Modifying Ability of an Al–Zr Master Alloy.

The possibility to apply an electrolytically produced master alloy for grain refinement and improvement of the properties of aluminum alloys is discussed. A commercial Al–Si–Fe alloy with addition of various amounts of an Al–Zr master alloy with 10 wt % zirconium is tested at 900°C. The influence of the zirconium content in the aluminum melt and the cooling rate on its structure and properties is analyzed. Structural analysis demonstrates that addition of 0.1 wt % zirconium decreases the average grain size by 4–5 times without variations in shape and structure. The hardness measurements of the produced alloy demonstrate that, upon addition of zirconium to high-purity aluminum, the hardness increases by 1.5 times at a zirconium content of 0.4 wt % or higher with an increase in the zirconium content. At the same time, a zirconium addition to an AK6 alloy does not influence the Brinell hardness, which is likely to be due to a more pronounced action of other alloying elements. The absence of intermetallic compounds in the produced alloy modified by an Al–Zr master alloy containing intermetallic inclusions up to 50 μm in size indicates that the initial Al–Zr master alloy can be cast into ingots and cooled under any conditions, excluding the remelting stage in a mixer and other types of treatment. [ABSTRACT FROM AUTHOR]