钕与旋锻对AZ71镁合金力学性能的影响

摘要

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 brittleβ-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.%探讨钕的添加对AZ71镁合金的力学性能和塑性加工性能的影响。添加0.5%~2.0%的钕时，AZ71镁合金的晶粒尺寸和脆性β-Mg17Al12相的含量均随着钕添加量的增加而降低，并形成纳米级的AlxNdy析出相。经过32%旋锻和退火后，加钕AZ71镁合金的晶粒尺寸由350µm减小到30µm以下。当钕的添加量达到1%时，合金的强度与延性可同时获得提升；当钕的添加量超过1%时，组织中杆状Al11Nd3以及块状Al2Nd聚集析出，导致合金的强度与延性降低。因此，1.0%钕添加量为AZ71镁合金的最佳添加量，添加1.0%钕的AZ71镁合金可以获得253 MPa的抗拉强度和10.7%的伸长率，在铸态或经旋锻退火后均具有最高的韧性。