| Compared with the cast magnesium alloy, the wrought magnesium alloy has the better mechanical properties, which is useful to extend the application fields of magnesium alloy. However, the poor plasticity at room temperature and the higher preparation make its development restricted. In order to cut down the cost and improve the plasticity, the twin roll casting(TRC) was used to product the AM30+0.5%Y magnesium alloy sheet in this paper, and then proceeded by warm rolling and the annealing treatment. We made the compared experiment with ingot casting(IC) magnesium alloy which had the same composition to prove the superiority of the TRC magnesium alloy. Both of them were observed by metallographic microscope、electron microprobe、scanning electron microscope、X-ray diffraction and tensile experiment, which were analysed to understanding the evolution of the microstructure and the structural characteristics in warm rolled sheet and annealing shee、texture and mechanical properties. At last, the conclusions were as follow:(1) The TRC magnesium alloy that had a well-developed columnar dendrites in surface and equiaxed dendrites in the center region. Because of the fast solidification, the second phase, which were Mg24Y5and a small amount of Al12Mn, were finely dispersed in the interdendritic boundary, and the size was less than1μm. Traditional IC magnesium alloy, the grains were coarse and large (about150μm). the second phase which were Mg2Y and a small amount of Al17Mn12phase were distributed with the form of net in the grain boundary, and the particle size was about10μm.(2) The microstructure of the TRC and IC AM30+0.5%Y magnesium alloy sheet which were warm rolled at350℃were differences. The TRC sheet consisted of the deformation bands or shear bands which was made by the basal plane slipping and the non-basal plane slipping, and there was few twins, and the grain of dynamic recrystallization was small relatively. On the other hand, it could be observed some quantities of twins and after the warm rollina. there were all of dvnamic recrvstallization grains in the IC sheet. (3) The TRC and IC samples, which were the final-step warm rolled sheets, were annealed at350℃for1hour, Static recrystallization process was happened in TRC sheet, and its grains were small (average size was10μm), the second phases (about1μm) dispersed in matrix completely; the grain growth was happened in IC sheet, the average grain size of which was about25μm, and the second phases that were chain structure penetrate through the intergrains and grain boundaries.(4) The texture analysis results which included this two original magnesium alloys sheets、hot rolling sheets、annealed sheets, were show that:a. the (0002) basal texture displayed very strong in original TRC sheet, at the same time, the texture intensity in columnar dendrites region was much higher than the center equiaxed dendrites. The texture strength in original IC sheet displayed very weak, and the orientation of grains presented free. b. After the first hot rolling,(0002) basal texture in IC strip intensified rapidly, but later it declined with the increased amount of rolling. However, the (0002) basal texture in TRC strip was declined after the first rolling, and then became weaker with the increased amount of rolling, c. After annealed, the intensity of (0002) basal texture in TRC sheet was much weaker than in IC sheet, and the (0002) basal texture was some degree of deflection and diffusion.(5) The results of tensile test showed that:The intension of TRC sheet and IC sheet was almost the same(σs are about227MPa、221MPa respectively). However, the plasticity of TRC sheet (elongation was17.7%. and reduction of area was27.5%) was much higher than the IC sheet (elongation was10.5%, and the reduction of area was17.9%). That indicated the TRC technology in prepare the wrought magnesium alloy had a certain advantages. |
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