Papers - HAGIHARA Koji
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Fracture behavior and toughness of NbSi2-based single crystals and MoSi2(C11(b))/NbSi2(C40) duplex crystals with a single set of lamellae Reviewed
K. Hagihara, T. Nakano
ACTA MATERIALIA 59 ( 10 ) 4168 - 4176 2011.06
Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD
The fracture behavior and toughness of (Mo0.85Nb0.15)Si-2 suicide crystals were investigated by three-point bending tests. Crystals with two different microstructures, namely the C40 single-phase single-crystalline form and MoSi2(C11(b))/NbSi2(C40) duplex crystals with an oriented single set of lamellae, were prepared, and their fracture behaviors were compared. The duplex microstructure improved the toughness, exhibiting higher values than the C40 single-phase single crystals at almost all loading orientations. An increase of more than 20% in the fracture toughness was obtained in a duplex specimen, A-2, in which the lamella boundaries are parallel to the side surface and have a notch face parallel to (1 (2) over bar 1 0)(C40). A complicated morphology appeared in the fracture surface of specimen A-2 as a result of significant deflection of crack propagation. Crack deflection occurred predominantly along the plane parallel to {1 0 (1) over bar 0} cleavage planes in the constituent C40 phase. The C11b lamella effectively prevented the initial rapid propagation of cracks along the notched plane, because the ease of gliding of its dislocations and its deformability effectively accommodated stress concentration. This induced crack deflection, resulting in improved fracture toughness. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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Plastic Deformation Behavior of Mg12ZnY LPSO-Phase with 14H-Typed Structure Reviewed
K. Hagihara, Y. Sugino, Y. Fukusumi, Y. Umakoshi, T. Nakano
MATERIALS TRANSACTIONS 52 ( 6 ) 1096 - 1103 2011.06
Language：English Publishing type：Research paper (scientific journal) Publisher：JAPAN INST METALS
We investigated the influence of a change in the stacking sequence of the close-packed plane in a Mg12ZnY long-period stacking ordered (LPSO) phase on its mechanical properties. A 14H-typed LPSO-phase crystal was fabricated by annealing a directionally solidified (DS) crystal with a 18R-typed LPSO-structure at 525 degrees C for 3 days, and the temperature dependence and orientation dependence of the yield stress were examined via compression tests. (0001)< 11 (2) over bar0 > basal slip was identified as a dominant deformation mode, and deformation kink bands were formed under compression in the case of suppression of basal slip motion. The deformation mechanism of the 14H-typed LPSO-phase is almost similar to that of the 18R-typed LPSO-phase, even though a slight difference was observed at temperatures above 300 degrees C. [doi:10.2320/matertrans.MC201007]
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Effect of multimodal microstructure evolution on mechanical properties of Mg-Zn-Y extruded alloy Reviewed
Michiaki Yamasaki, Kenji Hashimoto, Koji Hagihara, Yoshihito Kawamura
ACTA MATERIALIA 59 ( 9 ) 3646 - 3658 2011.05
Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD
A high strength Mg-Zn-Y alloy featuring increased ductility and a multimodal microstructure is developed. The microstructure of the extruded Mg-Zn-Y alloy consists of three regions: a dynamically recrystallized alpha-Mg fine-grain region with random orientation; a hot-worked alpha-Mg coarse-grain region with strong basal texture; and a long-period stacking ordered (LPSO) phase grain region. Having found that bimodal microstructure evolution in the alpha-Mg matrix is influenced by the morphology of the LPSO phase in the as-cast state, the authors investigate the effect of secondary dendrite arm spacing (SDAS) in the cast state on the microstructure evolution and mechanical properties of the extruded Mg-Zn-Y alloy. Mg-Zn-Y alloy ingots with various SDAS are obtained by temperature-controlled solidification techniques at various cooling rates. Mg-Zn-Y ingots are extruded at 623 K and an extrusion ratio of 10. A decrease in SDAS is associated with dynamic recrystallization of the alpha-Mg phase region and a high dispersion of fiber-shaped LPSO phase during extrusion. An increase in dynamically recrystallized alpha-Mg grains with very weak texture improves ductility; the effective dispersion of the hot-worked alpha-Mg grains with a strong basal texture and the fiber-shaped LPSO phase grains conspire to strengthen the alloy. (C) 2011 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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Effects of Cr-addition and lamellar microstructure on the oxidation behavior of single crystal (Mo0.85Nb0.15)Si-2 Reviewed
