There are some bad experiences with the latest microcasted pistons, at some pistons it seems the side to the exhaust port is overheated, they have a very strange roughness.
I think the current marketing will say they have bettered the piston.
Friction and expansion is related but as mentioned some ingredients do make the specs.
Iron makes the strength but makes a lot of friction. Copper on the other hand makes it low friction but makes the material weak for higher temperatures.