Page 59 - Mechanical Behavior of Materials

58 Chapter 2 Structure and Deformation in Materials

Figure 2.22 Slip bands and slip steps caused by the motion of many dislocations resulting
from cyclic loading of AISI 1010 steel. (Photos courtesy of R. W. Landgraf, Howell, MI.)

Figure 2.23 Some slip planes and directions frequently observed for BCC, FCC, and HCP
crystal structures. Considering symmetry, there are additional combinations of slip plane and
direction similar to each of these, giving a total of twelve slip systems similar to each of (a),
(b), and (c), and three for each of the two cases in (d). (Adapted from [Hayden 65] p. 100;
used with permission.)

2.5.2 Discussion of Plastic Deformation

The result of plastic deformation (yielding) is that atoms change neighbors and return to a stable
configuration with new neighbors after the dislocation has passed. Note that this is a fundamentally
different process than elastic deformation, which is merely the stretching of chemical bonds. Elastic
deformation occurs as an essentially independent process along with plastic deformation. When