A new mechanism of strain transfer in polycrystals

Abstract

At the grain boundaries of plastically deforming polycrystals, strain transfer mechanisms can accommodate the shear strain carried by slip bands and mechanical twins to prevent stress build-ups and damage. So far, only the accommodation obtained through slip (and twinning) alone has been considered in the mechanism known as slip (and twin) transfer. Here, a strain transfer mechanism that also requires the rotation of the crystal lattice is demonstrated. A region of accumulated slip develops perpendicular to the active slip plane in the impinged grain. The slip gradients enable a localized lattice rotation that accommodates the shear strain in the incoming band, preventing the build-up of interfacial stresses. The mechanism operates preferentially at the boundaries between highly misoriented grains. Facilitating strain transfer at these interfaces opens up new possibilities to improve the mechanical properties of polycrystals, as discussed.

Deformation of lamellar γ-TiAl below the general yield stress

“…9(f). This latter strain transfer mechanism has been characterised extensively by the authors in a recent publication [31].…”

Experimental investigation of early strain heterogeneities and localizations in polycrystalline α-Fe during monotonic loading

“…Finally, strain will accumulate where the higher amount of slip systems is found. This corresponds mostly to triple junctions and grain boundaries, as pointed out in subsection 3.2, where it has been shown that internal stresses are the highest [13,14] and more systems are required to accommodate the deformation [26,69].…”

A Feasible Surface Patterning Method for SEM-DIC: Achieving High-Resolution In Situ Mapping of Local Strain and Microstructure to Reveal the Effect of Slip Transfer on Shear Strain Near Grain Boundaries

“…Also, the slip transfer behavior at the grain boundary played a significant role in governing the mechanical properties of polycrystals (Bieler et al, 2014; Sun et al, 2019). Since the stress build-ups and damage of the grain boundary were mainly attributed to the shear strain ( ε xy ) caused by the slip bands or mechanical twins (Di Gioacchino et al, 2020), the present study on slip transfer here mainly started from the ε xy map shown in Figure 10d. The m ′ of each grain boundary was calculated based on the activated slip systems of associated grains (see Table 1) is shown in Figure 10d marked with light blue or yellow digitals.…”