1. Deformation and Recrystallization of Mg Alloy AZ31 M.A.Sc: Shenglong Liang Supervisor: Hatem S. Zurob

2. Background Motivation Experimental & Result --deformation --recrystallization Prospects Acknowledgement 2

3. Background The Hexagonal Close-Packed materials typically have low formability due to the limited number of independent active slip systems and their asymmetric distribution in crystallography; basal slip{0002} ; prismatic slip{11-20} ; pyramidal slip{10-11} /{11-22} ; Deformation of HCP materials depends on the c/a ratio. 3

4. {0002} {10-10} “The c/a ratio determines the activation of different slip systems” Ref: Y.N Wang, J.C. Huang, materials chemistry and physics, 81(2003) 11-26 Mg: 1.624 “The origin of such textures may be understood in terms of the slip systems operating on basal planes” 4

5. Motivation Examine texture evolution during deformation and related annealing process Step 1: deformation Step 2: annealing Mg alloys exhibit very high strength/density ratio which makes Mg the potential structure material Low formability! 5

6. Table 1:Experiment methods PurposeDeformationRecrystallization Optical Microscopy (OM) a. Microstructure observation √√ X-ray Diffraction (XRD) b. Texture analysis √ Electron Backscattered Diffraction (EBSD) a &b√√ Transmission Electron Microscopy (TEM) a(Fine scale observation) √√ Experimental 6

7. AZ31 pre-deform treatment: As-received AZ31sheet → 400 ℃ for 24 hrs (solid solution treatment) → 5% cold rolled → 470 ℃ for 2 hrs annealing (grain growth) 7

8. Section1: Deformation 8

9. the sample was cold cross rolled from the equivalent strain 0 to 90% with a small amount of reduction in each pass 1 Cold Rolling Deformation Cross Sections CRD TEM & XRD OM & EBSD 2.01mm ~15mm 9

10. Deformation 2 results 2.1 microhardness 10

11. 2.2 Microstructure evolution Deformation 0% 11

12. 12

13. 30% 13

14. 40% 14

15. 15

16. 16

17. 2.4 TEM Deformation 5% 10% 30% 77% 17 At low magnification, dark bands with rhombus (diamond) structure are distinctly observed. These characteristics of microstructures are similar to deformation bands or shear bands observed in fcc and bcc materials

18. 2.5 XRD—{0002} pole figures Deformation a) 0% b)10% c) 30% d)40% e) 56% f) 77% 18

19. 3 Conclusion Deformation 2. Increasing the strain, the contraction/double twin fraction increases; nano-twins clusters could be observed at 30% and more frequently at higher strain; 3. Relatively homogeneous distributed shear bands were developed during the cold rolling, fine scale twin clusters could transform into shear bands but this study is still in progress; 1. At low strain levels, plenty of basal slips were activated due to its low CRSS, and responsible for the strengthening of the texture and the increase of the microhardness ; 19

20. Section 2: Recrystallization 20

21. 1. Annealing Experiment c e 10S 250 ℃ 30S 250 ℃ 1000S 250 ℃ 1800S 250 ℃ 10S 215 ℃ 600S 215 ℃ 10% √√ 30% √√√ 77% √√ Recrystallization Table 2: annealing experiment 21

22. 10%250 ℃ 30s Recrystallization 30%250 ℃ 30s 2. Results 22

23. Recrystallization 77%215 ℃ 10s77%215 ℃ 10mins 2. Results 23

24. 24

25. 3.Conclusion 1.The twins are the preferred nucleation sites; the nuclei at intersections of twin- twin or twin-grain boundaries could reorient the lattice, then randomize the texture; 2. The recrystallization in the shear bands provides different orientations instead of the strong basal texture as well, but the weak point is that microcracks were developed in the shear bands. 25

26. Future work a)A TEM observation through cross section was planned to better understand shear banding in AZ31; b)The modeling on recrystallization needs to be modified based on our updated information. 26

27. Acknowledgement Dr Hatem. S. Zurob Dr Xiang Wang Dr David Embury Chris Butcher&Flo Jim Britten 27

28. Thank you! 28