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Journal Articles

${it In situ}$ neutron diffraction revealing the achievement of excellent combination of strength and ductility in metastable austenitic steel by grain refinement

Mao, W.; Gong, W.; Harjo, S.; Morooka, Satoshi; Gao, S.*; Kawasaki, Takuro; Tsuji, Nobuhiro*

Journal of Materials Science & Technology, 176, p.69 - 82, 2024/03

 Times Cited Count:0 Percentile:0(Materials Science, Multidisciplinary)

The yield stress of Fe-24Ni-0.3C (wt.%) metastable austenitic steel increased 3.5 times (158 $$rightarrow$$ 551 MPa) when the average grain size decreased from 35 $$mu$$m (coarse-grained [CG]) to 0.5 $$mu$$m (ultrafine-grained [UFG]), whereas the tensile elongation was kept large (0.87 $$rightarrow$$ 0.82). ${it In situ}$ neutron diffraction measurements of the CG and UFG Fe-24Ni-0.3C steels were performed during tensile deformation at room temperature to quantitatively elucidate the influence of grain size on the mechanical properties and deformation mechanisms. The initial stages of plastic deformation in the CG and UFG samples were dominated by dislocation slip, with deformation-induced martensitic transformation (DIMT) also occurring in the later stage of deformation. Results show that grain refinement increases the initiation stress of DIMT largely and suppresses the rate of DIMT concerning the strain, which is attributed to the following effects. (i) Grain refinement increased the stabilization of austenite and considerably delayed the initiation of DIMT in the $$<$$111$$>$$//LD (LD: loading direction) austenite grains, which were the most stable grains for DIMT. As a result, most of the $$<$$111$$>$$//LD austenite grains in the UFG specimens failed to transform into martensite. (ii) Grain refinement also suppressed the autocatalytic effect of the martensitic transformation. Nevertheless, the DIMT with the low transformation rate in the UFG specimen was more efficient in increasing the flow stress and more appropriate to maintain uniform deformation than that in the CG specimen during deformation. The above phenomena mutually contributed to the excellent combination of strength and ductility of the UFG metastable austenitic steel.

Journal Articles

Cryogenic deformation behavior of a dual-phase Mg-Li alloy investigated by in-situ neutron diffraction

Gong, W.; Gholizadeh, R.*; Kawasaki, Takuro; Aizawa, Kazuya; Harjo, S.

Magnesium Technology 2024, p.89 - 90, 2024/03

Journal Articles

Hierarchical deformation heterogeneity during L$"u$ders band propagation in an Fe-5Mn-0.1C medium Mn steel clarified through ${it in situ}$ scanning electron microscopy

Koyama, Motomichi*; Yamashita, Takayuki*; Morooka, Satoshi; Yang, Z.*; Varanasi, R. S.*; Hojo, Tomohiko*; Kawasaki, Takuro; Harjo, S.

Tetsu To Hagane, 110(3), p.205 - 216, 2024/02

Journal Articles

Martensitic transformation behavior of Fe-Ni-C alloys monitored by ${it in-situ}$ neutron diffraction during cryogenic cooling

Yamashita, Takayuki*; Harjo, S.; Kawasaki, Takuro; Morooka, Satoshi; Gong, W.; Fujii, Hidetoshi*; Tomota, Yo*

ISIJ International, 64(2), p.192 - 201, 2024/01

Journal Articles

Probing deformation behavior of a refractory high-entropy alloy using ${it in situ}$ neutron diffraction

Zhou, Y.*; Song, W.*; Zhang, F.*; Wu, Y.*; Lei, Z.*; Jiao, M.*; Zhang, X.*; Dong, J.*; Zhang, Y.*; Yang, M.*; et al.

