In this paper is presented the structure and proprieties of the cast magnesium alloys as
cast state and after heat treatment cooled with different cooling rate, depending on the cooling
medium (furnace, water, air). For investigations samples in shape of 250x150x25 mm plates were
used. The presented results concern X-ray qualitative and quantitative microanalysis as well as
qualitative and quantitative X-ray diffraction method, tensile tests, hardness measurement. In the
analysed alloys a structure of α %solid solution and fragile phase β (Mg17Al12) occurred mainly on
grain borders as well as eutectic and phase AlMnFe, Mg2Si. Investigation are carried out for the
reason of chemical composition influence and precipitation processes influence to the structure and
mechanical properties of the magnesium cast alloys with different chemical composition in as cast
alloys and after heat treatment.