AZ系列鎂合金在高於100ºC溫度下，容易因γ-Mg17Al12於晶界固溶而衍生潛變問題。藉由提高鋅含量，使鋅/鋁比值相對鋁含量達特定範圍的ZA系列鎂合金，會抑制γ相生成，產生固溶溫度較高的Mg32(Al.Zn)49、MgZn相，因此具有較佳的高溫抗潛變性。本研究以具α-Mg、準晶Q-Mg32(Al.Zn)49 及少量Al¬-Mn相之Mg-13Zn-7Al合金擠型材(ZA137-F)，沿其平行、夾45º、垂直擠型方向進行拉伸試驗，並利用退火(O)與過固溶(OT4)熱處理改變基地相織構及第二相分佈，以釐清第二相分佈對拉伸性質之影響。
實驗結果顯示：改變拉伸方向對ZA137-F之降伏強度(YS)、抗拉強度(UTS)、均勻延伸率(UE)三者差異影響不大，而拉伸方向為平行擠型方向時，有較佳總延伸率(TE)約15%。ZA137-O之UTS與YS略降，而平行擠型方向之TE增加到約22%，延性明顯提升。ZA137-T4之TE僅約2%，延性明顯劣化。
而ZA137之高強度是由分散的硬質Q相與粒徑小的α-Mg所貢獻；OT4材強度不佳，是由於集中的φ-Mg5Zn2Al2+Q相與α-Mg粒徑較大。F材與O材基地相之basal plane平行ND方向所佔的比例僅約1/4，因此F材與O材具有相當程度的延伸率；TD面與ED面的優選方位相似，故改變拉伸方向對F材之YS、UTS、UE三者差異影響並不大。由破斷次表面之觀察發現裂縫皆始於硬脆的Q相，裂縫生成後沿著Q相分佈互相連結，最後導致材料破裂。因此O材可能因Q相分散較均勻，且基地相釋放殘留應力，有助於阻止裂縫傳播，使得明顯延性提升；而OT4材之φ+Q相集中於晶界處，導致延性明顯劣化。

AZ-series Mg-Al-Zn alloys may encounter creep problems resulted from the γ-Mg17Al12 dissolution at grain boundaries for higher than 100ºC. ZA-series Mg-Zn-Al alloys with high Zn content and certain Zn/Al ratio to Al contents can have better creep resistance at higher temperatures because the Mg32(Al.Zn)49 or MgZn compounds with higher dissolution resistance can inhibit the formation of γ phase. The extrusion ZA137-F Mg-Zn-Al alloy, which is consist of α-Mg, quasi-crystal Q-Mg32(Al.Zn)49 phase and a few Al-Mn phase, is used to study the effect of matrix texture, Q phase distribution and post-heat treatments on the tensile properties with parallel, 45º and perpendicular to the extrusion direction (ED).
Experimental results show that less effect on the variation of the yield stress (YS), the ultimate tensile stress (UTS) and the uniform elongation (UE) of ZA137-F with varying tensile directions, but the total elongation (TE) is about 15% better for tensile tests parallel to ED. The tensile strength of ZA137-O is slightly reduced, but the TE is raised to about 22% in the parallel ED condition. The TE of ZA137-T4 is decreased to only 2%, which shoes significant low ductility.
The high strength is due to the dispersed Q phase and the small particle size of α-Mg. ZA137-OT4 has low strength because of the concentration of the φ-Mg5Zn2Al2+Q phase and the bigger particle size of α-Mg. About 1/4 the basal plane are parallel to the ND in ZA137-F and ZA137-O. Therefore, they have substantial elongation; The preferred orientations are similar in TD surface and ED surface. Therefore, it has substantial elongation and less difference to the UTS, YS and UE for varying tensile directions. Fracture sub-surfaces observations reveal that initial cracks occurred within Q phase. Failures are resulted from cracks propagation and interlinkage along Q phase. Therefore, the elongation of ZA137-O is increased obviously because of the uniform distribution of Q phase and releasing the residual stress in the matrix. After the OT4 treatment, the elongation has been deteriorated due to the concentration of the φ+Q phase at the grain boundary.

