Porosity reduction and mechanical properties improvement in die cast engine blocks

This paper presents an experimental investigation into the reduction of porosity and improvement of mechanical properties of die cast engine blocks. The focus of this research was to seek improvement in mechanical properties of aluminum die cast engine blocks by a reduction in the secondary dendrite arm spacing, modification of the acicular Si microstructure in the eutectic phase and reduction of porosity. Introducing additional cooling in the thick sections of the casting resulted in reduction of secondary dendrite arm spacing and consequent improvement of mechanical properties. However the effect of increased cooling faded with increasing distance from the core. 3D porosity measurements using CT Scan showed significant reduction in porosity in sections incorporating a cooling core. Eutectic modification was achieved by modification with Sr. A target modification of 140 ppm led to significant improvements in elongation. (C) 2011 Elsevier B.V. All rights reserved.