Fabrication of Mg-Al alloy foam with close-cell structure by powder metallurgy approach and its mechanical properties

• A powder metallurgy approach was developed to fabricate the close-cell Mg-Al alloy foams with good pore structure.
• The key point of successful foaming is Al addition and a proper sintering treatment, which lead to intermetallics formation in the precursor.
• The intermetallics in the cell walls make the Mg alloy brittle, and the less Al addition, the higher yield strength of the Mg alloy foams.
• Compared with the Al based foams, the Mg8Al2 alloy foams exhibit excellent strength with reduced weight and particularly possess the superior specific strength.

A powder metallurgy (PM) approach was developed to fabricate Mg-(15–50)at.% Al foams with closed-cells, where CaCO3 is selected as the blowing agent. The key point of successful foaming is Al addition and the proper sintering treatment, which lead to the formation of intermetallic compounds and can make the gas release reaction between Mg melt and CaCO3 happen during the foaming process. Besides, the high precursor compact degree, proper foaming temperature (∼620 °C) and foaming time (∼150 s) are required to fabricate Mg-Al alloy foam with good cellular structure. The compressive stress–strain curves of Mg-Al alloy foams are serrated during the plateau region due to the intermetallics in the cell walls, and the less Al addition, the less intermetallics formed in the cell walls, the higher yield strength of the Mg-Al alloy foams.