4. Relaxation and stabilization treatments

4.1 Casting alloys

A number of parts have dimensional characteristics that are difficult to obtain directly by molding. They require subsequent machining operations, sometimes very extensive, to achieve the required dimensions. Others must not deform in service. Finally, welded parts may be subject to stress corrosion.

Shrinkage counteracted by the mold during solidification, different quenching speeds in different zones of the parts, machining operations, etc., are all sources of residual stresses. Although these residual stresses are low in magnesium alloys, the low Young's modulus of magnesium alloys means that they generate significant deformations. It is therefore essential to carry out stress-relieving and stabilizing treatments, sometimes even repeated...