Abstract
The effect of growth rate on mechanical properties of Al-12.87Si-0.04Sr (wt.%) alloy was studied. This material was directionally solidified by Bridgman method at growth rate in the range from 3 to 1250 µm/s. It was revealed, that the growth rate has a strong effect on the interparticle spacing of silicon particles and hence on mechanical properties, as well. The higher growth rate, the smaller interparticle spacing and the higher values of ultimate tensile strength, yield strength, elongation to fracture, reductions of area, and hardness. The validity of modified Hall-Petch equation was confirmed for relations UTS, Y.S. and hardness versus growth rate and interparticle spacing for growth rate in the range from 3 to 100 µm/s. The strong dependence of yield strength on hardness in the range of the studied growth rate provides a possibility to predict the mechanical properties on the basis of the hardness results. The increase of elongation to fracture with increasing growth rate was proved by the fracture observation.

Key words
growth rate, mechanical properties, Al-based alloy, Bridgman method

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