temperature is between 1080 °C and 1120 °C, the volume fraction of primary γ′ phase in the alloy is high, and the size of the near spherical tertiary γ′ phase gradually grows, and the grain structure is fine and uniform. The dislocation slip mainly cuts and bypasses the spherical γ′ phase and leaves a small slip band, indicating that the γ′ precipitates can effectively hinder the expansion of the slip band, the alloy has good fatigue performance. When the solution temperature is rise to 1140 °C, the primary γ′ phase dissolves unevenly, inducing the obvious mixed grain size distribution, and the morphology of tertiary γ′ phase gradually transforms into square shape. The size of parallel slip bands increases obviously, and the internal deformation of the material has occurred to a large extent, and the fatigue resistance of the material decreases. When the solution treated temperature is over the γ′ phase transformation point, such as at 1180 °C, the γ′ phase completely dissolves, and resulting in the coarse grain structure.The slip bands cross each other and pass through the grain boundary, which seriously reduces the fatigue resistance of the alloy.