Technical Program
TUESDAY AM
9:55 AM Break
48
10:25 AM Diffraction-Amalgamated Grain-Boundary Tracking (DAGT) Technique and Its Application to an Aluminium Alloy: Darren LeClere1; Hiroyuki Toda1; Masakazu Kobayashi1; Takanobu Kamiko1; Yoshio Suzuki2; Akihisa Takeuchi2; Kentaro Uesugi2; 1Toyohashi University of Technology; 2Japan Synchrotron Radiation Research Institute A novel method which provides accurate analysis of individual grains during deformation has been developed by amalgamating X-Ray diffraction (XRD) microscopy with grain boundary tracking (GBT). XRD and GBT are both non-destructive in-situ analysis techniques for characterizing bulk materials, which can be carried close to the point of fracture of metals. DAGT provides accurate information about individual grain orientations from near field XRD analysis, whilst the GBT accesses 1 micron level analysis of grain morphologies in 3-dimensions. XRD employed an X-ray pencil beam to analyze a specimen of Al-3mass%Cu before and after deformation. The morphology of the grains were determined by computer tomography (CT) imaging and liquid metal wetting, after which GBT provided an accurate description of the position and morphology of the grains. The integrated technique, DAGT, identified which diffraction spots were related to which grain, making it possible to describe misorientation between grains. 10:45 AM Effect of Composition and Pre-ageing on the Natural Ageing and Paint-baking Behaviour of Al-Mg-Si Alloys: Paul Rometsch1; Sam Gao1; Malcolm Couper1; 1Monash University Two 6xxx series aluminium alloys were designed to have the same total solute content but very different Mg/Si ratios. An excess Mg alloy (Al-1.2Mg-0.5Si) and an excess Si alloy (Al-0.5Mg-1.2Si) were cast and rolled to 1 mm thick sheet. Both were naturally aged for 30 days and then artificially aged for 0.5 h at 170°C to simulate an automotive body panel paint-baking cycle. In order to improve the paint-bake response, pre-ageing treatments of 20 s at 200°C and 2 h at 100°C were tested and evaluated using atom probe tomography, transmission electron microscopy and hardness testing. The results show that the excess Mg alloy tends to have coarser clusters/precipitates than the excess Si alloy, and that the Mg/ Si ratio of the smaller clusters is closer to the alloy composition than that of the larger clusters and precipitates. Depending on the pre-ageing treatment, both alloys can give good paint-baking responses. 11:05 AM High Resolution Microscopy of Al 2199 Alloy: Raynald Gauvin1; Nicolas Brodusch1; Mathieu Brochu1; Michel Trudeau1; 1McGill University This paper describes what state-of-the-art field-emission scanning electron microscopy can achieve to the micro-characterization of a 2199 aluminum-lithium alloy. Bulk samples observed with a Backscattered Electron detector at an acceleration voltage of 3kV and thin foils investigated by Scanning Transmission Electron Microscopy at 30kV, coupled with X-ray microanalysis, reveals a micro structure which has never been observed so completely and easily by other established techniques. Microanalysis has been performed on all types of precipitates, and, although lithium cannot be analysed with the Energy Dispersive Spectrometer, it is however possible to conclude on their chemical nature. Our results are in good agreement with those reported in the literature but reveal some differences, especially in regard to the T1 precipitates, that should be taken into account to understand the true microstructure of the alloy. Comparison with state-of-the-art field-emission transmission electron microscopy will also be presented. 11:25 AM Nanoscale Precipitation-Strengthened Al-Sc-Ta Alloys: Keith Knipling1; 1 Naval Research Laboratory Conventionally-solidified Al-Sc alloys, strengthened by Al3Sc (L12)
precipitates, exhibit remarkably high coarsening and creep resistance at 300 °C, which can be improved with ternary additions of Zr. Zirconium has a much smaller diffusivity than Sc, resulting in Al3(Sc1-<em>x</ ,Zr<em>x</em>) precipitates that are enveloped in a thin (~1 nm thick) Zrem> rich shell. The slower-diffusing Zr atoms limit coarsening and, since they substitute for Sc in the precipitates, can also reduce the relatively high cost of Sc additions. Like Zr, Ta may also be a beneficial alloying addition to Al-Sc alloys. Tantalum forms an Al3Ta trialuminide and Ta is soluble in Al3Sc. Tantalum is also expected to be a slower diffuser than Zr, offering improved thermal stability than Al-Sc-Zr alloys. This study investigates, using transmission electron microscopy and 3-D atom-probe tomography, the structure and composition of the complex Al3(Sc1-<em>x</em>,Ta<em>x</em>) precipitate formed during aging at 200 to 600 °C. 11:45 AM Towards New Aluminium Alloys through Advances in Atom Probe Microscopy: Leif Viskari1; G. Sha1; S.P. Ringer1; 1The University of Sydney The development of Al alloys has through the years significantly relied on advances in materials characterization techniques to allow deeper understanding of microstructural properties. Today, alloy development has reached a level where many of these properties are no longer discussed on micrometre or even nanometre scale, but rather on atomic scale. Consequently, atom probe microscopy (APM) has received greatly increased attention. APM is a powerful characterization technique with unmatched capability of three dimensional (3D) atomic scale studies of the structure and chemistry of materials. This presentation focusses on our on-going development of APM analysis techniques for studies of Al alloys and also demonstrates why APM has earned a vital position in the development road-maps for new alloys. Key aspects of the enabling science are presented and applied to studies of Al alloys. Methods to study solute hierarchy and nano-scale crystallography are emphasized.
Casting & Solidification Keynote
Program Organizers: William Cassada, Alcoa Technical Center; Hasso Weiland, Alcoa Technical Center; Anthony Rollett, Carnegie Mellon University Symposium Organizers: Ralf Napolitano, Iowa State University; MG Chu, Alcoa Inc. Tuesday AM June 5, 2012
Room: McConomy Auditorium Location: University Student Center
Session Chair: Men Chu, Alcoa Technical Center 8:30 AM Keynote It’s Not Your Father’s Cast House Any More: Robert Wagstaff1; 1 Novelis Solatens Technology Center To many the Cast House is where scrap metal is transformed into ingots for subsequent processing to sheet or plate, is still perceived as an area where innovation is all but impossible. Given the very fundamental role that the Cast House plays in the overall production of aluminum sheet and plate, there are significant technical, and production challenges that must be overcome to successfully introduce advancements in either cost or quality of the final product. If new concepts are sufficiently reviewed and tested, the Cast House can be a springboard for significant innovation and creativity. This presentation provides a brief review of the current state of the Direct Chill (DC) casting process, which remains the largest process for the production of rolling stock for aluminum sheet and plate, and highlights some recent technical advances in the Cast House, with particular attention to their effect(s) upon the entire production chain.