Effects of Nd and rotary forging on mechanical properties of AZ71 Mg alloys

The effects of Nd addition on the mechanical properties and plastic deformability of AZ71 Mg alloys were investigated. 0.5%-2.0% (mass fraction) Nd was added to AZ71 Mg alloys. The grain size and the amount of brittle β;-Mg17Al12 phase reduce with increasing the Nd addition, while nanosized AlxNdy precipitates form. In combination with 32% rotary forging and subsequent annealing, the grain size of Nd-added AZ71 Mg alloys reduces greatly from over 350 μm to below 30 μm. Both tensile strength and ductility increase with the Nd addition up to 1.0%. The addition of Nd beyond 1.0% leads to the aggregations of rod-shaped Al11Nd3 and blocky Al2Nd precipitates, thereby deteriorating both strength and ductility. The 1.0% Nd-added AZ71 Mg alloy shows tensile strength up to 253 MPa and elongation of 10.7%. It is concluded that adding 1.0% Nd to AZ71 Mg alloy yields the optimum toughness, whether under as-cast or rotary forging and annealing conditions.