热处理对Inconel 718高温合金断裂特征和锯齿屈服的影响

Effect of Heat Treatment on Fracture Characteristics and Serrated Yielding of Inconel 718 Superalloy

摘要:

由于断裂特征和锯齿屈服在镍基高温合金应用中的影响逐渐突出，探讨了Inconel 718高温合金的热拉伸性能，包括断裂行为、力学性能和塑性行为。该实验选用了3种热处理制度和2种拉伸方向。结果表明，不同的热处理方式使得晶粒尺寸有差异。大尺寸晶粒使纵断面不平整，并且减少了晶界和碳化物的数量，限制了韧窝生成，最终降低了材料塑性。晶界的减少会减少位错，增加达到锯齿屈服平衡条件对热活化能的需求，并改变锯齿类型。另外，热处理也会使沉淀物不同。碳化物可以促进韧窝的形成。针状δ相在晶界和孪晶界析出，并略向轧向倾斜。因此，针状δ相沿横向的钉扎效应显著，这会对韧窝聚集和位错运动产生影响，最终在断裂特征、力学性能和锯齿屈服方面表现出各向异性。

Abstract:

Due to the gradually prominent impact of fracture characteristics and serrated yielding in the application of nickel-based superalloys, the hot tensile properties of Inconel 718 superalloy were studied, including fracture behavior, mechanical properties, and plastic behavior. The experiments adopted three heat treatment regimes and two tensile directions. Results show that various heat treatments make grain sizes different. The larger-sized grains make the vertical surface uneven, which also decrease the number of grain boundaries and carbides, restricting the occurrence of dimples and ultimately reducing the material plasticity. The reduced grain boundaries can decrease dislocations, increase the demand for thermal activation energy, and transform the serration mode of serrated yielding. In addition, various heat treatments also make precipitates different. Carbides can promote the formation of dimples. The needle-shaped δ phase precipitates at grain boundaries and twin boundaries, and slightly inclines towards the rolling direction. Therefore, its pinning effect is outstanding along the transverse direction, which can affect the dimple aggregation and the dislocation movement, ultimately exhibiting anisotropy in fracture characteristics, mechanical properties, and serrated yielding.