Question

Speculate the differences in properties between an HCP and an FCC material.

Please indicate the physical, electrical, Chemical, Optical and mechanical properties that differentiate the two crystal structures.

Answer 1

HCP FCC

Atoms in unit cell 6 4

Coordination number 12 12

a/r ratio 2 2.82

Stacking sequence ABABAB ABCABCABC

Metal Mg,Zn,Co Al,Cu,Pb

Important point:

1. Ductility of FCC compound is high as compare to HCP. It means that HCP metal is more brittle as compare to FCC metal.

2. FCC component is more electro negative as compare to HCP.