Cyclic Deformation and Fracture Behavior of L1_2-Type Intermetallic Compounds Using Magnetic Properties

研究了具有L1_2结构的Ni3Fe和Ni3(Al，Ti)单晶的循环变形行为和断裂机制，重点研究了循环硬化/软化曲线、形变亚结构以及位错和平面断层引起的磁性能变化。而有序Ni3Fe单晶在初始循环硬化后表现出循环软化现象。在循环硬化阶段，透射电子显微镜观察到了较为发达的持久滑移带。磁自旋之间的相互作用和位错周围的内应力对磁性能有影响。利用疲劳Ni3Fe单晶的磁各向异性，确定了位错和平面断层。在循环硬化的初始阶段，位错作为一对由反相界结合在一起的位错发生往复运动。变形集中在PSB区，无序化发生在局域PSB区。局域无序导致了循环软化。局部形变引发微裂纹，导致晶体断裂。

Cyclic deformation behavior and fracture mechanism in Ni_3Fe and Ni_3(Al,Ti) single crystals with the L1_2 structure were examined focusing on the cyclic hardening/softening curves, the deformation substructure and changes in magnetic properties due to dislocations and planar faults.In a disordered state, Ni_3Fe showed monotonically cyclic hardening during cyclic loading. In contrast, ordered Ni_3Fe single crystals exhibited cyclic softening after initial cyclic hardening. In the stage of cyclic hardening, the well-developed persistent slip bands were observed by transmission electron microscopy. Magnetic properties were influenced by the interaction between magnetic spins and internal stress around dislocations. Using the magnetic anisotropy in fatigued Ni_3Fe single crystals, dislocations and planar faults were determined. At the initial stage of cyclic hardening, the to-and-fro motion of dislocations as a pair combined by an anti-phase boundary occurred. Deformation was concentrated in the PSB region and the disordering occurred in the localized PSB region. The localized disordering induced the cyclic softening. The localized deformation initiated a micro crack resulting in fracture of crystals.