IMX Talks - Strengthening and strain hardening from solute clusters in Aluminium alloys

In this presentation, I will first provide a brief introduction to my group and the physical and mechanical metallurgy activities at Monash University. I will then provide an example of work on cluster effects in Al alloys.
We will first discuss the effects of solute clusters on the strengthening of Al alloys by comparing the clusters formed during natural aging, and those formed during cyclic plasticity, in commercial Al alloys. Using atom probe tomography, we demonstrate that these different processing routes lead to important differences in the chemistries of the clusters formed. The shearing strength of the individual cluster is quantified and shown to be proportional to the solute content of the cluster, across a range of age hardenable Al alloys.
We then consider the effects of these solute clusters on the strain hardening behaviour and compare them with the effects of shearable precipitates formed through conventional artificial aging. We demonstrate that some alloys show that dynamic recovery first becomes more difficult as the yield strength increases, then, after passing through a minimum in dynamic recovery rate, dynamic recovery becomes easier as the yield strength continues to increase. We propose a model to link the macroscopic dynamic recovery behaviour to the underlying mechanisms of plasticity in relation to the distribution of solute, clusters and precipitates in the studied alloys.

Bio: Professor Christopher Hutchinson’s research covers all aspects of the metallurgy of engineering alloys. This includes work on Steels and Stainless steels, Aluminium alloys, Copper and Brasses, Titanium alloys and Magnesium alloys.
Christopher’s emphasis is on manipulation of the chemistry and processing of engineering alloys to create new alloy structures that exhibit improved combinations of mechanical properties such as strength, elongation, impact, wear and fatigue etc.
Approximately half of his research is conducted in collaboration with Industry (automotive, aerospace, rail, manufacturing, oil and gas) and half funded by fundamental research agencies such as the Australian Research Council (ARC). Professor Hutchinson was a recipient of an ARC Future Fellowship in the inaugural round of 2009, was a Chief Investigator in the ARC Centre of Excellence for Design in Light Metals (2005-2013) and is currently a Chief Investigator in the ARC Industry Transformation Training Centre in Alloy Innovation for Mining Efficiency (2016-2021).
Christopher’s work combines, in roughly equal parts, advanced experimentation and characterisation (including electron microscopy, synchrotron x-ray radiation and neutron diffraction) and theory and computer modelling of the response of alloy structures to changes in materials processing and deformation.
Current projects include the development of new ultra-high strength steels (>2GPa) for the automotive industry, process optimization for 3^rd generation advanced high strength steels (AHSS), new ‘dynamically responding’ fatigue resistant Al alloys with properties that improve rather than deteriorate during loading, recrystallization studies of commercial Al alloys, surface modification of engineering alloys, 3D printing of stainless steels for on-demand replacement parts, and process optimisation for thermo-mechanical processing of Brasses.
In addition to his core metallurgy focus, Professor Hutchinson is involved in a large range of Civil Engineering and Architecture projects where he provides metallurgy expertise.