In-situ Methods for Unraveling Structure-Property Relationships in Light Metals: Diffraction and Other Novel Methods
Sponsored by: TMS Light Metals Division, TMS: Aluminum Committee, TMS: Magnesium Committee
Program Organizers: Dmytro Orlov, Lund University; Wim Sillekens, European Space Agency

Tuesday 2:00 PM
February 28, 2017
Room: 5B
Location: San Diego Convention Ctr

Session Chair: Wim Sillekens, European Space Agency; Kristian Máthis, Faculty of Mathematics and Physics, Charles University

2:00 PM  
Structural Evolution of Metals at High Temperature: Complementary Investigations with Neutron and Synchrotron Quantum Beams: Klaus-Dieter Liss1; 1Australian Nuclear Science and Technology Organisation
    In-situ neutron and synchrotron X-ray diffraction deliver unique and complementary insight into the microstructural evolution of metals at high temperature. Neutrons illuminate a larger bulk volume and reveal quantitative phase abundance, bulk texture, lattice parameter changes and other ensemble averaged quantities. In contrast, fine-bundled high-energy X-rays deliver reflections from a number of individual grains. For each constituting phase, their statistics and behavior in time reveal information about grain growth or refinement, subgrain formation, static and dynamic recovery and recrystallization, slip systems, twinning, etc. While monochromatic methods are well developed, white-beam Laue diffraction is emerging for the comprehensive study of orientation space, allowing to follow the recrystallization process of a fine- to coarse-grained material. Features will be discussed on selected metallic systems, focused on light metals, and an outlook given to build the Materials Oscilloscope.

2:20 PM  
Advanced Aluminum Alloys Development and In-Situ Fitness-for-Service Testing in Automotive Lightweighting: Dimitry Sediako1; David Weiss2; Ahmed Nabawy1; 1Canadian Nuclear Laboratories; 2ECK Industries Inc.
    Lightweighting has led to increased use of aluminum alloys in many automotive systems, including the powertrain, body-in-white, and suspension. Fitness-for-service certification of new alloys for these applications frequently requires development of new testing methods that would subject the test components to realistic conditions of temperature and load, while studying the long-term materials’ response. As the typical lifetime of a vehicle exceeds 3000 hours, the new testing methods must provide clear indication on the material suitability for a target application over a more realistic timeframe. In-situ study of the creep behavior using neutron diffraction quickly reveals the response of individual crystallographic planes to the applied load under the in-service operating conditions, yielding the critical information on the expected lifetime of the targeted component. This knowledge helps to identify alloy chemistry and processing conditions that result in manufacturing components capable of sustaining the thermal mechanical loads over the expected life cycle of a vehicle. Two advanced aluminum alloys, based on Al-Si and Al-Cu systems, have been the focus of in this research.

2:40 PM  
In-situ X-ray Synchrotron Profile Analysis during High Pressure Torsion of Ti: Erhard Schafler1; Michael Kerber1; Florian Spieckermann2; Torben Fischer3; Roman Schuster4; Cornelia von Baeckmann5; 1University of Vienna, Faculty of Physics; 2University of Leoben; 3Deutsches Elektronen-Synchrotron DESY; 4University of Vienna, Faculty of Earth Schiences; 5University of Vienna, Faculty of Chemistry
    X-Ray Line Profile Analysis is a powerful method to characterize the microstructure of deformed materials, especially when high energy and brilliant Synchrotron radiation enables investigations with high time and spatial resolution. Parameters like dislocation density, dislocation arrangement as well as scattering domain size and it's distribution are parameters of a physical model of peak broadening, which can be applied to high quality diffraction measurements. A small sample high-pressure-torsion-machine was designed in order to perform in-situ diffraction experiments during the deformation process at hydrostatic pressures up to 8GPa in order to follow the strain as well as pressure induced microstructural characteristics of any material deformed. This was possible with the ideal design and equipment at the High-Energy-Materials-Science-beamline at PETRA III in Hamburg. Recent and first results of experiments on HPT-deformed Ti are presented.

3:00 PM  
The Effect of Grain Refinement on Hot Tearing in AZ91D Magnesium Alloys: Tyler Davis1; Lukas Bichler1; Francesco D'Elia2; Norbert Hort2; 1University of British Columbia; 2Helmholtz-Zentrum Geesthacht
    The AZ91 magnesium alloy is widely used for diverse casting applications, despite its high susceptibility to hot tearing during solidification. In this work, the effect of grain refinement on hot tearing was quantitatively studied. Specifically, the relationship between the alloys’ cooling rate and in-situ force evolution during solidification was related to the severity of hot tears. The results suggest that the load evolution rate and microstructure morphology were critical determinants of the hot tear severity for both unrefined and grain-refined alloys. The grain refiners were seen to significantly reduce the overall force and force rate, which contributed to the elimination of hot tearing in the AZ91 alloy under standard casting conditions.

