7. A certain aluminum alloy contains 5% volume fraction of equally spaced precipitates having an average diameter of 0.1 µm. If the Burger's vector for aluminum is 0.29 nm, and the shear modulus G = 27 GPa, calculate the tensile yield strength of this material.
Hints: neglect the intrinsic lattice resistance. To determine the precipitate spacing L, imagine the precipitates are arranged on a rectangular grid. The fraction of area occupied by the precipitates equals the volume fraction. How many precipitates are there per square unit cell? How big is the cell?