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Yukichi Umakoshi - One of the best experts on this subject based on the ideXlab platform.
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Pseudoelasticity in Fe3Al single crystals under cyclic loading
2016Co-Authors: Hiroyuki Y. Yasuda, Keisuke Yamaoka, Yukichi UmakoshiAbstract:boundary Abstract. D03-ordered Fe3Al single crystals containing 23, 25 and 28at.%Al were cyclically deformed at [ 491] loading axis in tension-compression mode. Giant Pseudoelasticity took place in Fe-23 and 25at.%Al single crystals at an early stage of cyclic deformation, while a slight strain recovery was observed in Fe-28at.%Al. In Fe-23 and 25at.%Al single crystals, superpartial dislocations with Burgers vector of 1/4[111] moved individually dragging the nearest neighbour anti-phase boundary (NNAPB). The NNAPB pulled back the superpartials during unloading, resulting in giant Pseudoelasticity and low residual dislocation density. In contrast, a couplet of the superpartials was observed to bow out leaving two superpartials in Fe-28at.%Al. This means that the dislocation couplet dragged the next-nearest neighbour anti-phase boundary (NNNAPB). The surface tension of NNNAPB is lower than that of NNAPB resulting in a slight strain recovery in Fe-28at%Al. As cyclic deformation proceeded, residual dislocation density increased with an increase in the number of cycles even in Fe-23 and 25at.%Al. In particular, persistent slip bands (PSB) were formed in Fe-23at.%Al single crystals, though PSB is seldom observed in fatigued intermetallic compounds. To-and-fro motion of superpartials during loading and unloading was suppressed by dislocatio
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Pseudoelasticity of D0_3-Type Fe_3Al and Fe_3Ga-Based Alloys
MRS Online Proceedings Library, 2011Co-Authors: Hiroyuki Y. Yasuda, Yukichi UmakoshiAbstract:The pseudoelastic behavior of Fe_3Al and Fe_3Ga alloys with the D0_3 structure is reviewed. In general, Pseudoelasticity of shape memory alloys is based on a thermoelastic martensitic transformation. However, Pseudoelasticity regardless of the martensitic transformation is found to take place in D0_3-ordered Fe_3Al and Fe_3Ga alloys. For instance, a 1/4 superpartial dislocation in Fe_3Al alloys moves independently dragging an antiphase boundary (APB). During unloading, the APB pulls back the superpartial to decrease its energy resulting in Pseudoelasticity, which is called “APB Pseudoelasticity”. Moreover, D0_3-type Fe_3Ga alloys were found to demonstrate three types of Pseudoelasticity based on the dislocation motion, twinning and martensitic transformation depending on the chemical composition, degree of D0_3 order, loading axis, stress sense and deformation temperature. The mechanism of the pseudoelasticities in the D0_3-type intermetallics is discussed based on some in situ observations. The effects of chemical composition, deformation temperature and crystal orientation on the pseudoelastic behaviors are also discussed.
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Pseudoelasticity of D0 3 -Type Fe 3 Al and Fe 3 Ga-Based Alloys
MRS Proceedings, 2011Co-Authors: Hiroyuki Y. Yasuda, Yukichi UmakoshiAbstract:The pseudoelastic behavior of Fe 3 Al and Fe 3 Ga alloys with the D0 3 structure is reviewed. In general, Pseudoelasticity of shape memory alloys is based on a thermoelastic martensitic transformation. However, Pseudoelasticity regardless of the martensitic transformation is found to take place in D0 3 -ordered Fe 3 Al and Fe 3 Ga alloys. For instance, a 1/4 superpartial dislocation in Fe 3 Al alloys moves independently dragging an antiphase boundary (APB). During unloading, the APB pulls back the superpartial to decrease its energy resulting in Pseudoelasticity, which is called “APB Pseudoelasticity”. Moreover, D0 3 -type Fe 3 Ga alloys were found to demonstrate three types of Pseudoelasticity based on the dislocation motion, twinning and martensitic transformation depending on the chemical composition, degree of D0 3 order, loading axis, stress sense and deformation temperature. The mechanism of the pseudoelasticities in the D0 3 -type intermetallics is discussed based on some in situ observations. The effects of chemical composition, deformation temperature and crystal orientation on the pseudoelastic behaviors are also discussed.
