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Nanostructures give alloy super strength

07 September 2010, Sydney, NSW, Australia

Today, work on a new super-strength light alloy has been published in Nature Communications. The alloy is much stronger than expected and the reasons behind this are being revealed by top-end microscopy and microanalysis at the University of Sydney node of the Australian Microscopy & Microanalysis Research Facility (AMMRF). Dr Peter Liddicoat and Prof. Simon Ringer at the Australian Centre for Microscopy & Microanalysis (ACMM), working together with Dr Xiaozhou Liao of the School of Aerospace, Mechanical and Mechatronic Engineering, at the University of Sydney, have headed up this international collaborative project. Its purpose is to understand the relationship between the alloy's properties and its structure at the atomic level.

The importance of developing new lightweight alloys cannot be overestimated and will enable improved technologies, particularly in aerospace and automotive applications and in construction. The alloy produced by Dr Liddicoat and the rest of the team is much stronger than previous crystalline metals. It has high strength and good ductility, a highly sought-after combination, and the physical improvements observed were significantly beyond what was predicted by standard rules. To understand this improvement, Dr Liddicoat characterised the nanostructure of the alloy by using atom probe tomography at the ACMM, allowing the structure of the grains and tiny clusters of solute atoms to be visualised. The grains were just tens of nanometres in diameter with accumulations of solute atoms apparent along the boundaries between the grains.

The unexpectedly high level of strengthening appears to be due to two factors. Firstly, the way that the alloying elements are arranged within the grains is thought to increase the dislocation-storage capacity of the alloy. Secondly, the clustering of elements between the grains could limit nanocrystal growth, increase the cohesion of the grains, and resist embrittlement and defect generation.

Dr Liddicoat is very enthusiastic about understanding alloys in this way. “Being able to really see what is happening inside our alloys at the atomic level has been a huge help in investigating their amazing properties. An exciting aspect of the study was our development of breakthrough new atom probe methods to measure the orientation of nanometre-sized crystals to assess ‘nanotexture’.”

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About AMMRF
The AMMRF is Australia’s peak research facility for the characterisation of materials by means of advanced microscopy and microanalysis, providing capability and services to all areas of the physical, environmental and biological sciences, to engineering, to medicine and to technology development.

Established under the Commonwealth Government’s National Collaborative Research Infrastructure Strategy (NCRIS), the AMMRF is a truly national research facility with nodes at the University of Sydney (which also serves as the national headquarters), the University of Queensland, the University of New South Wales, the University of Western Australia, Australian National University, Flinders University, the University of Adelaide, and the University of South Australia. The facility is funded by the Commonwealth Government through NCRIS and the State Governments of New South Wales, Queensland, South Australia and Western Australia.

The facility unites microscopy and microanalysis centres at these universities into a national collaborative grid of laboratories, unified in terms of both equipment and research expertise. The AMMRF provides new, state-of-the-art instruments to researchers from Australia on a merit basis at nominal rates.

Contact: Dr Jenny Whiting, AMMRF Marketing & Business Development Manager, ph. 02 9114 0566.

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Tomographic view of solute nanostructures on grain boundaries of the 7075 alloy. Scale bar is 10 nm.
 
Tomographic view of solute nanostructures on grain boundaries of the 7075 alloy. Scale bar is 10 nm.