Effects of an oxyde layer on the tensile behavior of pure nickel foils

We present in this paper the consequences of an oxide scale grown on pure nickel on the mechanical behaviour. The presence of the oxide layer hardens the metal for low strain level, and reduces the ductility. Activation volumes as measured during stress relaxation experiments show that the dislocation motion mechanism is not affected by the presence of the oxide and it relies on forest interactions. It is shown that the main contribution of the oxide is to act as a barrier for dislocations and accelerates the storage of dislocations thus increasing the total dislocation density which causes hardening of the metal