Temperature dependence of dislocation structure of L12–Al3Sc

Superdislocations in Al3Sc deformed at various temperatures were observed by TEM (transmission electron microscopy). Emphasis was placed on the low temperature range. Below room temperature, dislocations in pile ups dissociated into two a/3<112> superpartials separated by a SISF (superlattice intrinsic stacking fault). At 77 K, triple dislocation nodes separated by SISF were observed. SISF energies estimated from the separation width of superpartial dislocations are 170 mJ m−2 at 77 K, 230 mJ m−2 at 210 K and 290 mJ m−2 at 293 K. The experimentally determined temperature dependence of dissociation mode in Al3Sc is similar to that of Co3Ti reported previously. Taking into account the results of the above TEM observations and also of strength measurements, the dislocation structure in L12–Al3Sc is discussed.