Dislocation substructure-controlled softening of Cu-20Ni-20Mn alloy

The dislocation strengthening effect is generally considered to be controlled by dislocation density; however, in the present study the dislocation substructure is shown to play an even more important role for Cu-20Ni-20Mn alloy. The hardness and microstructural evolution during annealing in a hot-forged Cu-20Ni-20Mn alloy are investigated. Microstructure analysis of annealed samples indicated variation in the number of dislocations and dislocation substructure related to softening of the Cu-20Ni-20Mn alloy during static recovery. The tangled dislocations formed a regular array during annealing at 600 degrees C, leading to a high softening fraction of 95%. In addition, rapid dislocation annihilation and sub-boundary disintegration occurred during annealing owing to the dislocation climb at 650 degrees C. The number of mobile dislocations within the grains decreased considerably, leading to softening in the Cu-20Ni-20Mn alloy annealed at 650 degrees C.