Effects of Grain refinement on the Microstructure, Mechanical properties and Reliability of AlSi7Cu3Mg Gravity Die cast Cylinder heads

The effect of grain refinement on the microstructure and mechanical properties of a secondary AlSi7Cu3Mg gravity die cast cylinder head is reported. Metallographic and image analysis techniques have been used to quantitatively examine the macro- and microstructural changes occurring with the addition of grain-refining agent. The results indicate that the AlTi5B1 addition produces a fine and uniform grain structure throughout the casting and this effect is more pronounced in the slowly solidified regions. The initial contents of Ti and B, which are present as impurity elements in the supplied secondary alloy ingots, are not sufficient to produce an effective grain refinement. The combined addition of AlTi5B1 and Sr doesn’t produce any reciprocal interaction under the present casting conditions. Grain refinement improves the mechanical properties of as-cast AlSi7Cu3Mg alloy and increases the reliability of the castings, as evidenced by the Weibull analysis