The transformation properties of Cu-Al-Ni alloys modified by the additions of boron and manganese have been interpreted by studying the reversibility and stability of the martensitic transformation as a function of heat treatment and of manganese concentration between 2 and 4 wt%. The alloy containing 2% Mn exhibits a lack of thermoelasticity due to a decrease of the degree of B2 order and supression of DO3 order during quenching and the increase of both types of order during annealing. From the determination of the activation energies responsible for the martensitic and reverse transformations, we have deduced that, in both cases, the kinetics of the transformation are controlled by an atomic jump at the interface between the two phases.

The basic concept underlying the alloy design and microstructural control method utilised in developing a new type of β(B2)+ γ (A1) two-phase ductile shape memory alloy in the Ni-Al base systems is briefly reviewed. The characteristic features of the shape memory effect (SME) in the Ni-Al-Fe and Ni-Al-Fe-Mn alloys are reported with particular reference to the transformation and deformation temperatures, the volume fractions of the γ phase, the morphology of the β + γ structure and the effect of cycling. Training by cycling treatment has a significant effect on the degree of shape recovery and pseudo-elasticity in the β + γ two-phase alloys. These duplex β + γ alloys also exhibit a combination of relatively high damping capacity and high yield strength. It is emphasized that these alloys could be expected to fill the need for a new group of shape memory alloys which operate at elevated temperatures over 100°C.

This paper investigates the microstructure and ductility of Al - 66 at.% Ni by means of melt spinning technology combined with La microalloying. It shows that the Al - 66 at.% Ni without La exhibits coarse equiaxed martensite grains with Ni3Al precipitating at the grain boundaries (GBs). An addition of 0.05 wt.% La suppresses the precipitation of Ni3Al and a microstructure of complete martensite is obtained. When the amount of La is 0.2∼0.8 wt.%, a “supersaturated” single phase of B2 structure NiAl results. The elongation of Al - 66 at.% Ni without La is only 0.8%. When 0.05, 0.2, and 0.8 (wt.%) La are added to the alloy, their elongations can be as high as 2.6, 3.0, and 3.2% respectively. This shows that the elongation increases with increasing La content. The microstructural morphology and the ductility enhancement mechanism are discussed.

The shape memory alloy TiNi is produced by either Vacuum Induction Melting (VIM) or by Vacuum Arc Remelting (VAR) of pure metal ingots for actuator applications. Powder metallurgy techniques provide an alternative fabrication route for their use in passive damping applications where porosity and deviations in chemical homogeneity can be tolerated. In this study TiNi compacts were cold pressed from the blended elemental powders and sintered in vacuum for varying times at temperatures from 800°C to 1000°C. Two heating rates were used, 5 K/min. and 10 K/min. A TiNi microstructure could be produced after annealing at 1000°C for 6 h., although some TiNi3 was still observed. Sintering above 900°C produced porous microstructures with green densities approaching 3.5 gm/cm3.

The evolution of the R-phase transformation temperature with iron concentration is studied by Mössbauer spectroscopy (MS), magnetic susceptibility and calorimetric measurements in a series of three Ti50Ni50-xFex, samples, with x = 1, 2 and 3. The changes in the Mössbauer spectra, from a single line at room temperature to a quadrupole doublet when the temperature is lowered below 280 K, are related to structural transformations occurring in the system. The temperature changes in the magnetic susceptibility are interpreted in terms of a gap opening characteristic of charge density waves (CDW) formation when the R-phase transformation takes place. The calorimetric measurements show specific heat fluctuations near room temperature in two of the samples (x = 1 and 3) whose peaks shift during the cooling and heating cycles.

The utility of superelastic Ni-Ti alloys in the medical industry has been rather dramatically demonstrated in recent years. A great number of devices are now in production, and still others are staged to enter production during the next few years. This surge in interest from the medical community stems from an increased acceptance of Ni-Ti because of its biocompatibility, advances in micromachining techniques and trends towards less-invasive surgical techniques. In addition, there are a variety of new developmental concepts that will have a major influence on this and other markets during the next 5 years of commercialization. This review will highlight many of the properties of Ni-Ti by illustration in a variety of recent medical applications, and then discuss some of the newer developmental concepts. Medical applications that will be presented here include guidewires, laparoscopic surgical instruments, implants, stents, retrieval baskets, and bone anchors. Some of the new concepts and capabilities that are reviewed include microvalves made from thin films, high temperature alloys, fatigue resistant composites, and robotic actuators with tactile feedback.

