Aluminum’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.
Zirconium 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.
Aluminium Vanadium is used in the manufacture of various alloys. Vanadium enhances strength, raises the recrystallization temperature and reduces the thermal expansion co-efficient.
Aluminum beryllium master alloys can be introduced into aluminum magnesium melts to reduce magnesium losses. Small beryllium additions to the melt also result in improved surface quality of DC billet, and impart improved mechanical properties for premium quality aluminum castings.
The electrical and thermal conductivity of aluminum can be improved by the addition of trace amounts of boron to eliminate the undesirable effects of chromium, titanium, vanadium, and zirconium. Aluminum boron master alloys provide a convenient mechanism for making the desired boron addition. Boron has also been acknowledged as an effective grain refiner for silicon aluminum alloys.
AMG Aluminum has recently developed a proprietary method to manufacture conventional ingot metallurgy based aluminum scandium master alloys. These alloys are designed to support the development of new and emerging aerospace and high performance aluminum alloys containing the element scandium. Currently an Al-2% Sc product is available in standard waffle ingot form but the manufacturing process is sufficiently adaptable to meet the specific product requirements of the advanced aluminum alloy design community.
Modification of the silicon-aluminum phase from coarse platelets to a fine fibrous structure in hypoeutectic aluminum silicon alloy castings results in improved soundness and mechanical properties, particularly ductility. The use of strontium to “modify” the structure of hypoeutectic aluminum silicon casting alloys is an effective and widely accepted practice.