Effect of temperature on the dislocation structure of the ordered alloy Ni3(Fe,Cr)

Transmission electron microscopy is used to study the dislocation structure of ordered polycrystalline Ni₃(Fe, Cr) alloy after deformation at temperatures of 293, 473, 673, and 773°K. The flow stress σ is plotted as a function of the density of dislocations ρ. It is observed that there is a direct proportionality between σ and ρ^1/2, which indicates that the relation τ= αGbρ^1/2 is satisfied, where τ is the shear stress, G is the shear modulus, b is the Burgers vector, and α is a coefficient weakly dependent on the density of dislocations. The values of α are found for different deformation temperatures from the slope of the lines. It is found that α decreases with increasing deformation temperature. When the temperature is increased from 293 to 773°K the reduction in α is about 20% in agreement with estimates of the resistance to motion by superdislocations caused by nonconservative drag of dislocation jogs.