3:20 PM  
Formability of Magnesium Alloy AZ31B from Room Temperature to 125C under Biaxial Tension: Isaac Chelladurai1; Andrew Orme1; Michael Miles1; David Fullwood1; John Carsley2; Raj Mishra2; Irene Beyerlein3; Marko Knezevic4; 1Brigham Young University; 2General Motors; 3Sandia National Laboratory; 4Univeristy of New Hampshire
    Magnesium AZ31B sheets, of 2 mm thickness, were stretch formed using a 100 mm diameter punch at room temperature and for temperatures ranging from 25°C - 125°C. Surface strains were measured using digital image correlation method to verify biaxial stretching. The punch height vs load curve was found to be the same for temperatures of 25°C and 50°C, while at 75°C the load for a punch height begins to decrease. This difference seems to indicate a change in deformation mechanism between 50°C and 75°C. Electron Backscatter Diffraction (EBSD) was used to quantify microstructure features in the as-received and the strained specimens. Rather than a sudden transition from twinning to slip at low temperatures, it appears that twinning gradually decreases and slip activity increases as temperatures rise across the range from 25°C - 125°C. The twin activity involves formation of compression twins which rapidly transform into secondary twins for strain accommodation.

3:40 PM Break

4:00 PM  Keynote
Ambient Pressure X-ray Photoelectron Spectroscopy in Light Element Materials Investigations: Joachim Schnadt1; Ashley Head2; 1Lund University; 2Lawrence Berkeley National Laboratory
    X-ray photoelectron spectroscopy (XPS) is a widely used standard method in the analysis of surfaces. In its conventional form a vacuum technique, it was adapted to samples in ambient pressures up to around 1 mbar already in the 1970s. However, it is only during the past 15 years that ambient pressure x-ray photoelectron spectroscopy (APXPS) has become a standard in situ measurement technique, as a result of the advent of third-generation synchrotron light sources and improved electron energy analysers. We will provide an introduction to APXPS, its technical realisation, and, using a number of case studies, its capabilities for the identification of surface species, structure, and reactions. In particular, we will discuss how we have used APXPS in the in situ study of the atomic layer deposition (ALD) of light and heavier element materials. The presentation will also include an overview of APXPS studies of Mg and other materials.

4:30 PM  
In-situ Real-time Monitoring of Aging Processes in an Aluminum Alloy by High-precision Dilatometry: Martin Luckabauer1; Elisabeth Hengge1; Gregor Klinser1; Wolfgang Sprengel1; Roland Würschum1; 1Graz University of Technology
    Hardening of industrial aluminum alloys mostly occurs due to highly complex precipitation processes. Characterization of often metastable precipitates/phases can be well performed, e.g., by advanced microscopic techniques, however, accessing the kinetics of the precipitation process is in general more demanding. As formation, transformation or dissolution of phases are mostly accompanied by volume changes dilatometric techniques are highly feasible. Only here most commercially available dilatometric devices lack the resolution ΔL/L < 10-5 and long-term stability up to t = 106s. We present in-situ isothermal, high-precision length-change measurements during artificial aging of a commercial aluminum alloy (AW6060) at different temperatures. Measurements were performed with a laser-dilatometer of which major parts are self-designed giving now access to the required resolution and stability regimes. The results support the precipitation sequence proposed for Al-Mg-Si alloys clearly showing the transitions between the different steps towards the stable Mg2Si phase. Supported by Austrian Science Fund (FWF): P25628-N20.

4:50 PM  
Analysis of Microstructure and Damage Evolution in Ultra-thin Wires of the Magnesium Alloy MgCa0.8 at Multipass Drawing: Andrij Milenin1; Piotr Kustra1; Dorota Byrska-Wójcik1; Olexandr Grydin2; Mirko Schaper2; Thorben Mentlein3; Gregory Gerstein3; Florian Nürnberger3; 1AGH University of Science and Technology; 2Paderborn University; 3Leibniz Universität Hannover
    A combined multipass hot and cold drawing process was implemented to manufacture ultra-thin wires of the magnesium alloy MgCa0.8 with a final diameter of 0.05 mm. FE simulations were applied to design the drawing process of 40 passes regarding the microstructure evolution. Parameters such as the recrystallized material volume fraction or the damage criterion were calculated. To parametrize the corresponding models, stress relaxation hot deformation tests as well as in situ tensile tests in a scanning electron microscope were performed. Analysis of the MgCa0.8 wires featuring diameters below 0.1 mm revealed no intergranular crack initiation, which is usually a damage reason of the MgCa0.8 alloy at the microscale. The grain size of the ultra-thin wires is within the range of 30 nm to 500 nm where the grains are elongated in the drawing direction depending on the deformation parameters. The fine-grained microstructure provides high mechanical strength properties of the alloy.

5:10 PM  
Effect of the Zn Content on the Compression Behaviour of Mg5Nd(Zn): An In Situ Synchrotron Radiation Diffraction Study: Domonkos Tolnai1; Tim Kärcher1; Ricardo Buzolin1; Tungky Subroto1; Francesco D'Elia1; Serge Gavras1; Andreas Stark1; Norbert Schell1; Norbert Hort1; Karl Kainer1; 1Helmholtz Zentrum Geesthacht
    The property profiles of commercially viable Mg alloys are not sufficient for many of the envisaged applications. The combination of Zn and rare earth metals is one of the most effective ways to enhance the mechanical property profile of Mg alloys. In situ synchrotron radiation diffraction is a unique method to investigate the dynamic microstructural processes occurring during deformation. Azimuthal angle - time plots give information on grain structure changes that can be correlated with grain rotation, twinning, recovery and recrystallization. As-cast Mg5Nd, Mg5Nd3Zn, Mg5Nd5Zn and Mg5Nd7Zn alloys were investigated during compression at room temperature and at 350°C with a strain rate of 10-3s-1 until 10% deformation. The results and post mortem EBSD maps from the samples suggest that the alloys deform by grain rotation and crystallographic slip to obtain the final texture, while at room temperature twinning is the dominant deformation mechanism.