Shape memory alloys (SMAs) are a type of smart material that can temporarily alter their shape, reverting to their original form at certain temperatures. They have innovative applications in aerospace, automotives, robotics, and biomedicine. Nitinol, or nickel-titanium, has been used as an SMA since the 1960s. Copper-based shape memory alloys are emerging as a modern alternative due to their cost-effectiveness, high thermal conductivity, and straightforward fabrication.
Learn about the properties of copper SMAs and potential use across industries.
What Are Shape Memory Alloys and How Do They Work?
Shape memory alloys are unique metallic materials that can change their structures at certain temperatures. This occurs as the SMA moves between two phases: martensite and austenite.
Below the transformation temperature, the alloy is in a martensite state and has a soft, rubbery texture. It has a less-stable crystalline structure, allowing for temporary shape changes. Once the SMA returns to its transformation temperature, it’s in an austenite state. Its structure allows one orientation, and the alloy recovers its initial, rigid form.
SMAs also exhibit a property known as superelasticity above the transformation temperature. The material can be distorted with slight pressure, returning to its initial configuration once the pressure is removed. The two most common SMAs for commercial and industrial applications are copper-based and nickel-titanium.
The Unique Advantages of Copper Shape Memory Alloys
The properties of a shape memory alloy depend on its materials. Some of the unique features of copper-based SMAs, compared to Nitinol, include:
- Higher thermal conductivity
- Lower electric resistivity
- Higher transformation temperature
- Higher density
Copper-based SMAs are straightforward to manufacture. They use traditional liquid and powder metallurgy methods, which makes them less expensive than nickel-titanium. The process for Nitinol is more involved due to the reactivity of titanium.
Another key advantage of copper SMAs is the potential for customization. The properties of binary alloys, such as Cu-Zn, Cu-Al, and Cu-Sn, can be refined by adding other materials and adjusting the composition or its proportions. This can improve ductility, thermal stability, mechanical properties, and transformation temperatures to enable more precise applications.
Nitinol has advantages for certain applications. It’s biocompatible and more corrosion resistant, making it better suited for biomedical purposes. It also offers a higher recoverable strain and can undergo greater deformation than copper.
Applications of Copper Shape Memory Alloys: Current and Emerging Uses
Copper-based SMAs are used in many industries, including engineering, manufacturing, aerospace, biomedicine, marine, and robotics. They have diverse applications due to their conductivity, superelasticity, and ability to recover their shape in different environments.
SMAs are used for antennas, eyeglass frames, guide wires, sensors, valves, connectors, vibration dampers, medical devices, and actuators. They can activate a car’s clutch fan at a specific temperature or serve as release mechanisms in aeronautics. New applications continue to emerge as copper SMAs enable precise movement without complex electronics or motors.
Why Copper Shape Memory Alloys Are the Future of Adaptive Materials
Customized to respond dynamically to their environment, copper shape memory alloys are an affordable complement or alternative to Nitinol. Research into the exciting potential of copper SMAs is ongoing. New classes of shape memory alloys with more sensitivity and improved performance will expand their usage and applications in the future.
Belmont Metals provides high-quality copper alloys tailored for shape memory applications. Contact us to learn more.