COPPER-RICH INVAR BY MECHANICAL ALLOYING

An fcc alloy of composition Fe64Cu26Cr7Ni3 With a0 = 0.362 nm and an a verage crystallite size of 5 nm was produced by high-energy ball milli ng iron and copper powder in a stainless-steel container. The average number of electrons per atom is 8.7. The Curie temperature of the allo y is 410 K and the room-temperature magnetization is 48 JT-1 kg-1. The Mossbauer spectrum at 15 K shows a broad distribution of hyperfine fi eld with an average of 15.6 T, which indicates coexistence of high and low moment states for iron. The alloy decomposes exothermically at 77 5 K to yield a mixture of bcc and fcc phases, but 50% of the iron rema ins in the fcc form with a low moment.