Shape Memory Alloys and SMST 2013

Interview conducted by G.P. ThomasOct 22 2012

John F. Boylan, current SMST President, talks to AZoM about the upcoming SMST 2013 conference, ASM International and shape memory alloys.

Could you give a brief overview of ASM International and the history behind this society?

ASM International (original the American Society for Metals) is a worldwide professional organization for materials scientists and engineers. Founded in 1913, the Society original focused on metals but it has expanded its scope to include ceramics, polymers and composites. Its members include industrialists, educators and students from around the world.

ASM International is preparing to celebrate its centenary in 2013 – how has the role of the society changed in this time?

The role of the society has expanded to pace materials technologies development. From its roots as a steel treating society, ASM International has evolved into a society covering all forms of advanced materials and processes. ASM provides authoritative information and knowledge on all types of materials and processes, from the structural to the nanoscale.

Could you tell us a little bit about the current series of ASM Handbooks?

The ASM Handbooks provides comprehensive and practical information on the properties and performance of materials—with a particular emphasis on industrially important metals and alloys—and the processes used in the manufacture and fabrication of components.

The current series includes volumes on properties and selection, phase diagrams, heat treating, surface engineering, welding, powder metallurgy, mechanical testing, metallography and microstructures, materials characterization, failure analysis, fractography, corrosion, forming and forging, casting, machining, non-destructive testing, tribology, fatigue, and modelling.

What are some of the sectors that ASM and its members have an interest in?

Quite simply, if it’s about materials then ASM and its members are interested. Of course, every individual member has a personal and specific focus on their own technical areas, be it testing, processing or a class of materials.

Registration has recently opened for SMST 2013 – could you tell us about this conference and who it is aimed at?

SMST is an affiliate society of ASM International. SMST stands for “Shape Memory and Superelastic Technologies”. The conference focuses on the science, engineering and industrial exploitation of these unique materials.

Could you provide an overview of shape memory alloys – how are these created and what are they used for?

There are several alloy systems that demonstration shape memory behavior. By far the most commercially exploited are those alloys known as nitinol, the binary alloy of nickel and titanium and several ternary alloys of nickel, titanium and a third element. Nitinol alloys have superior properties to other shape memory alloy systems, with approximately eight percent recoverable strain. That is a phenomenal amount of recoverable strain when compared to conventional metals and alloys which have substantially less than one percent recoverable strain! Consider that stainless steel has a yield strain of only approximately 0.1 percent.

Shape memory depends on a reverse transformation from a cooler martensitic phase to a warmer austenitic phase. Essentially, a nitinol component is fabricated in its austenitic state, and then cooled to its martensitic state where it is deformed by up to eight percent strain. Upon heating back to its austenitic state, the component recovers virtually all of the deformation and returns to its original shape – thus shape memory.

One of the classic original applications of shape memory nitinol was aircraft hydraulic couplings. The couplings were machined at room temperature, cooled in liquid nitrogen and expanded to eight percent strain. Upon installation and return to room temperature, they recovered their original diameter and produced a leak-tight hydraulic seal.

Some shape memory alloys exhibit superelasticity – could you explain this property and where it can be applied in materials science?

Superelasticity is essentially isothermal shape memory. In shape memory, martensite is produced thermally by cooling. For superelasticity, martensite is created mechanically, so called stress induced martensite. For example, a straight, superelastic nitinol wire is simply bent, stress inducing martensite in the bend.

When the load is removed, the wire returns to its original, straight and austenitic condition. Superelastic nitinol has been exploited for vascular self-expanding stents and other medical devices, partly because the human body is an ideal isothermal environment.

The conference includes the SMA Education Course –what is this and who is it aimed at?

The Education Course teaches the basics of shape memory and superelasticity. It is intended for those individuals who are somewhat new to the technologies and want to learn its capabilities and limits. It is an excellent introductory course on SMA technology.

Why has Prague been chosen to host the conference?

Prague is a beautiful city with an outstanding university that has a peer recognized excellent shape memory program. Historically, SMST has attempted to conduct half of its conferences at non-US locations. We have conducted conferences in Belgium, China (twice), Germany, Japan and Italy. It is a natural sequence to return to Europe in May of 2013. I’m looking forward attending the conference and seeing the beauty of Prague and the Czech Republic.

How do you see the smart materials sector progressing over the next decade?

“Predictions are hard to make, especially about the future”. Smart materials is a much broader technological category than simply shape memory alloys. In either category, I have simply no idea since technology advances at such a continuously accelerating pace. I know that the immediate future for SMAs includes substantial shape memory actuator applications for automotive and aerospace applications. Beyond that, I do know that there will be numerous as yet unknown applications for shape memory and smart materials.

Lastly, how can people join ASM International and how can they register for SMST 2013?

It’s very easy. Simply go to www.asminternational.org and follow the obvious links to join ASM International or to register for the SMST 2013 Conference. As an alternative, one may call 440-338-5151, ext. 0, to join or register over the phone.