Answer
Tempered martensite is harder and stronger in as much as there is more ferrite-cementite phase boundary area for the smaller particles. Thus, there is greater reinforcement of the ferrite phase and more phase boundary barriers to dislocation motion.
Work Step by Step
Tempered martensite is harder and stronger in as much as there is more ferrite-cementite phase boundary area for the smaller particles. Thus, there is greater reinforcement of the ferrite phase and more phase boundary barriers to dislocation motion.