THE EFFECT OF GROWTH-RATE ON STRUCTURE AND PROPERTIES OF AGE-HARDENED AL-SI ALLOY

Microstructure and mechanical properties as a function of growth rate of age-hardened Al-9.5Si-0.18Mn-0.19Mg-0.54Fe (wt.%) silumin have been studied. The relation between primary dendrite spacing lambda1 and growth rate R in the range of growth rate 2.78 up to 97.2 mum/s was established. Modified Hall-Petch relation was successfully used for expression of dependence between ultimate tensile stress and primary dendrite spacing. Linear dependence between ultimate tensile stress and growth rate was observed. The different growth rate has a small effect on yield stress and macrohardness but some effect was found at the relatively higher growth rate.