Self-Accommodating Nature of Martensite Formation in Shape Memory Alloys

2014 ◽  
Vol 213 ◽  
pp. 114-118
Author(s):  
Osman Adiguzel
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Parent Phase ◽  
Alloy System ◽  
Phase Region ◽  
Martensite Formation ◽  
Martensite Variant ◽  
Β Phase ◽  
Phase Condition

Shape memory effect is a peculiar property exhibited by certain alloy system. This behavior is facilitated by martensitic transformation, and shape memory properties are intimately related to the microstructures of alloys; in particular, the morphology and orientation relationship between the various martensite variants. Martensitic transformation occurs in thermal manner, on cooling the materials from high temperature parent phase region. Thermal induced martensite called self-accommodated martensite or multivariant martensite occurs as multivariant martensite in self-accommodating manner and consists of lattice twins. Shape memory alloys are deformed in low temperature martensitic phase condition, and deformation proceeds through a martensite variant reorientation. Copper based alloys exhibit this property in metastable β - phase region.

The Role of Twinned and Detwinned Structures on Memory Behaviour of Shape Memory Alloys

2015 ◽  
Vol 1105 ◽  
pp. 78-82 ◽  
Author(s):  
Osman Adiguzel
Keyword(s):  
High Temperature ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Parent Phase ◽  
Martensitic Transformations ◽  
Phase Region ◽  
Finish Temperature ◽  
Β Phase

Shape memory alloys have a peculiar property to return to a previously defined shape or dimension when they are subjected to variation of temperature. Shape memory effect is facilitated by martensitic transformation governed by changes in the crystalline structure of the material. Martensitic transformations are first order lattice-distorting phase transformations and occur with the cooperative movement of atoms by means of lattice invariant shears in the materials on cooling from high temperature parent phase region. The material cycles between the deformed and original shapes on cooling and heating in reversible shape memory effect. Thermal induced martensite occurs as twinned martensite, and the twinned martensite structures turn into detwinned structures by deforming the material in the martensitic condition. Deformation of shape memory alloys in martensitic state proceeds through a martensite variant reorientation. The deformed material recovers the original shape on first heating over the austenite finish temperature in reversible and irreversible shape memory cases. Meanwhile, the parent phase structure returns to the twinned structure in irreversible shape memory effect on cooling below to martensite finish temperature and to the detwinned structure in reversible shape memory effect. Therefore, the twinning and detwinning processes have great importance in the shape memory behaviour of the materials. Copper based alloys exhibit this property in metastable β-phase region, which has bcc-based structures at high temperature parent phase field, and these structures martensitically turn into layered complex structures with lattice twinning following two ordered reactions on cooling.

SEM study of diffusion bonded interfaces in Cu-Al(11,46)-Mn(6,62) and Cu-Al(6,94)- Zn(18,86) copper-based shape memory alloys

1990 ◽  
Vol 48 (4) ◽  
pp. 1004-1005
Author(s):  
F.A. Calvo ◽  
J.M. Gómez de Salazar ◽  
A. Ureña ◽  
F.J. Méndez ◽  
J.M. Guilemany
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Diffusion Bonding ◽  
Diffusion Processes ◽  
Experimental Unit ◽  
Β Phase ◽  
Sem Study ◽  
Temperature Time

The copper-based alloys studied belong to the group of those materials showing Shape Memory Effect (SME). Diffusion Bonding (DB) procedure is an alternative joining method of welding copper-based Shape Memory Alloys, traditionally welded by techniques like electron bean welding (EBW). However EBW provides embrittlement to the joint. This situation has been corrected by DB as confirm the SEM-EDS study presented here.A material shows SME when once has been thermomechanically deformed, it is able to recover its original (as fabricated) shape by means of a simple heat-up. This pheno menom is possible only for those materials which have β phase prone to undergo martensitic transformation. DB technique estimulates diffusion processes betwen materials by the combination of pressure, temperature, time, surface materials roughness and atmosphere condition in the experimental unit with the aid, sometimes, of a third material, in foil or plated form, which is known by the name of interlayer. The parameter set and details of attaing diffusion bonding joints procedure are under a patent developed recently by the authors .

