Dr Ritwik Basu
The Northcap University, Gurgaon
One of the major breakthroughs in the world of materials and manufacturing is the development of smart materials in last two decades. These are materials which exhibit a change in some property with change in the temperature, pressure, stress, magnetic or electrical field. These comprise of a variety of materials which include piezoelectric, shape memory materials, magnetostrictive, pH-sensitive polymers, halochromic materials, ferrofluid, photomechanical materials and many more. Of all these different materials shape memory alloys find the widest applications to date.
Shape memory alloys exhibit two very important properties; shape memory effect(SME) and the pseudo elasticity (PE). SME is the property in which a material when cooled below a critical temperature causesa phase transformation from high temperature phase austenite to a low temperature phase martensite. Deforming the material in the low temperature condition and then reheating back causes the material to regain the high temperature shape and phase. It is very easy to deform the material in the martensitic condition Pseudo-elasticity is the property in which the material undergoes phase transformation from austenite to martensite upon application of stress i.e. the material exhibit softening with increased stress. The high temperature equilibrium phase and shape is restored when the applied stress is withdrawn. Both shape memory and pseudo elasticity isexploited for a large number of products and applications. These include actuators used in aircrafts, eye-glass frames, cardio-vascular stents, dental braces etc.