Shape Memory and Superelastic Ceramics at Small Scales

Shape memory materials are a class of smart materials able to convert heat into mechanical strain (or strain into heat) by virtue of a martensitic phase transformation. Some brittle materials such as intermetallics and ceramics exhibit a martensitic transformation but fail by cracking at low strains...

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Bibliographic Details
Published in:Science (American Association for the Advancement of Science) 2013-09, Vol.341 (6153), p.1505-1508
Main Authors: Lai, Alan, Du, Zehui, Gan, Chee Lip, Schuh, Christopher A.
Format: Article
Language:English
Subjects:
Austenite
Ceramic materials
Ceramics
Condensed matter: structure, mechanical and thermal properties
Cross-disciplinary physics: materials science
rheology
Damping
Elasticity, elastic constants
Exact sciences and technology
General equipment and techniques
Heat
Heat transfer
Instruments, apparatus, components and techniques common to several branches of physics and astronomy
Martensite
Martensitic transformation
Martensitic transformations
Materials science
Mechanical and acoustical properties of condensed matter
Mechanical properties
Mechanical properties of solids
Memory
Phase diagrams and microstructures developed by solidification and solid-solid phase transformations
Physics
Shape memory alloys
Shape memory materials
Stress analysis
Structural strain
Transducers
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Summary:Shape memory materials are a class of smart materials able to convert heat into mechanical strain (or strain into heat) by virtue of a martensitic phase transformation. Some brittle materials such as intermetallics and ceramics exhibit a martensitic transformation but fail by cracking at low strains and after only a few applied strain cycles. Here we show that such failure can be suppressed in normally brittle martensitic ceramics by providing a fine-scale structure with few crystal grains. Such oligocrystalline structures reduce internal mismatch stresses during the martensitic transformation and lead to robust shape memory ceramics that are capable of many superelastic cycles up to large strains; here we describe samples cycled as many as 50 times and samples that can withstand strains over 7%. Shape memory ceramics with these properties represent a new class of actuators or smart materials with a set of properties that include high energy output, high energy damping, and high-temperature usage.
ISSN:0036-8075
1095-9203
DOI:10.1126/science.1239745