[InFlight]

One of the reasons magnesium (and it's alloys) isn't used much is because it corrodes at a very high rate in comparison to aluminum.

In terms of strength to weight ratio, both Titanium and Alluminum are ahead of Magnesium.

Magnesium prices tend to be volatile, cost is typically quite a bit more than Alluminum but less than Titanium. Magnesium tends to be used for castings and occasionally forgings;, but not normally drawn bar/sheet or extrusion stock.