To the main advantages of magnesium alloys belongs their low density, and just because of such property the alloys are used in aviation and rocket structures, and in all other applications, where mass of products have significant importance for conditions of their operation. To additional advantages of the magnesium alloys belongs good corrosion resistance, par with or even surpassing aluminum alloys. Magnesium is the lightest of all the engineering metals, having a density of 1.74 g/cm 3 . It is 35% lighter than aluminum (2.7 g/cm 3 ) and over four times lighter than steel (7.86 g/cm 3 ). The Mg-Li alloys belong to a light-weight metallic structural materials having mass density of 1.35-1.65 g/cm 3 , what means they are two times lighter than aluminum alloys. Such value of mass density means that density of these alloys is comparable with density of plastics used as structural materials, and therefore Mg-Li alloys belong to the lightest of all metal alloys. In the present paper are discussed melting and crystallization processes of ultra-light weight MgLi12,5 alloys recorded with use of ATND methods. Investigated magnesium alloy was produced in Krakow Foundry Research Institute on experimental stand to melting and casting of ultra-light weight alloys. Obtained test results in form of recorded curves from ATND methods have enabled determination of characteristic temperatures of phase transitions of the investigated alloy.

The paper presents test results concerning an effect of the heat treatment on microstructure and mechanical properties of eutectic EN AC-AlSi12CuNiMg (EN AC-48000) alloy according to the EN 1706:2010 (tensile strength -R m , hardness -HB 10/1000/30) modified with strontium. Solution heat treatment and ageing treatment temperature ranges were selected on base of heating (melting) curves recorded with use of the ATD method. Temperatures of the solution heat treatment were 500, 520, and 535• C ±5 • C, while the solution time ranged from 0.5 to 3 h (0.5; 1.5 and 3 h). Temperature of the solution heat treatment amounted to 180, 235 and 310• C, while the ageing time ranged from 2 to 8 h (2, 5 and 8 h). Obtained results have enabled determination of optimal parameters of the T6 heat treatment in aspect of improvement of tensile strength R m and hardness HB of the alloy, with reduced time of individual treatments and determination of mathematical relationships enabling prediction of these mechanical properties.Keywords: aluminum alloys, heat treatment, mechanical properties W pracy przedstawiono wyniki badań dotyczące wpływu obróbki cieplnej na właściwości mechaniczne (wytrzymałość na rozciąganie -R m , twardość -HB 10/1000/30) i mikrostrukturę eutektycznego stopu EN AC-AlSi12CuNiMg (EN AC-48000) zgodnie z PN-EN 1706:2011 modyfikowanego strontem. Zakresy temperatur zabiegów przesycania i starzenia zostały dobrane w oparciu o krzywe nagrzewania (topienia) zarejestrowane metodą ATD. Temperatury przesycania wynosiły 500, 520 i 535• C ± 5• C, a czas przesycania mieścił się w zakresie od 0.5 do 3 godzin (0.5; 1.5 i 3 h). Temperatura starzenia wynosiła 180, 235 i 310• C. Czas przesycania mieścił się w zakresie od 2 do 8 godzin (2, 5 i 8 h). Uzyskane wyniki pozwoliły na określenie optymalnych parametrów obróbki cieplnej T6 w aspekcie poprawy wytrzymałości na rozciąganie R m i twardości HB stopu, przy ograniczeniu czasu poszczególnych zabiegów oraz wyznaczenie zależności matematycznych umożliwiających predykcje tych właściwości mechanicznych.

Very well-known advantages of aluminum alloys, such as low mass, good mechanical properties, corrosion resistance, machining-ability, high recycling potential and low cost are considered as a driving force for their development, i.e. implementation in new applications as early as in stage of structural design, as well as in development of new technological solutions. Mechanical and technological properties of the castings made from the 3xx.x group of alloys depend mainly on correctly performed processes of melting and casting, design of a mould and cast element, and a possible heat treatment. The subject-matter of this paper is elaboration of a diagrams and dependencies between parameters of dispersion hardening (temperatures and times of solutioning and ageing treatments) and mechanical properties obtained after heat treatment of the 356.0 (EN AC AlSi7Mg) alloy, enabling full control of dispersion hardening process to programming and obtaining a certain technological quality of the alloy in terms of its mechanical properties after performed heat treatments. Obtained results of the investigations have enabled obtainment of a dependencies depicting effect of parameters of the solutioning and ageing treatments on the mechanical properties (R m , A 5 and KC impact strength) of the investigated alloy. Spatial diagrams elaborated on the basis of these dependencies enable us to determine tendencies of changes of the mechanical properties of the 356.0 alloy in complete analyzed range of temperature and duration of the solutioning and ageing operations.

Heat Treatment of AlZn10Si7MgCu Alloy and its Effect on Change of Mechanical Properties The most important parameters which predetermine mechanical properties of a material in aspects of suitability for castings to machinery components are: tensile strength (Rm), elongation (A5, hardness (HB) and impact strength (KCV). Heat treatment of aluminum alloys is performed to increase mechanical properties of the alloys mainly. The paper comprises a testing work concerning effect of heat treatment process consisting of solution heat treatment and natural ageing on mechanical properties and structure of AlZn10Si7MgCu alloy moulded in metal moulds. Investigated alloy was melted in an electric resistance furnace. Run of crystallization was presented with use of thermal-derivative method (ATD). This method was also implemented to determination of heat treatment temperature ranges of the alloy. Performed investigations have enabled determination of heat treatment parameters' range, which conditions suitable mechanical properties of the investigated alloy. Further investigations will be connected with determination of optimal parameters of T6 heat treatment of the investigated alloy and their effect on change of structure and mechanical/technological properties of the investigated alloy.

Mechanical and technological properties of castings made from 3xx.x alloys depend mainly on properly performed process of melting and casting, structure of a casting and mould, as well as possible heat treatment. Precipitation processes occurring during the heat treatment of the silumins containing additives of Cu and/or Mg have effect on improvement of mechanical properties of the material, while choice of parameters of solutioning and ageing treatments belongs to objectives of research work performed by a number of authors. Shortened heat treatment, which is presented in the paper assures suitable mechanical properties (Rm), and simultaneously doesn’t cause any increase of production costs of a given component due to long lasting operations of the solutioning and ageing. Results of the research concern effects of the solutioning and ageing parameters on the Rm tensile strength presented in form of the second degree polynomial and illustrated in spatial diagrams. Performed shortened heat treatment results in considerable increase of the Rm tensile strength of the 320.0 alloy as early as after 1 hour of the solutioning and 2 hours of the ageing performed in suitable.