Cu-based shape memory alloys (SMAs) and among these copper–zinc (Cu–Zn), copper–aluminum (Cu–Al), and copper–tin (Cu–Sn) alloys both with and without ternary additions have shown potential due to their good shape recovery, ease of fabrication, excellent conductivity of heat and electricity. However, their applications are still limited because of the shortcomings of thermal stability, brittleness, and mechanical strength, which are closely related with microstructural characteristic of Cu-based SMAs, such as coarse grain sizes, high elastic anisotropies, and the congregation of secondary phases or impurities along the grain boundaries. Efforts are being made to overcome these drawbacks with proper ternary additions, adopting alternative processing routes and also optimizing the heat treatment cycles. The present article will deal with the current status of research and commercialization of Cu-based SMAs and dwell upon the future directions in which research should be targeted and future prospects of converting the research into components for commercial use.

Oxide composites are a class of materials with potential uses for nuclear, space, and coating applications. Exploiting their promise, however, requires a detailed understanding of their interfacial structure and chemistry. Using analytical microscopy, we have examined the radiation damage behavior at the interface of a model oxide bilayer, SrTiO3/MgO. The as-synthesized SrTiO3 thin film contained both (100) and (110) oriented domains. We found that after ion beam implantation the (110) domains amorphized at a lower radiation fluence than the (100) domains. Further, a persistent crystalline layer of SrTiO3 forms at the interface even as the rest of the SrTiO3 film amorphizes. We hypothesize that the enhanced amorphization susceptibility of the (110) domains is a consequence of how charged irradiation-induced defects at the interfaces interact with the charged planes of the (110) domains. These results demonstrate the complex relationship between interfacial structure and radiation damage evolution at oxide interfaces.

The nature of morphological instabilities in sputtered titanium and niobium nitride thin films grown on amorphous borosilicate glass and single-crystal Si (311) substrates is investigated. All the films were grown by RF magnetron sputtering at constant power and pressure but with thickness varying from 40 to 400 nm and substrate temperatures of 250–300 °C. The surfaces of the thin films can be divided into two areas: one in which the morphology is smooth with densely packed grains and the other in which there are morphological instabilities. A closer observation of the morphological instabilities reveals the coexistence of elastic strain-induced Asaro–Tiller–Grinfeld (ATG) type of instability and dendritic and snowflake structures due to diffusion-limited aggregation (DLA). The ATG instabilities extend over lengths of several tens of micrometers, whereas the DLA structures are confined to lengths of less than 10 μm in the same film. At low thickness (40–100 nm) only the elastic strain-induced instabilities emerge. High growth rates and a thickness of 150 nm are required to cause DLA and coexistence of the two kinds of instabilities. It has also been found that crystallization is not a prerequisite for the formation of dendritic structures.

Utilization of PbZrxTi1−xO3 (PZT) nanofibers as functional flexible fillers in sensing and energy harvesting applications requires uniform, submicrometer fibers with a large aspect ratio. Previous studies concentrated on the rheological effects on the fiber's diameter and morphology. However, reports on the effect of electric field on these fiber properties are still scarce. In this paper, the effects of surface charge and electric field on the fiber branching are decoupled. We show unequivocally that the external electric field governs this phenomenon. Low viscosity (∼0.12 Pa s) PZT sols yielded a sharp step-like transition from a large to a small diameter regime at electric fields above 0.8 kV/cm. On the other hand, high viscosity sols (∼0.74 Pa s) yielded a transition from a single to a bimodal distribution at the same electric field, due to the branching effect. An ability to obtain a single or bimodal diameter distribution in the range of 100–800 nm was demonstrated.

A technique has been developed for determining coefficients in the power approximation of the “stress–strain” diagram by results of scratch testing with a Berkovich indenter under a normal load of 5 mN on the indenter. The procedure is based on a comparison of experimental results with the finite element simulation of the test process. The technique is intended for application on nanomechanical testing equipment enabling one to perform tests with recording of loading diagrams in terms of the “normal force – indenter displacement” coordinates. To obtain correct results, one must observe the following restrictions: indenter penetration depth > 150 nm under a loading of 5 mN with the indenter tip curvature radius R < 50 nm; indenter penetration depth > 250 nm with 50 < R < 100 nm; the tested metal must be ductile enough, for a scratch to be formed by the mechanism of plastic deformation rather than fracture.

