Abstract
Understanding the local strain enhancement and lattice distortion resulting from different microstructure features in metal alloys is crucial in many engineering processes. The development of heterogeneous strain not only plays an important role in the work hardening of the material but also in other processes such as recrystallization and damage inheritance and fracture. Isolating the contribution of precipitates to the development of heterogeneous strain can be challenging due to the presence of grain boundaries or other microstructure features that might cause ambiguous interpretation. In this work a statistical analysis of local strains measured by electron back scatter diffraction and crystal plasticity based simulations are combined to determine the effect of M23C6 carbides on the deformation of an annealed AISI 420 steel. Results suggest that carbides provide a more effective hardening at low plastic strain by a predominant long-range interaction mechanism than that of a pure ferritic microstructure. Carbides not only influence local strain directly by elastic incompatibilities with the ferritic matrix, but also the spatial interactions between ferrite grains. Carbides placed at the grain boundaries enhanced the development of strain near ferrite grain boundaries. However the positive effect of carbides and grain boundaries to develop high local strains is mitigated at regions with high density of carbides and ferrite grain boundaries.
Highlights
It is well known that strain development in metallic alloys is critically affected by the microstructural characteristics such as grain size of matrix phases as well as size, density and nature of existing precipitates
We study the effect of large M23C6 carbides in the local strain development and strain hardening of an annealed AISI420 stainless steel
The microstructure of annealed AISI 420 consists of ferrite with various precipitate particles, predominantly M23C6 carbides and MX carbonitrides [21]
Summary
It is well known that strain development in metallic alloys is critically affected by the microstructural characteristics such as grain size of matrix phases as well as size, density and nature of existing precipitates. These characteristics influence the dislocation motion in the structure and play a fundamental role in the mechanical behaviour of the metallic alloys. Understanding the evolution of complicated dislocation structures in metals and their effect on the hardening behaviour of the materials during deformation is a major issue in materials science. Existing GNDs locally interact with moving dislocations by forming jogs that provide macroscopic isotropic hardening under strain development [1,2]. The relative significance of each mechanism varies with the overall imposed strain and size of microstructure elements related to material strengthening [2]
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