In-situ deformation experiments on a TRIP steel

Steels with the transformation-induced plasticity (TRIP) effect exhibit phase transformations of austenite into martensite triggered by plastic deformation. This transformation enhances strain hardening, which leads to a combination of excellent strength and ductility. In spite of the fine microstructure of the material investigated, the deformation induced phase transformation of single austenitic grains can be studied using high-resolution scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The accompanying transformation strains in the surrounding matrix can be quantified by local deformation measurements.

Undeformed microstructure with austenite grains (γ).    Undeformed microstructure (left) and microstructure after 2.5% global strain (right). The austenite grains (γ) exhibit phase transformation. From R. Kasberger, O. Kolednik, Verformungsinduzierte Phasenumwandlung einzelner Austenitkörner. In: XXXII Verformungskundliches Kolloquium Planneralm, B. Buchmayr, Ed., Lehrstuhl für Umformtechnik, Leoben, 2013.

Local deformation measurements are based on a system for digital image analysis which finds identical points on SEM-micrographs captured at different deformation stages. The method provides, with high accuracy and resolution, the local in-plane strains that occur in the loading step considered. A similar digital image analysis system has been applied for quantitative fracture surface analysis.

Deformation- and fracture behavior of advanced materials

 

Important publications on similar topics

J. Stampfl, S. Scherer, M. Berchthaler, M. Gruber, O. Kolednik, Determination of the fracture toughness by automatic image processing. International Journal of Fracture 78 (1996) 35-44.

C.O.A. Semprimoschnig, J. Stampfl, R. Pippan, O. Kolednik, A new powerful tool for surveying cleavage fracture surfaces. Fatigue & Fracture of Engineering Materials and Structures 20 (1997) 1541-1550.

A. Tatschl, O. Kolednik, A new tool for the experimental characterization of micro-plasticity. Materials Science and Engineering A339 (2003) 265-280.

A. Tatschl, O. Kolednik, On the experimental characterization of crystal plasticity in polycrystals". Materials Science and Engineering A364 (2004) 384-399.

O. Kolednik, The characterization of local deformation and fracture properties – a tool for advanced materials design. Advanced Engineering Materials 8 (2006) 1079-1083.

A. Musienko, A. Tatschl, K. Schmidegg, O. Kolednik, R. Pippan, G. Cailletaud, 3D Finite Element simulation of a copper polycrystalline specimen. Acta Materialia 55 (2007) 4121-4136.

M. Kapp, T. Hebesberger, O. Kolednik, A micro-level strain analysis of a high-strength dual-phase steel. International Journal of Materials Research 102 (2011) 687-691.

Zechner, M. Janko, O. Kolednik, Determining the fracture resistance of thin sheet fiber composites – Paper as a model material. Composites Science and Technology 74 (2013) 43-51.