There are some factors that can be responsible for this, you can try to be specific in term of the material you are talking about so as to get the right answers.
Grain growth depends strongly on the presence of growing and dissolving precipitates. In case of steels, grain size control through the pinning of grain boundaries with micro alloyed precipitates is widely applied.
Dear Tawfiq Alhammad,
In most cases the answer will be: nothing.
Grain size control after casting is only possible if the basic alloy system concerned shows transformation lines, e.g. the Fe-C system. Note that this condition might appear necessary but insufficient (cf. the Ti-based alloys). In most cases the resulting grain sizes after casting depend on the casting conditions, like undercooling, cooling rates and the presence of grain refiners. So, additional research will be necessary. Good luck!
Once the casting with coarse grain is produced, the only solution for grain refinement is by heat treatment providing the alloy shows transformation lines. Control of casting parameters are not possible in that case. Generally normalizing treatment or quenching and tempering will produce refined structures.
I kindly remind you all that after casting a heat treatment alone would only increase the grain size. I very surprized to see that unfortunately there are so many comments suggesting otherwise. And if one is referring to possibility of a martensitic transformation, be it in steel or in Ti- alloys, this is never named or considered as "grain refinement" process.
Based on the phase equilibrium diagram of a system can be determined as; type of heat treatment may be applied to the alloy and the temperature ranges in which the treatment should be carried out.
Accordingly, the process of heat treatment of steel to be seen using an equilibrium phase diagram of the iron-cementite. Temperature phase equilibrium in the system and temperature changes (critical points) generally accepted to mean the letter A with the corresponding indicator. The lowest of these temperatures A1 corresponds to the balance of ferrite and austenite cementite (line PSK). A2 is the temperature of the transition temperature of the magnetic ferrite (line MO). Temperature A3, defined by points lying on a line GS is the temperature limit of the austenite ferrite balance. Temperature Acm (line SE) to limit temperature equilibrium with the austenite cementite secondary.
To distinguish the beginning and end of the temperature change during the heating of the temperature thereof during cooling is added to the letter A, the C in the case of heating or cooling rate of r in the case (for example. Ac1, Ar 3).
Exceeding the temperature Ac1 transformation marked by a sudden decrease in the grain that is newly formed austenite grains are always very small and basically their dimensions do not depend on the size of grains of perlite, which formed austenite. Grain refinement of austenite at the time of change is associated with the formation of a large number of nuclei for new grains unusual and very high surface area interface between ferrite and cementite.
Dear Piotr,
What you described is intercritical annealing and may be applied to, obviously, steel and small sized parts (due to inevitable inhomogeneous heating). However, the question stated does not mention steel as a specific example.
Regards
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