|SCSCMA is a new material manufactured at TiNi Aerospace from Copper-Aluminum- Nickel (Cu-Al-Ni). This alloy exhibits significantly enhanced performance over commercially available SMA made from Titanium-Nickel (TiNi). Like SMAs (Shape Memory Alloys), SCSMAs have the ability to return to a predetermined shape either by heating to its transition temperature or by relieving the applied load when austenitic. By comparison, however, SCSMAs provide the following key advantages over SMAs:
SCSMAs are manufactured by "growing" a single crystal from a melt, by a similar method as that used by the semiconductor industry to fabricate silicon boules. This process enables TiNi to manufacture materials which have significantly enhanced properties which approach theoretical limits. The "grown" material is generally fabricated as a rod but can have a range of cross sections (i.e. solid, hollow, flat, or oval). The material can also be subsequently formed into other shapes by traditional fabrication methods such as grinding, machining, or EDM (Electro-Discharge-Machining).
SCSMAs are remarkable materials which can be used in the following ways:
- Significantly Greater Strain Recovery (9% vs. 3%)
- True Constant Force Deflection
- Wider Transition Temperature Range
(-270°C to + 250°C)
- Very Narrow Loading Hysteresis
- Recovery which is 100% Repeatable & Complete
- As a Superelastic Spring: As shown in figure 1, the material while in the high temperature state (Austenite) has a unique stress-strain profile. Comparing SCSMA to traditional spring materials such as Stainless Steel or Beryllium Copper which have an elastic limit of less than 0.5%, SCSMAs are 20 times more elastic and can fully recover from deformations in excess of 9 %. The greater elasticity is also largely delivered at a constant force which is a great advantage in minimizing the total energy dissipated during recovery or spring back.
- As a Thermal Actuator: As shown in figure 2, the material while in the low temperature state (Martensite) can be deformed up to 9% and then heated to full recovery by raising its temperature above its transition temperature*. This process results in a powerful actuator capable of delivering recovery forces (stresses) up to 600 MPa.
* Note: The materials "transition temperature" is largely dependent on its composition and can be readily tuned to be between -270°C to +250°C.
Figure 1: SCSMA Stress-Strain Property: Note that the material is 100% elastic up to 9% strain (<100> direction) when in the austenitic state*. The actual plateau stress is dependent on the transition temperature and increases at a rate of 3.5 MPa/oC.
Figure 2: SCSMA Shape Memory Property: Shows how the thermally induced transition Austenite D Martensite can be used as an actuator