A quantitative study of stress fields ahead of a slip band blocked by a grain boundary in unalloyed magnesium

Abstract

Stress localization ahead of a slip band blocked by a grain boundary is measured for three different grain boundaries in unalloyed Mg using high-resolution electron backscatter diffraction (HR-EBSD). The results are compared with a theoretical dislocation pileup model, from which slip system resistance and micro-Hall-Petch coefficients for different grain boundary types are deduced. The results indicate that grain boundary character plays a crucial role in determining micro-Hall-Petch coefficients, which can be used to strengthen classical crystal plasticity constitutive models to make predictions linked to the effect of grain boundary strengthening.

The role of grain boundaries in low-temperature plasticity of olivine revealed by nanoindentation

“…In the context of low-temperature plasticity of olivine-rich materials under geological conditions (e.g., lithosphere bending) the distribution of grain boundaries with different abilities to transmit slip could impact local strain hardening and localization, before bulk hardening of the material (e.g., Marquardt et al, 2015;Sangid et al, 2011;Andani et al, 2020). In our experiments, the SB is transparent to slip transfer, and does not generate plasticity at stresses lower than in the bulk crystal.…”

“…Sutton & R.W.Balluffi (1995, Ch 12)). Consequently, intracrystalline dislocations interacting with grain-boundary regions with an enhanced density of dislocations due to microplasticity could increase the intracrystalline stresses in fine-grained aggregates (e.g., Guo et al, 2020Guo et al, , 2014Andani et al, 2020). TEM observations of single crystals of olivine deformed in the low-temperature regime and the data in Figure 11 reveal tangled dislocations and intersecting slip planes (e.g., Phakey et al, 1972;Gaboriaud et al, 1981;Druiventak et al, 2011;Wallis et al, 2020;Mussi, Nafi, et al, 2015).…”

Resolving intragranular stress fields in plastically deformed titanium using point-focused high-energy diffraction microscopy

“…The behavior of plastic deformation at and across grain boundaries is related to defect accumulation, stress concentrations, and orientation relationships, also becoming preferential sites for damage and failure nucleation [42][43][44][45][46][47][48][49]. As a result, the direct experiment observation of the complex stress evolution at and across grain boundaries is of great interest to the material science community [18,[50][51][52][53][54][55][56].…”

Crystal Plasticity Simulation of Magnesium and Its Alloys: A Review of Recent Advances

“…Traditional crystal plasticity models were developed largely without a connection to grain size and shape effects. In Magnesium alloys, it has been observed that the grain size strengthening follows the Hall-Petch effect [98]. The incorporation of grain size effect into constitutive models for single slip began in 1962 with Armstrong et al [99], who modified the Hall-Petch equation to correspond to the flow stress on a slip system (the "micro-Hall-Petch relation").…”

“…Improved modeling of slip/twin and grain boundary interactions: Effects of grain size in different Mg alloys using crystal plasticity models, specifically via micro-Hall Petch models whose parameters can be inferred through experiments [98,102] and including the effect of grain boundary on twin nucleation and growth in crystal plasticity models.…”