Simplified method of porosity prediction in directionally solidified Al–4·5 wt-%Cualloy

An experiment was carried out to verify a simplified theory of porosity formation during the unidirectional solidification of Al–4·5 wt-%Cu alloy in cylindrical moulds 1·5 and 2·4 cm in diameter. For specimens 1·5 cm in diameter, a higher thermal gradient G and a lower solidus velocity V_s at low drawing speeds are measured compared with the specimens 2·4 cm in diameter, while this difference tends to be reversed at high drawing speeds. The experimental results also conjirm the roles of interdendritic fluid flow and surface tension effects in the formation of porosity. The porosity content tends to increase with increasing local solidification time or a decrease in G^0·4/V_s^1·6when this parameter is less than about 1·0 K^0·4min^1·6cm⁻².

MST/3122