Surface plasticity associated with the effective surface energy, gamma //e//f//f, for cleavage initiation has been evaluated with an electron channeling technique. Detailed examination of one Fe-4 at%Si single crystal with cleavage initiation at a 6 mu m carbonitride particle gives gamma //e//f//f*** approximately 23 J/m**2. Qualitatively, when compared to other single crystal cleavage data, it appears that a simple plastic strip model which predicts gamma //e//f//f varies directly as rho can account for differences in toughness at initiation. Additional detailed fractographic measurements show this to be partially fortuitous in that some of the surface plasticity occurs in the form of ligaments and ledges after the crack-tip has passed. These act as elastic restraining forces which increase the effective surface energy. The relative contribution of crack-tip plasticity versus these elastic restraining forces to gamma //e//f//f is yet to be determined.
|Original language||English (US)|
|Title of host publication||Unknown Host Publication Title|
|Publisher||Metallurgical Soc Inc|
|Number of pages||16|
|State||Published - 1985|