沉淀相的尺寸与形态对镍基合金蠕变行为的影响

镍基合金具有优良的高温力学性能,广泛应用于涡轮叶片等热端部件.沉淀相的尺寸和形态是影响镍基合金力学性能的重要因素.论文在考虑应变梯度的镍基合金晶体塑性本构模型的基础上,引入了各向异性损伤张量,研究了包含两种不同尺寸和三种不同长细比的沉淀相形态的镍基合金蠕变行为.结果表明,该模型能够很好地反映沉淀相的尺寸对镍基合金蠕变行为的影响,与实验结果符合较好.同时,沉淀相的形态也对镍基合金的力学性能产生重要影响,随着沉淀相长细比的增加,镍基合金的蠕变寿命延长,这体现了粗化和形态对镍基合金蠕变行为影响的一种竞争的机制.

PRECIPITATE SIZE AND MORPHOLOGY EFFECTS ON THE CREEP BEHAVIOR OF NICKEL-BASE SUPERALLOYS

Nickel-base superalloys are used extensively in the hot regions of gas turbines, because they have excellent mechanical properties at high temperature. The morphologies and sizes of γ’ precipitates have strong effects on the creep properties of the alloys. In this paper, a crystal plasticity constitutive model is developed, which considers damage and strain gradient to reflect the size effect of the creep property. The creep behavior of Nickel-base superalloys with two different precipitate sizes and three different precipitate morphologies are studied. The results show that the model can reflect the size effect on the creep behavior of the alloy very well. At the same time, the precipitate morphologies also have important effects on the mechanical properties of the alloy. With the increase of the slenderness ratio of the precipitate, the creep life of the nickel-base superalloys is extending. This phenomenon indicates that the precipitate coarsening and morphologies influence the creep behavior of the alloy as a competitive mechanism.