Effects of Nd and rotary forging on mechanical properties of AZ71 Mg alloys
(1. Institute of Materials Science and Engineering, National Taipei University of Technology, Taipei 10608;
2. Foxconn Technology Group, New Taipei 23680)
2. Foxconn Technology Group, New Taipei 23680)
Abstract: 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.
Key words: AZ71 Mg alloys; Nd; rotary forging; mechanical properties; recrystallization