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Die cast Mg-Al alloys in the AM, AS, AZ and AE series have been corrosion tested by salt spray and immersion in 5% NaCl solution. The corrosion rate increases rapidly when the Al-content decreases below about 4% for all alloy systems. AE alloys exhibit a high resistance to localized attack because the Al-rich coring along grain boundaries appears to act as an efficient barrier against pit propagation in these alloys. The role played by different intermetallic phases found in the Mg-Al alloy systems is evaluated, based on electrochemical data obtained from synthetically prepared phases. Fe-rich phases are particularly detrimental, but Al-Mn phases with a low Al/Mn ratio may also have a high cathodic current output. The phases Mg2Si and Al4MM (MM = Misch Metal) appear to be harmless from a corrosion point of view.

Dry machining of five commercial magnesium alloys with aluminium content in the range 2-9 % has been investigated by turning tests. At high cutting speeds, workpiece material may build up on the flank sides of carbide tools (FBU). The critical speed for FBU formation is dependent on the presence of β-phase (Mg17Al12). The amount of β-phase increases with increasing aluminium content, and depends on the temper condition of the alloy. The formation of FBU can be eliminated by the use of a suitable cutting fluid or a PCD tool.