What are common slip systems in FCC metals?

• A. {111} planes with <110> directions
• B. {110} planes with <111> directions
• C. {100} planes with <010> directions
• D. {112} planes with <111> directions

Answer: (A)

In FCC metals, slip is easiest on planes and directions that are most densely packed, because atoms can rearrange with the least disruption. The closest-packed planes in the FCC lattice are the {111} planes, and within each of those planes the shortest lattice translations lie along the <110> directions. That combination provides the smallest Burgers vector and the highest planar shear components, so dislocations glide most readily along these paths. Hence the common slip systems in FCC metals are {111} planes with <110> directions. The other options involve planes or directions that are not the most densely packed or do not lie entirely within the plane, making slip far less favorable in practice.