hiromuhisazawa/published_papers/33777992 Hiromu Hisazawa Morphology Evolution of γ′ Precipitates during Isothermal Exposure in Wrought Ni-Based Superalloy Inconel X-750 Materials Transactions null null 20170425 hiromuhisazawa/published_papers/33777991 Hiromu Hisazawa The Effect of Nb/Ti Ratio on Hardness in High-Strength Ni-Based Superalloys Metals null null 20170223 hiromuhisazawa/misc/33777722 Hisazawa Hiromu 久澤大夢 Kashiwase Sakiko 柏瀬早季子 Terada Yoshihiro 寺田芳弘 Coherency evaluation of α-Mg/C15-Al2Ca interface for a Mg-Al-Ca alloy Mg-Al-Ca合金におけるα-Mg/C15-Al2Ca界面の整合性評価 The C15-Al2Ca precipitates were observed using high-resolution transmission electron microscopy (HRTEM) to identify the coherency of the α-Mg/C15-Al2Ca interface for the Mg-5Al-1.5Ca alloy aged at the temperature range from 548 to 598 K. The α/C15 coherent interface turned to the semi-coherent one by the introduction of misfit dislocations on the planar surface of the C15 precipitates for the alloy aged at 598 K for 1 h, whereas the coherency was maintained for the alloy aged at 548 K for 10 h. The curve showing the loss of interface coherency was drawn in the TTP diagram for the Mg-5Al-1.5Ca alloy, which is indicated that the α/C15 interface coherency has remained within 3.6×107 s (10000 h) at 500 K. The Japan Institute of Light Metals 一般社団法人軽金属学会 Journal of Japan Institute of Light Metals 軽金属 0451-5994 71 2 127 129 20210000 10.2464/jilm.71.127 hiromuhisazawa/misc/33777708 Iwamaru Arata 井和丸新 Hisazawa Hiromu 久澤大夢 Terada Yoshihiro 寺田芳弘 Precipitation Behavior of Wrought Fe-Ni-Based Alloy HR6W 鍛造Fe-Ni基合金HR6Wにおける時効析出挙動 Age-hardening behavior of Fe-Ni-based alloy HR6W was investigated at the temperature range between 973 K and 1073 K. Two-step increase in hardness is detected for the alloy at each temperature; the first increase in hardness results from the precipitation of M23C6 phase and the second one corresponds to that of Laves phase. The TTP (time-temperature precipitation) diagram for the alloy is established based on the results of hardness measurement and microstructure observation, where the precipitation of Laves phase is slower than that of M23C6 phase by three orders of magnitude and the nose temperature of Laves phase is above 1073 K. The M23C6 phase precipitates with plate-like morphology along grain-boundaries at the early stage of aging, followed by the precipitation of Laves phase with granular morphology with increasing aging time. It is found that the M23C6 and Laves phases are aligned under stress condition, due to their precipitation on the dislocations introduced during creep deformation. The Japan Institute of Metals and Materials 公益社団法人日本金属学会 Journal of the Japan Institute of Metals and Materials 日本金属学会誌 0021-4876 83 1 30 35 20190000 10.2320/jinstmet.J2018046 hiromuhisazawa/misc/33777707 Kashiwase Sakiko 柏瀬早季子 Unekawa Mariko 畝川真梨子 Hisazawa Hiromu 久澤大夢 Terada Yoshihiro 寺田芳弘 Three-Dimensional Morphology of C15-Al2Ca Precipitates in a Mg-Al-Ca Alloy Mg–Al–Ca合金におけるC15–Al2Ca析出相の三次元的形状 The three-dimensional morphology and thickness of the C15–Al2Ca Laves phase, which precipitated within the primary α-Mg grains, were investigated for the Mg–5Al–1.5Ca alloy over-aged at 523 K for 100 h using the high-resolution transmission electron microscopy (HRTEM). The C15–Al2Ca phase precipitated with a hexagonal plate-like morphology along the (0001)α basal plane of the α-Mg matrix phase, where the sides of the hexagonal plates were parallel to the second columnar plane {1120}α of the α matrix. The typical coffee bean contrast was clearly visible around the precipitates, indicative of coherent precipitation of the C15–Al2Ca phase. The thickness of the C15–Al2Ca precipitates, which corresponds to the six layers of (111)C15 plane composed of Ca atoms, was