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Pseudoelastic Behavior of Fe-Al Polycrystals
ISIJ International, 2010Co-Authors: Hiroyuki Y. Yasuda, Keiji Kouzai, Yuuki Kawamura, Yukichi UmakoshiAbstract:Pseudoelastic behavior of Fe–Al polycrystals at room temperature was examined focusing on Al concentration, the crystallographic texture and the grain size. Perfect Pseudoelasticity derived from the reversible motion of 1/4 ‹111› superpartial dislocations dragging the anti-phase boundaries (APB) took place in Fe–25.0at%Al polycrystals at a total strain of 1.0%. The amount of strain recovery in Fe–Al polycrystals showed a maximum at 25.0 at% Al and the deviation from the concentration led to a decrease in strain recovery. The backward stress due to APB and dislocation configuration in Fe–Al alloys was closely related to the dependence of the Pseudoelasticity on Al concentration. The pseudoelastic behavior of Fe–25.0at%Al polycrystals depended strongly on the loading axis, which could be accounted for in terms of the Taylor factor. Moreover, recovery strain of Fe–23.0Al polycrystals increased with increasing average grain size suggesting that the grain boundaries suppressed the forward and backward motion of the superpartials and were harmful for the Pseudoelasticity.
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Pseudoelastic behaviour of Fe3Al single crystals with D03 structure
Intermetallics, 2010Co-Authors: Hideyuki Yasuda, Yukichi UmakoshiAbstract:Abstract Pseudoelasticity which shape memory alloys reveal is generally based on a thermoelastic martensitic transformation. However, Fe-rich Fe3Al single crystals with the D03 structure demonstrate Pseudoelasticity regardless of the martensitic transformation. It is strongly suggested that the Pseudoelasticity of Fe3Al crystals originates from the peculiar dislocation motion dragging an antiphase boundary (APB). During loading, a 1 / 4 〈 111 〉 superpartial dislocation moves individually dragging the APB. On the other hand, the APB pulls back the superpartial during unloading due to its tension resulting in the Pseudoelasticity of which recoverable strain is as much as 5%. Hence, this phenomenon is called “APB Pseudoelasticity”. This article summarizes the recent progress in the understanding of the pseudoelastic behaviour of D03-ordered Fe3Al single crystals and the effects of Al concentration, deformation temperature, loading axis and third element addition are discussed.
Hideyuki Yasuda - One of the best experts on this subject based on the ideXlab platform.
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Pseudoelastic behaviour of Fe3Al single crystals with D03 structure
Intermetallics, 2010Co-Authors: Hideyuki Yasuda, Yukichi UmakoshiAbstract:Abstract Pseudoelasticity which shape memory alloys reveal is generally based on a thermoelastic martensitic transformation. However, Fe-rich Fe3Al single crystals with the D03 structure demonstrate Pseudoelasticity regardless of the martensitic transformation. It is strongly suggested that the Pseudoelasticity of Fe3Al crystals originates from the peculiar dislocation motion dragging an antiphase boundary (APB). During loading, a 1 / 4 〈 111 〉 superpartial dislocation moves individually dragging the APB. On the other hand, the APB pulls back the superpartial during unloading due to its tension resulting in the Pseudoelasticity of which recoverable strain is as much as 5%. Hence, this phenomenon is called “APB Pseudoelasticity”. This article summarizes the recent progress in the understanding of the pseudoelastic behaviour of D03-ordered Fe3Al single crystals and the effects of Al concentration, deformation temperature, loading axis and third element addition are discussed.
