THE EFFECT OF HEAT TREATMENT ON MECHANICAL PROPERTIES OF SQUEEZE CASTINGS FROM AISi7Mg ALLOYS

The characteristics of cast aluminum alloys are shown in the paper with particular emphasis put on AISi(7)Mg alloy and method of silumin modification. Heat treatments have been described to enhance the mechanical properties of cast aluminum alloy. The work presents the melting process, modification and casting of the AISi7Mg alloy by gravity method and squeeze casting. The paper describes the influence of solution heat treatment and ageing treatment to mechanical properties of AK7 silumin. Based on the research, it has been found that squeeze casting ensures the production of high-quality AISi(7)Mg casting alloy. Modification with strontium improves the strength properties and significantly increases the elongation of gravity castings - the relative increase of A(5) in these castings has reached about 40 %. In all tested castings the treatments of solution heat and ageing have increased the strength of the material by 33-40 MPa. A combination of modification, heat treatment and squeeze casting allows to manufacture of AISi(7)Mg alloy with high mechanical properties, R-m = 280 MPa, R-p0.2 = 190 MPa, A(5) = 16 %.