evaluated to be approximately 1.5 nm. The Japan Institute of Metals and Materials 日本金属学会 Journal of the Japan Institute of Metals and Materials 日本金属学会誌 0021-4876 83 6 193 197 20190000 10.2320/jinstmet.J2019009 hiromuhisazawa/misc/33777706 Kashiwase Sakiko 柏瀬早季子 Unekawa Mariko 畝川真梨子 Hisazawa Hiromu 久澤大夢 Terada Yoshihiro 寺田芳弘 Coarsening of Plate-Like C15-Al2Ca Precipitates in a Mg-Al-Ca Alloy Mg–Al–Ca合金における平盤状C15–Al2Ca析出相の粗大化過程 The coarsening kinetics of the fine C15–Al2Ca Laves phase with a plate-like morphology, which precipitated within the primary α-Mg grains, were investigated for the Mg–5Al–1.5Ca alloy aged at 523 K. The Al2Ca precipitate coarsened with remaining coherency in the aging time below 300 h, and the quantitative relationship was obtained between precipitate length, l, and aging time, t, as follows; l ∝ t 0.23. By contrast, the α/C15 coherent interface turned to the semi-coherent one by the introduction of misfit dislocations on the planar surface of the precipitates in the aging time above 300 h, which resulted in the promotion of Al2Ca coarsening. The Al2Ca phase was deduced to precipitate through a nucleation and growth mechanism rather than spinodal decomposition, and its coarsening was explained using the terrace-ledge-kink mechanism. The aspect ratio of Al2Ca precipitates was predominantly decided by the aging temperature, and it decreased at higher aging temperatures. The Japan Institute of Metals and Materials 公益社団法人日本金属学会 Journal of the Japan Institute of Metals and Materials 日本金属学会誌 0021-4876 83 8 282 287 20190000 10.2320/jinstmet.J2019022 hiromuhisazawa/misc/33777711 Nomoto Asahi 野本朝輝 Kashiwase Sakiko 柏瀬早季子 Nakagawa Kyosuke 中川恭輔 Hisazawa Hiromu 久澤大夢 Terada Yoshihiro 寺田芳弘 Strengthening of Mg-Al-Ca Die-Cast Alloy with Fine C15-Al2Ca Precipitates Mg-Al-Caダイカスト合金における微細C15-Al2Ca相による析出分散強化 Age-hardening behavior of a Mg-4.98Al-1.46Ca (mass%) die-cast alloy was investigated at the temperature range between 473 and 623 K. Transmission electron microscopy shows that fine C15-Al2Ca precipitates with a disc-shaped morphology are placed on the (0001) basal plane of the α-Mg matrix phase at the 523 K/10 h peak-aged condition, while they coarsen at the 623 K/100 h over-aged condition. The ultimate tensile strength of the peak-aged alloy is usually higher than that of the over-aged alloy for approximately 40 MPa at both 298 and 473 K, indicating that the precipitation strengthening by fine C15-Al2Ca precipitates is operative even at high temperatures. Dislocations are introduced within the α-Mg matrix phase of the alloy during die-casting; the dislocations are mostly a type and the dislocation segments are mainly located on the (0001) basal plane. The interrelation between fine C15-Al2Ca precipitates and dislocations during tensile deformation is discussed based on the results of tensile tests. The Japan Institute of Metals and Materials 公益社団法人日本金属学会 Journal of the Japan Institute of Metals and Materials 日本金属学会誌 0021-4876 82 4 94 101 20180000 10.2320/jinstmet.JBW201702 hiromuhisazawa/misc/33777710 Yamaguchi Yoshiya 山口義矢 Hisazawa Hiromu 久澤大夢 Terada Yoshihiro 寺田芳弘 Microstructure Quantification in Wrought Ni-Based Superalloy Udimet 720Li 鍛造Ni基超合金 Udimet 720Liにおける析出相形態の定量的評価 The morphology of γ′ precipitates was quantitatively evaluated for wrought Ni-based superalloy Udimet 720Li by using the absolute moment invariant technique. The diameter of secondary γ′ precipitates, d, increases continuously with the decrease of cooling rate, v, after the solution treatment at 1473 K/1 h along the following equation; d ∝ v-0.4. It is found that the secondary γ′ precipitates changes from spherical to octo-dendrite in shape with the decrease of cooling rate. In the case of oil-quenched alloy after the solution treatment, the