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 disordered α solid solution transforms to the cubic α′ ordered on the fcc lattice at temperatures below 1000°C. 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 <55 pct Co showed dimple type ductile rupture with elongation over 40 pct at room temperature. The correlation of ductility with ordered structure is discussed. © 1979 The Metallurgical of Society of AIME.
