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On the microscale deformation of an austenitic stainless steel at ambient and
elevated temperatures
Dong-Feng Li and Noel P. O’Dowd
Materials and Surface Science Institute
Department of Mechanical and Aeronautical Engineering
University of Limerick, Limerick, Ireland
E-mail: dongfeng.li@ul.ie (D.F. Li); noel.odowd@ul.ie (N.P. O’Dowd)
Abstract
In this study, three dimensional crystal plasticity based
finite element models are presented to examine the
multiscale deformation behaviour of austenitic stainless
steels at ambient and elevated temperatures by
accounting for realistic micromorphology, thermally
activated kinematics of dislocation slip, ratedependence,
lattice rotation or texture evolution, latenthardening
and geometric distortion at finite
deformation. As an application, the macroscopic stressstrain
response, the microscopic lattice strain evolution
and the texture development during uniaxial tension for
austenitic stainless steels are simulated with validation
through the in-situ neutron diffraction measurements.
Overall, the predicted lattice strains are in very good
agreement with these measured in both longitudinal
and transverse directions (parallel and perpendicular
to tensile loading axis, respectively). Furthermore,
apparent effects associated with the latent hardening of
multiple slip systems are also identified as a result of
altered work hardening at the microscale.
1. Introduction
The macroscopic response of materials is controlled
to a large extent by deformation and damage
mechanisms operating at the microscale—for
polycrystalline engineering alloys the relevant length
scale is the grain (crystallite) size. Thus, simulations
and experiments conducted at the microscale can
provide important insight into the macroscale integrity
of engineering materials or components.
Micromechanical finite-element (FE) method has
been applied to examine the mechanical response of
engineering alloys [1, 2]. The present study will focus
on the microscale deformation of austenitic stainless
steels especially on the strain hardening effect at finite
strains.
2. Method
Three dimensional Voronoi constructions are created
to explicitly represent the realistic microstructure of the
polycrystalline materials. The mechanical response of
individual grains is simulated by the crystal plasticity
model on the basis of thermally activated kinematics of
dislocation slip to be able to account for texture
evolution and anisotropic latent hardening. As an
application of the presented models, finite element
based micromechanics analysis of representative
volume element (RVE) is carried out in conjunction
with in-situ neutron diffraction (ND) measurement to
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investigate the microscale deformation in austenitic
stainless steels under uniaxial monotonic tension.
3. Results
Fig.1 Comparison of lattice strain evolution in
longitudinal direction (parallel to the loading axis)
between in-situ neutron diffraction measurements and
predictions of three dimensional columnar (3DC) and
equiaxed (3DE) finite element models (FEM).
4. Conclusion
Predictions from finite element modelling study
show very good agreement with the ND measurements,
particularly providing a precise prediction on the
nonlinear lattice strain response as material deforms
plastically. In addition, apparent latent hardening
effects of multiple slip systems are identified to alter
lattice strain evolution through the modification of
work hardening at the microscale.
5. References
[1] D.F. Li, N.P. O’Dowd, C.M. Davies, S.Y. Zhang,
“Microscale prediction of deformation in an austenitic
stainless steel under uniaxial loading”, European Journal of
Mechanics-A/Solids, in press, 2011.
[2] D.F. Li, N.P. O’Dowd, C.M. Davies, S.Y. Zhang,
“Evaluating the mechanical behaviour of 316 stainless steel at
the microscale using finite element modelling and in-situ
neutron scattering”, Proceedings of 2010 ASME Pressure
Vessels and Piping Division Conference - ASME PVP/K-PVP
2010 Conference, July 18th--22nd 2010, Bellevue, WT, USA.