rare earth metal alloys

The metallurgical industry, a heavy user of rare earths has long added small amounts of misch metal and cerium to other metals or alloys to remove their nonmetallic impurities. Misch metal, an alloy of 50% finely divided cerium, 25% lanthanum, 15% neodymium and 10% other rare-earth metals and iron, makes a more malleable nodular iron when added to cast iron. Added to some steels, it makes them less brittle. The addition of misch metal to certain alloys reportedly increases the tensile strength while improving the hot workability and the high-temperature oxidation resistance. Misch metal is also used to remove oxygen in vacuum tubes. Yttrium metal reportedly works even better than misch metal in removing impurities from certain materials. Lighter flints (spark-producing agents) are made from misch metal alloyed with iron. As an alloying agent in magnesium, misch metal contributes to high-temperature strength and creep resistance—that is, resistance to slow deformation under prolonged use. Misch metal also makes superior castings if small amounts of zirconium or other metals are added, and such alloys are used in jet engine and precision castings. The addition of small amounts of rare-earth elements to aluminum has also been reported to give better castings. In iron–chromium and iron–chromium–nickel alloys, the rare earths are particularly effective in improving a number of their properties, especially their resistance to oxidation and corrosion. A cobalt-samarium alloy is used to make a magnet unparalleled in its resistance to demagnetization.