Vibrational behavior of the β phase near martensitic transformation in Cu–Al–Ni shape memory alloys

2004 ◽  
Vol 378 (1-2) ◽  
pp. 243-247 ◽  
Author(s):  
J.I. Pérez-Landazábal ◽  
V. Recarte ◽  
J.M. Ezpeleta ◽  
P.P. Rodrı́guez ◽  
J. San Juan ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Vibrational Behavior ◽  
Β Phase

Martensitic Transformation and Microstructural Characteristics in Copper Based Shape Memory Alloys

2012 ◽  
Vol 510-511 ◽  
pp. 105-110 ◽  
Author(s):  
Osman Adiguzel
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Martensitic Transformations ◽  
Microstructural Characteristics ◽  
Shape Memory Property ◽  
Martensite Variant ◽  
Cooperative Movement ◽  
Β Phase

Martensitic transformations are first order solid state phase transitions and occur in the materials on cooling from high temperature. Shape memory effect is an unusual property exhibited by certain alloy systems, and based on martensitic transformation. The shape memory property is characterized by the recoverability of previously defined shape or dimension when they are subjected to variation of temperature. The shape memory effect is facilitated by martensitic transformation, and shape memory properties are intimately related to the microstructures of the materials. Martensitic transformations occur as martensite variant with the cooperative movement of atoms on {110}β - type plane of austenite matrix. Martensitic transformations have diffusionless character, and the atomic movement is confined to interatomic lengths in the materials. The basic factors which govern the martensitic transformation are Bain distortion and homogeneous shears. Copper based alloys exhibit this property in metastable β-phase field.

Microstructures and Mechanical Properties of Biologically-Inspired Ti-Nb Based Alloys with Ternary Element Additions

2007 ◽  
Vol 539-543 ◽  
pp. 647-652 ◽  
Author(s):  
Han Sol Kim ◽  
Won Yong Kim
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Martensitic Transformation ◽  
Alloy System ◽  
Phase Region ◽  
Present Alloy ◽  
Β Phase ◽  
Nb Content ◽  
Microstructures And Mechanical Properties ◽  
Ternary Alloying

Microstructures and mechanical properties including elastic modulus were investigated in terms of ternary alloying elements Si addition, Nb content variations and tensile test. Martensite structure with α'(hcp) or α"(orthorhombic) was observed in Ti-xNb-1.5at.%Si, where x=10-20at.%. The crystal structure of martensite formed from water quenching process was largely dependent upon Nb content but does not on Si content. On the basis of experimental results obtained, it is suggested that Si has an effective role to suppress the precipitation of ω phase leading to reduction in elastic modulus in the metastable β phase region. Metastable β phase region was superior to reduce the elastic modulus than stable β phase region in the present alloy system. The minimum value of elastic modulus was measured to 48GPa. We have found that stress-induced martensitic transformation takes place during the deformation in the present alloys. Within the alloys having β(bcc) phase studied Nb-poor region appeared to exhibit a dominant behavior for stress-induced martensitic transformation than Nb-rich region. This result suggests that metastable β phase is superior to stable β phase for the occurrence of stress-induced martensitic transformation in the present alloy system.

Phase Transitions and Elementary Processes in Shape Memory Alloys

2015 ◽  
Vol 1101 ◽  
pp. 124-128
Author(s):  
Osman Adiguzel
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Smart Materials ◽  
Structural Changes ◽  
Elementary Processes ◽  
Cooperative Movement ◽  
Β Phase

Shape memory effect is a peculiar property exhibited by certain alloy systems, and shape memory alloys are recognized to be smart materials. These alloys have important ability to recover the original shape of material after deformation, and they are used as shape memory elements in devices due to this property. The shape memory effect is facilitated by a displacive transformation known as martensitic transformation. Shape memory effect refers to the shape recovery of materials resulting from martensite to austenite transformation when heated above reverse transformation temperature after deforming in the martensitic phase. These alloys also cycle between two certain shapes with changing temperature.Martensitic transformations occur with cooperative movement of atoms by means of lattice invariant shears on a {110} - type plane of austenite matrix which is basal plane of martensite.Copper based alloys exhibit this property in metastable β-phase field. High temperature β-phase bcc-structures martensiticaly undergo the non-conventional structures following two ordered reactions on cooling, and structural changes in nanoscale level govern this transition cooling. Atomic movements are also confined to interatomic lengths due to the diffusionless character of martensitic transformation.

