Ordered structure and solute-suppressed atomic ordering in iron-cobalt alloys

The slowly cooled Fe-25 wt% Co alloys generally suffer from poor ductility due to the atomic ordering. Combining DFT calculations and experiments, ordered L60-Fe3Co structure was first demonstrated to crystallize in the slowly cooled similar to 25 wt% Co alloys and lead to brittleness. The stable existence of L60-Fe3Co structure is of great significance to further understand the binary Fe-Co phase diagram. Metal elements (e.g. V and Nb) are generally added into FeCo alloy to improve ductility and workable ability. The toughening mechanism of these solutes is mainly realized by suppressing atomic ordering. The reduced antisite defect energies by V and Nb additions lowers the maximum degree of order and antiphase boundary (APB) energies. The key to suppress atomic ordering is reducing antisite defect energy or site-exchange energy. A comprehensive theoretical understanding on the mechanism of suppressing atomic ordering is helpful to further find alloying elements which simultaneously improve mechanical and magnetic properties for Fe3Co or other ordered alloys.

Automated summary

The addition of metal elements to FeCo alloy can improve ductility and workable ability by suppressing atomic ordering. The key to suppressing atomic ordering is reducing antisite defect energy or site-exchange energy.