The velocity of selectively-introduced edge dislocations in99.999 percent pure copper crystals has been measured as a functionof stress at temperatures from 66°K to 373°K by means of a torsiontechnique. The range of resolved shear stress was 0 to 15 megadynes/cm^2 for seven temperatures (66°K, 74°K, 83°K, 123°K, 173°K, 296°K, 296°K, 373°K.
Dislocation mobility is characterized by two distinct features;(a) relatively high velocity at low stress (maximum velocities of about9000 em/sec were realized at low temperatures), and (b) increasingvelocity with decreasing temperature at constant stress.
The relation between dislocation velocity and resolved shearstress is:
v = v_o(τ_r/τ_o)^n
where v is the dislocation velocity at resolved shear stress τ_r, v_ois a constant velocity chosen equal to 2000 cm/ sec, τ_ois the resolved shear stress required to maintain velocity v_o, and n is the mobility coefficient. The experimental results indicate that τ_o decreases from 16.3 x 10^6 to 3.3 x 10^6 dynes/cm^2 and n increases from about 0.9 to 1.1 as the temperature is lowered from 296°K to 66°K.
The experimental dislocation behavior is consistent with aninterpretation on the basis of phonon drag. However, the completetemperature dependence of dislocation mobility could not be closelyapproximated by the predictions of one or a combination of mechanisms.
