Tension and compression experiments were conducted on body-centered cubic Fe -47.8 at
pct. Cr single crystals. The critical resolved shear stress (CRSS) magnitudes for slip
nucleation, twin nucleation and twin migration were established. We show that the
nucleation of slip occurs at a CRSS of about 88 MPa, while twinning nucleates at a CRSS of
about 191 MPa with an associated load drop. Following twin nucleation, twin migration
proceeds at a CRSS that is lower than the initiation stress (≈114–153 MPa). The experimental
results of the nucleation stresses indicate that the Schmid law holds to a first
approximation for the slip and twin nucleation cases, but to a lesser extent for twin
migration particularly when considerable slip strains preceded twinning. The CRSSs were
determined experimentally using digital image correlation (DIC) in conjunction with
electron back scattering diffraction (EBSD). The DIC measurements enabled pinpointing
the precise stress on the stress–strain curves where twins or slip were activated. The crystal
orientations were obtained using EBSD and used to determine the activated twin and slip
systems through trace analysis.