Ou Zhu, Lanting Zhang, Jinxing Yu, Aidang Shan, Jiansheng Wu, Koji Hagihara, Takayoshi Nakano
JOURNAL OF ALLOYS AND COMPOUNDS 509 ( 5 ) 1511 - 1516 2011.02
Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE SA
The oxidation behavior of (Mo0.85Nb0.15)Si-2 single crystals and the influence of Cr-addition were studied focusing on its microstructure dependence. Cr-addition to single-phase C40-structured (Mo0.85Nb0.15)Si-2 crystal induced the formation of crystalline silica, leading to slightly larger weight gain during the oxidation test at 1200 degrees C. Furthermore, Cr-addition to C40/C11(b) duplex-phase (Mo0.85Nb0.15)Si-2 crystal with lamellar structure strongly suppressed the internal oxidation of the C11(b) phase, resulting in excellent oxidation resistance. C40/C11(b) lamellae-structured crystals showed better oxidation resistance than the C40-structured crystals. (C) 2010 Elsevier B.V. All rights reserved.
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OS2017 Mg基LPSO相の塑性挙動に及ぼす組織学的因子(OS20-3 チタンおよびLPSO型マグネシウム合金,OS-20 HCP金属の実験力学と計算力学)
萩原 幸司, 木下 昭人, 福住 嘉浩, 山崎 倫昭, 河村 能人
M&M材料力学カンファレンス 2011 ( 0 ) _OS2017 - 1_-_OS2017-2_ 2011
Language：Japanese Publishing type：Research paper (scientific journal) Publisher：一般社団法人 日本機械学会
Microstructural factors that govern the plastic deformation of the long-period stacking ordered (LPSO) phase were examined. The decrease in length of the long-axis for the plate-like shape of LPSO-phase grains increases the yield stress of the alloy in which basal slip is predominant in deformation. On the other hand, the yield stress tends to increase as the thickness of the plate-like shapes of the grains decreases for the alloy in which the formation of deformation kinks carries the strain.
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Low Young's modulus of Ti-Nb-Ta-Zr alloys caused by softening in shear moduli c ' and c(44) near lower limit of body-centered cubic phase stability Reviewed
M. Tane, S. Akita, T. Nakano, K. Hagihara, Y. Umakoshi, M. Niinomi, H. Mori, H. Nakajima
ACTA MATERIALIA 58 ( 20 ) 6790 - 6798 2010.12
Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD
The composition and temperature dependence of the elastic properties and phase stability of quaternary Ti-Nb-Ta-Zr beta-phase alloys with a body-centered cubic structure, developed for biomedical applications, were investigated using their single crystals, in order to clarify the origin of the low Young's modulus in polycrystals. Transmission electron microscopy observations clarified that alpha '' martensitic transformation occurred in a temperature range that depended on the beta-phase stability below room temperature. Electromagnetic acoustic resonance measurements clarified that the shear moduli c' and c(44) of single crystals softened upon cooling from room temperature and became rather low near the martensitic transformation start temperature, i.e. the lower limit of beta-phase stability. An analysis by the Hill approximation indicates that low c' and c(44) caused the low Young's modulus, and thus it is probable that the softening in c' and c(44) is the origin of the low Young's modulus. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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Effect of long-period stacking ordered phase on mechanical properties of Mg97Zn1Y2 extruded alloy Reviewed
K. Hagihara, A. Kinoshita, Y. Sugino, M. Yamasaki, Y. Kawamura, H. Y. Yasuda, Y. Umakoshi
ACTA MATERIALIA 58 ( 19 ) 6282 - 6293 2010.11
Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD
The mechanical properties of Mg97Zn1Y2 extruded alloy, composed of Mg matrix phase and a long-period stacking ordered phase, the so-called LPSO phase, with a volume fraction of approximately 24%, were investigated using compression tests at room temperature. The microstructure was varied to a large degree by various heat treatments at high temperatures above 400 degrees C, and the relationship between the microstructure and mechanical properties was clarified. The plastic behavior of the Mg,/LPSO two-phase alloy was compared with that of Mg99.2Zn0.2Y0.6 alloy, composed almost Mg-solid-solution phase, and the strengthening mechanisms at work in the Mg97Zn1Y2 extruded alloy are discussed. The existence of the LPSO phase strongly enhanced the refinement of Mg matrix grains during extrusion, which led to a large increase in yield stress through the Hall-Petch relationship. In addition, the LPSO phases, which were aligned along the direction of extrusion in the Mg97Zn1Y2 extruded alloy, acted as hardening phases, being roughly coordinated with the short-fiber reinforcement mechanism. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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Effect of Extrusion Parameters on Mechanical Properties of Mg97Zn1Y2 Alloys at Room and Elevated Temperatures Reviewed
Masaaki Hirano, Michiaki Yamasaki, Koji Hagihara, Kenji Higashida, Yoshihito Kawamura
MATERIALS TRANSACTIONS 51 ( 9 ) 1640 - 1647 2010.09
Language：English Publishing type：Research paper (scientific journal) Publisher：JAPAN INST METALS
The effects of alloy extrusion parameters such as extrusion ratio temperature and speed on the mechanical properties at room and elevated temperatures and the microstructure evolution were investigated in the production of high strength Mg-Zn Y alloys The alloy used is a Mg97Zn1Y2 (at%) which is engineered to acquire a long period stacking ordered (LPSO) structure phase to increase alloy strength The microstructure of the extruded Mg97Zn1Y2 alloy consists of hot-worked and dynamically recrystallized (DRXed) alpha Mg grains that includes a fiber shaped LPSO phase elongated along the direction of extrusion Whereas an increase in average equivalent strain promotes the DRX of alpha-Mg matrix and the dispersion of the fiber shaped LPSO phase an increase in average metal flow rate is conductive to the DRX of alpha-Mg grams but is not to the dispersion of LPSO phase The mechanical properties of the extruded Mg Zn Y alloys are affected by changes in the area fraction of the DRXed grains and the dispersion of the fiber-shaped LPSO phase As the extrusion ratio and extrusion speed increase overall DRX bringing gram growth in its train in the alpha Mg matrix phase decreases the tensile strength of alloys, but the dispersed fiber shaped LPSO phase remaining in the DRXed grains region makes good the adverse effect of overall DRX followed by grain growth [doi 10 2320/matertrans MAW201026]
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Plastic deformation behavior of Mg97Zn1Y2 extruded alloys Reviewed
K. Hagihara, A. Kinoshita, Y. Sugino, M. Yamasaki, Y. Kawamura, H. Y. Yasuda, Y. Umakoshi
TRANSACTIONS OF NONFERROUS METALS SOCIETY OF CHINA 20 ( 7 ) 1259 - 1268 2010.07
Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCIENCE BV
The mechanical properties of the Mg97Zn1Y2 extruded alloy containing the long-period stacking ordered phase, the so-called LPSO-phase, with a volume fraction of 24%-25%, were examined by compression tests and cyclic tension compression deformation tests. The plastic behavior of the extruded alloys with compositions of Mg99.2Zn0.2Y0.6 and Mg89Zn4Y7 (molar fraction, %), which were almost the same compositions of Mg matrix phase and LPSO phase in Mg97Zn1Y2 Mg/LPSO two-phase alloy, respectively, were also prepared. By comparing their mechanical properties, the strengthening mechanisms operating in the Mg97Zn1Y2 extruded alloy were discussed. Existence of the LPSO-phase strongly enhanced the refinement of Mg matrix grain size during extrusion, which led to a large increment of the strength of alloy. In addition, the LPSO-phases, which were aligned along the extrusion direction in Mg97Zn1Y2 extruded alloy, acted as hardening phases, just like reinforced fibers.