To produce the magnetic core of electric motors, nonoriented electrical steels (NOESs) are used with an electrically insulating coating applied to the surface. Residual stress is induced during the coating process, which will alter the hardness and magnetic domain structure of the NOES. In this study, the effect of the coating is examined, specifically, its role in creating a residual stress near the coating/steel interface. This stress was investigated by the nanoindentation technique. With this method, a ∼30 µm deep affected area was observed for NOES along both the rolling and transverse cross section directions, when in the presence of the coating. A biaxial tensile stress of ∼200 MPa was calculated from the measured hardness values in the NOES, which was linked to variations in the magnetic domain structure near the interface. The observed magnetic domain structure was simplified by the reduction of supplemental domain structure near the coating/steel interface.

Cu and Cu–Al alloys with different stacking fault energies (SFEs) were processed using rolling and the Split Hopkinson pressure bar followed by rolling. The effect of strain rate on the microstructures and mechanical properties of the alloys were investigated using x-ray diffraction analyses, transmission electron microscopy, and tensile tests. Tensile testing results demonstrated that the strength and ductility of the samples increased simultaneously with decreasing SFE. Microstructural observations indicated that the average grain size of the samples decreased with decreasing SFE, but the twin and dislocation densities increased. With decreasing SFE, twinning becomes the dominant deformation mechanism. Our findings indicated that the SFEs significantly affect the strength and ductility of the materials because they play a key role in determining the deformation mechanism. Decreasing the SFE of Cu alloys has proved to be the optimum method to improve the ductility without compromising the strength of the material.

When properly designed at ultra-low density, hollow metallic microlattices can fully recover from compressive strains in excess of 50%, while dissipating a considerable portion of the elastic strain energy. This article investigates the physical mechanisms responsible for energy loss upon compressive cycling, and attributes the most significant contribution to a unique form of structural damping, whereby elastic local buckling of individual bars releases energy upon loading. Subsequently, a simple mechanical model is presented to capture the relationship between lattice geometry and structural damping. The model is used to optimize the microlattice geometry for maximum damping performance. The conclusions show that hollow metallic microlattices exhibit exceptionally large values of the damping figure of merit, (Young's modulus)1/3(loss coefficient)/(density), but this performance requires very low relative densities (<1%), thus limiting the amount of energy that can be dissipated.

The process of laser-induced brazing constitutes a potential option for connecting several ceramic components (n- and p-type ceramic bars and ceramic substrate) of a thermoelectric generator (TEG) unit. For the construction of the TEGs, TiOx and BxC were used as thermoelectric bars and AlN was used as substrate material. The required process time for joining is well below that of conventional furnace brazing processes and, furthermore, establishes the possibility of using a uniform filler system for all contacting points within the thermoelectric unit. In the work reported here, the application-specific optimization of the laser-joining process is presented as well as the adapted design of the thermoelectric modules. The properties of the produced bonding were characterized by using fatigue strength and microstructural investigations. Furthermore, the operational reliability of the modules was verified.

In this study, bioactive glass powders were synthesized via an inexpensive hydrothermal chemical route by the use of ultrasonic energy irradiation. Soda lime, calcium nitrate tetrahydrate, and diammonium hydrogen phosphate were used as the precursor materials to synthesize low-sodium bioactive glass materials based on the conventional 45S5 Bioglass®. The morphological properties of the synthesized powders and the microwave-sintered dense compact were investigated. The mechanical properties of the fabricated dense bioactive glasses were characterized and were found to be very good. The ability to form biological apatite under physiological conditions was demonstrated with simulated body fluid (SBF). The material was shown to be highly biocompatible using the 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) assay with osteoblast-like MG63 cells. The cell adhesion and proliferation behavior of osteoblast-like MG63 cells were investigated and found to be excellent.