The Study of Phase Transformations of AlSi9Cu3 Alloy by DSC Method

With the use of differential scanning calorimetry (DSC), the characteristic temperatures and enthalpy of phase transformations were defined for commercial AlSi9Cu3 cast alloy (EN AC-46000) that is being used for example for pressurized castings for automotive industry. During the heating with the speed of 10 degrees C.min(-1) two endothermic effects has been observed. The first appears at the temperature between 495 degrees C and 534 degrees C, and the other between 555 degrees C and 631 degrees C. With these reactions the phase transformation enthalpy comes up as +6 J g(-1) and + 327 J g(-1). During the cooling with the same speed, three endothermic reactions were observed at the temperatures between 584 degrees C and 471 degrees C. The total enthalpy of the transitions is -348 J g(-1). Complimentary to the calorimetric research, the structural tests (SEM and EDX) were conducted on light microscope Reichert and on scanning microscope Hitachi S-4200. As it comes out of that, there are dendrites in the structure of alpha(Al) solution, as well as the eutectic (beta) silicon crystals, and two types of eutectic mixture: double eutectic alpha(Al)+beta(Si) and compound eutectic alpha+Al2Cu+beta.