Manganese is an effective element used for the modification of needle intermetallic phases in Al-Si alloy. These particles seriously degrade mechanical characteristics of the alloy and promote the formation of porosity. By adding manganese the particles are being excluded in more compact shape of “Chinese script” or skeletal form, which are less initiative to cracks as Al5FeSi phase. In the present article, AlSi7Mg0.3 aluminium foundry alloy with several manganese content were studied. The alloy was controlled pollution for achieve higher iron content (about 0.7 wt. % Fe). The manganese were added in amount of 0.2 wt. %, 0.6 wt. %, 1.0 wt. % and 1.4 wt. %. The influence of the alloying element on the process of crystallization of intermetallic phases were compared to microstructural observations. The results indicate that increasing manganese content (> 0.2 wt. % Mn) lead to increase the temperature of solidification iron rich phase (TAl5FeSi) and reduction this particles. The temperature of nucleation Al-Si eutectic increase with higher manganese content also. At adding 1.4 wt. % Mn grain refinement and skeleton particles were observed.
In Al-Si alloy the iron is the most common impurity and with presence of other elements in alloy creates the intermetallic compounds, which decreases mechanical properties and increases of porosity. The cause of the negative effect of intermetallic particles on the mechanical properties is that it is more easily break off the tension load as the aluminium matrix or small particles of silicon. By adding suitable alloying elements, also known as iron correctors, is possible to reduce this harmful effect. In the article is evaluated influence of manganese on microstructure with performed EDX analysis selected intermetallic phases and tensile test and measurement of length of Al5FeSi phase. For realization experiments was used AlSi7Mg0.3 alloy with increased iron content. Manganese was added in the amount 0.3 wt. %, 0.6 wt. %, 0.8 wt.% and 1,2 wt. %. From performed measurements it has been concluded, that increased amount of manganese, i.e. Mn/Fe ratio, does not have significant influence on mechanical properties AlSi7Mg0.3 alloy in the melted state.