New, intelligent materials for use in mechanical actuators

A research team at the Department of Physics at the Public University of Navarre are developing new, “intelligent” materials which have the capacity for changing shape when a magnetic field is applied to them. These materials may be used for the generation of ultrasonic signals, in the manufacture of loudspeakers and sonars or in actuators, amongst other applications. The project is a three-year one.

Specifically, the group at the Public University of Navarre is working on the optimisation of materials which were discovered at the beginning of the nineties: metal alloys having a ferromagnetic shape memory (FSMA). These alloys have the ability to change shape under mechanical pressure, in a magnetic field or with temperature variation, and to return, in a reversible manner, to its original shape when the stimulus ceases or is removed.

Magnetic modification

The principal use for these alloys having a ferromagnetic shape memory is in the manufacture of actuators, those devices which, on the application of a magnetic field, modify their dimensions in order to carry out operations. The advantage of these devices is that the operations in question can be controlled remotely using magnetic fields, without the need to resort to manual contact. As a result of the modification of the dimensions, the actuator can press a button or carry out any other mechanical operation in an industrial process.

Moreover, these metal alloys with ferromagnetic shape memory have a capacity for changing shape much greater than that of other metals, thereby providing us with an alternative to the current piezoelectric actuators, currently the most commonly used in industrial processes.

Beyond this use, the field of application of this type of alloy stretches from the generation of ultrasonic signals (for ultrasonic cleaning or ultrasonic transducers such as those used in ecographys…), to the application of a constant force (lineal force engines, positioners…), and taking in the cores of speaker and sonar devices, vibration dampers and a whole series of devices based on piezoelectric and magnetostrictor materials.

Development of new alloys

The aim of this research project is to find new alloys having a ferromagnetic shape memory, introducing materials such as aluminium, tin, cobalt, nickel or gallium.

To achieve this, in the first place, the Public University of Navarre is studying the vibrational behaviour and the elastic constants of monocrystalline alloys, for the subsequent application thereof to the more abundant polycrystalline alloys.

The monocrystal alloys are ordered structures, perfect crystallographic networks which enable the study of their properties with ease. Nevertheless, monocrystals involve a costly and demanding manufacture process so it is the polycrystals that are more frequent in commercial applications.