Question

In the case of pure metals, liquid metal should be cooled above their freezing points.

(a) True

(b) False

This question was posed to me in a job interview.

I'd like to ask this question from Mechanism of Solidification topic in section Cooling and Solidification of Casting-Forming-Welding I

Answer 1

Right option is (b) False

Easy explanation: Liquid metal always needs to be cooled below their freezing points before the solidification starts. This is because the energy is required to create surfaces for new crystals and the degree of super-cooling necessary is also reduced by the presence of particles which serve as the initial nuclei for crystal growth.