Microstructure characterization of 316L deformed at high strain rates using EBSD

Microstructure characterization of 316L deformed at high strain rates using EBSD. Access to the published version may require subscription. a b s t r a c t a r t i c l e i n f o Specimens from split Hopkinson pressure bar experiments, at strain rates between ~1000–9000 s −1 at room temperature and 500 °C, have been studied using electron backscatter diffraction. No significant differences in the microstructures were observed at different strain rates, but were observed for different strains and temperatures. Size distribution for subgrains with boundary misorientations N 2° can be described as a bimodal lognor-mal area distribution. The distributions were found to change due to deformation. Part of the distribution describing the large subgrains decreased while the distribution for the small subgrains increased. This is in accordance with deformation being heterogeneous and successively spreading into the undeformed part of individual grains. The variation of the average size for the small subgrain distribution varies with strain but not with strain rate in the tested interval. The mean free distance for dislocation slip, interpreted here as the average size of the distribution of small subgrains, displays a variation with plastic strain which is in accordance with the different stages in the stress-strain curves. The rate of deformation hardening in the linear hardening range is accurately calculated using the variation of the small subgrain size with strain. 1. Introduction Understanding the relation between the mechanical properties and the microstructure is a cornerstone for most of the process steps in the metal manufacturing industry [1–3]. One of the more challenging areas is to understand the microstructural development for high velocity and high temperature processes such as metal cutting and rolling. For machining simulations this knowledge is important to be able to model the mechanical behavior. During machining the strain rate is in the range of 10 3 to 10 6 s −1 and the homologous temperature is in the range 0.16–0.9 [4]. To simulate high strain rate processes, a commonly used approach is split Hopkinson pressure bar (SHPB) tests [5]. The development in the research field of modeling plastic deformation has been intimately related to development of analytic tools such as X-ray diffraction, scanning and transmission electron microscopy (SEM and TEM, respectively), and electron backscatter diffraction (EBSD) [6–12]. When modeling the flow stress, σ, during plastic deformation by dis-location slip the following equation is commonly used [13–16]: σ …