Influence of thermomechanical treatment on recrystallization and softening resistance of Cu−6.5Fe−0.3Mg alloy

The recrystallization and softening resistance of a Cu−6.5Fe−0.3Mg (mass fraction, %) alloy prepared by Process 1 (cold rolling heat treatment) and Process 2 (hot/cold rolling heat treatment) were studied using Vickers hardness tests, tensile tests, scanning electron microscopy and transmission electron microscopy. The softening temperature, hardness and tensile strength of the alloy prepared by Process 2 were 110 °C, HV 15 and 114 MPa higher, respectively, than those of the alloy prepared by Process 1 after aging at 300 °C. The recrystallization activation energy of the alloys prepared by Process 1 and Process 2 were 72.83 and 98.11 kJ/mol, respectively. The pinning effects of the precipitates of the two alloys on grain boundaries and dislocations were basically the same. The softening mechanism was mainly attributed to the loss of dislocation strengthening. The higher Fe fiber density inhibited the average free migration path of dislocations and grain boundary migration in the alloy, which was the main reason for higher softening temperature of the alloy prepared by Process 2.