Following their discovery in the early 1960s, there has been a continuous quest for ways to take advantage of the extraordinary properties of shape memory alloys (SMAs). These intermetallic alloys can be extremely compliant while retaining the strength of metals and can convert thermal energy to mechanical work. The unique properties of SMAs result from a reversible diffussionless solid-to-solid phase transformation from austenite to martensite. The integration of SMAs into composite structures has resulted in many benefits, which include actuation, vibration control, damping, sensing, and self-healing. However, despite substantial research in this area, a comparable adoption of SMA composites by industry has not yet been realized. This discrepancy between academic research and commercial interest is largely associated with the material complexity that includes strong thermomechanical coupling, large inelastic deformations, and variable thermoelastic properties. Nonetheless, as SMAs are becoming increasingly accepted in engineering applications, a similar trend for SMA composites is expected in aerospace, automotive, and energy conversion and storage-related applications. In an effort to aid in this endeavor, a comprehensive overview of advances with regard to SMA composites and devices utilizing them is pursued in this paper. Emphasis is placed on identifying the characteristic responses and properties of these material systems as well as on comparing the various modeling methodologies for describing their response. Furthermore, the paper concludes with a discussion of future research efforts that may have the greatest impact on promoting the development of SMA composites and their implementation in multifunctional structures.

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Review and perspectives: shape memory alloy composite systems

Nitric oxide-releasing chitosan nanoparticles alleviate the effects of salt stress in maize plants.

To further enhance the performances of Cu-based shape memory alloys (SMAs), grains of a CuAlMn SMA were efficiently refined by using Cu51Zr14 as the inoculant. The effects of grain size on the microstructure, tensile mechanical properties as well as low frequency damping behaviors of the CuAlMn SMA were studied. It was found that the mean grain size of the CuAlMn SMA could be reduced from around 1050 µm to around 37 µm. And it was very interesting that both the tensile mechanical property and the damping capacity at relatively low temperatures increased with the decrease of the mean grain size of the CuAlMn SMA. The associated mechanisms were discussed.

Effects of grain refinement on the structure and properties of a CuAlMn shape memory alloy

A novel strategy to control the precipitation behavior of the austenitic phase, and to obtain large-sized, transformation-induced, plasticity-reinforced bulk metallic glass matrix composites, with good tensile properties, is proposed. By inducing heterogeneous nucleation of the transformable reinforcement via potent nucleants formed in situ, the characteristics of the austenitic phase are well manipulated.

Microstructural Control via Copious Nucleation Manipulated by In Situ Formed Nucleants: Large-Sized and Ductile Metallic Glass Composites.

In the present study, the influence of rare earth element gadolinium (Gd) on Cu-Al-Be polycrystalline shape memory alloy has been investigated Cu 8813 Al 1142 Be 045 ternary alloy with addition of Gd from 005 to 015 wt% has been used for investigation The tests have been carried out for microstructure, morphology, ductility, phases, crystal structure, phase transformation temperatures and shape recovery ratio Refinement of the grain size resulted as gadolinium increased from 0 to 008 wt%, the grain size decreases from 46345 to 8180 µm with reduction of 8234% The tensile strength has increased from 39893 to 58142 MPa with improvement in the ductility from 1005% to 2372% at 008 wt% gadolinium The phase transformation temperatures increases as gadolinium increases and reduction in shape recovery ratio from 97% to 65%

Influence of Gd on the microstructure, mechanical and shape memory properties of Cu-Al-Be polycrystalline shape memory alloy

Effects of aging on the microstructures and damping behaviors of a porous CuAlMn shape memory alloy were studied. It is found that after aging at 350 °C both the damping capacity of the alloy in the martensite state and the height of the internal friction peak arising from the reverse martensitic transformation increase due to the refining of martensitic structure and the annihilation of quenched-in vacancies. It is also found that the atomic ordering and the annihilation of quenched-in vacancies can promote the reverse martensitic transformation to take place, resulting in a significantly decreased temperature of the internal friction peak.

Effects of aging on the structure and damping behaviors of a novel porous CuAlMn shape memory alloy fabricated by sintering–dissolution method

Internal friction as a function of frequency in a CuAlMn shape memory alloy was systematically investigated through the method of forced vibration over a wide temperature range. The operative mechanisms of the typical internal friction behaviors were discussed in terms of the different relaxation processes in different temperature ranges.

J. Yang

Papers

Effects of grain refinement on the structure and properties of a CuAlMn shape memory alloy

Effects of aging on the structure and damping behaviors of a novel porous CuAlMn shape memory alloy fabricated by sintering–dissolution method

Internal friction of a CuAlMn shape memory alloy studied as a function of frequency