报告题目：Precipitation in Aluminium alloys
报告人：Prof. Christopher Hutchinson（澳大利亚Monash大学）
High strength Al alloys exploit solid state precipitation to tailor their mechanical response. This precipitation requires two ingredients: a thermodynamic driving force and atomic mobility. For a given alloy chemistry, the heat treatment (precipitation) temperature is chosen as a compromise between having sufficient driving force for precipitation and sufficient atomic mobility so that the precipitation reaction occurs in a reasonable time and results in a ‘not too coarse’ precipitate distribution. It is this compromise that frames the competition between nucleation, growth and coarsening that constrains the possible precipitate distributions and hence mechanical responses.
In this presentation, we demonstrate a new approach to precipitation hardening that does not use thermal treatments and therefore allows independent control over the thermodynamic driving force and atomic mobility. This provides a means to fully alter the competition between precipitate nucleation, growth and coarsening and new microstructures, with new combinations of properties are obtained.
The approach uses small amplitude cyclic plasticity at room temperature as a means of continually pumping vacancies into the system to achieve atomic mobility under conditions of high thermodynamic driving force. The approach is self-regulating (in both space and particle size) and results in extremely uniform and fine-scale microstructures. The approach can be used either as a new processing route for high strength Al alloys, or as a ‘training’ routine to improve the high cycle fatigue properties of precipitate strengthened Al alloys. Both examples will be shown in this presentation.
Prof. Christopher Hutchinson, Associate Dean (Research), Faculty of Engineering, Monash university, Australia. 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 3rd 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.