Metal Magic

Dr Chris Hutchinson

For centuries now, engineers have been fascinated and intrigued by metals and alloys.  Although now very much the fabric of modern society, there is still a great deal of ground breaking research being done in this area.  One Monash researcher, Christopher Hutchinson, is so highly regarded within this field he has recently been awarded a prestigious Australian Research Council Future Fellowship.  The Fellowships are awarded to leading research projects across the country in an effort to promote Australia as an innovation centre and advance key industries.

Like many great engineering ideas, Doctor Hutchinson’s work is focused on a very simple principle. As most first year materials engineering students will tell you, strength in metals is achieved by creating barriers to the movement of defects known as dislocations.  Dislocations however also promote ductility, allowing a metal to deform when subjected to a stress.  This results in a trade-off between strength and ductility.  So for example, very strong materials are typically very brittle whereas ductile materials are typically very weak.  However, in most engineering applications, it is desirable to have materials that are both strong and ductile. 

Hutchinson and his team however are looking at how an alloy’s microstructure can be altered to overcome this problem.  Taking inspiration from nature, Hutchinson uses the example of a tree where “a sapling is very flexible and supple, but a mature tree is strong and rigid – yet the tree is still made from the same material.  We are looking at how we can alter the microstructure of metals once they are in service to achieve similar results.”

The idea is to create what are termed “Dynamically Responding Microstructures,” that change their behaviour depending on the type of load applied.  Such technology could have incredible uses in many practical applications where a combination of high strength and high ductility (or toughness) are required.  For example, a car panel needs to have high strength to avoid unnecessary deformation and save weight, but in a crash situation, ductility is required to help absorb impact energy.

To help overcome this strength-ductility conundrum, Hutchinson is looking at novel ways of altering material properties.  Rather than using traditional methods like work hardening and heat treatment to improve strength pre-installation, it may be possible to use alternative energy sources found in-situ to achieve the same effect.  For example cars repetitively rolling over a bridge could strengthen steel re-enforcement leading to improved material properties over time.  Or when a relatively brittle material starts to deform a transformation may occur to make it becomes more ductile to blunt the cracking.

Hutchinson highlights that thanks to facilities like the Monash Centre for Electron Microscopy (MCEM) he is able to immediately see the results of his experiments at the finest length scale.  Located on the Clayton Campus, the MCEM is a world class facility and one of the most stable buildings in Australia.  “Characterisation used to be a serious bottleneck for us because we couldn’t actually see all the details of the micro-structures we were creating…now we can see how dislocations interact with, and in some cases, modify the microstructure and how that affects material properties.  The synchrotron has also provided us with some new and exciting visualisation techniques, Hutchinson continues, so this is definitely a very exciting area at the moment.”

It would seem the future of metals and alloys is as shiny and lustrous as ever.