Abstract
Thermal expansion of FeCo alloys in the bcc range have been measured. The volume changes due to the ordering of 30∼70 at%Co alloys decrease at the order-disorder transition temperature Tc, and the expansivities of these alloys decrease as the long-range order parameter increases. The mean expansivities of the ordered 25∼70 at%Co alloys are less than those of the disordered ones in the temperature range from 100 to 200°C. The volume change due to the ordering at room temperature decreases in 27.5∼33.3 at%Co and increases in 40∼70 at%Co.
The volume increase due to the ordering at room temperature of the 40∼70 at%Co alloys is more affected by the decrease of the expansivity than the contraction due to the ordering.
