20 pts Many years ago in some places tombstones were made of

(20 pts) Many years ago in some places, tombstones were made of tin. During the evening if the temperature dropped to less than 13º C (55º F), a crying sound could be heard coming from the graveyard. From a microstructural perspective, what could be responsible for this \'tin cry\'? Consider your answer on the basis of pure tin exists in two allotropes, -tin and -tin.

Solution

The sound is caused by the shearing of the crystals in the metal. When we start lowering the temperature of tin, crystal twinning occurs at transition phase(i.e. transition from beta to alpha) where separate crystals share lattice points and overgrow each other. The tin cry actually is a relatively soft sound, sort of a crackling whine.