K4169合金循环加载过程中的微观组织演变  

Microstructure Evolution of K4169 Alloy During Cyclic Loading

作　　者：吴贇 刘雅辉[1] 康茂东[1,2] 高海燕[1,2] 王俊[1,2] 孙宝德[1,2] WU Yun;LIU Yahui;KANG Maodong;GAO Haiyan;WANG Jun;SUN Baode(School of Materials Science and Engineering,Shanghai Jiao Tong University,Shanghai 200240,China;Shanghai Key Laboratory of Advanced High-Temperature Materials and Precision Forming.Shanghai Jiao Tong University,Shanghai 200240,China)

机构地区：[1]上海交通大学材料科学与工程学院,上海200240 [2]上海交通大学上海市先进高温材料及其精密成形重点实验室,上海200240

出　　处：《金属学报》2020年第9期1185-1194,共10页Acta Metallurgica Sinica

基　　金：国家自然科学基金项目No.51971142;国家科技重大专项项目No.2017-Ⅵ-0013-0085;航空科学基金项目No.2018ZE57012;上海交通大学新进青年教师启动计划项目No.18X100040027。

摘　　要：通过熔模精密铸造、循环加载和微观组织表征等方法研究了K4169合金循环加载过程中的微观组织演变特征,重点分析了不同循环周次后Laves相和δ-Ni3Nb相的变形和断裂特征。结果表明,在室温380 MPa应力幅值循环加载实验中,循环寿命主要取决于显微疏松体积分数,裂纹优先萌生于试样表面的显微疏松位置。Laves相的断裂不受循环周次的影响,在循环加载初期,显微疏松附近的长带状Laves脆性相容易开裂,其内部还产生平行排列的二次裂纹,成为裂纹扩展的敏感区域。δ-Ni3Nb层片呈现2种变形和断裂特征:沿长度方向的开裂;层片表面滑移和断裂。循环加载初期,显微疏松附近的δ-Ni3Nb层片容易产生沿长度方向的开裂,而随着循环周次的增加,远离显微疏松的δ-Ni3Nb层片表面滑移迹线逐渐增多直至滑移断裂。γ-Ni基体在循环加载过程中产生孪生变形特征,导致应变局部化程度加剧,进而使Laves相和δ-Ni3Nb层片周围产生应力集中。K4169 nickel-based superalloy has been widely used to fabricate high-strength components in aircraft engine. When in service, especially affected by vibration and start-stop process, this alloy is inevitably affected by the external cyclic stress. Therefore, it is of great significance for researchers to understand the microstructure evolution in K4169 while cyclic loading. In the present study, the microstructure evolution of K4169 during cyclic loading has been examined and discussed in detail by using investment casting, cyclic loading and microstructure characterization methods. The cyclic loading test with stress amplitude of 380 MPa was carried out on a pull-push type fatigue machine at room temperature.The dependence of cycle times or fatigue life of specimens with different casting conditions on microporosity content has been discussed. Special emphases have been put on investigating the deformation and fracture characteristics of Laves and δ-Ni3Nb phases under the influence of microporosity. The results show that the cyclic life was mainly dominated by the content of microporosity. The crack initiation occurred mainly near the microporosity of the specimen surface. The specimen with high microporosity content exhibits the characteristic of complete brittle fracture, while the specimen with low microporosity content exhibits obvious transgranular fracture characteristics. In addition, the fracture of Laves phase was not apparently affected by cycle number. At the beginning of cyclic loading, the long-striped Laves phase near the microporosity was easy to crack, which became the sensitive area of crack growth, and extending in the manner of parallel secondary cracks. The δ-Ni3Nb plates near microporosity exhibited two obvious cyclic deformation and fracture characteristics depending on their arrangement(or growth orientation) relative to external loading axis: cracking along length direction(or denoted as branch cracking);and exhibiting slip lines and cracks on the surface of δ-Ni3Nb plates. At the init

关 键 词：K4169高温合金 循环应力 微观组织演变 LAVES相 δ-Ni3Nb相 

分 类 号：TG132.3[一般工业技术—材料科学与工程]