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Unusual pseudoelastic behaviour of Fe3Ga shape memory alloys
Journal of Physics: Conference Series, 2009Co-Authors: Hideyuki Yasuda, Yasuhiro Oda, Kouki Fukushima, M. Aoki, Yukichi UmakoshiAbstract:Pseudoelastic behaviour of Fe-23.8at%Ga single crystals compressed with different loading axes at room temperature was examined focusing on the activated deformation mode. In the crystals, {101} slip and {211} twin were mainly activated depending on the loading axis. Pseudoelastic behaviour of the crystals depended strongly on the deformation mode. If {101} slip was operative, sole and paired 1/4 superpartial dislocations moved dragging antiphase boundaries (APB). During unloading, the APB pulled back the superpartials due to its tension resulting in Pseudoelasticity. In contrast, twinning and untwinning of {211} pseudo-twins also led to large strain recovery accompanying a serrated flow during loading and unloading. It is suggested the energy of the pseudo-twin interface was the driving force for the twinning Pseudoelasticity.
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multimode Pseudoelasticity in fe 23 8 at ga single crystals with d03 structure
Intermetallics, 2008Co-Authors: Hideyuki Yasuda, Yasuhiro Oda, M. Aoki, Kouki Fukushima, Yukichi UmakoshiAbstract:Abstract Pseudoelastic behaviour of D0 3 -ordered Fe–23.8 at% Ga single crystals subjected to different heat treatments was examined focusing on the deformation mode. There existed three kinds of deformation modes in the crystals depending on the heat treatment: stress-induced martensitic transformation, dislocation glide and twinning which had a potential to show large Pseudoelasticity. Numerous martensites with the 14M structure were stress-induced during loading and disappeared during unloading resulting in perfect Pseudoelasticity with small stress–strain hysteresis. On the other hand, 1/4[111] superpartial dislocations dragging the antiphase boundaries (APB) moved backward during unloading due to the APB tension, which also led to large strain recovery. Twinning and untwinning of 2.2 T -type pseudo-twins accompanying both a serrated flow and a clicking sound were also responsible for the Pseudoelasticity. It was also found that the pseudoelastic behaviour associated with the three deformation modes was strongly affected by stress sense and loading axis.
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Multimode Pseudoelasticity in Fe–23.8 at% Ga single crystals with D03 structure
Intermetallics, 2008Co-Authors: Hideyuki Yasuda, Yasuhiro Oda, M. Aoki, Kouki Fukushima, Yukichi UmakoshiAbstract:Abstract Pseudoelastic behaviour of D0 3 -ordered Fe–23.8 at% Ga single crystals subjected to different heat treatments was examined focusing on the deformation mode. There existed three kinds of deformation modes in the crystals depending on the heat treatment: stress-induced martensitic transformation, dislocation glide and twinning which had a potential to show large Pseudoelasticity. Numerous martensites with the 14M structure were stress-induced during loading and disappeared during unloading resulting in perfect Pseudoelasticity with small stress–strain hysteresis. On the other hand, 1/4[111] superpartial dislocations dragging the antiphase boundaries (APB) moved backward during unloading due to the APB tension, which also led to large strain recovery. Twinning and untwinning of 2.2 T -type pseudo-twins accompanying both a serrated flow and a clicking sound were also responsible for the Pseudoelasticity. It was also found that the pseudoelastic behaviour associated with the three deformation modes was strongly affected by stress sense and loading axis.
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Effect of the ordering process on Pseudoelasticity in Fe3Ga single crystals
Acta Materialia, 2007Co-Authors: Hideyuki Yasuda, M. Aoki, Yukichi UmakoshiAbstract:Abstract The pseudoelastic behaviour of Fe3Ga single crystals with the D03 structure was investigated focusing on the annealing conditions and Ga content. In these D03–ordered Fe3Ga single crystals, uncoupled and paired 1/4[1 1 1] superpartial dislocations moved, dragging the nearest-neighbour and next-nearest-neighbour anti-phase boundaries (APBs), respectively. These APBs pulled back the superpartials during unloading, resulting in Pseudoelasticity, though a martensitic transformation never occurred in the crystals. The amount of strain recovery increased with increasing Ga content up to 25.4 at.% when the crystals were annealed at 853–893 K within 10 h. In particular, nearly perfect Pseudoelasticity with a recoverable strain of 5% was obtained at 24.2 and 25.4 at.% Ga after an appropriate heat treatment. Isothermal annealing in the D03 single phase region was effective in improving pseudoelastic properties. Moreover, the metastable D03 phase also exhibited Pseudoelasticity, even if the (α + L12) or (D03 + L12) dual phase was thermally stable in the equilibrium state.
