The response of dislocations, low angle grain boundaries and high angle grain boundaries at high strain rates

As a most widely applied structure material, the deformed characteristics of steels primarily presented the adiabatic shear band (ASB) formation and phase transitions, instead of its intrinsic structure evolution at different strain rates. In previous works, seldom investigations on the high strain rates dependence of the dislocations, low angle grain boundaries (LAGBs) and high angle grain boundaries (HAGBs) were reported, and the transition mechanism among the three microstructural factors was not clear. Here, we used a gas gun to generate shock wave to compress the AISI 1045 steels and investigated their structures under different stain rates of 4.3 x 10(5) s(-1) (low) and 3.3 x 10(6) s(-1) (high), respectively. A gradient structure was formed along shock compression direction. Surprisingly, the structure evolution of the steel has a strong rate effect. At high strain rates, the dislocations would form the LAGBs, while the LAGBs would difficultly transform into HAGBs. At low strain rates, the LAGBs preferred to transform into HAGBs. Furthermore, the LAGBs to HAGBs transformation was accompanied with the grain rotation. The texture under the low strain rates was changed from annealing {111} < 211 > to R-Cube {001} < 110 >, while that of the high strain rates became R-Goss {110} < 110 >-> Goss {011} < 100 >-> Cube {001} < 100 >. These results indicate that the rate effect of the structures under loading plays an important role in guiding the materials design and applications.

Automated summary

The structure evolution of steels under different strain rates shows a strong rate effect, with dislocations forming low angle grain boundaries at high strain rates and low angle grain boundaries more likely to transform into high angle grain boundaries at low strain rates. The transformation from low angle grain boundaries to high angle grain boundaries is accompanied by grain rotation, and the texture of the steel changes accordingly. These results highlight the importance of the rate effect in guiding materials design and applications.