Hall-Petch relations and strengthening of Al-ZnO composites in view of grain size relative to interparticle spacing

Abstract We investigated the Hall-Petch relations in Al-ZnO composites with different matrix grain size ( D ) relative to interparticle spacing ( L ). For samples with D  >  L , it was found that grain refinement as described by Hall-Petch relation and particle strengthening by Orowan mechanism both significantly contribute to the strengthening of the composites. For samples with D  ≤  L , variation of microhardness with grain size was found to follow a good Hall-Petch relation with an enhanced Hall-Petch slope. Our study indicates the different coupling of strengthening mechanisms in metal matrix composites with different microstructure length scales.