Journal of Alloys and Compounds, 971, p.172635_1 - 172635_7, 2024/01

 Times Cited Count:0 Percentile:0(Chemistry, Physical)

Journal Articles

Principal preferred orientation evaluation of steel materials using time-of-flight neutron diffraction

Xu, P. G.; Zhang, S.-Y.*; Harjo, S.; Vogel, S. C.*; Tomota, Yo*

Quantum Beam Science (Internet), 8(1), p.7_1 - 7_13, 2024/01

Journal Articles

Recrystallization of bulk nanostructured magnesium alloy AZ31 after severe plastic deformation; An in situ diffraction study

Liss, K.-D.*; Han, J.-K.*; Blankenburg, M.*; Lienert, U.*; Harjo, S.; Kawasaki, Takuro; Xu, P. G.; Yukutake, Eitaro*; Kawasaki, M.*

Journal of Materials Science, 23 Pages, 2024/00

 Times Cited Count:0 Percentile:0.01(Materials Science, Multidisciplinary)

Journal Articles

Stress evaluation method by neutron diffraction for HCP-structured magnesium alloy

Harjo, S.; Gong, W.; Kawasaki, Takuro

Quantum Beam Science (Internet), 7(4), p.32_1 - 32_13, 2023/12

Journal Articles

Effects of dislocation arrangement and character on the work hardening of lath martensitic steels

Dannoshita, Hiroyuki*; Hasegawa, Hiroshi*; Higuchi, Sho*; Matsuda, Hiroshi*; Gong, W.; Kawasaki, Takuro; Harjo, S.; Umezawa, Osamu*

Scripta Materialia, 236, p.115648_1 - 115648_5, 2023/11

 Times Cited Count:0 Percentile:0(Nanoscience & Nanotechnology)

Journal Articles

Measurement of mechanical behavior of $$^{11}$$B-enriched MgB$$_{2}$$ wire using a pulsed neutron source

Machiya, Shutaro*; Osamura, Kozo*; Hishinuma, Yoshimitsu*; Taniguchi, Hiroyasu*; Harjo, S.; Kawasaki, Takuro

Quantum Beam Science (Internet), 7(4), p.34_1 - 34_17, 2023/10

Journal Articles

Quantitatively evaluating the huge L$"u$ders band deformation in an ultrafine grain stainless steel by combining ${it in situ}$ neutron diffraction and digital image correlation analysis

Mao, W.; Gao, S.*; Gong, W.; Harjo, S.; Kawasaki, Takuro; Tsuji, Nobuhiro*

Scripta Materialia, 235, p.115642_1 - 115642_6, 2023/10

 Times Cited Count:1 Percentile:0(Nanoscience & Nanotechnology)

In the present study, a hybrid ${it in situ}$ neutron diffraction and digital image correlation measurement was performed on tensile deformation of an ultrafine grain (UFG) stainless steel exhibiting a huge L$"u$ders band deformation to evaluate the individual contribution of the austenite matrix and the deformation-induced martensite to the strain hardening during the propagation of the band. Quantitative analysis revealed that the strain hardening of the austenite matrix was insufficient to maintain a uniform deformation when the flow stress was greatly enhanced by the UFG structure. The strain hardening required for the L$"u$ders band to propagate was mostly provided by the formation of martensite and the high internal stress within it.

Journal Articles

Quantitatively evaluating respective contribution of austenite and deformation-induced martensite to flow stress, plastic strain, and strain hardening rate in tensile deformed TRIP steel

Mao, W.; Gao, S.*; Gong, W.; Bai, Y.*; Harjo, S.; Park, M.-H.*; Shibata, Akinobu*; Tsuji, Nobuhiro*

Acta Materialia, 256, p.119139_1 - 119139_16, 2023/09

 Times Cited Count:5 Percentile:90.35(Materials Science, Multidisciplinary)

