Manufacturing and research of complex Al-12Ti-8Zr master-alloy structure and efficiency

Abstract

The paper presents a method of obtaining and further study of a complex master-alloy, based on aluminum, which contains a total 20 %wt. of modifying components – titanium and zirconium. The master-alloy was obtained under the conditions of electron beam casting technology by gradual fusion of metal components and subsequent casting in the mold under vacuum conditions. The obtained master-alloy is characterized by an inhomogeneous coarse-grained structure. Intermetallic phases Al3(Ti, Zr) are characterized by a tetragonal structure of the crystal lattice and occupy 50 % vol. of the resulting master-alloy. In the composition of intermetallics, zirconium replaces about 25 % of titanium. Modification of AlSi5Cu4 alloy by the obtained master-alloy showed that the modifying phase Al3(Ti, Zr) is able to decompose and dissolve in melts of such alloys and per-forms its germinating and grain-refinement function. In this case, in the rapidly crystallized sample of the modified alloy, the solid solution based on aluminum contains only titanium and a small amount of copper, and in the crystallized – slowly con-tains both titanium and zirconium. The grain sizes of the primary solid solution based on aluminum in both samples can be estimated as the same. Titanium is also present in small amounts in iron-containing Al5SiFe needle-like phases. Zirconium is found mostly in eutectic zones, which contain both silicon and copper-enriched zones. Wider and uniform zones of eutectic are observed in the sample, crystallized with slow speed. It is determined that large particles of the modifying phase during the staying in a melt can be partially dissolved, giving part of the titanium and simultaneously react with silicon, forming more refractory intermetallic particles Al4(Ti, Zr)3Si5. The obtained data indicates the potential suitability and simultaneous need to grind the structure of such master alloys.