Thermal cycling effects in high temperature Cu–Al–Ni–Mn–B shape memory alloys

1997 ◽  
Vol 12 (9) ◽  
pp. 2288-2297 ◽  
Author(s):  
J. Font ◽  
J. Muntasell ◽  
J. Pons ◽  
E. Cesari
Keyword(s):  
High Temperature ◽  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Thermal Cycling ◽  
Shape Memory ◽  
Parent Phase ◽  
Aluminum Boride ◽  
Transformation Temperatures ◽  
Dsc Measurements ◽  
Number Of Cycles

The effects of thermal cycling through the martensitic transformation have been studied in three Cu–Al–Ni–Mn–B high temperature shape memory alloys. An increase of the martensitic transformation temperatures with the number of cycles (up to ∼7 K after 60 cycles) has been generally observed by DSC measurements. The microstructure of these alloys is rather complicated, with the presence of big manganese or aluminum boride particles and small boron precipitates, as well as the formation of dislocations during thermal cycling. By means of aging experiments, it has been shown that the evolution of transformation temperatures during cycling is mainly due to the step-by-step aging in parent phase accompanying the thermal cycling, and that the dislocations formed during cycling have only a very small effect, at least up to 60 cycles.

TEM Studies on the Microstructure in Ferromagnetic Shape Memory Alloys

2008 ◽  
Vol 47-50 ◽  
pp. 515-518
Author(s):  
Y. Murakami ◽  
T. Yano ◽  
Daisuke Shindo
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Parent Phase ◽  
Magnetic Domain ◽  
High Temperature Phase ◽  
Phase Changes ◽  
Temperature Phase ◽  
Ferromagnetic Shape Memory Alloys ◽  
Ferromagnetic Shape Memory

The magnetic domain structures of the cubic parent phase (high-temperature phase) in ferromagnetic shape memory alloys (SMAs) have been studied by electron holography. In a Ni51Fe22Ga17 alloy, the magnetic flux distribution in the parent phase changes dramatically before the onset of martensitic transformation. In contrast, a Ni45Co5Mn36.7In13.3 alloy—a recently developed ferromagnetic SMA—does not show appreciable changes in the magnetic domain structure upon cooling. The anomaly observed in the Ni51Fe22Ga17 alloy appears to be due to lattice distortions, which become more pronounced as the temperature approaches the martensitic transformation start temperature, Ms.

scholarly journals Martensite Variant Identification For Shape Memory Alloys By Using Graph Neural Networks

2021 ◽  
Author(s):  
YI-Ming Tseng ◽  
Pei-Te Wang ◽  
Nan-Yow Chen ◽  
An-Cheng Yang ◽  
Nien-Ti Tsou
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Md Simulations ◽  
Current Work ◽  
Training Dataset ◽  
Post Processing ◽  
Martensite Variant ◽  
Atomistic Calculations ◽  
Graph Neural Networks

Abstract Detailed microstructure evolution in shape memory alloys (SMAs) is typically studied by molecular dynamics (MD) simulations. However, the conventional post-processing tools for atomistic calculations, such as CNA and PTM, fail to identify distinct crystal variants and to reveal twin alignments in SMAs. In the current work, a powerful and efficient post-processing tool based on GraphSAGE neural network is developed, which can identify multiple phases in martensitic transformation, including the orthorhombic, monoclinic and R phases. Where the network was trained by the results of sets of temperatureand stress-induced martensitic transformation MD calculations. The accuracy and generality were also verified by the application to the cases which did not appear in the training dataset, such as unrecoverable nanoindentation process. The proposed method is rapid, accurate, and is ready to be integrated with any visualization tool for MD simulations. The outcome of the current work is expected to accelerate the pace of atomistic studies on SMAs and related materials.

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