Stamping Magnesium: Why It Wants Heat and How AZ31B Differs From the Cast Alloys

Magnesium generally requires heat to form. Its hexagonal close-packed crystal structure has few active slip systems at room temperature, giving it very poor cold formability, low elongation and a strong tendency to crack at bends, so cold stamping is limited to the gentlest shapes and is usually impractical for real parts. Warmed to roughly 200-300°C, additional slip systems activate and magnesium becomes genuinely ductile, forming bends and shallow draws comparable to aluminum. For that reason magnesium stamping is almost always warm stamping, using heated blanks and heated dies with temperature as a controlled process parameter. This adds equipment, cycle time, and cost relative to cold stamping of aluminum or steel. If a buyer expects to cold-stamp magnesium like aluminum, the part will crack; the right plan is warm forming of AZ31B sheet, and accepting the heated-tooling cost that comes with it.

AZ31B is the magnesium alloy used for stamping. It is the dominant wrought sheet and plate alloy, it warm-forms well, and it is the standard choice for lightweight stamped panels, brackets, and covers in aerospace and electronics where reducing mass matters. The other commonly named magnesium alloys are not stamping materials. AZ91D is primarily a die-casting alloy; its high aluminum content makes it excellent for casting but it is not a standard wrought sheet product, so AZ91D parts are die cast, not stamped. WE43 is a specialized rare-earth alloy used for high-temperature aerospace and for bioabsorbable medical implants; although wrought forms exist, it is expensive and most WE43 parts are cast, extruded, or machined. So the practical answer is to design any stamped magnesium part in AZ31B sheet, and recognize that AZ91D belongs to die casting and WE43 to specialty casting, extrusion, or machining processes.

Bulk magnesium sheet does not readily ignite during stamping, but the fire risk is real once you generate fine particles. Grinding, deburring, sawing, or machining magnesium produces fine swarf and dust that is genuinely flammable and, if ignited, burns intensely and reacts violently with water. Shops that run magnesium use dedicated dust collection, keep magnesium fines isolated and clean, prohibit water-based extinguishing on magnesium fires, and stock Class D dry-powder extinguishing media specifically for metal fires. Warm forming itself adds heat to the process, so housekeeping and temperature control matter. Not every stamping shop is equipped or trained for magnesium, so it is important to confirm the supplier has the proper fire-safety protocols and equipment before placing magnesium work. The hazard is manageable with the right controls, and experienced magnesium shops handle it routinely, but it is a real consideration that distinguishes magnesium from aluminum and steel.

Stamped magnesium almost always needs a protective finish because magnesium is chemically active and corrodes readily, and it is galvanically very anodic, meaning it corrodes quickly when in electrical contact with more noble metals like steel or aluminum fasteners. The common protective treatments are chromate conversion coating, anodizing (including proprietary processes such as the well-known magnesium anodize systems), and organic finishes like powder coat or primer-plus-topcoat, often layered for durability. Just as important as the coating is galvanic isolation: designers must specify isolating washers, coatings, or compatible fasteners wherever magnesium contacts dissimilar metals, because an unprotected galvanic couple in a humid or salt environment will corrode the magnesium aggressively. Edges and any post-finish machining or drilling expose bare metal and need touch-up. In short, bare magnesium should never go into service, and the corrosion-protection scheme, coating plus galvanic isolation, has to be designed in from the start rather than added as an afterthought.