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Plastic deformation behavior of Mg89Zn4Y7 extruded alloy composed of long-period stacking ordered phase Reviewed
K. Hagihara, A. Kinoshita, Y. Sugino, M. Yamasaki, Y. Kawamura, H. Y. Yasuda, Y. Umakoshi
INTERMETALLICS 18 ( 5 ) 1079 - 1085 2010.05
Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD
The deformation behavior of an Mg89Zn4Y7 (at.%) extruded alloy composed mostly of the long-period stacking ordered (LPSO) phases, was investigated at room temperature. Several heat-treatments were conducted for the extruded alloy in the temperature range between 400 and 525 degrees C, and the correlation between the microstructure and the mechanical properties were quantitatively examined. The yield stress of the as-extruded alloy showed extremely high value of similar to 480 MPa. The deformation of the as-extruded alloy proceeded accompanied by the formation of deformation kinks and small amounts of non-basal slips. The microstructure of the extruded alloy was highly thermally stable and the yield stress showed little change by heat-treatments below 400 degrees C. However, the yield stress was gradually decreased by annealing above 400 degrees C. The yield stress of the alloys annealed at and above 475 degrees C showed discontinuous decreases with increasing annealing temperature. The yield stress of the annealed specimens could be estimated by the Hall-Petch relationship by regarding the length of the long-axis of plate-like grains as the grain size. This suggests that the basal (0001) slip governed the plastic behavior of the LPSO-phase alloy composed of randomly oriented grains. (C) 2010 Elsevier Ltd. All rights reserved.
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Improvement of aligned lamellar structure by Cr-addition to NbSi2/MoSi2 duplex-silicide crystals Reviewed
K. Hagihara, T. Nakano, S. Hata, O. Zhu, Y. Umakoshi
SCRIPTA MATERIALIA 62 ( 8 ) 613 - 616 2010.04
Language：English Publishing type：Research paper (scientific journal) Publisher：PERGAMON-ELSEVIER SCIENCE LTD
The addition of Cr to (Mo0.85Nb0.15)Si-2 crystals significantly improves the thermal stability of the lamellar structure composed of C11(b)-MoSi2 and C40-NbSi2 phases. Analysis using electron microscopy indicates the segregation of Cr atoms at the C40/C11(b) lamellar interface. This leads to a decrease in the lattice misfit strain at the interface and better thermal stability of the lamellae. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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Plastic deformation behavior of Ni-3(Ti0.7Nb0.3) single crystals with D0(19) structure Reviewed
K. Hagihara, H. Fujimoto, T. Nakano, Y. Umakoshi
INTERMETALLICS 18 ( 4 ) 434 - 440 2010.04
Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD
We have investigated the plastic deformation behavior of Ni-3(Ti0.7Nb0.3) crystals with the D0(19) structure in the temperature range of -196 to 1200 degrees C. The (0001) < 2<(1)over bar>(1) over bar0 > basal slip, {1 (1) over bar 00} < 11<(2)over bar>0 > prism slip, and {(2) over bar 111} < <(2)over bar>11 (6) over bar; > pyramidal slip are operative depending on the temperature and loading orientation. A strong yield stress anomaly (YSA) is caused by slip on the basal plane similar to that observed in other hcp-derivative geometrically close-packed (GCP) compounds such as D0(a)-Ni3Nb and D0(24)-Ni3Ti, due to the Kear-Wilsdorf (K-W) locking of screw dislocations. The features of YSA by basal slip, such as the profile of the temperature vs. critical resolved shear stress (CRSS) curve are quite similar in those Ni-3(Ti0.7Nb0.3), Ni3Nb, and Ni3Ti crystals; nevertheless, the profiles of the temperature vs. CASS curves observed in the case of prism slip are significantly different for each crystal. The results indicate that in the case of these hcp-derivative GCP compounds, although the K-W locking, which is the origin of YSA, accompanies the thermally activated cross-slip of the screw partial dislocations from the (0001) primary slip plane onto the {01 (1) over bar0} prism plane, the mobility of dislocations on the prism plane does not directly influence the YSA behavior of basal slip. (C) 2009 Elsevier Ltd. All rights reserved.
