TiNi Alloy (United States)

All space instruments contain mechanisms or moving mechanical assemblies that must move (sliding, rolling, rotating, or spinning) and their successful operation is usually mission-critical. Generally, mechanisms are not redundant and therefore represent potential single point failure modes. Several space missions have suffered anomalies or failures due to problems in applying space mechanisms technology. Mechanisms require a specific qualification through a dedicated test campaign. This paper covers the design, development, testing, production, and in-flight experience of the PICARD/SODISM mechanisms. PICARD is a space mission dedicated to the study of the Sun. The PICARD Satellite was successfully launched, on June 15, 2010 on a DNEPR launcher from Dombarovskiy Cosmodrome, near Yasny (Russia). SODISM (SOlar Diameter Imager and Surface Mapper) is a 11 cm Ritchey-Chretien imaging telescope, taking solar images at five wavelengths. SODISM uses several mechanisms (a system to unlock the door at the entrance of the instrument, a system to open/closed the door using a stepper motor, two filters wheels using a stepper motor, and a mechanical shutter). For the fine pointing, SODISM uses three piezoelectric devices acting on the primary mirror of the telescope. The success of the mission depends on the robustness of the mechanisms used and their life.

A direct current magnetron target assembly with rotating adjustable magnets arrangement has been used for thin film sputter deposition from a 200 mm diameter TiNi target in a PE 4450 sputtering system. It was found that for a simple circular magnet arrangement placed 20 mm off the rotation axis the films deposited on the stationary pallet have significant variation in M s temperatures as measured from the center of the magnetron. This variation across the 100 mm wafer is as large as -100°C. The gradient in M s for the sputtered film can be significantly lowered by using an appropriate configuration of magnets, which in combination with rotation of the pallet, results in narrowing the difference in M s to less than 10°C. Further adjustment of transformation temperatures of the film can be accomplished by simultaneous sputtering on the rotating pallet from two targets. Depending on which direction the transformation intervals need to be moved, the second target should be either Ti or Ni. The deposition rates for the TiNi and Ni targets were calibrated and calibration results were applied for calculating the power settings to sputter film with A f = ∼15°C. The transformation intervals and stress-strain curves across a 100 mm wide area were measured for this film.

Deformation behaviour and the structure of the M phases of the single crystal of the Cu-12mass%Al and Cu-13.4mass% alloy were investigated by tensile deformation and EM observation. In the present work it was found that the direct transition from 18R to 3R or 2H to 3R does not take place but transition undergoes passing through a new long period(L.P.) intermediate M phase (from 10 to 45 stacking) and reaches the final 3R(DO 22 ) M phase. During L.P.to 3R transition a typical pseudoelastic behaviour was observed during loading-unloading cycle and the width of the hysteresis loop between loading and unloading varied with testing temperature and the tensile cycling. The width of the loop decreses with increasing testing temperature and also with increasing testing cycle in both the alloys. These facts suggest that in the Cu-Al alloys a kind of continuous M to M transformation exhibits during cyclic tensile deformation in addition to the ordinary successive 18R or 2H to 3R transformation.

ABSTRACTA new actuator for silicon micro-valves has been developed and tested. A thin film shape memory alloy provides for large deflections with high speed, low power, and small size. The actuator is batch fabricated with planar processes.

The objective of this research is to establish a shape-memory effect in sputter-deposited films of nickel titanium. The alloy, generically called nitinol, was prepared from sputtering targets in two different compositions. Films were deposited up to 10 μm in thickness on glass substrates using a dc magnetron sputtering source. The as-deposited films were amorphous in structure and did not exhibit a shape memory. The amorphous films were crystallized with a suitable annealing process, and the transformation properties were measured using differential scanning calorimetry. The crystallized films showed transition temperatures that were much lower than those of the parent material. X-ray diffraction patterns indicated that the films were not a single phase but showed evidence of a second phase. However, the annealed films demonstrated a strong shape-memory effect. Stress/strain measurements and physical manipulation were used to evaluate the shape recovery. These tests demonstrated sustained tensile stresses of up to 480 MPa in the high-temperature phase, and a characteristic plastic deformation in the low-temperature phase.