refractory metals

Refractory metals, those with high melting points, include titanium, vanadium, chromium, zirconium, niobium, molybdenum, hafnium, tantalum, tungsten, and rhenium. Of these, the group 4 metals titanium, zirconium, and hafnium, together with group 7’s rhenium, exhibit a hexagonal close-packed crystalline structure, whereas the structure of the remaining six—members of groups 5 or 6—is body centered cubic.