STORED ENERGY DRIVEN ABNORMAL GRAIN GROWTH IN Fe

Abnormal grain growth was studied in an Fe-1%Si alloy using automated Electron Backscattered Diffraction (EBSD). Industrially processed samples were temper rolled to reductions of 0%, 1.5% and 8% and then annealed in a range of atmospheres for various times followed by quenching in water. Abnormal grain growth was observed regardless of atmosphere although a moist hydrogen-nitrogen mixture resulted in slower kinetics than air and some strengthening of the Goss texture component. The matrix grains remained essentially static and did not coarsen. Analysis of the grain boundary character of the interfaces between abnormal grains and the matrix showed only general high angle boundaries with no special boundary types present at high (or low) frequencies; this suggested that grain boundary character was not a factor in controlling the AGG. The influence of stored energy was evaluated by examining intragranular orientation gradients; this showed drastic reductions in orientation spread associated with large growing grains. This suggests that variations in stored energy are present, even in the material that was not subjected to temper rolling and that differences in stored energy were the main driving force for AGG.