新型高性能镍基粉末高温合金拉伸变形行为和机制研究

Deformation Behavior and Mechanisms of Tensile in A Advanced High-performance Nickel-Based PM Superalloy

采用SEM和TEM研究了室温(23℃)和中温(650、750、815℃)下第3代镍基粉末高温合金(FGH98)拉伸变形显微组织、行为和机制。结果表明:含有多模尺寸分布γ′相的合金具有优良的拉伸性能,室温拉伸主要变形机制为位错剪切γ′相形成层错,并在γ′相周围形成位错环,阻碍后续位错运动。中温拉伸变形机制为位错剪切γ′相形成层错和形变孪晶,随着变形温度的升高,形变孪晶增多。给出了a/3<112>不全位错剪切γ′相形成层错和形变孪晶共存的模型,随着应变量的增加,在连续相邻的{111}滑移面上层错堆积变多,促进连续孪晶的形成,协调了γ和γ′相两相之间的变形,有助于释放两相之间的变形应力和提高合金强韧性。

The deformation microstructures, deformation behavior and mechanisms of FGH98 after tensile tests at room temperature(23℃) and intermediate temperatures(650, 750, 815℃) were investigated by scanning electron microscopy(SEM) and transmission electron microscopy(TEM). The results show that FGH98 alloy, with multi-mode size distribution γ′ phase, obtains excellent tensile properties at room temperature and intermediate temperature. The dislocations shear γ′ phase, forming stacking fault(SF) in the γ′precipitate and a dislocation loop around the γ′ precipitate, which is the dominant deformation mechanism during the tensile deformation at room temperature. The dislocation loop hinders the subsequent dislocation movement. However, forming SFs and deformation twins by dislocations shearing γ′ phase becomes the dominant deformation mechanisms at intermediate temperatures. With the increasing of the deformation temperature, the deformation mechanisms transfer from SFs to deformation twins, and the density of twins increases. The model of a/3<112> partial shearing the γ′ precipitate forming stacking faults and twins was given. With the increase of strain, the stacking faults accumulate on the adjacent {111} planes, promoting the formation of continuous twins. The formation of continuous twins can coordinate the deformation between the γ and γ′ phase and release the deformation stress, resulting in enhancement of the alloy plasticity.