Expansion upon freezing is a rare property. By memory, I knew only water and gallium plus few other metals. Quick googling seems to suggest that some other solvents might expand too, but I didn't find which ones. I addition, they are liquid at room temperature, so melting in the +20 to +50°C range would need a somewhat adapted molecule, which means a development effort.
A different path would try to imitate water by seeking molecules that build several hydrogen bonds, needing a less compact organization when frozen. Polyols, polyglycols, polyamines, others? With luck you stumble upon a banal existing one, if not it's a significant research effort.
is an other extremely rare property, met essentially by ore. The cheapest processed materials cost a bit under 1$/kg, the most elementary oil derivatives do. Basic food, like sugar, falls in this price category. Even polypropylene costs a bit more presently.
Both properties from one compound is very unlikely. Try your luck searching for the cheapest mass-produced compounds like polyols and polyglycols.
Adding "high friction" won't help. Consider yourself extremely lucky if one compound fulfills the two first demands.
Melting hexahydrate: the source I read contradict an other. Some tell "hexahydrate melts at +117°C upon rapid heating" and others "hexahydrate decomposes at +118°C"https://en.wikipedia.org/wiki/Magnesium_chloridehttps://de.wikipedia.org/wiki/Magnesiumchlorid
It must be possible to regenerate (rehydrate) the hexahydrate after decomposition, but not necessarily in a way that suits your application.
Worth trying? Heat the hexahydrate under pressure of liquid water
(or rather of saturated water solution), hoping that the magnesium chloride retains its crystallization water then. At +117°C it's a trivial pressure. Last chance at +374°C, then you need 218 atm. An approximate formula: P~(°C/100)4