EFFECTS OF COOLING RATE ON LATENT-HEAT RELEASED MODE OF NEAR PURE ALUMINUM AND ALUMINUM-SILICON ALLOYS

The information concerning solid fraction with respect to temperature in the mushy range is very important to solidification models which em ploy the effective specific heat method. The computer aided cooling cu rve analysis (CA-CCA) method is used in this study to measure the rela tionships between solid fraction (f(s)) and temperature/time for alumi nium alloys of different composition for various cooling rates. The pr esent study examined near pure aluminium, A356.2, A390, and A413 (near eutectic) alloys. The results of the measurements and analyses show t hat a rather large temperature range is observed near the end of solid ification for both near pure aluminium and A413 alloys. This mushy ran ge becomes longer as cooling rate increases. For the A356.2 and A390 a lloys, the solidus temperature, liquidus temperature, eutectic tempera ture, and maximum solid fraction at the eutectic temperature decrease as cooling rate increases. This is not true, however, for cooling rate s higher than 9.5 K s(-1). It is also known that a functional relation ship of f(s) with temperature is very convenient when it is applied to a solidification model. Two non-linearity factors n(e) and n(p) are r equired to define the function; n(e) and n(p) are found to increase as cooling rate increases. The relationship between n(e) and n(p) and co oling rate can also be obtained. A reasonable estimation of the solid fraction data for the cooling rate not measured can then be made. (C) 1996 The Institute of Materials.