scholarly journals Microstructure Formation in Cast TiZrHfCoNiCu and CoNiCuAlGaIn High Entropy Shape Memory Alloys: A Comparison

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4227 ◽  
Author(s):  
Tetiana A. Kosorukova ◽  
Gregory Gerstein ◽  
Valerii V. Odnosum ◽  
Yuri N. Koval ◽  
Hans Jürgen Maier ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Microstructure Characterization ◽  
Microstructure Formation ◽  
High Entropy

The present study is dedicated to the microstructure characterization of the as-cast high entropy intermetallics that undergo a martensitic transformation, which is associated with the shape memory effect. It is shown that the TiZrHfCoNiCu system exhibits strong dendritic liquation, which leads to the formation of martensite crystals inside the dendrites. In contrast, in the CoNiCuAlGaIn system the dendritic liquation allows the martensite crystals to form only in interdendritic regions. This phenomenon together with the peculiarities of chemical inhomogeneities formed upon crystallization of this novel multicomponent shape memory alloys systems will be analyzed and discussed.

A chemical-structural model for coherent martensite/parent interface in Mn-based antiferromagnetic shape memory alloys

2016 ◽  
Vol 18 (43) ◽  
pp. 29923-29934 ◽  
Author(s):  
S. Shi ◽  
J. F. Wan ◽  
X. W. Zuo ◽  
N. L. Chen ◽  
J. H. Zhang ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Structural Model ◽  
Significant Part ◽  
Magnetic Shape Memory ◽  
Coherent Interface

The martensite/parent coherent interface of Mn-based shape memory alloys (SMAs) is a significant part in the research of their martensitic transformation, reversible shape memory effect and magnetic shape memory effect.

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.

Unexpected Constrained Twin Hierarchy in Equiatomic Ru-Based High Temperature Shape Memory Alloy Martensite

2013 ◽  
Vol 738-739 ◽  
pp. 195-199 ◽  
Author(s):  
Philippe Vermaut ◽  
Anna Manzoni ◽  
Anne Denquin ◽  
Frédéric Prima ◽  
Richard Portier
Keyword(s):  
High Temperature ◽  
Martensitic Transformation ◽  
Shape Memory Alloy ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Martensitic Transformations ◽  
Single Transition

Among the different systems for high temperature shape memory alloys (SMA’s), equiatomic RuNb and RuTa alloys demonstrate both shape memory effect (SME) and MT temperatures above 800°C. Equiatomic compounds undergo two successive martensitic transformations, β (B2) → β’ (tetragonal) → β’’ (monoclinic), whereas out of stoechiometry alloys exhibit a single transition from cubic to tetragonal. In the case of two successive martensitic transformations, we expect to have a finer microstructure of the second martensite because it is supposed to develop inside the smallest twin elements of the former one. In equiatomic Ru-based alloys, if the first martensitic transformation is “normal”, the second one gives different unexpected microstructures with, for instance, twins with a thickness which is larger than the smallest spacing between twin variants of the first martensite. In fact, the reason for this unexpected hierarchy of the twins size is that the second martensitic transformation takes place in special conditions: geometrically, elastically and crystallographically constrained.

Martensitic transformation, ductility, and shape-memory effect of polycrystalline Ni56Mn25 –xFexGa19alloys

2005 ◽  
Vol 96 (8) ◽  
pp. 843-846 ◽  
Author(s):  
Yunqing Ma ◽  
Lihong Xu ◽  
Yan Li ◽  
Chengbao Jiang ◽  
Huibin Xu ◽  
...  
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect

Synthesis and characterization of biodegradable, amorphous, soft IPNs with shape-memory effect

2011 ◽  
Vol 23 (3) ◽  
pp. 382-388 ◽  
Author(s):  
Yakai Feng ◽  
Haiyang Zhao ◽  
Licai Jiao ◽  
Jian Lu ◽  
Heyun Wang ◽  
...  
Keyword(s):  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Synthesis And Characterization

On the impact of lattice parameter accuracy of atomistic simulations on the microstructure of Ni-Ti shape memory alloys

2021 ◽  
Author(s):  
Lorenzo La Rosa ◽  
Francesco Maresca
Keyword(s):  
Molecular Dynamics ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Lattice Parameter ◽  
Lattice Parameters ◽  
Atomistic Simulations ◽  
Interatomic Potentials ◽  
The Impact

Abstract Ni-Ti is a key shape memory alloy (SMA) system for applications, being cheap and having good mechanical properties. Recently, atomistic simulations of Ni-Ti SMAs have been used with the purpose of revealing the nano-scale mechanisms that control superelasticity and the shape memory effect, which is crucial to guide alloying or processing strategies to improve materials performance. These atomistic simulations are based on molecular dynamics modelling that relies on (empirical) interatomic potentials. These simulations must reproduce accurately the mechanism of martensitic transformation and the microstructure that it originates, since this controls both superelasticity and the shape memory effect. As demonstrated by the energy minimization theory of martensitic transformations [Ball, James (1987) Archive for Rational Mechanics and Analysis, 100:13], the microstructure of martensite depends on the lattice parameters of the austenite and the martensite phases. Here, we compute the bounds of possible microstructural variations based on the experimental variations/uncertainties in the lattice parameter measurements. We show that both density functional theory and molecular dynamics lattice parameters are typically outside the experimental range, and that seemingly small deviations from this range induce large deviations from the experimental bounds of the microstructural predictions, with notable cases where unphysical microstructures are predicted to form. Therefore, our work points to a strategy for benchmarking and selecting interatomic potentials for atomistic modelling of shape memory alloys, which is crucial to modelling the development of martensitic microstructures and their impact on the shape memory effect.

scholarly journals Fabrication and Shape Memory Characteristics of Highly Porous Ti-Nb-Mo Biomaterials

2017 ◽  
Vol 62 (2) ◽  
pp. 1367-1370 ◽  
Author(s):  
Y.-W. Kim ◽  
T.W. Mukarati
Keyword(s):  
Martensitic Transformation ◽  
Shape Memory ◽  
Shape Memory Effect ◽  
Memory Effect ◽  
Differential Scanning Calorimetric ◽  
Porous Scaffolds ◽  
High Porosity ◽  
Porous Ti ◽  
Human Body Temperature ◽  
Rapidly Solidified

AbstractNon-toxic Ti-Nb-Mo scaffolds were fabricated by sintering rapidly solidified alloy fibers for biomedical applications. Microstructure and martensitic transformation behaviors of the porous scaffolds were investigated by means of differential scanning calorimetric and X-ray diffraction. Theα″–βtransformation occurs in the as-solidified fiber and the sintered scaffolds. According to the compressive test of the sintered scaffolds with 75% porosity, they exhibit good superelasticity and strain recovery ascribed to the stress-induced martensitic transformation and the shape memory effect. Because of the high porosity of the scaffolds, an elastic modulus of 1.4 GPa, which matches well with that of cancellous bone, could be obtained. The austenite transformation finishing temperature of 77Ti-18Nb-5Mo alloy scaffolds is 5.1°C which is well below the human body temperature, and then all mechanical properties and shape memory effect of the porous 77Ti-18Nb-5Mo scaffolds are applicable for bon replacement implants.

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