Hiroyuki Y. Yasuda - One of the best experts on this subject based on the ideXlab platform.
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Pseudoelasticity in Fe3Al single crystals under cyclic loading
2016Co-Authors: Hiroyuki Y. Yasuda, Keisuke Yamaoka, Yukichi UmakoshiAbstract:boundary Abstract. D03-ordered Fe3Al single crystals containing 23, 25 and 28at.%Al were cyclically deformed at [ 491] loading axis in tension-compression mode. Giant Pseudoelasticity took place in Fe-23 and 25at.%Al single crystals at an early stage of cyclic deformation, while a slight strain recovery was observed in Fe-28at.%Al. In Fe-23 and 25at.%Al single crystals, superpartial dislocations with Burgers vector of 1/4[111] moved individually dragging the nearest neighbour anti-phase boundary (NNAPB). The NNAPB pulled back the superpartials during unloading, resulting in giant Pseudoelasticity and low residual dislocation density. In contrast, a couplet of the superpartials was observed to bow out leaving two superpartials in Fe-28at.%Al. This means that the dislocation couplet dragged the next-nearest neighbour anti-phase boundary (NNNAPB). The surface tension of NNNAPB is lower than that of NNAPB resulting in a slight strain recovery in Fe-28at%Al. As cyclic deformation proceeded, residual dislocation density increased with an increase in the number of cycles even in Fe-23 and 25at.%Al. In particular, persistent slip bands (PSB) were formed in Fe-23at.%Al single crystals, though PSB is seldom observed in fatigued intermetallic compounds. To-and-fro motion of superpartials during loading and unloading was suppressed by dislocatio
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In Situ Observation of Pseudoelasticity in Fe3Al Single Crystals with D03 Structure
MATERIALS TRANSACTIONS, 2014Co-Authors: Hiroyuki Y. Yasuda, Yasuhiro Oda, Takenori Maruyama, Mayumi Ojima, Yoshitaka AdachiAbstract:In order to clarify the mechanism of Pseudoelasticity in Fe23.0Al (at%) single crystals with the D03 structure, in situ observation of tensile deformation was performed at room temperature using an optical microscope (OM), an electron back-scatter diffraction (EBSD) device and an X-ray Laue back-reflection (XLBR) machine. In the present study, neither martensite nor twin was observed during the Pseudoelasticity. In particular, the whole of the tensile specimen could be indexed with respect to the D03 structure by in situ EBSD measurement. (��), (� 101) and (� 211) slips were confirmed to occur depending on the loading axis by in situ OM observation. When (�) [111] slip was activated, coarse slip bands parallel to (� 101) slip plane were formed during loading. The area fraction of the slip bands increased linearly with increasing plastic strain up to 0.066. During unloading, the slip bands disappeared, resulting in Pseudoelasticity. From in situ XLBR tests, the crystal rotation of the loading axis toward [111] slip direction took place during loading. The rotation angle and the plastic strain satisfied the Schmid-Boas relationship at small plastic strains, especially for (��) and (� 211) slips. These results suggest that the reversible motion of 1=4h111i superpartial dislocation dragging an antiphase boundary (APB) was responsible for the Pseudoelasticity in Fe23.0Al single crystals. [doi:10.2320/matertrans.M2013461]
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Effect of Ga concentration on twinning Pseudoelasticity in Fe–Ga single crystals
Journal of Alloys and Compounds, 2013Co-Authors: Hiroyuki Y. Yasuda, Takuya Kishimoto, Yasuhiro Oda, Takenori MaruyamaAbstract:Abstract The effect of Ga concentration on the twinning Pseudoelasticity in Fe–Ga single crystals with 20.0–24.4 at%Ga was examined. In Fe–20.0 to 24.4Ga (at%) single crystals, 2.2 T -type pseudo-twins with {1 1 2} twin plane were formed during compression at low temperatures, especially at 93 K. The energy of the pseudo-twins was so high that the twins disappeared during unloading, resulting in the twinning Pseudoelasticity. At 93 K, the amount of strain recovery caused by the twinning Pseudoelasticity increased with increasing Ga concentration depending on the energy of the pseudo-twins. On the other hand, Fe–23.0Ga and Fe–24.4Ga single crystals with the D0 3 structure exhibited Pseudoelasticity even at room temperature, which is based on reversible motion of 1/4[1 1 1] superpartial dislocations dragging antiphase boundaries. At 20.0 at%Ga, the twinning deformation was predominant at and below 173 K while large strain recovery due to the twinning Pseudoelasticity at 24.4 at%Ga was observed only at 93 K. It is also noted that the stress–strain hysteresis at 93 K was greater at 24.4 at%Ga than at 23.0 at%Ga, which was closely related to a lattice distortion accompanying the pseudo-twin formation.
