scholarly journals Two-Way Shape Memory Effect Induced by Tensile Deformation in Columnar-Grained Cu71.7Al18.1Mn10.2 Alloy

Materials ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2109 ◽  
Author(s):  
Pei-Sheng Yao ◽  
Hai-You Huang ◽  
Yan-Jing Su ◽  
Jian-Xin Xie
Keyword(s):  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Tensile Deformation ◽  
Shape Change ◽  
Uniaxial Tensile ◽  
Scanning Calorimetry ◽  
Transformation Temperatures ◽  
Deformation Strain ◽  
The Relationship

Columnar-grained Cu71.7Al18.1Mn10.2 shape memory alloy (SMA) was prepared by a directional solidification method and exhibited a high superelasticity of 8.18% and excellent ductility at room temperature, which provided the possibility of obtaining high shape memory. However, proper pre-deformation is an essential part of repeatedly obtaining large and stable shape change. In this paper, one-time uniaxial tensile pre-deformation was carried out at the temperature range −70–−80 °C. Then, the two-way shape memory effect (TWSME) of the alloy was evaluated by the martensitic transformation strain (εM) which was measured by a thermal expansion test to investigate the relationship between the pre-deformation strain (εT) and the TWSME. The results showed that εM of the columnar-grained Cu71.7Al18.1Mn10.2 alloy increased at first and then decreased with the increase of εT. The maximum value 2.91% of the εM could be reached when εT was 6%. The effects of the εT on transformation temperatures were also measured by differential scanning calorimetry. Based on the variations of transformation temperatures, the relationship between the internal stress induced by the pre-deformation process and the εM, and the influence mechanism of the pre-deformation strain on the TWSME in columnar-grained Cu71.7Al18.1Mn10.2 alloy, were discussed. The results obtained from this work may provide reference for potential applications of Cu-based SMAs, such as self-control components, fasteners, etc.

Martensitic Transformation Behavior and Shape Memory Effect of an Aged Ni-rich Ti-Ni-Hf High Temperature Shape Memory Alloy

2008 ◽  
Vol 138 ◽  
pp. 399-406 ◽  
Author(s):  
Xiang Long Meng ◽  
Yu Dong Fu ◽  
Wei Cai ◽  
J.X. Zhang ◽  
Qing Fen Li ◽  
...  
Keyword(s):  
High Temperature ◽  
Martensitic Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Aging Temperature ◽  
Transformation Behavior ◽  
Transformation Temperatures ◽  
Solution Treated

The martensitic transformation behavior and shape memory effect (SME) have been investigated in a Ni-rich Ti29.6Ni50.4Hf20 high temperature shape memory alloy (SMA) in the present study. After aging, the transformation temperatures of Ti29.6Ni50.4Hf20 alloy increase obviously due to the precipitation of (Ti,Hf)3Ni4 particles. And the transformation sequence changes from one-step to two-step. When the experimental alloy is aged at different temperatures for 2h, the transformation temperatures increase rapidly with increasing the aging temperature and then change slightly with further increasing the aging temperature. Most of the martensite variants preferentially oriented in the aged Ti29.6Ni50.4Hf20 alloy. The aged Ti29.6Ni50.4Hf20 alloy shows the better thermal stability of transformation temperatures than the solution-treated one because the precipitates depress the introduction of defects during thermal cycling. In addition, the proper aged Ti29.6Ni50.4Hf20 alloy also shows the larger SME than the solution-treated one since the precipitates strengthen the matrix strongly.

