E Hall 1951-N Petch 1953 σ_y = σ_0 + k/√d grain-size strengthening; modern modern foundational text + nano-grain breakdown 2024 ML-prediction.
E Hall 1951-N Petch 1953 σ_y = σ_0 + k/√d grain-size strengthening; modern modern foundational text + nano-grain breakdown 2024 ML-prediction.