Which liquefied metal expand on solidification?

Answer 1

grey cast iron because during solidification the graphite flakes expands

Bismuth and antimony are metallic elements that expand on solidification (~3-4%). These elements solidify in a monoclinic (not close-packed) structure which becomes more dense when it transforms from a solid to a liquid. A range of bismuth alloys are used for low temperature melt applications that have take advantage of the expansion to get close tolerance die castings. Gallium is a third metal element that expands during solidification (31 deg C).

Answer 2

Water and bismuth are examples of liquefied metals that expand on solidification. When water freezes, it forms ice which is less dense than liquid water, causing it to expand. Bismuth also expands when it solidifies due to its unique crystalline structure that leads to a less densely packed arrangement of atoms, resulting in expansion.