Elementary mechanisms governing basal twist grain boundary shearing at room temperature in titanium

Recent investigations of fatigue failures in titanium alloys suggested a key role of low stress deformation events occurring at basal twist grain boundaries (BTGBs). The present study aims at clarifying the underlying mechanisms focusing on two representative BTGB configurations. Experimental characterization of the deformation behavior using high-resolution digital image correlation and molecular dynamics sim-ulations highlighted differences in mechanical responses, although shear localization was exhibited along both BTGBs. The different strengths originate from kagome and triangular morphologies of the interfacial dislocation networks (IDN). Shear accommodation at low stress (i.e.,∼100 MPa) was observed by collective glide of the triangular IDNs along [1 -1 0 0]. In contrast, shear localization at kagome IDNs was trigger by a transformation into triangular IDNs occurring at a higher stress level (i.e.,∼1 GPa). The essential role of the stacking faults in the mechanical response is finally discussed.