Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Initialising ...
Shoji, Mizuki*; Kurihara, Kensuke*; Lobzenko, I.; Tsuru, Tomohito; Serizawa, Ai*
Keikinzoku, 74(12), p.535 - 545, 2024/12
While Plate-like Guinier-Preston (GP) zones are formed during aging process in Al-Cu alloys, spherical nanocluster formation occurs in the early stage of aging in Al-Mg-Si alloys. Unlike well-known GP (I) zone in Al-Cu, there is no specific configurations within the nanocluster. However, the solute concentration and local configuration should play decisive role in subsequent formation of precipitations. In the present study, the first-principles calculations were performed to investigate the factors determining the stable shape during the formation process of GP zones and clusters in Al-Cu and Al-Mg-Si alloys. As a result of formation energy of three-body bonds, the Cu-Cu-Cu triplet with the bond angle of 90deg was the most stable. Monte Carlo simulations with newly developed machine-learning potential were then performed, and consequently the segregation of Cu atom formed with bond angle of 90deg are observed more frequently. In contrast, three-body triplet in Al-Mg-Si alloy was most stable without any specific directional anisotropy, when the bond angle was 60deg, resulting in the formation of spherical nanoclusters. These results suggest that the intrinsic feature of the stability of local bonding dominates the shape of GP zones and nanoclusters, in which planar- or spherical-like cluster is formed.
Kurihara, Kensuke*; Lobzenko, I.; Tsuru, Tomohito; Serizawa, Ai*
Materials Transactions, 64(8), p.1930 - 1936, 2023/08
Times Cited Count：2 Percentile：17.79(Materials Science, Multidisciplinary)Nanoclusters formed in Al-Mg-Si alloys affect the aging behavior of the alloys depending on the formation temperature. In the present study, first-principles calculations were carried out to evaluate the two- and three-body interactions between Mg, Si atoms and vacancies in the Al matrix and estimate the effect of local bonding on the formation of nanoclusters. Monte Carlo simulations were subsequently performed to investigate the stable structure of the nanocluster formed in Al-0.95 mass pct Mg-0.81 mass pct Si alloy. We found that the Mg-Si and Si-Vac pairs are stable in the Al matrix. The result shows that the solute atoms easily aggregate with different types of solute atoms and that the Si atom has a strong attractive interaction with a vacancy. Furthermore, Mg-Si-vacancy three-body clusters is more stable than Mg-Si and Si-vacancy pairs in the Al matrix. The nanoclusters in the Al matrix were thermally stabilized by the stable configurations between solute atoms and vacancy. Thus, the electronic structure calculations suggested that the local bondings within a nanocluster play a significant role in not only the thermal stability but also the formation and growth behavior of nanoclusters during aging at low temperatures.
Kurihara, Kensuke*; Lobzenko, I.; Tsuru, Tomohito; Serizawa, Ai*
Keikinzoku, 72(7), p.427 - 429, 2022/07
Nanoclusters formed of the Al-Mg-Si alloy affect the aging behavior of the alloy depending on the formation temperature. Since Al, Mg and Si have adjacent atomic numbers, it is difficult to analyze them using the X-ray diffraction method. Therefore, in recent years, Al-Mg-Ge alloys in which Si is replaced with the homologous element Ge have been used. Attempts have been made to analyze the structure of the precipitate. In this study, we quantitatively evaluate the interaction between solute atoms and pores in Al-Mg-Si alloys and Al-Mg-Ge alloys using first-principles calculations based on the density general function theory, and solute atoms. From the viewpoint of bond stability between pores and pores, the precipitation behavior of both alloys was compared and examined.
Kurihara, Kensuke*; Lobzenko, I.; Tsuru, Tomohito; Serizawa, Ai*
Keikinzoku, 72(2), p.47 - 53, 2022/02
Nanoclusters formed in Al-Mg-Si alloys affect the aging behavior of the alloys depending on the formation temperature. In the present study, first-principles calculations were carried out to evaluate the two- and three-body interactions between Mg, Si atoms and vacancies in the Al matrix and to estimate the effect of local bond structures on the formation of nanoclusters. Monte Carlo simulations were subsequently performed to investigate the stable structure of nanocluster formed in Al-Mg-Si alloy. We found that Mg-Si bond and Si-Vac bond were stable in Al matrix. The result showed that the solute atoms are easy to aggregate with another type of atoms and that Si atom had a strong attractive interaction with a vacancy. Mg-Si-vacancy three-body bond were more stable than Mg-Si two-body bond and Si-vacancy two-body bond in Al matrix. Therefore, vacancies were strongly trapped within the cluster region due to the stable local bonds composed of Mg and Si atoms which indicates that the nanoclusters in Al matrix were thermally stabilized by the stable bonds between solute atoms and vacancy. In addition, these results suggested that inner bonds of nanocluster played a significant role in not only the thermal stability but also the formation and growth behavior of nanoclusters during aging at low temperatures.
