Orientation-dependent grain boundary characteristics in tantalum upon the change of strain path

Although grain boundary (GB) exhibits crucial influence on grain subdivision and work hardening of tantalum (Ta), GB characteristics and the role it plays in deformation have not sufficiently investigated yet. By means of electron backscatter diffraction analysis and Vickers hardness measurements, we systematically analyzed microstructure and stored energy at GBs deformed under unidirectional rolling (UR) and 135 degrees clock rolling (CR), respectively. Geometrical necessary dislocation densities of GB regions were calculated based on kernel average misorientation. GB deformation mechanisms were deduced from Schmid factor analysis. Results show that in UR-Ta {111}< uvw > (< 111 >//normal direction) and {100} < uvw >(< 100 >//normal direction) grains tend to be deformed in uniserial and multiple slipping, respectively, while only multiple slipping is activated in CR-Ta. Hence, in UR-Ta, uniserial slipping induces dense intragranular micro-shear bands (MSBs), 23 degrees-45 degrees relative to rolling direction, which penetrate through adjacent {111} grains, while in {100} grains multiple slipping introduces orientation-gradient cells instead of similar MSBs observed in {111} grains. Compared to orientation-dependent grain subdivisions in UR-Ta, the multiple slipping in CR-Ta generates only cell structures in both {111} and {100} grains. Interaction effects between {100}-{100},{100}-{111} and {111}-{111} grains are therefore varies with varying rolling paths.