Structure And Texture Development And Dynamic Anistropy Of AZ31 Alloy Processed By ECAP

In the present study, AZ31 magnesium was extruded by equal channel angular pressing (ECAP) for different passes at different temperatures, and then annealed at 450℃for 30 minutes. The developments of textures and microstructures in the alloy were investigated. The effect of recrystallization textures on the dynamic properties was also investigated through anisotropy analysis.The results indicated that while extruded at 180℃~350℃, the initial large grains in the alloy are obviously refined. The lower the extrusion temperature, the more effective the refinement was. When it is extruded from 1 to 12 passes at 440℃, as the extrusion pass increases, the initial large grains are fragmented and refined. Simultaneously some dynamic recrystallization grains were formed on the boundaries of fragments in the initial large grains. After 12 passes extrusion, the initial large grains were basically refined, however there were still some fragmented large grains existed in the microstructures. All the initial large grains in microstructures were disappeared after annealed at 450℃and 30minites because of the recrystallization. The mechanism of the large grain refinement was investigated in the paper based on the orientation analysis.The texture analysis indicates that: with the passes increasing, the intensities of {0002} texture component increase from 1 to 8. But the intensity of {0002} texture component for 12 passes was weaker than that of 8. The mainly reason was that the orientation of fragments came from the large grains formed by extrusion rotated to the extrusion direction(ED), and the orientation of new dynamic recrystallization grains formed in the boundary of the fragmented grains inherited the orientation of the initial large grains. There was a mainly {0002}<11-20> texture component in the samples after 8 passes extrusion, eg. {0002} planes of the grains were paralleled to the extrusion plane, and <11-20> direction paralleled to the extrusion direction. However, the intensity of {0002}<11-20> texture of all the samples was decreased after annealed at 450℃and 30minites, and their orientations distribution became more scatter. The impacting compress results indicated that: there was obvious anisotropy for the sample which cut in different directions under 0.5MPa and 0.2MPa pressure, eg. the strain rate which impact loading was paralleled to ED was lower than that of paralleled to the transverse direction(TD).The results showed that the grain size was refined by route A during ECAP with the 120°of cross angular. However, this refining is not very obvious, and the mainly reason is the change of the orientation of the large grain. With the extrusion passes increasing, the tendency that formed {0002}<11-20>texture component was enhanced during ECAP, and there was little other texture component in the samples after 12 passes extrusion. Although, the grain size became larger and its texture distribution became more scatter after annealed, they still influenced the anisotropy of AZ31 alloy notably under the impact compress.