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Publications	Highlights	Collaborators	Project Team

Modern diffraction methods applied to Thermo-Mechanical Processes in material science. 

The project "Modern Diffraction Methods Applied to Thermo Mechanical Processes in Materials Science" will use diffraction methods to study deformation processes in metals, particularly related to high temperature processing and performance under extreme conditions. This project brings together the experts of instrumentation, materials physics and mechanical engineering.

Metals are used throughout engineering in many parts of our life, such as steel for construction, light metal for the transportation industry, heat resistant alloys and intermetallic compounds for high-temperature engines to name but a few.

The mechanical properties strongly depend on the microstructure, the admixtures and the thermo-mechanical production process, such as rolling or annealing. On the other hand, mechanical load, heat or radiation leads to fatigue and failure of the material, which itself are thermo-mechanical processes.

The fundamental understanding of the material from the microstructure to the atomic scale plays an important role for reduced cost in the production, lighter weight and a better prediction of the lifetime before failure.

News and highlights

Directional Atomic Rearrangements During Transformations Between the Alpha  and Gamma Phases in Titanium Aluminides.

Phase diagrams and microstructures of titanium aluminides are rather complex and, so far, little data were observed in-situ at elevated temperatures. We report on two-dimensional high energy X-ray  diffraction  and  complementary  laser  scanning  confocal  microscopy  to  characterize  the appearing phases and to follow the phase evolution in-situ and in real time (figure 1). 

As an example, the microstructure evolution of a quenched γ-TiAl alloy, consisting of α2-Ti3Al grains at room temperature, has been followed in both reciprocal and direct space as a function of  temperature up  to 1400 °C. At 700 - 800 °C  extremely  fine  γ-laths are  formed  in α2-grains occurring through an oriented rearrangement of atoms.

Streaks linking reflections of both phases testify  from  coherent  lattice  and  orientation  gradients  in  the  transforming  crystallite.  At temperatures  around  the  eutectoid  temperature  recrystallization  effects  and  the  γ → α phase transition take place leading to grain refinement.
 

Figure 1: Tial Movie

Figure 1, Making movies in-situ at glowing temperatures up to 1300°C through a microscope (false colour image) and from two-dimensional X-ray diffraction (movie frames) reveal the lattice correlations, gradients and intermediate structures during phase transformations in titanium aluminide. A quenched, α2-rich γ-based TiAl first approaches its equilibrium by α2 → γ on a heating ramp, disorders α2 → α and then evolves reversely γ → α, which are morphologically different processes. Cover story of Adv. Eng. Mater. 4/2008.

Synchrotron 3D Computed Tomography on Cast Magnesium

The microscopic morphology of magnesium alloy has been investigated by computed micro-tomography and compared to light microscopic studies. Precipitates of denser material are found but the information of microscopic studies alone are insufficient. In contrast, 3D computed tomography tomography reveals the full topology in three dimensions which may be relevant for the mechanical properties of the material. See figure 2.

Figure 2: Three Dimensional Microtomography

Figure 2. Three dimensional computed microtomography obtained with synchrotron radiation obtained at NSRRC in Taiwan (collaboration with Dr. Anton Stampfl, ANSTO).

In-situ Quantitative Phase Analysis of Titanium-Aluminides

Synchrotron high-energy X-ray diffraction has been used to record 2D powder diffraction patterns in the bulk of Titanium Aluminides (figure 3). A quantitative Rietveld analysis shows the evolution in phase fractions, lattice parameters and order / disorder as a function of temperature and gives detailed insight into the kinetics and the phase transitions in this system (figure 4).
 

Collaborators: LaReine A. Yeoh, Klaus-Dieter Liss, Arno Bartels, Harald Chladil, Maxim Avdeev, Helmut Clemens, Rainer Gerling, Thomas Buslaps
 

Figure 3: Diffraction Pattern

Figure 3. Diffraction pattern showing colour coded intensity in the dependence of momentum transfer (horizontal) and time (vertical) taken in-situ during temperature variations from room temperature to 1400oC.

Figure 4: Rietveld Model

Figure 4. Rietveld model result of phase composition, crystallagraphic parameter ratios and disorder in the alpha phase.

In-situ studies of light metals at the ESRF

The recently established collaboration, between ANSTO and the University of Melbourne (funded for the year 2006/2007), brings together the know-how of mechanical engineering and analysis with diffraction methods. We successfully collected about 100 GB of data on four Titanium Aluminium samples of different composition and microstructures measuring in-situ on high-temperature ramps using High-Energy X-Ray diffraction at ID15B at the European Synchrotron Radiation Facility (ESRF) .

Further room-temperature data of different thermo-mechanically processed samples, such as ball milling or ECAP, have been collected. At present, the data is being analysed.

Collaborators: LaReine A. Yeoh, Klaus-Dieter Liss, Kenong Xia, Wei Xu, Thomas Buslaps

Project team

Dr Klaus-Dieter Liss, Senior Researcher, project leader

Educated in general physics, Klaus is an expert in neutron and synchrotron X-ray scattering techniques. He has developed a great interest in employing these techniques in materials science over the past years.

Dr Ulf Garbe

Currently holds a Postdoc position. He is specialised in texture analysis and has first-hand experience using neutrons as well as high-energy X-ray beams for his studies. Further, he develops state-of-the-art software for the analysis of his data.

Ms Kun Yan

Works on her PhD project entitled "Phase Transformations and Microstructures of Metals under Thermo-Mechanical Load", which is co-supervised by Professor Rian Dippenaar, University of Wollongong and Dr Klaus-Dieter Liss.

Mr Ian Watson

Is a year-in-industry student. He studies physics at the University of New South Wales. He continues work on titanium aluminides and also tests out tomography experiments with synchrotron light.

Recently departed members w ho are still involved in collaboration are:

Mr Ross Whitfield

Year-in-industry student 2007. Ross studies physics at the Australian National University (ANU) and recently joined the team to take over the data analysis for high-energy x-ray diffraction data on steel and titanium aluminides.

Ms LaReine A. Yeoh, laboratory assistant, December 2007 - February 2008

Year-in-industry student, February 2006 - January 2007. LaReine studies physics and engineering at the University of Technology, Sydney (UTS) and is back as a laboratory assistant for the analysis and interpretation of diffraction data. In 2006, she performed synchrotron X-ray diffraction experiments at the ESRF, developed data reduction routines and presented an order-disorder Rietveld analysis on titanium aluminides.

Collaborators

• Institute of Materials & Engineering Sciences, ANSTO: Dr Phil Bendeich, Dr Huijun Li and Mr Dave Carr
• Bragg Institute, ANSTO: Dr Robert Knott
• University of Wollongong: Prof Rian Dippenaar and Dr Dominic Phelan
• University of Melbourne: A/Prof Kenong Xia, Dr Wei Xu and Dr Daniel Riley
• Bluescope Steel: Dr Jim Williams and Dr Frank Barbaro
• University of Technology Hamburg-Harburg, Germany: Dr Habil. Arno Bartels
• University of Leoben, Austria: Prof Helmut Clemens
• European Synchrotron Radiation Facility, France: Dr Thomas Buslaps