Isothermal heat treatment duration is to ensure temperature and chemical uniformity throughout the section of workpiece. If holding time is not adequate then different microstructure will be observed at different depth.

Dear Sharma. During any heat treatment isothermal holding time depend on the thickness of sample. Also there is additional time should be add to ensure than sample reach sample temperature of furnace.

Dear Abdullah. In semi solid isothermal heat treatment you have to ensure that sample reach to same temperature of furnace. In this case you will got a different in micro structure depend on fraction of liquid that you get at your semi- solid temperature.

Journal of Minerals and Materials Characterization and Engineering, 2014, 2, 26-31 Published Online January 2014 (http://www.scirp.org/journal/jmmce)

http://dx.doi.org/10.4236/jmmce.2014.21005

In the above study minimum 10 min. are used as holding time in semi-solid stat.

Dear Mohamed,

Thank you for your comments.

If I put the sample in the furnace while the heating on, how can I ensure that the sample reaches the same temperature of the furnace?

Thanks

Usually one time you can used thermo cuple to now time different. Usually 10 to 15 min. Depend on sample thickness

In case you want heat treatments affect full thickness you need full time. So time affect the thickness of the sample. To ensure that time needed for full thickness phase transformation is achieved.