Metal matrix composites (MMCs) are materials made of a metal alloy combined with another material, called a reinforcement, to give it specific properties. MMCs are used in situations where low weight, high strength, and high stiffness are important. One type of MMC, called particulate reinforced MMC, is made of small particles of the reinforcement material mixed into the metal alloy. These MMCs are attractive because they are easy to shape and have properties that are similar in all directions. However, they may have problems with an uneven distribution of particles, low ductility, and poor toughness and resistance to cracks. To improve the properties of particulate reinforced MMCs, including their ability to withstand damage, one option is to use a type of material called shape memory alloys (SMAs) as the reinforcement. SMAs can change their shape in response to certain conditions and have been added to soft and pliable metal or polymer matrices to improve their mechanical properties. Two SMAs that can produce a lot of strain and force when they change shape are NiTi alloys and Cu-based alloys. NiTi alloys are more expensive and have a higher density, but they are also stronger and more resistant to corrosion. Copper-based SMAs are cheaper and easier to work with, but they are not as strong and can lose their shape memory ability when exposed to temperature changes. The transformation of NiTi alloys from one phase to another can be affected by the alloy’s composition, heat treatment, applied stress, and the number of times it transforms. Researchers have used different methods to study the transformation behavior of NiTi alloys, including measuring electrical resistance, heat capacity, internal friction, magnetic susceptibility, and thermoelectric power.
In this study, we are looking at how NiTi particles behave when mixed into a particular type of aluminum alloy and how the microstructure and heat treatment of the aluminum alloy affects the NiTi particles. We studied the behavior of NiTi particles mixed into a type of aluminum alloy called AA2124 using different methods. We found that the NiTi particles improve the precipitation and damping properties of the AA2124 alloy. We also found that the transformation of the NiTi particles is affected by the heat treatment, the vibration frequency, and the cooling/heating rate. The presence of aluminum in the NiTi particles also affects the transformation, but it does not have a clear effect on the temperature at which the transformation occurs.
R.R. Thorat et al. “On the transformation behaviour of NiTi particulate reinforced AA2124 composites”.
In: Journal of Alloys and Compounds 477.1–2 (2009), pp. 307–315.
doi: 10.1016/j.jallcom.2008.11.002