Martensitic Transformations and the Shape Memory Effect in Biocompatible TiNiMoAl Alloys

The Au-Cd alloys continue to be important vehicles of research for the shape memory effect involving martensitic transformations and related phenomena.They transform to a variety of martensitic structures depending on the alloy composition and thermal history. Additionally, the Au-rich alloys display rubber like behavior involving thermo-elastic memory. Defects and diffusion play important roles in determining these properties. Defects and diffusion mechanisms in the Au- 47.5 - 50.5 at.% Cd alloys are examined. Diffusion in the nanometer regime and the states of defects are found to be important contributing factors to determine the shape memory effect, the variable martensitic transformations and the rubber like behavior, which are discussed in details.

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Extreme shape memory effect during martensitic transformations with a nanoinvariant habit plane

Russian Metallurgy (Metally) ◽

10.1134/s0036029515050110 ◽

2015 ◽

Vol 2015 (5) ◽

pp. 407-411

Author(s):

S. V. Khachin ◽

A. A. Il’in ◽

V. N. Khachin

Keyword(s):

Shape Memory ◽

Habit Plane ◽

Shape Memory Effect ◽

Memory Effect ◽

Martensitic Transformations

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Martensitic Transformation and Microstructural Characteristics in Copper Based Shape Memory Alloys

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.510-511.105 ◽

2012 ◽

Vol 510-511 ◽

pp. 105-110 ◽

Cited By ~ 9

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.

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Thermodynamic considerations of " solid state engines" based on thermoelastic martensitic transformations and the shape memory effect

Metallurgical Transactions A ◽

10.1007/bf02673666 ◽

1975 ◽

Vol 6 (1) ◽

pp. 29-32 ◽

Cited By ~ 28

Author(s):

H. C. Tong ◽

C. M. Wayman

Keyword(s):

Solid State ◽

Shape Memory ◽

Shape Memory Effect ◽

Memory Effect ◽

Martensitic Transformations ◽

Thermoelastic Martensitic Transformations

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

Materials Science Forum ◽

10.4028/www.scientific.net/msf.738-739.195 ◽

2013 ◽

Vol 738-739 ◽

pp. 195-199 ◽

Cited By ~ 1

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.

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