AZ80マグネシウム合金の室温多軸鍛造中の組織発達過程

抄録

Multi-directional Forging (MDF) method is one of the severe plastic deformation processes and can provide that stress-strain information during the manufacturing. Microstructural evolution and flow stress in AZ80 magnesium cast and extruded alloys during MDF at room temperature (RT-MDF) was investigated in this study. Maximum flow stress increased with increasing the number of MDF passes (in other word, cumulative strain) in both of cast and extruded AZ alloys. The maximum cumulative strain (∑Δε) of MDFed AZ80 alloy depends on strain increment (Δε), and ∑Δε increases with increasing Δε. Flow stress of extruded alloy during MDF is higher than that of extruded alloy in the early passes of RT-MDF since extruded alloy has lower initial grain size (about 30 μm) and strong texture. On the other hand, value of the maximum cumulative strain in AZ80 extruded alloy is almost the same as that in AZ80 cast alloy. The grain division was observed in MDFed specimen by the {101 2} twining. The distribution of twin boundaries is heterogeneously in cast AZ80 alloy and coarse “not-twinned” areas were observed in 19 passed MDFed specimens (∑Δε is 0.95). On the other hand, twinning occurs uniformly in AZ80 extruded alloy during MDF. The initial microstructures of AZ80 alloy affect the flow stress of initial MDF passes and distribution of twinning during RT-MDF.