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 10oCmin-1

two endothermic effects has been observed. The first appears at the temperature

between 495 oC and 534 oC, and the other between 555 oC and 631 oC. 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 oC and 471 oC. 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 α(Al) solution, as well as the eutectic

(β) silicon crystals, and two types of eutectic mixture: double eutectic α(Al)+β(Si) and compound eutectic α+Al2Cu+β.

The paper presents tribological properties of A390.0 (AlSi17Cu5Mg) alloy coupled in abrasive action with EN-GJL-350 grey cast-iron.

The silumin was prepared with the use of two different technologies which differed in terms of cooling speed. In the first case the alloy

was modified with foundry alloy CuP10 and cast to a standard tester ATD and in case of second option the modified alloy was cast into

steel casting die. Due to different speed of heat removal the silumins varied in structure, particularly with size of primary crystals of silicon

and their distribution in matrix which had a significant influence of friction coefficient in conditions of dry friction.