Hardeners

My Image 2Aluminum's mechanical and physical properties are enhanced with the use of alloying elements. These alloying elements are commonly referred to as hardeners. Aluminum-based master alloys which contain the hardener elements in high concentrations, provide a convenient and economical way to add them to aluminum to achieve desired properties. These master alloys readily go into solution at lower liquid aluminum temperatures, thus minimizing dross formation and solubility of hydrogen. Lower furnace temperatures also mean reduced energy consumption and longer furnace life. Hardeners are available in a number of alloys including Ca, Co, Cu, Cr, Mn, Mg, Ni, Si, Ti, V, Zr, Zr-V, and more. AMG Aluminum’s hardeners are available in a variety of concentrations depending on the alloy. Forms include waffle, slab, and ingot profiles.

Aluminum Zirconium

My Image 2Zirconium is added to certain aluminum-magnesium-zinc alloys such as 7050 which reduces stress corrosion susceptibility. Zirconium additions in the range 0.1 to 0.3% are used to form a fine precipitate of intermetallic particles that inhibit recovery and recrystallization. An increasing number of alloys, particularly in the aluminum-zinc-magnesium family, use zirconium additions to increase the recrystallization temperature and to control the grain structure in wrought products. Zirconium additions leave this family of alloys less quench sensitive than similar chromium additions. Higher levels of zirconium are employed in some superplastic alloys to retain the required fine substructure during elevated-temperature forming. Zirconium additions have been used to reduce the as-cast grain size, but its effect is less than that of titanium.

Magnesium Calcium

My Image 2The magnesium calcium alloy is primarily used in the removal of bismuth from lead for refinement purposes. The alkaline elements in the alloy react with the molten lead under controlled conditions. After treatment with magnesium calcium, the lead melt is cooled to the liquidus point which results in the alkaline–earth bismuth compounds to separate and float to the top of the melt where they are removed by skimming the melt.