Fabrication and Processing of Shape Memory Alloys

Shape memory alloys (SMAs) are “smart” materials that possess certain inherent properties, which make them suitable to be used in various automotive, aerospace, biomedical, and scientific applications. These alloys undergo extensive fabrication and processing operations while manufacturing actuators for automotive and industries; stents and surgical tools for medical field; engineered parts for aerospace, mechatronics, robotics, and many other fields. However, their fabrication and processing are not easy. This chapter introduces SMAs, highlights their properties and applications, and also discusses the difficulties encountered during their fabrication and processing along with the possible causes.

Shape memory alloys (SMAs) are considered as difficult-to-machine materials. This chapter sheds light on machinability aspects of SMAs and presents a comprehensive discussion on advanced and sustainable strategies and techniques for machining SMAs. It commences with an introduction to machinability, challenges of SMAs and possible solutions before discussing implementation of machining strategies and techniques to enhance machinability. The chapter ends with an outlook and selected avenues for possible future research capabilities of SMAs machining. As regards to the advanced machining of SMAs, the major focus of this chapter is on electric discharge (electric discharge), laser beam, and abrasive water jet machining. Whereas, in sustainable machining section, the use of advanced cooling and lubrication strategies during conventional turning, milling, drilling, and grinding of SMAs are emphasized. Some aspects of a recent experimental research conducted on MQL-assisted turning of NiTi shape memory alloy are also included in this chapter.

Shape memory alloys are difficult to weld due to their own special properties, which lead to the problems of joints such as low strength, formation of intermetallic compounds, variations in phase transformation effects and its temperature, and changes of shape memory effect. However, different welding and joining processes are attempted to solve these problems. In this chapter, various welding processes such as tungsten inert gas welding, plasma welding, laser beam welding, electron beam welding, resistance welding, friction stir welding, friction welding, explosive welding, ultrasonic welding, diffusion bonding, adhesive bonding, brazing, and soldering are discussed on process capabilities and challenges to obtain shape memory welds.

Processing of shape memory alloys is attempted abundantly considering its numerous applications in different sectors of industries. However, it is not easy to process shape memory alloys as it has unique properties of pseudoelasticity, tendency to form intermetallic compounds, different phase transformation temperatures and deformation behavior. Different processing techniques reported for shape memory alloys such as powder metallurgy, additive processing, mechanical processing, and thermo-mechanical processing are considered in this chapter that addresses process condition, process parameters, and properties after processing.