Origin to annealing-induced abnormal hardening in cold-rolled Ni-Mo binary alloys

Elucidating the origin of annealing-induced hardening (AIH) enables optimal utilization of AIH while mitigating its side effects. Here, we evaluated the response of a series of cold-rolled Ni-Mo binary alloys to subsequent annealing and find that the governing AIH switches as the concentration of Mo reaches a critical level of 5 at.%. Below the level, the maximum AIH decreases as Mo concentration increases and the exhaustion of mobile dislocations contributes primarily. Beyond the level, trend reversal occurs and two alternative outweighing mechanisms, including the enhancement of chemical inhomogeneities and formation of atomically ordered structures, consecutively become predominant.