Strength contributions from precipitates

A theory for the strength contribution from precipitates is developed based on the statistical particle-size and shape distributions and the corresponding obstacle strengths. The generic case of spherical precipitates and the special case of needle-shaped precipitates in the 6xxx aluminium alloy series are considered. It is accounted for that the largest precipitates are stronger and at the same time, intersect a larger number of slip planes than the smaller ones. For a considered peak aged AA6082, the improved model gives a 59% higher strength, which fits the experiments well without the need of previously introduced calibration parameter for the mean effective particle spacing in the slip plane.