value of d continuously increases with aging time at 1173 K, while the spherical shape remains unchanged during aging. On the contrary, for the furnace-cooled alloy, the shape of secondary γ′ precipitates evolves from octo-dendrite to spherical in shape with aging time under the almost constant value of d. The Japan Institute of Metals and Materials 公益社団法人日本金属学会 Journal of the Japan Institute of Metals and Materials 日本金属学会誌 0021-4876 82 10 375 383 20180000 10.2320/jinstmet.JAW201801 hiromuhisazawa/misc/33777709 Hisazawa Hiromu 久澤大夢 Nomoto Asahi 野本朝輝 Terada Yoshihiro 寺田芳弘 Dislocation analysis of a Mg-Al-Ca alloy by transmission electron microscopy 透過型電子顕微鏡法によるMg–Al–Ca合金の転位解析 The dislocation structure was analyzed in a Mg-4.98Al-1.46Ca (mass%) alloy using invisible criterion with transmission electron microscopy. Basal and non-basal segment of dislocation induced during die-casting is determined as much <a> and a few <a+c> dislocation. After the aging at 523 K for 10 h and tensile deformation at 473 K, only basal <a> dislocation can be observed. This dislocation structure is not observed in crept specimens, which support the difference in dominant strengthening mechanism between creep and tensile deformation. The dislocation structure was analyzed in a Mg–4.98Al–1.46Ca (mass%) alloy using invisible criterion with transmission electron microscopy. Basal and non-basal segment of dislocation induced during die-casting is determined as much 〈a〉 and a few 〈a+c〉 dislocation. After the aging at 523 K for 10 h and tensile deformation at 473 K, only basal 〈a〉 dislocation can be observed. This dislocation structure is not observed in crept specimens, which support the difference in dominant strengthening mechanism between creep and tensile deformation. The Japan Institute of Light Metals 軽金属学会 Journal of Japan Institute of Light Metals 軽金属 0451-5994 68 10 552 554 20180000 10.2464/jilm.68.552 hiromuhisazawa/misc/33777712 hisazawa hiromu 久澤大夢 hisazawa hiromu The evaluation of precipitation morphology in Ni-based superalloys with contriling volume fraction of γ' phase γ′析出相の体積率を制御した Ni 基超合金における析出形態の評価 null null 20170300 hiromuhisazawa/misc/33777713 Hisazawa Hiromu 久澤大夢 Terada Yoshihiro 寺田芳弘 Effect of Ti and Al Contents on γ' Morphology in Wrought Ni-based Superalloys 鍛造型Ni 基超合金におけるγ′相の析出形態に及ぼすTiおよびAl添加量の影響 The effect of the content of Ti and Al on the morphology of γ′ precipitates is examined for 13 kinds of Ni-based model alloys aged at 1073 K/100 h. The morphology of γ′ precipitates was evaluated using the absolute moment invariants technique. The magnitude of cuboidal for γ′ particles clearly depends on the lattice misfit, but does not depend on the volume fraction of the particles. More γ′ particles tend to form a flat and parallel interface pair or elongated shape when the Ti and Al content is increased. These results suggest that the lattice misfit makes γ′ particles cuboidal and volume fraction strengthens their interaction, leading to a unique morphology. The Japan Institute of Metals and Materials 日本金属学会 Journal of the Japan Institute of Metals and Materials 日本金属学会誌 0021-4876 81 5 244 250 20170000 10.2320/jinstmet.J2016062 Hiromu Hisazawa Yoshihiro Terada Academy for Co-creative Education of Environment and Energy Scienece 環境エネルギー協創教育院 The 3rd International Education Forum on Environment and Energy Science Best Presentation Award γ ' Morphology and Lattice Misfit in Wrought Ni-based Superalloy with Low Volume Fraction of γ' Phase 20141200 Hiromu Hisazawa 久澤大夢 Tokyo Institute of Technology 東京工業大学 Nittono Award 入戸野賞 20120300 Hiromu Hisazawa Kohki Izumi Yoshihiro Terada Masao Takeyama Japan Institute of Metals 日本金属学会 Incentive award 奨励賞 Morphology of γ' precipitates and lattice misﬁt! in wrought Ni-based superalloy 20120300