Abstract:Effect of Na₂B₄O₇, a new iron reduction agent, on iron reduction in magnesium alloys AZ31 and AZ91 was studied. The iron contents in the magnesium alloy AZ31 and AZ91 reduce dramatically to less than 0.002% (mass fraction) with the increasing addition of Na₂B₄O₇, and the corrosion resistance of the alloys was greatly improved. According to the thermodynamic analysis and the iron and boron distributions in different parts of the alloy melts, it can be inferred that the mechanism for iron reduction in magnesium alloys by Na₂B₄O₇ processing is that boron atoms combine with iron atoms and settle down in the melting sludge. The XRD result confirms it.

Key words: Na₂B₄O₇; iron reduction; corrosion resistance; AZ31 magnesium alloy; AZ91 magnesium alloy