Room-temperature plastic deformation of single crystals of cementite investigated by micropillar compression

The plastic deformation behavior of single crystals of binary Fe 3 C and ternary (Fe,Cr) 3 C has been investigated in micropillar compression at room temperature as a function of loading-axis orientation and specimen size. Six slip systems, (010)[100], (001)[010], (100)[001], {011}[100], {031}<0 1 ¯ 3> and {110}<1 1 ¯ 1> are identified to operate in both Fe 3 C and (Fe,Cr) 3 C. The average values of critical resolved shear stress for these slip systems are estimated to be 0.9 ± 0.2, 2.1 ± 0.4, 1.9 ± 0.4, 1.7 ± 0.2, 1.8 ± 0.4 and 1.9 ± 0.5 GPa, respectively for Fe 3 C and 1.1 ± 0.2, 2.3 ± 0.4, 2.3 ± 0.4, 2.1 ± 0.2, 2.5 ± 0.4 and 2.3 ± 0.4 GPa, respectively for (Fe,Cr) 3 C. The CRSS for (010)[100] slip is significantly lower than those for the other identified slip systems. The [100] dislocation on the (010) slip plane dissociates into two partial dislocations with the collinear but different Burgers vectors ( b 1 =1/4[100] and b 2 =3/4[100]). The slip plane for the [100] dislocation is identified to locate between the Fe atomic plane and the Fe-C atomic plane in the unit layer consisting of Fe 6 C trigonal prisms, so that Fe 6 C trigonal prisms are destroyed by (010) slip, in contrast to the long-time belief that (010) slip occurs between the neighboring unit layers so as not to break any Fe-C bonds within Fe 6 C trigonal prisms, giving rise to the lowest shear stress level. The implication is made on the mechanism for refinement and alignment of the pearlitic lamellar structure by wire drawing.