α+β型チタン合金の機械的性質と破壊に及ぼす微視組織の影響

京都大学0048新制・課程博士博士(工学)甲第22066号工博第4647号新制||工||1725(附属図書館)京都大学大学院工学研究科材料工学専攻(主査)教授 辻 伸泰, 教授 安田 秀幸, 教授 宇田 哲也学位規則第4条第1項該当Doctor of Philosophy (Engineering)Kyoto UniversityDFA

On the Aging Behavior of Ti-1.0 wt pct Fe Alloy With an Equiaxed α + β Initial Microstructure

The aging behavior (300 °C to 700 °C) of Ti-1.0 wt pct Fe alloy was investigated in this study, by means of various microstructural characterization techniques and micromechanical testing methods. The initial microstructure consisted of equiaxed α and β grains as well as athermal ω precipitates (ωath) with several tens of nanometers inside β grains. During the aging process, significant microstructural modifications took place within the β grains. At relatively lower aging temperatures (300 °C to 500 °C), the volume fraction of ωath gradually decreased with increasing aging temperature, until they were totally replaced by secondary α precipitates (αs) at 500 °C. With further increase of the aging temperature (500 °C ~ 700 °C), the size of αs precipitates substantially increased while the volume fraction gradually decreased, indicating a partial α to β reverse phase transformation. At aging temperatures higher than 600 °C, the re-precipitation of ωath from reverse-transformed β phase during water quench was identified. Due to an extremely high Fe concentration of these ωath that inherited from reverse-transformed β phase, their lattice constants were much smaller than those in the initial microstructure. The existence of ωath inside β phase promoted a homogeneous precipitation behavior of αs precipitates during aging, by providing much more potential intragranular nucleation sites. This led to the formation of plate-shaped αs precipitates with multiple crystallographic variants, in sharp contrast to the conventional α lamellar/colony structure with limited crystallographic variants obtained by thermomechanical processing in which αs precipitates directly transformed from β phase. Moreover, it was also revealed that the transformation of nano-sized ωath into αs precipitates as well as their subsequent coarsening led to a continuous decrease of the nano-hardness of prior β areas

Rapid acoustofluidic mixing by ultrasonic surface acoustic wave-induced acoustic streaming flow

Ultrasonic surface acoustic wave (SAW)-induced acoustic streaming flow (ASF) has been utilized for microfluidic flow control, patterning, and mixing. Most previous research employed cross-type SAW acousto-microfluidic mixers, in which the SAWs propagated perpendicular to the flow direction. In this configuration, the flow mixing was induced predominantly by the horizontal component of the acoustic force, which was usually much smaller than the vertical component, leading to energy inefficiency and limited controllability. Here, we propose a vertical-type ultrasonic SAW acousto-microfluidic mixer to achieve rapid flow mixing with improved efficiency and controllability. We conducted in-depth numerical and experimental investigations of the vertical-type SAW-induced ASF to elucidate the acousto-hydrodynamic phenomenon under varying conditions of total flow rate, acoustic wave amplitude, and fluid viscosity conditions. We conducted computational fluid dynamics simulations for numerical flow visualization and utilized micro-prism-embedded microchannels for experimental flow visualization for the vertical SAW-induced ASF. We found that the SAW-induced vortices served as a hydrodynamic barrier for the co-flow streams for controlled flow mixing in the proposed device. For proof-of-concept application, we performed chemical additive-free rapid red blood cell lysis and achieved rapid cell lysis with high lysis efficiency based on the physical interactions of the suspended cells with the SAW-induced acoustic vortical flows. We believe that the proposed vertical-type ultrasonic SAW-based mixer can be broadly utilized for various microfluidic applications that require rapid, controlled flow mixing

Transverse momentum and pseudorapidity distributions of charged hadrons in pp collisions at (s)\sqrt(s) = 0.9 and 2.36 TeV

Measurements of inclusive charged-hadron transverse-momentum and pseudorapidity distributions are presented for proton-proton collisions at sqrt(s) = 0.9 and 2.36 TeV. The data were collected with the CMS detector during the LHC commissioning in December 2009. For non-single-diffractive interactions, the average charged-hadron transverse momentum is measured to be 0.46 +/- 0.01 (stat.) +/- 0.01 (syst.) GeV/c at 0.9 TeV and 0.50 +/- 0.01 (stat.) +/- 0.01 (syst.) GeV/c at 2.36 TeV, for pseudorapidities between -2.4 and +2.4. At these energies, the measured pseudorapidity densities in the central region, dN(charged)/d(eta) for |eta| < 0.5, are 3.48 +/- 0.02 (stat.) +/- 0.13 (syst.) and 4.47 +/- 0.04 (stat.) +/- 0.16 (syst.), respectively. The results at 0.9 TeV are in agreement with previous measurements and confirm the expectation of near equal hadron production in p-pbar and pp collisions. The results at 2.36 TeV represent the highest-energy measurements at a particle collider to date