Magnesium is slowly gaining importance as a die casting† metal. Its low specific gravity compared to its strength has led to an increase in its popularity. It is commonly alloyed with aluminum, zinc and manganese. The aluminum-zinc family of alloys is the most widely used, while the aluminum-manganese alloys are used where good elongation, toughness and impact resistance are desired, although this does come at the expense of castability and strength. The aluminum zinc alloys have a melting range of 470 to 610°C (880 to 1130°F) while the aluminum manganese alloys tend to be somewhat higher ranging from 540 to 640°C (1000 to 1180°F). Most magnesium alloys have poor creep† resistance, which makes them unsuitable for parts that operate in a high temperature environment. A variety of new alloys have been developed to address this weakness. Most of them involve the incorporation of alkaline-earth or rare-earth metals into the alloy. Unfortunately, this tends to adversely affect the castability of these alloys, placing more strains on die lubrication.
Unlike the aluminum alloys, the main problems with die casting magnesium alloys are not related to solder. Since magnesium alloys solidify much more rapidly, proper filling of the die cavity† and prevention of cold flow defects are the primary concern of the die caster. Typically magnesium alloys are cast at much higher gate† velocities than aluminum alloys. Since it is not as aggressive towards steel as molten aluminum, it may be cast in hot chamber and cold chamber machines. Most magnesium alloys contain significant amounts of aluminum.
Magnesium is gaining popularity in a number of consumer electronic parts like laptop computer cases, GPS unit cases and cases for mobile phones.