collisions at 
= 200 GeVAdare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.
Physical Review D, 84(1), p.012006_1 - 012006_18, 2011/07
Times Cited Count：34 Percentile：75.46(Astronomy & Astrophysics)We report on the event structure and double helicity asymmetry (
) of jet production in longitudinally polarized collisions at = 200 GeV. Photons and charged particles were measured by the PHENIX experiment. Event structure was compared with the results from PYTHIA event generator. The production rate of reconstructed jets is satisfactorily reproduced with the next-to-leading-order perturbative QCD calculation. We measured = -0.0014 
0.0037 at the lowest 
bin and -0.0181 0.0282 at the highest bin. The measured is compared with the predictions that assume various 
distributions.
collisions at = 200 and 62.4 GeVAdare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Yasuyuki*; Al-Bataineh, H.*; Alexander, J.*; Aoki, Kazuya*; Aphecetche, L.*; Armendariz, R.*; et al.
Physical Review C, 83(6), p.064903_1 - 064903_29, 2011/06
Times Cited Count：194 Percentile：99.38(Physics, Nuclear)Transverse momentum distributions and yields for 
, and 
in collisions at = 200 and 62.4 GeV at midrapidity are measured by the PHENIX experiment at the RHIC. We present the inverse slope parameter, mean transverse momentum, and yield per unit rapidity at each energy, and compare them to other measurements at different collisions. We also present the scaling properties such as 
and 
scaling and discuss the mechanism of the particle production in collisions. The measured spectra are compared to next-to-leading order perturbative QCD calculations.
+ collisions at = 200 GeV and scaling properties of hadron productionAdare, A.*; Afanasiev, S.*; Aidala, C.*; Ajitanand, N. N.*; Akiba, Y.*; Al-Bataineh, H.*; Alexander, J.*; Aoki, K.*; Aphecetche, L.*; Armendariz, R.*; et al.
Physical Review D, 83(5), p.052004_1 - 052004_26, 2011/03
Times Cited Count：185 Percentile：98.32(Astronomy & Astrophysics)The PHENIX experiment at RHIC has measured the invariant differential cross section for production of 
, 
, 
and 
mesons in collisions at = 200 GeV. The spectral shapes of all hadron transverse momentum distributions are well described by a Tsallis distribution functional form with only two parameters, 
and 
, determining the high 
and characterizing the low regions for the spectra, respectively. The integrated invariant cross sections calculated from the fitted distributions are found to be consistent with existing measurements and with statistical model predictions.
Tobita, Kenji; Nishio, Satoshi; Enoeda, Mikio; Sato, Masayasu; Isono, Takaaki; Sakurai, Shinji; Nakamura, Hirofumi; Sato, Satoshi; Suzuki, Satoshi; Ando, Masami; et al.
Fusion Engineering and Design, 81(8-14), p.1151 - 1158, 2006/02
Times Cited Count：126 Percentile：98.94(Nuclear Science & Technology)no abstracts in English
Shoji, Mizuki*; Kurihara, Kensuke*; Du, J.-P.*; Ogata, Shigenobu*; Lobzenko, I.; Tsuru, Tomohito; Serizawa, Ai*
no journal, ,
Al-Mg-Si alloys are considered to have complex two-step aging behavior due to the contribution of nanoclusters that form in the early aging stage. In this study, the mechanism of nanocluster formation was investigated by using Kinetic Monte Carlo (KMC) calculations to explore the diffusion process of solute atoms in an Al-Mg-Si alloy model, taking into account diffusion barriers. The calculated diffusion behavior of solute atoms in the Al-Mg-Si alloy at 373 K reproduced the formation of nanoclusters with the Mg/Si ratio obtained experimentally.
