Polygonization in strongly deformed metals

A special micrographic technique shows that in cold rolled copper annealing develops sub-boundaries within the grains before actual recrystallization occurs.

In heavily cold worked aluminium the crystals are fragmented as shown by x-rays, so that a partial polygonization is already present. This is not true for slightly cold worked, impure aluminium.

During annealing of fragmented aluminium the drop of the elastic limit occurs in two stages. The first one corresponds to a progress of the polygonization, the second one to recrystallization.

The state of coarse polygonization thus reached corresponds to a special shape of the strees-strain curve.

Thermoelectric study proves that this progression of the polygonization is accompanied by a partial precipitation of impurities.

Recrystallization can occur in single crystals without previous polygonization (at least on an observable scale).