HARDNESS AND MECHANICAL PROPERTY RELATIONSHIPS IN DIRECTIONALLY SOLIDIFIED ALUMINUM-SILICON EUTECTIC ALLOYS WITH DIFFERENT SILICON MORPHOLOGIES

Hardness and tensile property measurements made on directionally solidified Al-Si eutectic alloys show that definite but different hardness-growth velocity and hardness-silicon interparticle spacing relationships exist for alloys with different silicon eutectic phase morphologies. Tensile property measurements show that hardness and 0.2% proof stress follow silicon interparticle spacing relationships of the same form. It is suggested that hardness can only be used to measure proof stress when the eutectic structure displays a single silicon eutectic phase morphology.