DIGITAL MATERIALS SCIENCE: WHY DO WE NEED MORE IMAGES AND

R.E. BOLMARO; H.-G. BROKMEIER; M. FERRANTE; A.L. FOURTY; J.F.C. LINS; J. MALARRÍA; R. MARTINO; H.R-Z. SAMDIM; J.W. SIGNORELLI; C. SOBRERO; V. SORDI

Rosario, Argentina

Congreso; 10th Inter-American Congress of Electron Microscopy 10th CIASEM; 2009

SAMIC

The concept of Digital Materials Science (DMS), although the name recalls a computer science environment, involves the close interaction between experiments and computer models. The lower the scale we pretend to simulate and describe by computer models, the lower the scale we need feedback from the experiments. However, the sole resource to a microscopic technique does not guarantee the proper integration of the data in a macroscopic model. The experimental data should be not only reliable but also statistically representative, and that is a condition not always achievable even by very sophisticated methods. On the field of materials science the physical laws have been successfully integrated while going up from the lowest level first principle laws until reaching the crystal size. On the other direction, that one coming from the macroscopic scale, engineer science has also succeeded in describing many of the most interesting properties. What seemed at first glance as just a matter of short time, for a profitable encounter of both strategies in the scale of the grain fragment-grain-few grains, was lately reveled as a very harsh task. The gap between single dislocation behavior scale and the scale represented by the constitutive equations have been the topic of research of the last 20 years. The progress, although at low pace, have been fruitful. However there are at least two main topics were the field is still lacking knowledge and completeness: a) The interaction between dislocations, field covered by Dislocation Dynamics theories and b) The interaction between fragments and grains. Being both strongly entangled, the first issue has disserved large efforts both coming from the experimental and the theoretical view points. Experiments are quite difficult when dealing with the problem of dense dislocation arrays, like Incidental Dislocation Boundaries (IDB), Cell Boundaries (CB), Geometrically Necessary Dislocation Boundaries (GNDB), etc. They are currently difficult to separate in their elementary dislocations. The second issue has also been a matter of intense research by using both theoretical and experimental tools. Recently, a quantitative microscopy technique has come to maturity and perfection. What is alternatively called Orientation Image Microscopy (OIM) or Electron Back Scatering Difraction (EBSD), heir of the old Electron Channeling Pattern technique and the new detectors and positioning system technologies. OIM-EBSD not only allows for the production of nice images but it is also a massive number data provider which can be used for further modeling and careful comparison with numerical simulations [1- 3]. The current paper shows preliminary results by EBSD, in three quite different materials, compared with results from “more macroscopic” or “less numerical” techniques, like X-ray diffraction, neutron diffraction and optical orientation measurements. The capabilities of the method are discussed and the potentials for the simulation-experiments feedback are analyzed. It is shown that the new technique improves and expands old ones and is able to provide a huge amount of numerical data that will be in search for new models and interpretations. Finite Element techniques, micromechanical modeling and Dislocation Dynamics simulations can be benefited from the extracted data [4, 5]. References [1] A.D. Rollett, S.-B. Lee, R. Campman, G.S. Rohrer. Annu. Rev. Mater. Res. 37 (2007) 627. [2] A. Bhattacharyya. “Investigating the Evolution of Grain Scale Microstructure during Large Plastic Deformation of Polycrystalline Aluminum”. PhD Thesis. Drexell University. 2002. [3] A. J. Schwartz, M. Kumar, B. L. Adams. “Electron Backscatter Diffraction in Materials Science” Kluer Academic/Plenum Publishers. New York. 2000. [4] K.-S Cheong, E. P. Busso. Acta mater. 52 (2004) 5665-5675. [5] G. Winther, X. Huang, A. Godfrey and N. Hansen. Acta mater. 52 (2004) 4437-4446.