In a previous paper, it was reported that the high recrystallisation temperature of Cu–Cr, Cu–Zr and Cu–Zr–Cr alloys was due to the formation of fine precipitates during recrystallisation, which obstructed dislocation climb, glide and grain boundary migration.
In the present paper, the recrystallisation 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 resistometric 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 during low temperature annealing. The mechanism of retardation of recovery is due to the binding of dislocation jogs by fine precipitates. In the high annealing temperature range, the growth of precipitates and crystal grains was observed by transmission electron microscopy and the effect of precipitates on the retardation of recrystallisation was also detected.
The size of precipitates formed during tempering before cold working did not affect the recrystallisation temperature, because the precipitates were broken up by heavy cold work and were thus made a constant size.