Low Pressure Sand Casting of Ultrasonically Degassed Al7SiMg Alloy: Modeling and Experimental Validation of Mould Filling H. Puga 1* , J. Barbosa 1 , T. Azevedo 2 , S. Ribeiro 2 , J. L. Alves 1 1 Centre for Micro-Electro Mechanical Systems, Department of Mechanical Engineering, University of Minho, Campus of Azurém, 4800-058 Guimarães, Portugal 2 FEUP, Department of Metallurgical and Materials Engineering, 4200-465 Porto, Portugal *Corresponding author: H. Puga (PhD) – puga@dem.uminho.pt Tel: +351253510220; Fax: +351253516007 Abstract The effect of combining smooth mould cavity filling and ultrasonic degassing by using a low pressure sand casting process with US melt treatment on the microstructure and mechanical properties of A356 alloy was investigated. Computational fluid dynamics (CFD) modelling and experimental validation was used to study the liquid metal flow behaviour and oxide film defect distribution for different filling rates, using two pressurization curves (p-t). The effect of ultrasonic degassing on the resultant microstructure (morphology and presence of porosities and inclusions) was studied for 650 and 700ºC melt degassing temperatures. Results show that ultrasonic degassing and mould filling velocities below 0.5 m/s improve the alloy microstructure and lead to high mechanical properties. Keywords Simulation, Ultrasonic degassing, Low Pressure Sand Casting, Mechanical properties, Oxides 1. Introduction Low Pressure Die Casting (LPDC) is a consolidated process that has been widely applied in the foundry industry for producing light alloy castings which request high mechanical performance. The process presents some advantages, such as smooth mold filling and feeding capacity [1]. Although die casting is very competitive for manufacturing aluminium alloy components [2], the