Which one of the following statements is true? Explain.
(a) Given values of the diffusion coefficient for carbon in iron at 850°C and 950°C, we can calculate the activation energy for the diffusion of carbon in iron.
(b) Given values of
a) the activation energy for self-diffusion in copper and
b) the activation energy for vacancy migration in copper, we can calculate the activation energy for vacancy formation in copper.
c) Self-interstitials do not form in pure metals.
d) Diffusion in crystalline solids can only occur if there are vacancies in the crystals.
e) At room temperature, the stress needed to cause significant creep will be lower for pure copper than for pure aluminium.