Effects of cooling rate on latent heat released mode of near pure aluminium and aluminium–silicon alloys

Abstract

The information concerning solid fraction with respect to temperature in the mushy range is very important to solidification models which employ the effective specific heat method. The computer aided cooling curve analysis (CA–CCA) method is used in this study to measure the relationships between solid fraction (fs) and temperature/time for aluminium alloys of different composition for various cooling rates. The present study examined near pure aluminium, A356.2, A390, and A413 (near eutectic) alloys. The results of the measurements and analyses show that a rather large temperature range is observed near the end of solidification for both near pure aluminium and A413 alloys. This mushy range becomes longer as cooling rate increases. For the A356.2 and A390 alloys, the solidus temperature, liquidus temperature, eutectic temperature, and maximum solid fraction at the eutectic temperature decrease as cooling rate increases. This is not true, however, for cooling rates higher than 9·5 K S−1. It is also known that afunctional relationship of fs with temperature is very convenient when it is applied to a solidification model. Two non-linearity factors ne and np are required to define the function; ne and np are found to increase as cooling rate increases. The relationship between ne and np and cooling rate can also be obtained. A reasonable estimation of the solid fraction datafor the cooling rate not measured can then be made.MST/3262