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Plastic deformation behavior of Mg12YZn with 18R long-period stacking ordered structure Reviewed
K. Hagihara, N. Yokotani, Y. Umakoshi
INTERMETALLICS 18 ( 2 ) 267 - 276 2010.02
Language：English Publishing type：Research paper (scientific journal) Publisher：ELSEVIER SCI LTD
The recent development of high-strength Mg alloys has focused on the role of the strengthening phase with a long-period stacking ordered (LPSO) structure. In this study, the plastic deformation behavior of Mg12ZnY with an 18R LPSO-structure was investigated using directionally solidified crystals. The (0001)<11<(2)over bar>0> basal slip was identified to be the dominant operative deformation mode in Mg12ZnY, whose critical resolved shear stress (CRSS) was estimated to be 10-30 MPa. When the stress was loaded parallel to the (0001) plane, where the Schmid factor for the basal slip is negligible, deformation kinks were initiated in the specimens and accommodated the compressive strain to some extent. These results showed that the plastic behavior of LPSO Mg12ZnY is highly anisotropic and, hence, the control of the microstructure is expected to be extremely important in order to improve the mechanical properties of the LPSO-phases in high-strength Mg alloys. (C) 2009 Elsevier Ltd. All rights reserved.
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Change in Microstructure by Heat-treatment and Corresponding Deformation Behavior in Ni3V Single Crystals Reviewed
Koji Hagihara, Mayumi Mori, Takuya Kishimoto, Yukichi Umakoshi
THERMEC 2009, PTS 1-4 638-642 1318 - + 2010
Language：English Publishing type：Research paper (international conference proceedings) Publisher：TRANS TECH PUBLICATIONS LTD
D0(22)-Ni3V contains three variants whose [001] c-axes are mutually perpendicular In addition, due to the order-disorder transition the anti-phase domains (APD) are also introduced under some heat-treatment conditions In this study, the influence of such microstructures; the size of variants and APDs, on the plastic deformation behavior of Ni3V was investigated by using single crystals, in which the microstructure was variously controlled by heat-treatments
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Temperature Dependence of Compressive Deformation Behavior of Mg89Zn4Y7 Extruded LPSO-Phase Alloys Reviewed
Koji Hagihara, Akihito Kinoshita, Yuya Sugino, Michiaki Yamasaki, Yoshihito Kawamura, Hiroyuki Y. Yasuda, Yukichi Umakoshi
PRICM 7, PTS 1-3 654-656 607 - + 2010
Language：English Publishing type：Research paper (international conference proceedings) Publisher：TRANS TECH PUBLICATIONS LTD
Deformation mechanisms of Mg89Zn4Y7 (at.%) extruded alloy, which is mostly composed of LPSO-phase, was investigated focusing on their temperature dependence. The yield stress of as-extruded alloy showed extremely high value of similar to 480 MPa at RT, but it largely decreased to similar to 130 MPa at 300 degrees C. The decreasing rate of the yield stress could be significantly reduced, however, by the annealing of specimen at 400 degrees C, by suppressing the microyielding which is considered to occur related by the grain boundary sliding in restricted regions. The yield stress of the annealed specimens with random textures could be estimated by the liall-Petch relationship by regarding the length of long-axis of plate-like grains as a grain size between RT and 300 degrees C. The yield stress of the annealed specimens maintained high values even at 200 degrees C, but it also showed large decreases at 300 degrees C.
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Multimodal Microstructure Evolution in Wrought Mg-Zn-Y Alloys with High Strength and Increased Ductility Reviewed
Michiaki Yamasaki, Kenji Hashimoto, Koji Hagihara, Yoshihito Kawamura
PRICM 7, PTS 1-3 654-656 615 - + 2010
Language：English Publishing type：Research paper (international conference proceedings) Publisher：TRANS TECH PUBLICATIONS LTD
High strength and ductile Mg96Zn2Y2 (at%) alloys with multi-modal microstructure are developed. Microstructure of the extruded Mg96Zn2Y2 alloy consists of three regions; the dynamically recrystallized alpha-Mg fine-grains region, the hot-worked alpha-Mg coarse-grains region elongated along extrusion direction, and the long-period stacking ordered (LPSO) phase region with kink deformation bands. Bimodal microstructure evolution in alpha-Mg matrix is influenced by the morphology of the LPSO phase in the as-cast state, therefore, the effect of secondary dendrite arm spacing in cast state on the microstructure evolution and mechanical properties of the extruded Mg-Zn-Y alloy is investigated. An increase in the dynamically recrystallized grains improves ductility of the extruded alloys; the effective dispersion of the LPSO phase enhances strengthening of the alloy.