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Effects of Ga Concentration, Heat Treatment and Deformation Temperature on Pseudoelasticity of Fe–Ga Polycrystals
MATERIALS TRANSACTIONS, 2013Co-Authors: Hiroyuki Y. Yasuda, Takenori MaruyamaAbstract:The pseudoelastic behavior of FeGa polycrystals was examined focusing on the effects of Ga concentration, heat treatment and deformation temperature. FeGa polycrystals solutionized at 800°C exhibited Pseudoelasticity at room temperature based on reversible motion of 1/4h111i superpartial dislocations dragging an antiphase boundary (APB) in the D03 superlattice structure. In particular, at and above 25at%Ga, paired 1/4h111i superpartials dragging the next-nearest-neighbor APB were found to play an important role in the Pseudoelasticity. The amount of strain recovery at room temperature was highest at 25at%Ga. Moreover, heat treatment strongly influenced the pseudoelastic behavior of FeGa alloys. For instance, the L12 and ½-like phases precipitating at higher Ga concentrations led to a decrease in strain recovery since the precipitates suppressed the reversible motion of 1/4h111i superpartials. On the other hand, Pseudoelasticity based on twinning and untwinning of 2.2 T -type pseudo-twins appeared at low temperatures, especially at ¹180°C. The energy of {211} pseudo-twins formed in the FeGa alloys was so high that the twins tended to disappear during unloading resulting in the Pseudoelasticity. However, the amount of strain recovery decreased if pseudoelasticities based on dislocation motion and twinning concurrently took place between ¹150 and ¹50°C. [doi:10.2320/matertrans.M2012266]
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Effect of Third Elements on Pseudoelasticity in Fe3Ga Alloys
Materials Science Forum, 2012Co-Authors: Hiroyuki Y. Yasuda, Tsuyoshi Furuta, Takenori MaruyamaAbstract:Pseudoelasticity of Fe3Ga polycrystals doped with third elements (Ti, V, Cr, Mn, Co, Ni, Si, Ge) was examined. Fe3Ga polycrystals with the appropriate heat treatment were found to exhibit large Pseudoelasticity based on reversible motion of dislocation dragging an antiphase boundary (APB). In Fe3Ga crystals with the D03 superlattice structure, paired 1/4 superpartial dislocations mainly moved dragging the next-nearest-neighbor APB during loading. During unloading, the APB pulled back the superpartial dislocations resulting in the Pseudoelasticity. The D03 ordered phase also developed in Fe3Ga polycrystals with 2at% of the third elements. However, the strain recovery of Fe3Ga polycrystals depended strongly on third element. Fe3Ga polycrystals doped with 2at% of Mn, Cr and Co demonstrated large Pseudoelasticity. In contrast, the other doped elements decreased the amount of strain recovery. The frictional stress of 1/4 superpartial dislocations and the back stress due to the APB, acting on the dislocations, changed by doping the third elements, which was closely related to the pseudoelastic behavior. It is also noted that there was a good correlation between the APB back stress and the ordering temperature from the B2 to D03 phase.
Sylvain Calloch - One of the best experts on this subject based on the ideXlab platform.
