If single crystals of aluminum copper magnesium and zinc are

If single crystals of aluminum, copper, magnesium, and zinc are tensile tested and the resolved shear stress is plotted against the shear strain, the data would be expected to appear as shown below. Explain this dramatic difference in mechanical behavior.

Solution

Cu and Al atom crystal structures are face centered cubic whereas Mg and Zn crystal structures are hexagonal close packed so both structure would have different closed packed plane or slip plane.we know resolve shear stress property is nothing but applied stress on different possible slip system.will certainly depend upon crystal arrangement.Hence we can conclude resolve shear stress is material property highly depends upon crystallographic arrangements.