THE INFLUENCE OF STRAIN AND GRAIN SIZE ON THE CREEP SUBSTRUCTURE OF FE-3.0% SI.

The dislocation substructure generated during creep of an Fe-3.0 Si alloy has been investigated using both etch pit and transmission electron microscopy techniques. Three different grain sizes were investigated, namely 0.05, 0.1 and 0.3 mm. The type of subgrain structure generated during creep is somewhat dependent on the grain size. The 0.05 mm grain size samples exhibit an equiaxed subgrain structure, whereas the 0.1 and 0.3 mm grain size samples exhibit both equiaxed and banded subgrain structures. The banded dislocation substructure is believed due to slip band formation. Measurements of the dislocation density, rho, not associated with subboundaries, reveal the following general trends. During primary creep, rho is a function of strain, decreasing with increasing strain. During steady state creep, rho is independent of both strain and grain size. Assuming that the density of dislocations not associated with subboundaries is an accurate measure of the mobile dislocation density, the average dislocation velocity, v, is also a function of strain during primary creep, generally decreasing as the strain increases. Author