The deformation behavior of single crystals of the sigma-phase compound FeCr with the tetragonal D8b structure has been investigated by micropillar compression at room temperature as a function of ...crystal orientation and specimen size. In spite of the repeatedly reported brittleness, plastic flow is observed at room temperature for all loading axis orientations tested. Three slip systems, {100}001, {100} and {111}<01¯1> are newly identified to be operative at room temperature depending on the loading axis, in addition to {110}001 slip we previously identified. The CRSS values for all the identified slip systems are very high exceeding 1.3 GPa and decrease with increasing specimen size, following an inverse power-law relationship with a very small power-law exponent. Similarly to {110}001 slip, {100}001 slip is confirmed to be carried by the motion of 001 zonal dislocations through atomic-resolution scanning transmission electron microscopy imaging of their core structures. dislocations gliding on {100} are confirmed to dissociate into two collinear partial dislocations, while <01¯1> dislocations gliding on {111} to dissociate into three collinear partial dislocations. The fracture toughness values estimated by micro-cantilever bend tests of chevron-notched micro beam specimens are indeed very low, 1.6∼1.8 MPa·m1/2 (notch plane // (001) and (100)), indicating significant brittleness of sigma FeCr.
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Dislocation glide to carry plastic deformation in simple metals and alloys is a well-understood process, but the process in materials with complex crystal structures is not yet understood completely ...as it can be very complicated often involving multiple atomic planes during dislocation glide. The zonal dislocation is one of the examples predicted to operate in complex materials, and during glide it involves multiple atomic planes called shear zone, in which non-uniform atom shuffling occurs. We report direct observation made by Z-contrast atomic-resolution microscopy of the zonal dislocation in the σ phase FeCr. The result confirms the zonal dislocation indeed operates in this material. Knowledge gained on the dislocation core structure will lead to improved understanding of deformation mechanisms in this and other complex crystal structures and provide ways to improve the brittleness of these complex materials.
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•Plastic deformation behavior of α-Mn single crystals was investigated by micropillar compression at room temperature.•α-Mn single crystals are found to plastically deform by dislocation motion at ...room temperature, accompanied by very high yield stresses of the range of 4–6 GPa.•Slip along 111 and 001 are identified to operate.•Any low-indexed slip planes cannot be assigned for both slip, because of the significantly wavy nature of slip lines.
The deformation behavior of single crystals of α-manganese has been investigated by micropillar compression at room temperature as a function of crystal orientation and specimen size. When the specimen size is reduced to the micrometer-range, single crystals of α-manganese are found to plastically deform by dislocation motion at room temperature for the first time, accompanied by very high yield stresses of the range of 4–6 GPa. Slip along 111 and 001 are identified to operate for compression axis orientations near 001 and near 011 and 1¯11, respectively. Any low-indexed planes cannot be designated as the slip plane for both slip along 111 and 001, because of the significantly wavy nature of slip lines caused by the occurrence of frequent cross-slip. Slip along 111 tends to prefer the slip plane of {112} rather than {110}. Slip along 001, on the other hand, tends to occur on the maximum resolved shear stress plane. The 1/2111 dislocation carrying slip along 111 moves as a perfect dislocation without dissociating into partials and does not have any preferred orientation. The 001 dislocation carrying slip along 001 also moves as a perfect dislocation without dissociating into partials. Although the Peierls stress for the motion of these dislocations must be very high, there seems no deep Peierls valleys along particular directions, unlike the screw direction for the 1/2111 dislocation in body-centered cubic metals.
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The living-donor lobar lung transplantation procedure has been developed clinically as an alternative approach for patients considered too ill to await cadaveric transplantation. With this procedure, ...2 lobes are implanted in the recipient in place of whole right and left lungs, respectively. However, the shortage of graft volume can be a problem when compared with full-sized cadaveric grafts. In an attempt to solve this problem, we have developed a native lobe-preserving lobar transplant technique using a large animal model. We report a first successful case of a patient undergoing native lobe-preserving lobar lung transplantation for severe pulmonary emphysema.
Dry pleural dissemination in non-small cell lung cancer, defined as solid pleural metastasis of lung cancer without pleural effusion, is a condition occurring in T4 lung cancer. Positron emission ...tomography (PET) has been reported to be useful for the diagnosis and staging of lung cancer. It has been reported that positive findings on PET scans of indeterminate pleural abnormalities at computed tomography (CT) are sensitive to malignancy. We encountered two cases of dry small pleural dissemination of adenocarcinoma of the lung preoperatively detected by PET/CT. A 75-year-old man and a 66-year-old man underwent CT scan, which demonstrated solitary tumor in the lung, an enlarged mediastinal lymph node, and a small pleural nodule less than 10 mm in size, all of which were positive findings on the fluorine 18 fluorodeoxyglucose (FDG) PET portion of an integrated PET/CT. Both patients underwent thoracoscopic biopsy of the dry pleural nodule revealing dissemination of adenocarcinoma of the lung (T4). Whereas histological thoracoscopic diagnosis remains mandatory before planning treatment, our cases may suggest that PET/CT will be useful as a screening modality for dry pleural dissemination of lung cancer.
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