Question

True-false: Heterogeneous phase transformations require more undercooling than homogeneous transformations.

explain your answer

Answer 1

False. Heterogeneous phase transformations require less undercooling than homogeneous transformations.

Homogenous transformation is such transformations where nucleation takes place throughout the liquid. In Heterogenous nucleation the critical nuclei is formed with the help of nucleating sites. These sites can be impurities, walls, cracks or intentionally added seeds to promote nucleation. As the nucleating sites assist nucleation at an higher temperature as compared to homoghenous transformation less undercooling is required.