Crack initiation and propagation behavior in γ’-Fe4N layer during monotonic and cyclic tensile deformation in the nitrided ultra-low carbon steel

In this study, the crack initiation and propagation behaviors of the gamma' layer in nitrided ultra-low carbon steel subjected to monotonic and cyclic tensile tests were investigated to comprehensively understand the deformation and fracture behavior of the Fe4N (gamma') phase. A gamma' layer with a grain size of approximately 2 mu m was successfully formed on the ferrite matrix through nitriding treatment by controlling the nitriding potential. After the monotonic tensile test until fracture, numerous microcracks were generated in the gamma' layer, and a few macrocracks were detected in the ferrite matrix propagated from the gamma' layer. The microcracks were initiated from the gamma' layer/ferrite matrix boundary and propagated to the surface along the {100}(gamma') in the grain or grain boundary during the monotonic tensile test. During the cyclic tensile test, after applying yield stress up to 10(5) cycles, microcracks were initiated from the voids around the surface and propagated to inside of the specimen along {111}(gamma') in the grain or grain boundary. The results demonstrated that, in the gamma' layer, the cracks propagated with the cleavage fracture on {100}(gamma') during the monotonic tensile test, and slipping-off occurred as a result of activating {111} slip systems during the cyclic tensile test. It is most likely that the macrocracks propagate in the ferrite grain where {100}(alpha) is parallel to the microcrack plane in the gamma' layer and lies in the direction perpendicular to the tensile direction.Web of Science5732207219

Ultrasound-Guided Peripheral Nerve Blocks Performed by Orthopedic Surgeons: A Retrospective, Multicenter Study in Akita Prefecture, Japan

The shortage of doctors is a societal problem, especially in rural areas such as Akita Prefecture, Japan. Therefore, it is not unusual in Akita for orthopedic surgeons to perform upper and lower limb surgeries under ultrasound-guided peripheral nerve blocks managed by the operators themselves. Multicenter studies of ultrasound-guided peripheral nerve blocks performed by orthopedic surgeons have not been reported. The purpose of this study was to clarify the safety and reliability of ultrasound-guided peripheral nerve blocks performed by orthopedic surgeons in Akita. A total of 1,674 upper extremity surgery cases operated under ultrasound-guided peripheral nerve blocks at 8 hospitals in Akita prefecture from April 2016 to April 2018 were investigated retrospectively. These blocks were performed by a total of 37 orthopedic surgeons, including senior surgeons and residents. In 321 of the 1,674 cases (19%), local anesthetics were added to the surgical field. Two cases with special factors were converted to general anesthesia. There were 2 cases of complications associated with the nerve block, but they were all transient and recovered promptly. The block site and the hospital where the block was performed showed a significant relationship with the addition of local anesthetics to the surgical site (P<0.001). Surgery time, age at surgery, and surgical site showed no significant relationships with the addition of local anesthetics. The volume of the anesthetic used for the nerve block showed a significant inverse relationship with the addition of local anesthetics (P=0.040). Many orthopedic surgeons in Akita prefecture began to perform ultrasound-guided peripheral nerve blocks, which had a reliable anesthesia effect with no noticeable complications, whether performed by residents or senior orthopedic surgeons, and this is a useful anesthetic technique for orthopedic surgeons