Tensile properties of spark plasma sintered AISI 316L stainless steel with unimodal and bimodal grain size distributions

A full-field crystal-plasticity analysis of bimodal polycrystals

“…However whereas the stress increase remains confined to a few grains close to the FG/CG interface, the stress relaxation develops along large and long longitudinal channels. This ability of the CG to accomodate the stresses of FG on a relatively long range along the tensile direction comes in agreement with our observations in the related experimental study [20]: a ductility improvement was obtained by introducing CG clusters in the FG material and this was correlated to a relaxation of the (long range interaction) backstress. Figure 19: Influence of the CG distribution on the mean responses per grain, for a grain size ratio of 10 and comparing the cases of isolated or clustered CG: (a) Axial stress-strain responses at 1% axial strain (b) the corresponding probability density functions (they have been normalized for the sake of visualization in a single diagram).…”

“…15 provides the stress-strain curves of all polycrystals. Two experimental curves corresponding to approximately the same average grain sizes of CG and FG and to 25% of CG in volume fraction are also represented [20]. As seen from the numerical results alone, the spatial distribution of CG plays a role only for the smallest size of FG (0.5 µm), and this effect increases with the grain size ratio.…”

“…The influence of the CG spatial distribution is analysed systematically, for four sets of CG and FG sizes taken from previous experimental works [20] and listed in Table 2. For each set, three different CG spatial distributions are considered: Fig.…”

“…Several methods have been proposed to elaborate bimodal polycrystals, such as rolling and annealing [15,16,17], severe plastic deformation [18], or powder metallurgy combined to conventional or spark plasma sintering (SPS) [19,13,17,20]. However, only the latter (and especially SPS) provides the direct, accurate control on the GS statistics (size distributions and volume fractions) required for analysing microstructure-property relationships in detail (although the amount of materials produced by SPS is much smaller than for deformationbased processes).…”

“…However, only the latter (and especially SPS) provides the direct, accurate control on the GS statistics (size distributions and volume fractions) required for analysing microstructure-property relationships in detail (although the amount of materials produced by SPS is much smaller than for deformationbased processes). Using this specific sintering route, the authors recently reported the influence of a bimodal distribution on the mechanical properties of 316L samples [20]. In particular an improvement of the strain to failure for a given yield stress has been observed for bimodal grain size distribution due to a modification of the backstress.…”