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en: Boron ion implantation on femtosecond-laser-irradiated diamond surface

en: Japanese Journal of Applied Physics

ja: Japanese Journal of Applied Physics


en: Creep Fracture of Copper Tricrystal along Grain Boundaries

en: The major objective of the present study was to investigate the creep fracture process of a copper tricrystal having 110 -tilt Σ3, 3, 9 grain boundaries. Creep tests at 0.81 TM (TM: melting temperature on the absolute temperature scale) under 4 MPa tensile stress were carried out for three samples prepared from the same tricrystal. Grain-boundary sliding occurred along only the Σ9 boundary, and the triple junction of the boundaries completely suppressed the sliding. The three samples were in different stages of creep deformation. Creep fracture was initiated by sliding-induced voids along the Σ9 boundary. Grain-boundary damage by the void formation developed into complete separation along the Σ9 boundary, and the Σ9 boundary crack induced surface grooves along one of the Σ3 boundaries, arranged almost perpendicular to the tensile axis. The crack propagation resulted in the final fracture of the tricrystal along the Σ9 and Σ3 boundaries. The formation of cavities in the Σ3 fracture surface suggested that the final fracture occurred in a ductile manner after the neighboring grains were partly separated along the Σ3 boundary.

en: Materials Transactions

ja: Materials Transactions


en: Coherency evaluation of α-Mg/C15-Al2Ca interface for a Mg-Al-Ca alloy

en: Journal of Japan Institute of Light Metals

ja: 軽金属


en: Creep fracture of aluminum and copper tricrystals having <110>-tilt Σ3, 3, 9 grain boundaries


en: Formation of ohmic Ni electrodes on femtosecond laser-modified 4H-SiC surface

en: Applied Physics. A, Materials Science & Processing


en: C15-Al2Ca Precipitation in a Mg-Al-Ca Alloy

en:
The coarsening kinetics of a fine C15Al2Ca Laves phase with a plate-like morphology precipitated within the primary α-Mg grains were investigated for Mg5Al1.5Ca alloy aged at 523 K. The Al2Ca precipitate coarsened as its coherence was retained in the aging time below 300 h, and a quantitative relationship was obtained between precipitate length (l) and aging time (t) as l t0.23. However, the α/C15 coherent interface changed into a semi-coherent interface by 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 assumed to precipitate through a nucleation and growth mechanism rather than spinodal decomposition, and its coarsening was explained using the terrace-ledge-kink mechanism. The result shows that the aspect ratio of the Al2Ca precipitates was predominantly determined by the aging temperature, and it decreased at higher aging temperatures.

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 83 (2019) 282287.


en: Local melting of Au/Ni thin films irradiated by femtosecond laser through GaN

ja: Applied Physics. A, Materials Science & Processing


en: Three-Dimensional Morphology of C15-Al2Ca Precipitates in a Mg-Al-Ca Alloy

en:
The three-dimensional morphology and thickness of an Al2Ca Laves phase with a C15 crystal structure, which precipitated within the primary α-Mg grain of a Mg5Al1.5Ca alloy that had been over-aged at 523 K for 100 h, were investigated using high-resolution transmission electron microscopy. The C15Al2Ca precipitate exhibits a hexagonal plate-like morphology, with a planar surface parallel to the (0001)α basal plane and the sides of the hexagonal plate parallel to the {1120} second columnar plane of the α matrix. A typical coffee bean contrast was clearly visible around the precipitate, which is indicative of the coherent precipitation of the C15Al2Ca phase with respect to the α-Mg matrix. The thickness of the Al2Ca precipitate, which corresponds to six layers of the (111)C15 plane composed of Ca atoms, was evaluated as approximately 1.5 nm.

This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 83 (2019) 193197.


en: Coarsening of Plate-Like C15/Al2Ca Precipitates in a Mg-Al-Ca Alloy

ja: Mg–Al–Ca合金における平盤状C15–Al2Ca析出相の粗大化過程

en: The coarsening kinetics of the fine C15Al2Ca Laves phase with a plate-like morphology, which precipitated within the primary α-Mg grains, were investigated for the Mg5Al1.5Ca 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.

en: Journal of the Japan Institute Metals

ja: 日本金属学会誌


ja: Mg–Al–Ca合金におけるC15–Al2Ca析出相の三次元的形状

en: The three-dimensional morphology and thickness of the C15-Al2-Ca Laves phase, which precipitated within the primary -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) basal plane of the Mg matrix phase, where the sides of the hexagonal plates were parallel to the second columnar plane {11-20} of the 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.


en: Microstructure Evolution of Fe-Ni-Based Alloy HR6W during Isothermal Aging


en: Microstructure Quantification in Nickel-Based Superalloy Udimet 720Li


en: Grain-Boundary Sliding and its Accommodation at Triple Junctions in Aluminum and Copper Tricrystals

en: Materials Transactions


en: Precipitation Behavior of Wrought Fe-Ni-Based Alloy HR6W

ja: 鍛造Fe-Ni基合金HR6Wにおける時効析出挙動

en: 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.


en: Femtosecond-laser-induced modifications on a 4H-SiC surface and their application to low-temperature diffusion at the Ni/SiC interface

en: Japanese Journal of Applied Physics


en: Dislocation analysis of a Mgla alloy by transmission electron microscopy

ja: 透過型電子顕微鏡法によるMg–Al–Ca合金の転位解析

en: 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 for 10 and tensile deformation at 473, 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.

en: Journal of Japan Institute of Light Metals


en: Microstructure Quantification in Wrought Ni-Based Superalloy Udimet 720Li

ja: 鍛造Ni基超合金 Udimet 720Li における析出相形態の定量的評価

en: 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.


en: Strengthening of Mg-Al-Ca Die-Cast Alloy with Fine C15-Al2Ca Precipitates

ja: 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

en: 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 -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 -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.


en: Morphology Evolution of γ' precipitates during Isothermal Exposure in Wrought Ni-based Superalloy Inconel X-750


en: The Effect of Nb/Ti Ratio on Hardness in High Strength Ni-based Superalloys

en: Metals

ja: Metals


en: Effect of Ti and Al Contents on γ Morphology in Wrought Ni-based Superalloys

ja: 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

en: 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.

en: Journal of the Japan Institute Metals


en: Low-temperature diffusion assisted by femtosecond laser-induced modifications at Ni/SiC interface

en: Applied Physics Express

ja: Applied Physics Express