Effect of Size of Precipitates on Recrystallization Temperature in Cu-Cr, Cu-Zr and Cu-Zr-Cr Alloys

Abstract

In a previous paper, the reason for high recrystallization temperature in Cu-Cr, Cu-Zr and Cu-Zr-Cr alloys was considered to be due to the formation of fine precipitates during recrystallization, which obstructed dislocation climbing or sliding and grain boundary migration.
In the present paper, the recrystallization behaviours in Cu-Cr, Cu-Zr and Cu-Zr-Cr alloys quenched, tempered (at 350, 450, 500, 550 and 700°C), heavily cold worked and annealed at various temperatures were studied by the resistmetric method, measurements of mechanical properties and transmission electron microscopy. No fine precipitates were detected at dislocations or sub-boundaries in the low temperature annealing stage, but fine precipitates, which retard recovery, must exist since electrical resistivity decreased by low temperature annealing. The mechanism of retardation of recovery is due to the binding of dislocation jogs and fine precipitates. In the high annealing temperature stage, the growth of precipitates and crystal grains was observed by transmission electron microscopy, and the effect of precipitates on retardation of recrystallization was also detected.
The size of precipitates by tempering before cold working did not affect the recrystallization temperature, because the precipitates were sheared by heavy cold working and became a constant size.