Aluminum alloys are used in almost all branches of industry because of their favorable ratio of mechanical, physico-chemical and technological properties. The mechanical properties of aluminum alloys are influenced by parameters such as size and shape of the grain, size and distribution of primary and secondary phases, distance between dendrite branches, and size and distribution of inclusions. By selection of adequate chemical compostion by the addition of major and minor alloying elements, elements influencing the development of microstructure, and present impurities, while metallurgical melt treatment by fluxing, grain refinement, degassing and modification provides effective solidification of eutectic (α-Al + β-Si) fibrous morphology. The aim of this paper is to determine the influence of retention time of the melt on the fading of the effect of the grain refining elements and modificators, and development of microstructure and mechanical properties of casting AlSi12 alloy for gravitational casting of tension clamps from the company Dalekovod d.o.o. Retention time of the melt has significant influence on the efficiency of metallurgical melt treatment, that is the impact of the grain refining elements and modificators. The research is based on the hypothesis that the retention time of the melt will influence the fading of the melt treatment, that is it will negatively affect the development of microstructure and mechanical properties.