Microstructure and texture in an extruded Mg-Al-Ca-Mn flat-oval tube

In the present study, mechanical property, microstructure and texture of an extruded Mg-1.0Al-1.5Ca-1.0Mn (wt.%) flat-oval tube in both the flat and the oval regions were systematically studied. Our results show that there exists a great difference in microstructure and texture between the flat and the oval regions. Both the flat and the oval regions have fine DRXed grains of 3-4 µm, while more row stacked grains are observed in the flat region. A large number of fine particles with a size of about 0.5 µm are dispersed in both the grain boundary and grain interior. The particles exhibit a uniform distribution in the oval region, while they tend to aggregate into bands along the extrusion direction (ED) in the flat region. The texture in the oval region is similar to that in extruded Mg rods with a preferred distribution of prismatic planes and random distribution of (0002) poles around the ED, while that in the flat region is close to that in extruded sheets containing two texture components, <0002>//normal direction (ND) and <0002>//transverse direction (TD). A high fraction of <0002>//TD component, about 52-62%, is observed in the flat region. The flat region has a tensile yield strength of 254 MPa, an ultimate tensile strength of 290 MPa and an elongation to failure of 4.3%.