10. What does a “face centered cubic” (fcc) atom arrangement look like? How many atoms?

A face centered cubic arrangement of atoms (austenitic) looks like a Las Vegas die with a five showing on all six faces. This can’t be seen visually by any type of microscope.

The number of atoms in any one cubic cell would be 14 – these do not stand alone but are attached to other cells which share some of the atoms.

11. How does a “body center cubic” (bcc) atom look? How many atoms?

The body center cubic structure would look like a die with a four on all faces and one atom in the center of the cube. The atomic arrangment of pure iron is bcc at room temperature and does not change until the temperature reaches 1674˚F. At this temperature it changes to austenite which is face center cubic (fcc). The addition of carbon to the iron lowers this transition temperature. This is the basis for heat treatment of steel. If the iron carbon alloy (steel) is quenched from the fcc field, the structure becomes martensite, a very hard strong condition.

12. What does a “stainless steel” atom arrangement look like? How many atoms?

A face centered cubic arrangement of atoms Stainless Steel 300 series is not heat-treatable. But heavy reduction (power dumping), in the cross section, during forging causes a dramatic increase in strength. This is the process ARP uses to make 304 Stainless Steel reach 170,000 psi UTS.

13. How do the space lattice or crystal structures appear?

All grains or crystals are composed of atoms bound together in a definite pattern. These structures are called space lattice or crystal structures. At a fixed temperature, the atoms in an array are spaced a definite distance from one another, although they vibrate about their mean position. Even though atoms are actually not held together in this manner, it is helpful to picture the crystals as a 3-dimensional latticework connected by imaginary lines. Metallurgists who primarily study ferrous metal are interested in only two basic crystal structures: bcc (body-centered cubic) and fcc (face-centered cubic).