An Experimental Investigation on Properties of Cu-Al-Be-X Shape Memory Alloys for Smart Structure Applications

Abstract

Smart materials are new class of materials, capable of sensing and responding to the change of its environment are of much interest in robotics, structural, biomedical and aerospace technologies. Shape memory alloys (SMA), Shape memory polymers (SMP), Hydrogels, Electrostrictive (ES), Electrorheological (ER), Piezoelectric (PE), and Magnetostrictive (MS), Magnetorheological (MRE) are the most common smart materials. Among these, shape memory alloys hold a peculiar property viz. deformed material can restore their actual shape either by an increase in temperature or removal of the load, known as shape memory effect and super-elasticity respectively. These two distinct properties attract the usage of SMA’s as actuators in smart structures to suppress flutter and in civil structures to isolate vibrations. Past decades, intense research has been carried out and still progressing in the development of a novel, economical and long functional SMA for the flutter suppression in the smart/adaptive structures. From 1960s to till today, Ni-Ti based SMAs are used mostly in applications because of their superior advantages i.e., high strain recovery, long functional life, however their utilization is limited due to the difficulties in processing and expensive. Cu-Al based shape memory alloys are selected as an alternative to Ni-Ti (Nitinol), because of ease of production and economical. This thesis is concerned with the design and development of Cu-Al-Be based shape memory alloys with improved microstructure, mechanical properties, and narrow thermal hysteresis with better shape/strain recovery for the actuator applications. The investigation has been carried out on the effect of variation in wt.% of Cu, Al, Be and the grain refiners viz. Boron (B), zirconium (Zr), and rare-earth elements, cerium (Ce) and gadolinium (Gd), and also manganese (Mn) on microstructure, mechanical and shape memory properties. The present investigation suggests that Al plays a vital role in the modification of martensitic fraction followed by Be. Boron and zirconium grain refiners enhance the grain refinement with minimal addition and better shape recovery. Cu-Al-Be-B shape memory alloys are chosen as suitable for the rapid response.