Martensitic Transformation and Shape Memory Effect of Ni53.25Mn21.75Ga25 Ferromagnetic Shape Memory Alloy

2012 ◽  
Vol 476-478 ◽  
pp. 1504-1507
Author(s):  
Hai Bo Wang ◽  
Shang Shen Feng ◽  
Pei Yang Cai ◽  
Yan Qiu Huo
Keyword(s):  
Magnetic Field ◽  
Martensitic Transformation ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Parent Phase ◽  
Transformation Strain ◽  
Scanning Calorimetry ◽  
Reversible Transformation ◽  
Ferromagnetic Shape Memory

The martensitic transformation, crystalline structure, microstructure and shape memory effect of the Ni53.25Mn21.75Ga25 (at.%) alloy are investigated by means of Differential Scanning Calorimetry (DSC), X-ray diffraction (XRD), Transmission Electron Microscope (TEM) and the standard metal strain gauge technique. The XRD results showed that the Ni53.25Mn21.75Ga25 alloy is composed of cubic parent phase at room temperature. TEM observation proved that the typical twin martensite is tetragonal structure and tweed-like contrast which is typical image for the parent phase. A large reversible transformation strain, about 0.54%, is obtained in this undeformed polycrystalline alloy due to martensitic transformation and its reverse transformation. This transformation strain is also increased to 0.65% by the external magnetic field. It is believed that the effect of the magnetic field on the preferential orientation of martensitic variants increases the transformation strain.

Thermoelastic Martensitic Transformations and the Nature of the Shape Memory Effect

1983 ◽  
Vol 21 ◽  
Author(s):  
C. M. Wayman
Keyword(s):  
Single Crystal ◽  
Shape Memory ◽  
Crystal Structures ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Shape Change ◽  
Parent Phase ◽  
Shape Deformation ◽  
Initial Shape ◽  
Plate Group

ABSTRACTInvestigations of the shape memory effect in alloys forming thermoelastic martensites with various crystal structures (2H, 3R, 9R and 18R) reveal that universal behavior exists. A unified explanation of the martensite deformation processes and subsequent shape recovery is now in hand, even though the various martensites are both internally twinned and internally faulted and, in addition, have different crystal structures. In cases studied to date, an initial parent phase single crystal transforms into self-accommodating arrangements of martensite variants (plates) which are characterized by “plate groups.” Each group consists of four variants. The average shape deformation in a plate group is essentially zero.Upon stressing below the Mf temperature the martensite undergoes deformation by detwinning (2H and 3R only), variant-variant coalescence and twinning processes, and further group-to-group coalescence. The deformed specimen eventually becomes a single crystal of martensite consisting of that particular habit plane variant whose shape deformation permits maximum extension in the direction of the applied stress. The deformed martensite persists after unloading has occurred; reverse rearrangements of twins and variants do not occur. Specimens deformed below Mf regain their initial shape characteristic of the initial parent phase upon heating from As to Af, during which the single crystal of martensite obtained by stressing the 24-variant configuration transforms back to the original parent phase single crystal in a unique manner, which is basically a simple “unshearing” process. The unshearing is the essence of the memory.The two-way shape memory effect results after the initial martensitic transformation upon cooling is preprogrammed by the introduction of stresses which preferentially bias the transformation so that only a single variant of martensite forms upon cooling. The shape change of this single variant causes the characteristic spontaneous “bending” upon cooling. The characteristic “unbending upon heating is as with the conventional “one-way” shape memory effect.

Synthesis and Characterization of IPDI Based Shape Memory Polyurethane

2020 ◽  
Vol 1010 ◽  
pp. 142-147
Author(s):  
Nur Athirah Rasli @ Rosli ◽  
Syazana Ahmad Zubir
Keyword(s):  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Soft Segment ◽  
Shape Memory Polymer ◽  
Palm Kernel ◽  
Hexamethylene Diisocyanate ◽  
Molar Ratio ◽  
Scanning Calorimetry ◽  
Chain Flexibility

Various polyurethane-based shape memory polymer was synthesized using polycaprolactone (PCL) as soft segment and, hexamethylene diisocyanate (HMDI) and isophorone diisocyanate (IPDI) as the hard segments. Palm kernel oil-based polyol was used to replace part of the petroleum-based polyol due to the increasing demand on renewable resources as a result of environmental awareness. The synthesis has been carried out using two step polymerization method. The effects of varying the molar ratio of IPDI/HMDI on material properties such as crystallinity, transition temperature, morphology, shape memory effect and tensile strength were investigated by using Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), shape memory test and tensile test. A high IPDI content in SMPU results in better shape memory effect, whereas increasing HMDI content leads to a better chain flexibility. In this work, the incorporation of IPDI contributes to the formation of phase separation which enhance the formation of crystalline soft segment structure while the incorporation of HMDI as isocyanate tend to promote phase mixing which enhance the chain flexibility of the SMPU backbone.

