COMMON LATTICE TYPES
Structure of Metals
Metals such as a-iron (Fe) (ferrite), chromium (Cr), vanadium (V), molybdenum (Mo), and
tungsten (W) possess BCC structures. These BCC metals have two properties in common, high
strength and low ductility (which permits permanent deformation). FCC metals such as g-iron
(Fe) (austenite), aluminum (Al), copper (Cu), lead (Pb), silver (Ag), gold (Au), nickel (Ni),
platinum (Pt), and thorium (Th) are, in general, of lower strength and higher ductility than BCC
metals. HCP structures are found in beryllium (Be), magnesium (Mg), zinc (Zn), cadmium (Cd),
cobalt (Co), thallium (Tl), and zirconium (Zr).
The important information in this chapter is summarized below.
A crystal structure consists of atoms arranged in a pattern that repeats periodically
in a three-dimensional geometric lattice.
Body-centered cubic structure is an arrangement of atoms in which the unit cell
consists of eight atoms at the corners of a cube and one atom at the body center
of the cube.
Face-centered cubic structure is an arrangement of atoms in which the unit cell
consists of eight atoms at the corners of a cube and one atom at the center of each
of the six faces of the cube.
Hexagonal close-packed structure is an arrangement of atoms in which the unit
cell consists of three layers of atoms. The top and bottom layers contain six atoms
at the corners of a hexagon and one atom at the center of each hexagon. The
middle layer contains three atoms nestled between the atoms of the top and bottom
Metals containing BCC structures include ferrite, chromium, vanadium,
molybdenum, and tungsten. These metals possess high strength and low ductility.
Metals containing FCC structures include austenite, aluminum, copper, lead, silver,
gold, nickel, platinum, and thorium. These metals possess low strength and high
Metals containing HCP structures include beryllium, magnesium, zinc, cadmium,
cobalt, thallium, and zirconium. HCP metals are not as ductile as FCC metals.