1. 陳錦修，『鎂合金在汽車工業之應用』，工業材料雜誌186期，民國91年6月，148-152頁。
2. P. Humble, “Towards a creep resistant magnesium alloy”, Mater. Forum, 1997, 21, pp.45-46.
3. Y. Kojima, T. Aizawa and S. Kamado, “Magnesium Alloys 2000”, Trans. Tech. Publications, 2000, pp.73-84.
4. M. Pekguleryuz and A. Kaya, “Creep resistant magnesium alloys for powertrain applications”, Advanced Eng. Mater., Vol.5, No.12, 2003, pp.866-878.
5. W. Xiao, S. Jia, J. wang, Y. Wu and L. Wang, “Effects of cerium on the microstructure and mechanical properties of Mg-20Zn-8Al alloy”, Mater. Sci. Eng., A474, 2008, pp.317-322.
6. J. Zhang, Z. S. Li, Z. X. Guo and F. S. Pan, “Solidification microstructural constituent and its crystallographic morphology of permanent-mould-cast Mg-Zn-Al alloys”, Trans. Nonferrous Met. Soc., China 16, 2006, pp.452-458.
7. J. Zhang, Z. X. Guo, F. S. Pan, Z. Li and X. Luo, “Effect of composition on the microstructure and mechanical properties of Mg-Zn-Al alloys”, Mater. Sci. Eng. A456, 2007, pp.43-51.
8. M. M. Avedesian and H. Baker, ASM Specialty Handbook, “Magnesium and Magnesium Alloys”, 1999, pp.13-43.

9. 蔡幸甫，『鎂合金產業技術及市場發展趨勢專題調查』，民國90年10月，2-5頁。
10. M. Avedesian and H. Baker, “ASM Metals Handbook-Metallography, Structures and Phase Diagrams”, Vol.8, 1973, pp.398.
11. M. M. Avedesian and H. Baker, “Magnesium and Magnesium Alloys”, ASM Int., 1999, pp.13-21.
12. G. S. Foerster, “Proceeding of the IMA 33rd Annual Meeting”, Montreal, Quebec, Canada, May 23–25, 1976, pp.35–39.
13. M. M. Avedesian and Noranda Magnesium Inc., “ASM Specialty Handbook-Magnesium and Magnesium Alloys”, Mater. Information Society, 1999, pp.14-15.
14. D. Shechtman, I. Blech, D. Gratias and J. W. Cahn, “Metallic phase with long-range orientational order and no translational symmetry”, Phys. Rev. Lett. 53, 1984, pp.1951.
15. D. Levine and P. J. Steinhardt, “Quasicrystals. I. definition and structure”, Phys. Rev. B34, 1986, pp.596.
16. K. Niizeki, “Mathematical and general”, Phys. A22, 1989, pp.205-218.
17. 王仁卉、胡承正、桂嘉年著，『準晶物理學』，科學出版社，2004，1-19頁。
18. T. Rajasekharan, D. Akhtar, R. Gopalan and K. Muraleedharan, “The quasi-crystalline phase in Mg-Al-Zn system”, Nature Vol. 322, 1986, pp.528-530.
19. D. Levine, T. C. Lubensky, S. Ostlund, S. Ramaswamy and P. J. Steinhardt, “Elasticity and dislocations in pentagonal and icosahedral quasicrystals”, Phys. Rev. Lett. 54, 1985, pp.1520.
20. J. E. S. Socolar, T. C. Lubensky and P. J. Steinhardt, “Phonons, phasons, and dislocations in quasicrystals”, Phys. Rev. B34, 1986, pp.3345.
