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細谷 佳弘*; 松村 雄太*; 友田 陽*; 小貫 祐介*; Harjo, S.
鉄と鋼, 106(3), p.154 - 164, 2020/03
被引用回数：2 パーセンタイル：12.36(Metallurgy & Metallurgical Engineering)By using a steel with standardized chemical composition and conventional manufacturing processes for flat-rolled steel strip, a 1,500 MPa class stainless steel sheet, whose product of yield strength (YS) and total elongation (El) exceeds 30,000 MPa%, was developed and its mass production was established. Besides the excellent YS-El balance, the developed steel sheet has excellent performance for not only an anti-secondary work embrittlement but also high cycle fatigue endurance. The microstructure formation during the R&P process and the deformation mechanism that would bring about the excellent strength-ductility balance are discussed based on the results obtained from the in situ neutron diffraction measurement. The results have revealed that the typical Luders-like stress-strain curve of R&P steel is caused by competitive plastic flow between austenite and martensite, and an effective transformation induced plasticity phenomenon.
依田 真一; 衛藤 基邦
Journal of Nuclear Materials, 118, p.214 - 219, 1983/00
被引用回数：3 パーセンタイル：44.31(Materials Science, Multidisciplinary)本研究は、原子炉用微粒等方性黒鉛材料の微細組織および引張変形挙動に及ぼす静水圧応力負荷の影響について調べたものである。走査電子顕微鏡観察の結果、黒鉛結晶の層面間で静水圧負荷によって、はくりが生じこれがマイクロクラックの形式に結びつくことが明らかとなった。また、静水圧負荷により黒鉛表面の凸凹が著しくなった。これは、静水圧負荷により黒鉛材料が塑性変形した結果生じた現象である。静水圧負荷後の黒鉛材料の引張変形挙動には、静水圧予応力の増加に伴い、Flow stressの低下、引張強さの低下、残留歪(塑性歪)の増加が認められた。これらの現象は、黒鉛材料が静水圧負荷によって弱くなることを意味する。これらの結果から、黒鉛材料では多軸応力下において静水圧成分の影響を無視できないと結論された。
Harjo, S.; Gong, W.*; 相澤 一也; 川崎 卓郎
no journal, ,
Magnesium alloys containing a long period stacking ordered (LPSO) phase show high strength after hot extrusion. Not only texture and grain refinement, kinks introduced in the LPSO phase during hot extrusion are suggested to have also contribution to the strengthening. To confirm the formation of kink and its role in strengthening during deformation, in situ neutron diffraction measurements of a magnesium alloy consisting of 25 vol.% LPSO (Mg
Zn
Y
) during compressive and tensile deformation were performed using TAKUMI, the engineering materials diffractometer in Materials and Life Science Experimental Facility of J-PARC. An as-cast MgZnY alloy and that after hot-extrusion were used in this study. The intensity ratio in the axial direction showing the random texture before deformation change in the different manner for compression and tension due to twinning and deformation slip. Details are presented and discussed.
Harjo, S.; Gong, W.; 相澤 一也; 川崎 卓郎; 山崎 倫昭*; 河村 能人*
no journal, ,
Interesting mechanical properties changes were found in MgZn
Y
alloy containing about 25-vol% long-period stacking ordered phase (LPSO) in the HCP structured 
matrix (Mg), by hot-extrusion. In situ neutron diffraction measurements during tensile loading were conducted on three MgZnY alloys with different processes: as-casted, and after hot-extrusion at 623 K with extrusion ratios of 5.0 and 12.5, to elucidate the relation between the changes in microstructure by hot-extrusion with the changes in mechanical property. The yield strength of Mg increased by the hot-extrusion, but when the extrusion ratio increased the Mg yield strength ironically decreased. LPSO was found to be strengthened monotonically as the extrusion ratio increased.
Harjo, S.; 相澤 一也; Gong, W.; 川崎 卓郎; 山崎 倫昭*; 河村 能人*
no journal, ,
The MgZnY alloy, a magnesium alloy with a duplex microstructure consisting of an phase (Mg) and a long period stacking ordered phase (LPSO) of approximately 25 vol.%, showed high strength and high ductility after hot extrusion at 623 K. To understand tensile deformation behavior of each phase and effect of kinks to the strength of the alloy, we have performed in situ neutron diffraction measurements during tensile tests of the alloys in an as-cast condition and after extruded at 623 K with different extrusion ratios.
Harjo, S.; 相澤 一也; Gong, W.; 川崎 卓郎
no journal, ,
Mg相とLPSO相で構成される2相Mg合金は、熱間押出により強度と延性が両方とも増加した。その原因及び変形メカニズムを明らかにするために、引張変形中の中性子回折実験を行い構成相それぞれの応力変化を調べた。得られた回折パターンから、変形中の格子ひずみ、集合組織等の変化を求め、そしてMg相及びLPSO相の相応力を評価し、変形メカニズム議論を行った。Mg相は軟質相として振る舞っているが、LPSO相の相応力は押出比とほぼ比例して大きくなった。
Harjo, S.; Gong, W.; 川崎 卓郎; 相澤 一也
no journal, ,
HCP構造のマグネシウム合金の場合、弾塑性変形を開始すると、外力に対して格子ひずみが増加するhkl結晶粒と減少するhkl結晶粒が現れる。そのため応力への換算には、複数のhkl格子ひずみの平均、リートベルト法やポーリ法で得られた格子定数は用いられず、特定のhkl格子ひずみの選定に関する報告もなかった。本研究では、マグネシウム合金のその場中性子回折実験を行い、得られた格子ひずみ及び結晶方位変化より応力評価方法を検討した。
