Non eqm cooling rate is very high so the nuclei formation is very difficult near to melting point (if nuclei forms then only solidification can start). Nucleation happens when temperature is somewhat below melting point, so that even with faster cooling rate , the energy of atoms are sufficiently low so that they can come together and form nuclei thus starting the solidification process
No hard and fast rule that B-C can't be linear. But generally speaking, for practical cooling rates(non eqm cooling) the rise in temp. is low at the start and with progress in dendrite formation it is higher , hence a 'sort of' exponential variation.
Sir plz explain volume and time dig for solidification
sir, for non equilibrium cooling why solidification starts below the melting point?
Non eqm cooling rate is very high so the nuclei formation is very difficult near to melting point (if nuclei forms then only solidification can start).
Nucleation happens when temperature is somewhat below melting point, so that even with faster cooling rate , the energy of atoms are sufficiently low so that they can come together and form nuclei thus starting the solidification process
Sir what about constitutional under cooling
Not discussed here. Can you elaborate on the question a bit more?
Sir, why isn't B-C linear?
No hard and fast rule that B-C can't be linear. But generally speaking, for practical cooling rates(non eqm cooling) the rise in temp. is low at the start and with progress in dendrite formation it is higher , hence a 'sort of' exponential variation.