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Controlling factors on the fatigue behaviour of Ti-Nb-Ta-Zr alloys single crystals Reviewed
K.Hagihara, T.Nakano, M.Niinomi
Proc. of PFAM 18 (Processing and Fabrication of Advanced Materials 1023 - 1030 2009.12
Language：English Publishing type：Research paper (international conference proceedings)
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Oxygen Distribution in Titanium Single Crystal Fabricated by Optical Floating-Zone Method under Extremely Low Oxygen Partial Pressure Reviewed
Koji Hagihara, Takahiro Tachibana, Keita Sasaki, Yoshiyuki Yoshida, Naoki Shirakawa, Tohru Nagasawa, Takayuki Narushima, Takayoshi Nakano
MATERIALS TRANSACTIONS 50 ( 12 ) 2709 - 2715 2009.12
Language：English Publishing type：Research paper (scientific journal) Publisher：JAPAN INST METALS
This study examines the properties of a titanium single crystal fabricated by the floating-zone-melting process in Ar gas flow atmosphere where the partial pressure of oxygen was maintained extremely low at P-O2 = similar to 10(-23) atm by the newly developed oxygen pump system. The distribution of solute oxygen atoms in the obtained single crystal exhibited a peculiar gradient. In the early stage of the titanium single crystal growth, the oxygen content in the single crystal (approximately 1600 ppm) was higher than that in the mother ingot (980 ppm). However, as the crystal growth progressed. the oxygen content gradually decreases and then reduced to 660 ppm in the final stage of crystal growth. Such a gradient of oxygen composition was not detected in titanium single crystals fabricated under conventional, commercial Ar gas flow atmosphere. owing to the unique gradient of oxygen content formed under extremely low oxygen partial pressure, the Vickers hardness of the single crystal decreased gradually along the crystal growth direction. [doi: 10.2320/matertrans.MA200903]
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Mg12ZnY長周期相の塑性変形機構、Mg合金強化機構 Reviewed
萩原幸司, 木下昭人, 杉野裕也, 山崎倫昭, 河村能人, 馬越佑吉
日本機械学会 M&M2009材料力学カンファレンス論文集 2009.07
Language：Japanese Publishing type：Research paper (scientific journal)
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RELATION BETWEEN THE MICROSTRUCTURE AND THE PLASTIC DEFORMATION BEHAVIOR IN Mg12ZnY WITH LPSO STRUCTURE Reviewed
Koji Hagihara, Akihito Kinoshita, Yuya Sugino, Naoyuki Yokotani, Michiaki Yamasaki, Yoshihito Kawamura, Yukichi Umakoshi
MAGNESIUM TECHNOLOGY 2009 477 - + 2009
Language：English Publishing type：Research paper (international conference proceedings) Publisher：MINERALS, METALS & MATERIALS SOC
Plastic deformation behavior of Mg12ZnY with long-period stacking ordered (LPSO) structure of basal plane, called LPSO-phase, was examined using three single-phase alloys of directionally solidified (DS), as-solidified and extruded alloys with different microstructures at room temperature.
By using DS alloy, the dominantly operative deformation mode in LPSO-phase was identified to be (0001)<11<(2)over bar>0> basal slip. In compression parallel to the growth direction where the Schmid factor for the basal slip is negligible, on the other hand, the deformation proceeds accompanied by the formation of deformation kink, leading to higher yield stress than those at other loading axes.
The yield stress of as-solidified alloy, in which LPSO-phase grains show relatively large plate-like morphology but no texture, exhibits low value of around 110MPa at RT, due to the frequent operation of basal slip. On the other hand, the yield stress of extruded alloy shows much higher value than others accompanied by strong orientation dependence. The refined microstructure in extruded alloys effectively hinders the operation of basal slip, resulting in large increase in yield stress.