Personal Environments™ is a Johnson Controls, Inc. system for the control of indoor office environments. In this system, four SMA coiled extension springs interact to control the position of two dampers. Two opposing SMA springs connected to one damper control the percentage of primary conditioned air entering the system, and two opposing SMA springs connected to the second damper control the percentage of room air reentering the system.

The interactive operation of the SMA springs is discussed and a model is presented on the interactive response of the SMA springs. The SMA spring transformation temperatures, force - strain relationship, and the experimentally measured interactive response to temperature are presented and discussed.

This paper presents the results from an experimental study on the durability of embedded Shape-Memory Alloy (SMA) hybrid composites. It shows that the cyclic actuation of such composites can be degraded due to the accumulation of internal damage within the host composite structure. This damage results from thermal effects within the host composite, and from mismatch in the strain capacities of the actuators and structural composite. The implications of this data for the design of embedded SMA actuator 'smart' composites is discussed.

Recently, shape memory alloy(SMA) is regarded as one promising material element natively with intelligent functions. I introduce the fundamental design concept and several trials for developing intelligent(smart) materials and structures by using shape memory alloy. Moreover, I introduce our recent works and point out the necessity for developing fundamental techniques to realize the intelligent materials using SMA.

The mathematical model of a flexible cantilever beam with a constrained viscoelastic layer and shape memory alloy layer called smart damping treatment (SDT) is presented. It is shown that a change of the elastic modulus of the shape memory alloy layer will affect the system loss factor and resonance frequency. The recovery stress of the SMA layer leads to an inhomogeneity in the governing differential equation. The recovery stress also functions as an excitation to the system. The effects of the different parameters found in the analysis are discussed in the paper.

We have been investigating several chemical microsensor technologies for the detection of chemicals found in propellant and rocket exhaust plumes and as contaminants for satellite components. In this work we have developed a catalytic metal sensor for the detection of H2 contamination in electronic device packages. The sensor is based on the resistance of a thin film Pd/Ni alloy. Data have been obtained on its response at room temperature to various levels of H2 as well as the effects of H2O and O2 on its performance. Hydrogen levels to 10.5 ppm have been detected and the responsivity is about twice that of similar sensors. The sensor is insensitive to H2O but its response to H2 is strongly inhibited by O2.

Calorimetric changes in a series of pure and doped single crystal and polycrystalline BaTiO3 were studied using differential scanning calorimetry over the temperature range of-110°C to 200°BC. The dopants, oxides of niobium and iron were varied from 0.5 to 8 mole percent, and strontium was varied from 5 to 35 mole percent. Endotherms were observed corresponding to three crystallographic transitions. The highest observed thermal transition corresponds to a tetragonal to cubic crystallographic transition and is also associated with the Curie temperature in these materals. Two additional endothermic transitions were also observed, an intermediatetemperature orthorhombic to tetragonal transition, and a low-temperature rhombohedral to orthorhombic transition. The three dopants decreased the crystallographic transition temperatures and Curie temperature as the dopant concentration was increased. X-ray diffraction was used to identify phases present and to determine the extent of solid solution. It is expected that these materials will display improved infrared detection as well as opto-electronic properties.

The ordered intermetallic NiAl with aluminum levels near 36% undergoes a B2 to martensite transformation. Shape memory alloys based on NiAl+Fe have the potential for transition temperatures of greater than 150°C. While binary alloys appear inherently brittle, alloying with iron and boron results in two phase alloys with L12 and B2 phases and with about 7% room temperature tensile ductility. These alloys show a two-way shape memory effect over a range of transition temperatures with austenite peak temperature, Ap, between 100 to 200'C based on composition. Unfortunately, the B2 phase and its low temperature body centered tetragonal martensitic form are not stable and both can transform to Ni5Al3 with a loss in ductility. These alloys with a constant tensile load show a two way shape recovery of up to 0.6% during temperature cycling between 100 and 200°C. A thorough survey of the shape memory properties of one such alloy with a composition of Ni-25.5 Al-16 Fe-0. 12 B (at.%) as a function of prior cold work, tensile loading and other training steps is presented. Nanoindentation was used to independently measure the mechanical properties of the two phases.