镍基单晶高温合金热机疲劳断裂特征

摘要

为了进一步提高镍基单晶高温合金的热机疲劳性能,通过微观结构解析研究了合金热机疲劳断裂特征.通过金相和扫描电子显微镜研究了热机疲劳断裂的断口特征和微观结构.研究表明：裂纹起源于形变孪晶与试样外表面的交截处,过程中的氧化有助于裂纹的长大;裂纹尖端的应力场诱发出大量形变孪晶,而形变孪晶的存在为裂纹进一步沿着孪晶界扩展提供了便利条件;镍基单晶高温合金的疲劳断裂主要是由于形变孪晶的形成以及裂纹沿孪晶界的扩展造成的.形变孪晶与高温合金疲劳断裂密切相关.%To improve the thermomechanical fatigue（TMF） property of Ni-base single crystal superalloy,fracture characteristics of the alloy were studied through microstructural analysis.The fracture characteristics and evolution of microstructures during thermomechanical fatigue tests were acquired using optical microscope as well as scanning electron microscope.The main crack is found to originate from the intersection of deformation twin plates with specimen surface,and then oxidation assists the growth of the crack.The stress concentration at the crack tip results in high density of deformation twins and the propagation of crack along the twin boundaries can lead to TMF failure of the specimen.The fracture failure of the Ni-base single crystal superalloy is attributed to the formation of deformation twins and the propagation of crack along the twin boundaries.