Magnesium alloys are the lightest, widely used structural material. They are often used in aeronautical and automotive industries, where the weight savings are essential. Magnesium alloys present acceptable mechanical properties but their high temperature properties are unsatisfactory. This led to development of magnesium alloys with rare earth elements addition. To achieve good mechanical properties these alloys are modified with zirconium. Modification affects positively also corrosion resistance of Mg-RE alloys. It is important to study impact of modifier amount on the structure and properties of these alloys. Unmodified and modified alloys were investigated. Three variants of modification were: modification according to Magnesium-Elektron specification, 50% and 100% more modifier. Mechanical and structural properties were investigated. Fractures were observed on scanning electron microscope. Results showed that grain refinement and yield strength increase with increasing amount of modifier. Impact of modification on tensile strength is unclear, probably because of non-metallic inclusions in the material’s structure. The inclusions sources are oxygenated nappe of liquid metal and fluxes, used during smelting.

Magnesium alloys are one of the lightest structural metallic materials. Their specific strength and stiffness is comparable to this, characterizing aluminum alloys and even some groups of steel and titanium alloys. Their main disadvantage is low maximum working temperature (about 120°C for Mg-Al-Zn alloys). This led to development of Mg-RE-Zr alloys, which can work up to 250°C. The paper presents results of the investigations of influence of subsequent melting operations on the Elektron 21 and WE43 magnesium alloys. Elektron 21 alloy had been prepared from the pure ingots, while WE43 alloy from the scrap material. Average area of the grain flat section and eutectics volume fraction had been evaluated quantitatively. The results of the evaluation have been verified by means of Mann-Whitney U-Test and Kolmogorov-Smirnov statistical tests. The liquid metal treatment led to refinement of the grain only in Elektron 21 alloy (from Ᾱ=3559μm2 to Ᾱ=1849 μm2). Multiple modification of the WE43 alloy does not lead to further decrease of the average area of grain flat section (from Ᾱ=1638μm2 to Ᾱ=1871 μm2).