Control of ordered structure and ductility of (Fe, Co, Ni)3V alloys

This study is directed toward improvement of the ductility of long-range ordered alloys through control of their ordered crystal structure. A series of ordered alloys was prepared with a base composition of Co₃V, where Co was partially replaced with Fe and Ni. The stability and structure of the ordered phases in these (Fe,Co,Ni)₃V alloys were characterized by various metallurgical methods. The results indicate that the ordered structure in this alloy system can be controlled by adjusting the electron density, and that the L1₂ type cubic ordered structure (α′) is stable in the alloys with electron density less than 7.888. The phase relation in the cubic ordered alloys depends on the Fe concentration. For the alloys containing 20 pct Fe, the α′ is formed through a peritectoid reaction, namely, α+σ→α′. Tensile tests indicate that the alloys with multilayered hexagonal ordered structure are very brittle, while the alloys with the cubic ordered structure are ductile at room temperature. The ductility of the cubic ordered alloys increases with decreasing Co content. The alloys with