Valutazione comparativa dell'effetto di tre differenti tipologie di affinante sulle proprietà meccaniche e microstrutturali della lega di alluminio A356 da fonderia [A comparative evaluation of the effects of three different grain refiners on mechanical and microstructural properties of A356 foundry aluminium alloy]

This paper presents the preliminary results of an experimental investigation on the effects of three commercial titanium and boron based grain refiners on impact toughness and Brinell hardness of A356 foundry aluminium alloy. A commercial A356 aluminium alloy was used in this study. The molten alloy was modified using several bars of Al-10%Sr master alloy in order to reach 200 ppm of Sr, and then degassed for 10 min by means of argon inert gas. Then, the melt was stirred and grain refined in the holding oven by the addition of three commercial grain refiners in form of can, tab and granulated flux, which were named respectively A1, A2 and A3. After that, the alloys were poured into a steel mould, obtaining a number of 20 castings, n°5 for each experimental condition. HB hardness samples and Charpy impact specimens were subsequently drawn from the castings, and T6 heat treated. The impact tests were performed on a CEAST instrumented Charpy pendulum, specifically designed for testing lig...