A Multiscale Physics-Based Framework for Dislocation Pinning by Nanoscale Precipitates in Aluminum Alloys Linking Particle Statistics, Thermally Activated Bypass, and Yield Strength

AbstractNanoscale precipitates strengthen aluminum alloys by impeding dislocation motion. Depending on precipitate size, chemistry, coherency, morphology, and spatial distribution, a dislocation may shear a precipitate, bypass it through Orowanlooping, or undergo a thermally activated transition between competing pathways.Classical strengthening equations capture important trends, but their direct usecan be inaccurate when precipitate distributions are heterogeneous, particles areanisotropic, or nanoscale dislocation-core effects are significant.This paper develops a testable, multiscale framework for estimating the precipitationrelated increment in yield strength. The framework combines a distribution-sensitive obstacle-spacing description, competing precipitate-shearing and bypass stresses,a thermally activated effective-obstacle relation, and a statistically defined onset criterion for macroscopic yielding. A proposed dimensionless pinning index is introduced to organize these effects. It is a modeling construct rather than an established universal law.The framework is intended to connect microscopy, atomistic calculations, discretedislocation dynamics, and tensile testing while accounting explicitly for uncertainty.It does not assume that one strengthening mechanism controls every alloy or agingcondition. No numerical yield-strength increment is claimed without alloy-specificmicrostructural measurements and mechanical testing.