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On the origin of residual strain in shape memory alloys: Experimental investigation on evolutions in the microstructure of CuAlBe during complex thermomechanical loadings
Smart Materials and Structures, 2017Co-Authors: Mahmoud Barati, Shabnam Arbab Chirani, Mahmoud Kadkhodaei, Luc Saint-sulpice, Sylvain CallochAbstract:The behaviors of shape memory alloys (SMAs) strongly depend on the presence of different phases: austenite, thermally-induced martensite and stress-induced martensite. Consequently, it is important to know the phase volume fraction of each phases and their evolution during thermomechanical loadings. In this work, a three-phase proportioning method based on electric resistivity variation of a CuAlBe SMA is proposed. Simple thermomechanical loadings (i. e. pseudoplasticity and Pseudoelasticity), one-way shape memory effect, recovery stress, assisted two-way memory effect at different level of stress and cyclic Pseudoelasticity tests are investigated. Based on the electric resistivity results, during each loading path, evolution of the microstructure is determined. The origin of residual strain observed during the considered thermomechanical loadings is discussed. A special attention is paid to two-way shape memory effect generated after considered cyclic loadings and its relation with the developed residual strain. These results permit to identify and to validate the macroscopic models of SMAs behaviors.
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Phase proportioning in CuAlBe shape memory alloys during thermomechanical loadings using electric resistance variation
International Journal of Plasticity, 2010Co-Authors: Shabnam Arbab Chirani, Sylvain Calloch, Pierre-antoine GédouinAbstract:The microstructure of shape memory alloys changes with the thermomechanical history of the material. During thermomechanical loading, austenite, thermally-induced martensite or stress-induced martensite can be simultaneously present in the material. In applications integrating SMA parts, utilization conditions seriously affect the microstructure and can generate macroscopic strain or stress. Consequently, during thermomechanical loadings, it is important to be able to proportion the different phases and consequently to understand the kinetic transformation. This is very useful in the development of constitutive equations. This study shows, by a series of tests, that the proposed experimental method, based on the measurement of the variation of electric resistance of CuAlBe wires, permits to determine the volume fraction of the different phases present in the material (i.e., austenite, stress-induced martensite and thermally-induced martensite). The proposed method is applied to the most common thermomechanical behavior met in engineering applications of shape memory alloys: Pseudoelasticity, pseudoplasticity, recovery-stress and stress-assisted two-way shape memory effect. The proportioning method based on a mixture law integrating the resistivity of pure phases present in the SMA is first performed on different two-phase mixture cases and then applied to a three phase mixture case.
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relation between the martensite volume fraction and the equivalent transformation strain in shape memory alloys
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Sylvain Calloch, Karine Taillard, Arbab S Chirani, Christian Lexcellent, E PatoorAbstract:This study concerns the Pseudoelasticity of shape memory alloys. A series of tests under multiaxial loadings and a micro-macro model are used to show the validity of a conjecture concerning the relation between the volume fraction of martensite and the equivalent transformation strain.
R. Liu - One of the best experts on this subject based on the ideXlab platform.
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Indentation behaviour and wear resistance of pseudoelastic Ti-Ni alloy
Materials Science and Technology, 2000Co-Authors: R. LiuAbstract:AbstractRecent studies demonstrate that near equiatomic Ti–Ni alloys possess high resistance to surface damage by wear. It is suggested that the high wear resistance of Ti–Ni alloys is closely correlated to their Pseudoelasticity, which is usually evaluated by tensile testing. However, when a Ti–Ni alloy is under wear, its surface is in a complex stress state. Since the thermoelastic martensitic transformation of Ti–Ni alloys responds differently to different stresses, it may not be appropriate to evaluate the Pseudoelasticity by tensile testing. The present paper reports recent work on pseudoelastic behaviour of a Ti–51 at.-%Ni alloy employing a microindentation technique as well as tensile testing methods. In the present work, the wear performances of Ti–51 at.-%Ni alloy specimens with different degrees of Pseudoelasticity were also investigated, and efforts were made to explain the beneficial effect of Pseudoelasticity on the wear resistance of Ti–Ni alloys.
