镍基单晶高温合金定向粗化行为及高温蠕变力学性能研究进展

镍基单晶高温合金是一种广泛应用于航空发动机和工业燃气轮机的两相叶片材料，由软的$\gamma $ 基体相和均匀镶嵌在其中的立方状 $\gamma'$ 沉淀强化相组成.它有个显著的特征，即在高温施加应力条件下, $\gamma '$沉淀相会发生定向粗化, 形成筏状.这种筏化行为直接影响了合金的蠕变疲劳寿命,是镍基单晶高温合金强化机制研究的重点. 此外,镍基单晶高温合金无晶界, 不存在高温晶界弱化、纵向晶界裂纹等问题.因此, $\gamma$/$\gamma'$相界面的位错运动、微观结构以及在载荷和温度作用下的演化决定了其蠕变力学性能.本文从镍基单晶高温合金的微观强化机制出发对定向粗化行为及蠕变力学性能进行了综述.重点介绍了定向粗化行为发生的微观机理、驱动力、影响因素和蠕变过程中界面微结构演化、蠕变力学模型以及定向粗化对高温蠕变力学性能的影响,指出了高温蠕变力学性能研究的发展方向和仍待解决的问题. 

RESEARCH PROGRESS OF THE DIRECTIONAL COARSENING BEHAVOR AND HIGH TEMPERATURE CREEP MECHANICAL PROPERTIES IN NI-BASE SUPERALLOYS

Ni-based single crystal superalloys are widely used as two-phase blade materials for aircraft engines and industrial gas turbines. The materials are strengthened by a high volume fraction of hard cubical $\gamma'$ precipitates embedded coherently in a softer $\gamma $ matrix. The materials exhibit a remarkable character that the $\gamma'$ cubic particles will transform into rafts under the combined influence of stresses and temperatures. This rafting behavior directly affects the creep fatigue life of Ni-based superalloys. Therefore, the directional coarsening mechanism is the key rule of precipitation hardening in Ni-based single crystal alloys. Furthermore, due to the fact that no grain boundary exists in Ni-based single crystal superalloys, some problems related with the grain boundary, such as the weakening of grain boundary at high temperature, and the longitudinal grain boundary cracking, etc, will not occur. The dislocations motion and the structural evolution of the misfit dislocation networks at $\gamma $/$\gamma ^{' }$phase interfaces under external loading and high temperature have great influences on the creep mechanical properties of Ni-based superalloys. Based on the analysis of the microscopic strengthen mechanism of Ni-based superalloys, this paper reviews the related researches on the directional coarsening behavior and creep mechanical properties. It focuses on describing the micro-mechanism of the directional coarsening, driving force, interfacial microstructure evolution, creep mechanical model and the effect of the directional coarsening on the high temperature creep mechanical properties. The existing problems and some topics for the future studies are pointed out.