Influence of Input Energy Density on Morphology of Unique Layered Microstructure of γ-TiAl Alloys Fabricated by Electron Beam Powder Bed Fusion

Microstructure and tensile properties of Ti–48Al–2Cr–2Nb (at%) rods fabricated by electron beam powder bed fusion (EB-PBF) process were investigated by changing input energy density (ED) which is one of the important factors affecting formation of the melt pool. We found that unique layered microstructure consisting of an equiaxed γ grain layer (γ band) and a duplex region can be formed by EB-PBF with ED in the range of 13 to 31 J/mm3. It is interesting to note that the width of the γ band and the volume fraction of the γ phase in the duplex region decrease with increasing ED. On the other hand, the α2/γ lamellar grain in the duplex region increases with increasing ED. These morphological changes in the layered microstructure are attributed to variation of temperature distribution from melt pool caused by increasing ED. Moreover, we also found for the first time the strength of the alloys can be improved by decreasing width of the γ band and increasing of the α2/γ lamellar grain in the duplex region. Whereas, the width of the γ band and the fraction of the equiaxed γ grain in the duplex region should be increased to enhance ductility of the alloys.Cho Ken, Morita Naohide, Matsuoka Hiromasa, et al. Influence of Input Energy Density on Morphology of Unique Layered Microstructure of γ-TiAl Alloys Fabricated by Electron Beam Powder Cho Ken, Morita Naohide, Matsuoka Hiromasa, et al. Influence of Input Energy Density on Morphology of Unique Layered Microstructure of γ-TiAl Alloys Fabricated by Electron Beam Powder Bed Fusion. MATERIALS TRANSACTIONS 64, 44 (2023); https://doi.org/10.2320/matertrans.MT-MLA2022015

Current-induced magnetization switching in MgO barrier magnetic tunnel junctions with CoFeB based synthetic ferrimagnetic free layers

We investigated the effect of using a synthetic ferrimagnetic (SyF) free layer in MgO-based magnetic tunnel junctions (MTJs) on current-induced magnetization switching (CIMS), particularly for application to spin-transfer torque random access memory (SPRAM). The employed SyF free layer had a Co40Fe40B20/ Ru/ Co40Fe40B20 and Co20Fe60B20/Ru/Co20Fe60B20 structures, and the MTJs(100x(150-300) nm^2) were annealed at 300oC. The use of SyF free layer resulted in low intrinsic critical current density (Jc0) without degrading the thermal-stability factor (E/kBT, where E, kB, and T are the energy potential, the Boltzmann constant, and temperature,respectively). When the two CoFeB layers of a strongly antiferromagnetically coupled SyF free layer had the same thickness, Jc0 was reduced to 2-4x10^6 A/cm^2. This low Jc0 may be due to the decreased effective volume under the large spin accumulation at the CoFeB/Ru. The E/kBT was over 60, resulting in a retention time of over ten years and suppression of the write current dispersion for SPRAM. The use of the SyF free layer also resulted in a bistable (parallel/antiparallel) magnetization configuration at zero field, enabling the realization of CIMS without the need to apply external fields to compensate for the offset field.Comment: 6 page