Transformation-induced plasticity (TRIP)-assisted steels exhibit an excellent combination of strength and ductility due to enhanced strain hardening rate associated with deformation-induced martensitic transformation (DIMT). Quantitative evaluation on the role of DIMT in strain hardening behavior of TRIP-assisted steels and alloys can provide guidance for designing advanced materials with strength and ductility synergy, which is, however, difficult since the phase composition keeps changing and both stress and plastic strain are dynamically partitioned among constituent phases during deformation. In the present study, tensile deformation with ${it in situ}$ neutron diffraction measurement was performed on an Fe-24Ni-0.3C (wt.%) TRIP-assisted austenitic steel. The analysis method based on stress partitioning and phase fractions measured by neutron diffraction was proposed, by which the tensile flow stress and the strain hardening rate of the specimen were resolved into factors associated with each phase, i.e., the austenite matrix, deformation-induced martensite, and the transformation rate of DIMT after differentiation, and then the role of each factor in the global strain hardening behavior was discussed. In addition, the plastic strain partitioning between austenite and martensite was indirectly estimated using the dislocation density measured by diffraction profile analysis, which constructed the full picture of stress and strain partitioning between austenite and martensite in the material. The results suggested that both the transformation rate and the phase stress borne by the deformation-induced martensite played important roles in the global tensile properties of the material. The proposed decomposition analysis method could be widely applied to investigating mechanical behavior of multi-phase alloys exhibiting the TRIP phenomenon.

Journal Articles

Strengthening of $$alpha$$Mg and long-period stacking ordered phases in a Mg-Zn-Y alloy by hot-extrusion with low extrusion ratio

Harjo, S.; Gong, W.; Aizawa, Kazuya; Kawasaki, Takuro; Yamasaki, Michiaki*

Acta Materialia, 255, p.119029_1 - 119029_12, 2023/08

 Times Cited Count:6 Percentile:95.52(Materials Science, Multidisciplinary)

Journal Articles

Journal Articles

${it In situ}$ neutron diffraction study on the deformation behavior of the plastic inorganic semiconductor Ag$$_{2}$$S

Wang, Y.*; Gong, W.; Kawasaki, Takuro; Harjo, S.; Zhang, K.*; Zhang, Z. D.*; Li, B.*

Applied Physics Letters, 123(1), p.011903_1 - 011903_6, 2023/07

 Times Cited Count:1 Percentile:54.89(Physics, Applied)

Journal Articles

Lattice parameters of austenite and martensite during transformation for Fe-18Ni alloy investigated through ${it in situ}$ neutron diffraction

Gong, W.; Harjo, S.; Tomota, Yo*; Morooka, Satoshi; Kawasaki, Takuro; Shibata, Akinobu*; Tsuji, Nobuhiro*

Acta Materialia, 250, p.118860_1 - 118860_16, 2023/05

 Times Cited Count:2 Percentile:74.65(Materials Science, Multidisciplinary)

Journal Articles

High-density nanoprecipitates and phase reversion via maraging enable ultrastrong yet strain-hardenable medium-entropy alloy

Kwon, H.*; Sathiyamoorthi, P.*; Gangaraju, M. K.*; Zargaran, A.*; Wang, J.*; Heo, Y.-U.*; Harjo, S.; Gong, W.; Lee, B.-J.*; Kim, H. S.*

Acta Materialia, 248, p.118810_1 - 118810_12, 2023/04

 Times Cited Count:13 Percentile:99.28(Materials Science, Multidisciplinary)

Journal Articles

Competitive strengthening between dislocation slip and twinning in cast-wrought and additively manufactured CrCoNi medium entropy alloys

Woo, W.*; Kim, Y. S.*; Chae, H. B.*; Lee, S. Y.*; Jeong, J. S.*; Lee, C. M.*; Won, J. W.*; Na, Y. S.*; Kawasaki, Takuro; Harjo, S.; et al.

Acta Materialia, 246, p.118699_1 - 118699_13, 2023/03

 Times Cited Count:11 Percentile:98.19(Materials Science, Multidisciplinary)

Journal Articles

Evolution of austenite lattice parameter during isothermal transformation in a 0.4 C low alloyed steel

Wang, Y.*; Tomota, Yo*; Omura, Takahito*; Gong, W.; Harjo, S.

Materialia, 27, p.101685_1 - 101685_9, 2023/03

Journal Articles

Neutron stress measurement of W/Ti composite in cryogenic temperatures using time-of-flight method

Nishida, Masayuki*; Harjo, S.; Kawasaki, Takuro; Yamashita, Takayuki*; Gong, W.

Quantum Beam Science (Internet), 7(1), p.8_1 - 8_15, 2023/03

443 (Records 1-20 displayed on this page)