Thermal Treatment Related Structure and Property Changes in a TiNi Alloy Presenting Shape Memory Effect

2014 ◽  
Vol 775-776 ◽  
pp. 733-737
Author(s):  
Everton Maick Rangel Pessanha ◽  
Lioudmila Aleksandrovna Matlakhova ◽  
Herval Ramos Paes ◽  
Ruben Jesus Sanchez Rodriguez ◽  
Veronica Scarpini Candido ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
High Temperature Phase ◽  
Tini Alloy ◽  
Temperature Phase ◽  
Scanning Calorimetry ◽  
Critical Temperatures ◽  
Structure And Property

Changes in the structure and properties of a TiNi alloy, which possesses shape memory effect by means of reversible martensitic transformation (RMT), after annealing at different temperatures in the interval of 300 to 550oC, were investigated. These changes were characterized by chemical analysis, X-ray diffraction, electrical resistivity, microhardness and differential scanning calorimetry. The results showed that the as-fabricated TiNi alloy presented a multiphase structure. An additional high temperature phase was revealed upon 550oC annealing. The alloy displayed sensible changes in its electrical resistivity that were attributed to the influence of the several existing phases. A tendency for the increase in the RMT critical temperatures was also observed with increasing annealing temperature.

A STUDY ON FATIGUE DAMAGE OF SHAPE MEMORY ALLOY COMPOSITE USING NDE TECHNIQUE

2006 ◽  
Vol 20 (25n27) ◽  
pp. 3775-3780 ◽  
Author(s):  
YOUNG-CHUL PARK ◽  
JIN-KYUNG LEE ◽  
SANG-PILL LEE ◽  
GYU-CHANG LEE ◽  
JOON-HYUN LEE ◽  
...  
Keyword(s):  
High Temperature ◽  
Shape Memory Alloy ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Fatigue Damage ◽  
Shape Memory Composites ◽  
The Relationship

TiNi shape memory alloy was used to recover the shape of transformed objects using its shape memory effect. This shape memory effect plays an important role inside metal matrix composite. A composite using shape memory alloy has a large advantage that can control crack initiation and propagation, when compared with other composites due to the shape memory effect of shape memory alloy under high temperature. In this study, TiNi/Al6061 and TiNi/2024 shape memory composites were fabricated by the hot press method, and a fatigue test was performed to evaluate the fatigue damage for the shape memory composites under room temperature and high temperature. The relationship of the crack growth rate and the stress intensity factor for these shape memory composites were clarified at both temperature conditions. The delay effect of crack propagation due to shape memory alloy was also evaluated under high temperature. In addition, an acoustic emission technique was used to evaluate the crack initiation and the control of crack propagation by shape memory effect under fatigue test nondestructively. The relationship between AE parameter and the degree of fatigue damage of the shape memory composites was discussed.

Numerical simulation of safety device executive element of the shape memory alloy for a safe electrical outlet

2019 ◽  
Author(s):  
S.M. Ganysh
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Nonlinear Differential Equations ◽  
Phenomenological Approach ◽  
Internal Force ◽  
Material Behavior ◽  
Transition Diagram ◽  
The Relationship

The article considers possibility of creating a safety element for a safe electrical outlet based on the shape memory effect. Numerical model of helical cylindrical spring of the shape memory alloy is developed. The phenomenological approach based on the phase transition diagram is used to describe material behavior. Shape memory effect is included using additional internal force factor i.e. the shape memory moment under torsion. An algorithm for constructing the relationship between the torque in cross section and the shape memory moment for isothermal loading is presented. The problem of simultaneous deformation of shape memory alloy spring and flat copper spring under heating is solved. The contact plate is replaced by an equivalent spring. Spring stiffness is obtained using a system of nonlinear differential equations describing the bending of a bar.

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