均匀化态GH4975合金热变形行为研究

Hot Deformation Behavior of Homogenized GH4975 Superalloy

摘要:

基于Gleeble热压缩模拟实验，研究了应变速率为0.1和1 s^–1及变形温度为1140~1200 ℃条件下均匀化态GH4975合金的热变形行为。通过EBSD、SEM等实验表征手段，结合合金微观组织演变情况探讨了均匀化态GH4975合金的动态再结晶机制。结果表明，在较低变形温度下，合金内以晶界处的不连续动态再结晶机制为主；随着变形温度的提高，逐渐向第二相粒子促进新晶粒形核的机制转变。这与合金内析出相的形态与分布密切相关。在GH4975合金内，γ′相促进动态再结晶。随着变形温度的提高，γ′相部分回溶，稀疏分布的γ′相将实现良好的动态再结晶晶粒组织。(γ+γ′)共晶相表面可作为再结晶形核点，促进动态再结晶。

Abstract:

Based on the Gleeble thermal compression simulation tester, the hot deformation behavior of the homogenized GH4975 superalloy was investigated at strain rates of 0.1 and 1 s^–1 with deformation temperature ranging from 1140 ℃ to 1200 ℃. EBSD and SEM were used to observe the microstructure evolution of the homogenized alloy to study the dynamic recrystallization (DRX) mechanism of GH4975 superalloy. The results show that the main DRX mechanism of GH4975 superalloy at low temperature is discontinuous dynamic recrystallization (DDRX) at grain boundaries. As the temperature increases, the mechanism gradually transitions to particle stimulated nucleation, where secondary phase particles promote the nucleation of new grains. This evolution is associated with the morphology and distribution of the precipitates. In the GH4975 superalloy, the γ′ phase promotes DRX. As the deformation temperature increases, the γ′ phase partially dissolves back into the matrix, and the sparsely distributed γ′ phase contributes to a well-developed dynamically recrystallized grain structure. Additionally, the surfaces of the (γ+γ′) eutectic phase can serve as nucleation sites for recrystallization, thereby further promoting DRX.