CFD Academy HAZMAT Practice Exam

When metals are cooled to cryogenic temperatures, their ability to deform plastically decreases and their tendency to fracture brittly increases. The limited thermal energy reduces dislocation motion and crack blunting, so cracks can propagate with less energy absorption. This is the ductile-to-brittle transition that many metals experience as temperature drops, making them behave more brittly rather than ductile.

So the statement that they become more brittle best matches what happens at very low temperatures: the material is more prone to brittle fracture under impact or stress rather than undergoing plastic deformation to distribute the load. Not all metals behave identically—some remain ductile under cryogenic conditions, but the common trend for many metals is indeed increased brittleness. The other options are inconsistent with this temperature-driven change in mechanical behavior.