不同取向镍基单晶高温合金650℃原位拉伸

In⁃situ tensile of nickel⁃based single crystal superalloys with different orientations at 650℃

镍基单晶高温合金作为飞机涡轮发动机叶片的主要使用材料,其在服役过程中受到各向应力作用产生变形导致材料失效,因此本文基于课题组自主研发的原位拉伸设备对[140]取向、[340]取向、[122]取向的镍基单晶高温样品进行了650℃原位拉伸。其中[140]取向样品在屈服阶段后样品硬化到塑性变形后期出现了幅度较小的应力下降,最后样品在应力作用下滑移迹线所在的基体发生开裂,裂纹沿着滑移迹线所在方向扩展至样品断裂。[340]取向样品在整个塑性变形阶段,样品的应力持续下降,孔洞缺陷处形成缺陷导致材料失效。[122]取向样品一直处于硬化阶段,到塑性变形后期样品出现了应力的下降,跟[340]取向样品失效方式相同,孔洞开裂形成裂纹源导致材料失效。本文针对三种取向样品的力学性能,塑性变形过程中的滑移情况以及对应的施密特因子变化、样品失效的方式进行了分析,对合金在真实服役过程中提高其服役寿命具有重要意义。

Nickel-based single crystal superalloys for aircraft turbine engine blades are generally subjected to anisotropic stresses during service processes,which result in material failures.Here,nickel-based single crystal superalloys with[140],[340]and[122]orientations were in-situ stretched at 650℃by self-developed in-situ stretching equipment.The[140]-oriented sample showed a small magnitude of stress drop after yielding stage when the sample was hardened to the late stage of plastic deformation.The sample was cracked in the matrix where the slip traces were located under the stress.The crack was extended in the direction of the slip traces until the samples were fractured.Continuous stress drop was observed in the[340]oriented sample during the whole plastic deformation.Defects were formed at holes,which led to the material failure.The[122]oriented sample was kept in the hardening stage.Stress drop was observed at the late plastic deformation stage.The sample showed the same manner as the[340]oriented sample.This work provides key insights into the improvement of the service life of alloys under working conditions.