The grain shape of NbC in a Co liquid varies between a well-faceted cube and a sphere depending on annealing temperature and addition of dopants such as B.
(a) What do you expect as the shape of NbC grains in Co without B at a low temperature?
(b) Explain the growth mechanisms of spherical and faceted NbC grains in Co. What are the kinetic equations of grain growth in compacts containing the two extreme types of grains?
(c) Which mechanism do you expect to be operative in the growth of round-edged (partially rounded) cubic NbC grains. Do you think the growth kinetics vary with the fraction of round-edged area? Explain.