COBALT OCCURS IN two atomic forms: a low temperature stable hexagonal close packed (hcp) form and a high temperature stable face centered cubic (fcc) form. The transformation temperature of pure cobalt is 417°C. Alloying elements such as nickel, iron, and carbon (within its soluble range) are known as fcc stabilizers, and suppress the transformation temperature. Chromium, molybdenum, and tungsten, on the other hand, are hcp stabilizers and have the opposite effect.