Quick Facts/or Benefits

Magnesium has the following properties and/or benefits:

• Magnesium's density is .066 lb/in³, compared with aluminum which is .99 lb/in³

• Exceptional dimensional stability is one of the outstanding characteristics of magnesium.  No annealing or stress relieving treatment are necessary.

• Magnesium has excellent damping capacity.

• Magnesium provides a good combination of impact strength and dent resistance, due to the elastic energy absorption characteristics of the material

• Magnesium has a low galling tendency.

• Magnesium alloys have very good fatigue limit at long life.

• Magnesium has high thermal conductivity, permitting rapid heat dissipation.

• Magnesium is non-magnetic and non-toxic.

• Molten magnesium does not react with die steels, providing for longer life of tooling.  Die life may last as much as two or three times longer than aluminum cast/molded parts.

• Compared with many other alloys, magnesium is among the easiest materials to machine..

Magnesium Alloy Characteristics

The most widely used general purpose alloy is AZ91D.  It possesses a good combination of mechanical and physical properties and is usually the first choice among specifiers.  This alloy can be die cast by both hot and cold chamber processes, as well as the thixomolding process.  When an application requires additional ductility and toughness, such as automotive steering wheel armatures, then an alloy with higher as-cast ductility may be specified.  AM50A and AM60B are typical of this class of alloys.  They have tensile and yield strengths slightly less than AZ91D but higher elongation. 

There are those applications which expose the die casting to higher temperature and, in many cases, continuous stress leading to concerns about long term deformation and creep.  Under these circumstances, AZ91D, AM50A, and AM60B may not have sufficient high temperature or creep strength.  These instances often require an alloy such as AS41B, which like AM50A and AM60B, and AS41B can be hot chamber die cast, but increased maintenance costs can be anticipated as a result of higher casting temperatures causing shorter life of goosenecks, plunger rings, etc.  The commercialization of AE42X1 (a rare earth containing alloy) offers additional high temperature capabilities when required.

Source:  International Magnesium Association "The Essentials of Magnesium Die Casting".