Williams症候群患者における口腔顎顔面領域の形態学的検討

Williams症候群は,1961年にWilliamsらが精神遅滞,大動脈弁上部狭窄および特異顔貌を有する症候群として報告した疾患で,染色体7q11.23にあるエラスチン遺伝子,LIMキナーゼ1遺伝子などを始めとする約20種類の遺伝子を含む領域の微小欠失が原因の隣接遺伝子症候群と考えられている.今回われわれは,本疾患群に対し口腔顎顔面領域の形態学的検討を行ったので報告する.対象は当院附属日本心臓血圧研究所循環器小児科でFISH法により染色体7q11.23の微細欠失が確認されWilliams症候群と確定診断された患者15例で,方法は頭部X線規格写真,顎態模型,口腔内およびX線所見による分析を行い,頭部X線規格写真分析の方法はRicketts法を使用した.結果は,頭部X線規格写真分析では下顎のアーク,下顎中切歯突出量,上顎大臼歯の位置,前頭蓋底の長さ,下唇の突出量が高値で日本人平均値と比較し有意差を認め,その結果,上顎前突,下顎前歯の唇側傾斜,下唇の突出および顔面形態ではdolicofacial patternなどがWilliams症例の顔貌上の特徴と考えられた,顎態模型,口腔内およびX線所見による分析では歯の先天性欠如が10例26歯に認められ,下顎側切歯が11歯(42.3%)と最も多かった.歯の奇形は10例(48歯)に認め,矮小歯が6例(14歯),短根歯が6例(34歯)であり,矮小歯では上顎側切歯が12歯(85.7%)と最も多く,短根歯では上顎第二小臼歯が9歯(26.5%)と最も多かった.このように顎顔面口腔領域の異常が高率に認められることからWilliams症候群においては定期的な歯科口腔外科的チェックと早期からの歯科矯正学的治療が重要であると考えられる.Williams syndrome was reported in 1961 by Williams and coworkers as a syndrome characterized by mental retardation, supravalvular aortic stenosis, and specific facies. It is thought to be a contiguous gene syndrome that is a neurocognitive disorder commonly caused by a 1.5 Mb deletion containing about 20 genes, for example the elastin gene, the LIM kinase 1 gene, on chromosome band 7q11.23. Accordingly, in the present study we conducted a morphological study of the oral and maxillofacial area in patients with Williams syndrome. The subjects were 15 patients found to have a microdeletion of chromosome 7q11.23 and diagnosed as having Williams syndrome. The methods used consisted of conducting analyses of cephalometric radiograms of the head and gnathostatic models, and the oral and radiographic findings. An analysis of cephalometric radiograms of the head revealed significantly higher values for mandibular arch, mandibular incisor protrusion, upper molar position, cranial length anterior, and lip protrusion than the mean values in Japanese, and as a result the facies of Williams syndrome patients appeared to be characterized by maxillary protrusion, labial inclination of the lower incisor, protrusion of the lower lip, and, in terms of facial description, a dolicofacial pattern. Analysis of gnathostatic models and the oral and radiographic findings showed congenitally missing teeth, microdontia, short-rooted teeth

Williams症候群患者における口腔顎顔面領域の形態学的検討

Williams症候群は,1961年にWilliamsらが精神遅滞,大動脈弁上部狭窄および特異顔貌を有する症候群として報告した疾患で,染色体7q11.23にあるエラスチン遺伝子,LIMキナーゼ1遺伝子などを始めとする約20種類の遺伝子を含む領域の微小欠失が原因の隣接遺伝子症候群と考えられている.今回われわれは,本疾患群に対し口腔顎顔面領域の形態学的検討を行ったので報告する.対象は当院附属日本心臓血圧研究所循環器小児科でFISH法により染色体7q11.23の微細欠失が確認されWilliams症候群と確定診断された患者15例で,方法は頭部X線規格写真,顎態模型,口腔内およびX線所見による分析を行い,頭部X線規格写真分析の方法はRicketts法を使用した.結果は,頭部X線規格写真分析では下顎のアーク,下顎中切歯突出量,上顎大臼歯の位置,前頭蓋底の長さ,下唇の突出量が高値で日本人平均値と比較し有意差を認め,その結果,上顎前突,下顎前歯の唇側傾斜,下唇の突出および顔面形態ではdolicofacial patternなどがWilliams症例の顔貌上の特徴と考えられた,顎態模型,口腔内およびX線所見による分析では歯の先天性欠如が10例26歯に認められ,下顎側切歯が11歯(42.3%)と最も多かった.歯の奇形は10例(48歯)に認め,矮小歯が6例(14歯),短根歯が6例(34歯)であり,矮小歯では上顎側切歯が12歯(85.7%)と最も多く,短根歯では上顎第二小臼歯が9歯(26.5%)と最も多かった.このように顎顔面口腔領域の異常が高率に認められることからWilliams症候群においては定期的な歯科口腔外科的チェックと早期からの歯科矯正学的治療が重要であると考えられる.Williams syndrome was reported in 1961 by Williams and coworkers as a syndrome characterized by mental retardation, supravalvular aortic stenosis, and specific facies. It is thought to be a contiguous gene syndrome that is a neurocognitive disorder commonly caused by a 1.5 Mb deletion containing about 20 genes, for example the elastin gene, the LIM kinase 1 gene, on chromosome band 7q11.23. Accordingly, in the present study we conducted a morphological study of the oral and maxillofacial area in patients with Williams syndrome. The subjects were 15 patients found to have a microdeletion of chromosome 7q11.23 and diagnosed as having Williams syndrome. The methods used consisted of conducting analyses of cephalometric radiograms of the head and gnathostatic models, and the oral and radiographic findings. An analysis of cephalometric radiograms of the head revealed significantly higher values for mandibular arch, mandibular incisor protrusion, upper molar position, cranial length anterior, and lip protrusion than the mean values in Japanese, and as a result the facies of Williams syndrome patients appeared to be characterized by maxillary protrusion, labial inclination of the lower incisor, protrusion of the lower lip, and, in terms of facial description, a dolicofacial pattern. Analysis of gnathostatic models and the oral and radiographic findings showed congenitally missing teeth, microdontia, short-rooted teeth