21. S. Takeuchi, H. Iwanaga and T. Shibuya, Jpn. J. Appl. Phys. 30, 1991, pp.361.
22. U. Koester, W. Liu, H. Liebertz and M. Michel, J. Non-Cryst. Solids 153/154, 1993, pp.446.
23. K. Edagawa, T. Suzuki, S. Takeuchi and T. Fujiwara, “Proceedings of 6th International Conference on Quasicrystals”, World Scientific, Singapore, 1998, pp.517.
24. 昌山正孝著、賴狄陽譯，『非鐵金屬材料』，復漢出版社，1993年1月，174頁。
25. C. R. Brooks, “Heat Treatment, Structure and Properties of Nonferrous Alloys”, ASM., 1982, pp.59-69.
26. T. Obara, H. Yoshinga and S. Morozumi, “﹛112(___)2﹜<1(___)1(___)23> slip system in magsium”, Acta Metall., Vol.21, 1973, pp.845-853.
27. J. F. Stohr and J. P. Poirier, “Electron microscope study of pyramidal slip﹛112(___)2﹜<1(___)1(___)23> in magnesium”, Phil. Mag. , vol. 25, 1972, pp.1313-1329.
28. S. Ando and H. Tonda, “Non-basal slip in magnesium-lithium alloy single crystals”, Mater. Trans. JIM, vol. 41, 2000, pp.1188-1191.
29. M. H. YOO, J. R. MORRIS, K. M. HO and S. R. AGNEW, “Nonbasal deformation modes of hcp metals and alloys: role of dislocation source and mobility”, Metall. Mater. Trans., Vol.33A, 2002, pp.813-822.
30. S. R. Agnew, J. A. Horton and M. H. Yoo, “Transmission electron microscopy investigation of <c+a> dislocation in Mg and α-solid solution Mg-Li alloys”, Metall. Mater. Trans., Vol.33A, 2002, pp.851-858.
31. S. K. Guan, C. X. Zhang, L. G. Wang, L. H. Wu, P. L. Chen and Y. L. Tang, “Phase selection of ternary intermetallic compounds during solidification of high zinc magnesium alloy”, Trans. Nonferrous Met. Soc., China 18, 2008, pp.593-597.
32. M. B. Yang, F. S. Pan, R. J. Cheng and J. Shen, “Effects of holding temperature and time on semi-solid isothermal heat-treated microstructure of ZA84 magesium alloy”, Trans. Nonferrous Met. Soc., China 18, 2008, pp.566-572.
33. N. Balasubremani, U. T. S. Pillai and B. C. Pai, “Optimization of heat treatment parameters in ZA84 magnesium alloy”, Journal of Alloys and Compounds. 457, 2008, pp.118-123.
34. R. Banerjee, R. T. Savalia, E. G. Baburaj, G. K. Dey and U. D. Kulkarni, “Microstructural studies on rapidly solidified Mg32(AlxZn1-x)49 potentially quasicrystal forming alloys”, Mater. Sci. Eng. A165, 1993, pp.149-156.
35. C. S. Barrett and T. B. Massalski, “Structure of Metals”, Mcgraw-Hill Inc., 1980, pp.203-205.
36. J. Koike, R. Ohyama, T. Kobayashi, M. Suzuki and K. Maruyama, “Grain-boundary sliding in AZ31 magnesium alloys at room temperature to 523K”, Mater. Trans. 44, 2003, pp.445.
37. H. Somekawa, H. S. Kim, A. Singh and T. Mukai, “Fracture toughness in direct extruded Mg-Al-Zn alloys”, J. Mater. Res. 22, 2007, pp.2598.
38. W. D. Callister, “Fundamentals of Materials Science and Engineering”, John Wiley and Sons Inc., 2005, pp.251-252.
39. W. D. Callister, “Fundamentals of Materials Science and Engineering”, John Wiley and Sons Inc., 2005, pp.243-245.
40. R. E. Reed-Hill and R. Abbaschian, “Physical Metallurgy Principles 3rd edition”, PWS Publishing Company, pp.746.