Observation of lattice defects, deformation behavior in duplex alloys and evaluation of their lifetime using magnetic properties.

金属材料在疲劳变形过程中会出现大量的位错和平面断层。高密度点阵缺陷附近的应力集中引发微裂纹，最终发生断裂。为了了解变形机制和评估可靠性，有必要对位错等晶格缺陷进行观察。一般来说，晶格缺陷的观察是用电子显微镜进行的。然而，由于位错附近的高残余应力，很难获得位错性质的准确信息。众所周知，铁磁材料的磁性对晶格缺陷非常敏感。用磁性技术对晶格缺陷进行了观察。本文制备了FeAl、Fe_3Al和Ni_3（Al,Ti）含小γ析出物单晶的变形行为，并用磁法研究了它们的疲劳行为。FeAl和Fe_3Al的高场磁化率和自发磁化率受变形的影响。位错和断层的类型由高场磁化率的各向异性决定。由于FeAl在疲劳断裂前的自发磁化强度迅速增加，因此可以通过监测自发磁化强度来估计其寿命。

Numerous dislocations and planar faults in metallic materials are introduced during fatigue deformation. Stress concentration near high density of lattice defects initiates a microcrack and finally fracture occurs. To understand the deformation mechanism and evaluate the reliability observation of lattice defects such as dislocations is necessary.. In general, the observation of lattice defects is performed using electron microscope. However, it is very difficult to obtain exact information about nature of dislocations due to high residual stress near the dislocations. It is known that magnetic properties are very sensitive to lattice defects in ferromagnetic materials. The lattice defects have been observed by magnetic technique. In this work, deformation behavior of FeAl, Fe_3Al and Ni_3(Al,Ti) containing small γ precipitates single crystals were prepared and their fatigue behavior was examined by magnetic technique. High-field susceptibility and spontaneous magnetization in FeAl and Fe_3Al were influenced by deformation. Type of dislocation and planar faults were determined by anisotropy of high field susceptibility. Lifetime of FeAl can be estimated by monitoring spontaneous magnetization because the spontaneos magnetization rapidly increases just before fracture during fatigue.