Mechanics of phase boundaries in multi-phase steels
Citation for published version (APA):
Dogge, M. M. W., Peerlings, R. H. J., & Geers, M. G. D. (2010). Mechanics of phase boundaries in multi-phase steels. Poster session presented at Mate Poster Award 2010 : 15th Annual Poster Contest.
Document status and date: Published: 01/01/2010 Document Version:
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Mechanics of MaterialsIntroduction
Environmental and economical issues require innova-tion in the automotive industry, where cars need to be lightweight, while preserving safety (Figure1).
Figure 1: Tradeoff between safety and lightweight.
Dual-Phase (DP) steel uses a special microstructure in or-der to tune the desired material properties. It contains a soft matrix (ferrite) and hard particles (martensite), so that a material is obtained which is both lightweight and strong. Dislocation movement is the main source of plas-tic deformation, which effect can be observed on differ-ent length-scales (Figure2). Dislocations can be Statisti-cally Stored (SSD) by random trappings or GeometriStatisti-cally Necessary (GND) due to non-homogeneous plastic defor-mation. The interaction between dislocations and the phase boundaries and the proper description thereof is the topic of our research.
Atomic Micro
Meso Macro
Figure 2: Multi-scale nature of dislocation modeling.
Aim of the project
A realistic numerical model is to be developed in order to optimize the microstructure of DP steels, including rele-vant mechanics of dislocations at the phase boundaries.
1-D Example
An example where dislocations pile-up against a rigid phase boundary is used (Figure3). Using the statistical approach of Groma et al. [1] and Yefimov et al. [2] we can track dislocation densities (Figure 3, bottom) instead of individual dislocations (Figure 3, top), by using balance equations for the total dislocation and the GND density, such that there is a coupling between the length scales of individual dislocations (micro scale) and individual crys-tals (meso scale).
Figure 3: Result of dislocation pile-up example.
Discussion
Analyzing different models and comparing with experi-mental work should result in a model capable of describ-ing and implementdescrib-ing the correct behavior of large col-lections of dislocations at phase boundaries.
Future work
• Propose a unified strain gradient model account-ing for the realistic behavior of dislocations, in-cluding relevant mechanics.
• Extend single slip model to multislip in two and three dimensions.
• Microstructural modeling for comparison with ex-perimental results.
References
[1] Groma, I. et al.(2003). Acta Mater. 51, 1271-1281. [2] Yefimov, S. et al (2004) J Mech Phys Solids 52,
279-300.
