Influence of the grain boundary misorientation on the intragranular deformation of 316L austenitic stainless steel; an in-situ SEM-EBSD-DIC investigation

초록

Mechanical properties of metallic alloys are controlled by tailoring the microstructure. In polycrystalline materials, its deformation response is closely related to the grain boundary characters, as well as properties of individual grains. In the present study, we investigated the influence of GB misorientation on the intragranular deformation and lattice rotation of 316L austenitic stainless steel, using mu-DIC and SEM-EBSD during in-situ tensile deformation. The in-plane axial strains (epsilon xx and epsilon yy) and shear strain (epsilon xy), and in-grain misorientation were measured to analyse the deformation behaviour of each grain. Three aspects of intragranular deformation in relation to the GB misorientations were summarised as follows: (i) heterogeneous and (ii) homogeneous deformation under combined low- and high-misorientation and equivalent misorientation GBs, respectively, and (iii) strain partitioning and lattice twist under the symmetric distribution of low- and high-misorientation GBs. A characteristic strain pattern showed that the epsilon xx strain (i.e., tensile component) accumulation is higher at the vicinity of relatively low-misorientation GBs, indicating a link to the intragranular deformation heterogeneity. The GB sliding or other complementary mechanisms occurred at relatively high-misorientation GBs, including & sum;3 boundaries, whilst the activation of slip systems was the primary mechanism at the vicinity of lowmisorientation GBs. The deformation disparity led to heterogeneous lattice rotation, resulting in the multiple slips and kink or cross-slip events. The misorientation-dependent interfacial energy and strain incompatibility of GBs, and the associated deformation mechanisms are discussed. The findings of this study provide a mechanistic link between the local structural features of GBs and intragranular strain response.

키워드