分流擠型為本實驗室新開發之等截面劇烈製程，除了保有先前等截面劇烈加工之特色：1、提供材料相當大之加工量細化微結構；2、加工後材料之截面積不會改變，亦可不斷加工至指定道次才將試片取出。要達到超塑性通常有兩項要求：一為小於10μm之細小等軸晶，其次是在0.5Tm（Tm為熔點溫度）左右之高溫變形。
本研究藉由形態分明之Zn-22wt.%Al共析合金在分流擠型製程中加工，觀察擠製前後微結構之改變，了解分流擠型之流線。並藉由改變擠製道次與溫度條件下，瞭解各截面微結構變化與均勻性，以及對超塑性之影響。
實驗結果顯示出合金經分流擠型製程擠製一道次之流線。微結構則隨著道次增加有逐漸細化與混鍊均勻之效果，且降低擠製溫度可得到更細小之微結構。而材料之超塑性亦隨著擠製道次增加與溫度下降有所提升，於200℃進行高溫拉伸之最佳應變速率為5×10-3s-1，合金經100℃下擠製十道次後，在此最佳初始應變速率(5×10-3)、200℃下進行高溫拉伸，其伸長量可達1092％。

A new cross-channel extrusion （CCE） process of serve plastic deformation can not only provide much strain energy and keep concomitant change in the cross-sectional dimensions but is with continuous processes was developed. The two basic requirements for achieving structural superplasticity are:(1). a fine, stable equiaxed grain size d of less than about 10μm(i.e. d≦10μm) ； and (2). a testing temperature T greater than about one half of absolute melting temperature of the material, Tm(i.e. T≧0.5Tm).
Effects of CCE processing with different number of passes and temperature of extrusions on stream line, microstructures and superplasticity of a Zn-22wt.% Al eutectoid alloy were investigated.
The results indicated the microstructures became more fine and uniform with increasing the number of passes and were finer with decreasing the temperature of extrusions. The superplasticity after CCE revealed a significant enhancement with increasing the number of passes and decreasing the temperature of extrusions. After 10 passes of CCE at a temperature of 100℃, the elongation at a testing temperature of 200℃ was up to 1092% at an initial strain rate of 5×10-3。

1. K. T. Park, F. A. Mohamed, "Effect of impurity content on cavitation in the superplastic Zn-22 pct Al alloy", Metallurgical Transactions A, V21A, 1990, pp.2605-2608.
2. K. Higashi, T. G. Nieh, M. Mabuchi and J. Wadswoth, "Effect of liquid phases on the tensile elongation of superplastic aluminum alloys and composites", Scripta Meterialia, Vol.32, 1994, pp.1079-1084.
3. Glossary of terms used in metallic superplastic materials, JIS H7007, Japanese Standard Association, 1995, p.3.
4. Terence G. Langdon, "An evaluation of the strain contributed by grain boundary sliding in superplasticity", Materials Science and Engineering, A174, 1994, pp.225-230.
5. K. T. Park, S. T. Yang, J. C. Earthman, F. A. Mohamed, "The effect of impurities on ductility and cavitation in the superplastic Zn-22%Al alloy", Materials Science and Engineering, A188, 1994, pp.59-67.
6. P. Zwigl and D. C. Dunand, "A non-liner model for internal stress superplasticity", Acta Metallurgica, Vol.45, 1997, pp.5285-5294.
7. R. C. Lobb, E. C. Sykes and R. H. Johnson, "Internal stress superplasticity in some materials", Materials Science and Engineering, vol.19, 1972, p.6.
8. O. A. Ruano, J. Wadsworth and O. D. Sherby, "Enhanced densification of white cast iron powders by cyclic phase-transformations under stress", Metallurgical Transactions, A13, 1982, p.355.
9. C. Schuh, D. C. Dunand, "Contributions to transformation superplasticity of titanium from rigid particles and pressurized pores", Scripta Materialia, Vol.40, 1999, pp.1305-1312.
10. O. D. Sherby and J. Wadsworth, "Superplastic-recent advances and future direction", Progress In Materials Science, vol.33, 1989, pp.169-221.
11. A. K. Mukherjee, "Superplasticity in metals, ceramics and intermetallics", in Superplastic Forming of a Symposium, ASM, 1985, pp.408-460.
12. J. Wadsworth, J. H. Lin, O. D. Sherby, "Superplasticity in a tool steel", Metals Technology, Vol.8, 1981, pp.190-193.
13. Marc Andre Meyers, Krishan Kumar Chawla, "Mechanical behavior of materials", Prentice Hall, 1999, p.126.
14. George E. Dieter, "Mechanical metallurgy", Addison wesley publishing company, 1989, pp.292-294.
15. B. P. Kashyap, "Interfacial phenomena and microstructural evolution during superplastic deformation",Surface and Interface Analysis, Vol.31, 2001, pp.547-559.
16. D. Lee, "The nature of superplastic deformation in the Mg-Al eutectic", Acta Metallurgica, Vol.17, 1969, pp.1057-1069.
17. A. S. Kori, B. S. Murty, M. Chakraborty, "Development of an efficient grain refiner for Al-7Si alloy and its modification with strontium", Microstructure and Processing, vol.283, 2000, pp.94-104.
18. V. L. Tellkamp, E. J. Lavernia, "Process and mechanical properties of nanocrystalline 5083 Al alloy", NanoStructured Materials, Vol.12, 1999, pp.249-252.
19. Y. Wu, L. Del Castillo, E. J. Lavernia, "Superplasticity of 5083 alloys produced by spray deposition", Scripta Materialia, Vol.34, 1996, pp.1243-1249.
20. A. smolej, M. Gnamus, E. Slacek, "The influence of the thermomechanical process and forming parameters on superplastic behavior of the 7475 aluminum alloy", Materials Processing Technology, vol.118, 2001, pp.397-402.
21. J. Adrien, E. Maire, R. Estevez, J. C. Ehrstrom, T. Warner, "Influence of the thermomechaincal treatment on the microplastic behavior of a wrought Al-Zn-Mg-Cu alloy", Acta mater., vol.52, 2004, pp.1653-1661.
22. Olaf Engler, Jurgen Hirsch, "Texture control by thermomechanical processing of AA6xxx Al–Mg–Si sheet alloys for automotive applications—a review", Materials Science and Engineering A, vol.336, 2002, pp.249-262.
23. C. Y. Nam, J. H. Han, Y. H. Chung, M. C. Shin, "Effect of precipitates on microstructural evolution of 7050 Al alloy sheet during equal channel angular rolling", Materials Science and Engineering, A265, 2003, pp.253-257.
24. Yuichiro Koizumi , Masanori Ueyama , Nobuhiro Tsuji , Yoritoshi Minamino , Kenichi Ota, "High damping capacity of ultra-fine grained aluminum produced by accumulative roll bonding", Alloys and Compounds, Vol.355, 2003, pp.47-51.
25. Yoshinori Nishida, "Rotary-die equal-channel angular pressing of an Al-7mass%Si-0.35mass%Mg alloy", Scripta Materialia, vol.45, 2001, pp.261-266.
26. S. Y. Yuan, C. H. Peng, J. W. Yeh, "Synthesis of fine Pb-50vol.-%Sn alloys by a new process of reciprocating extrusion", Mater. Sci. and Tech., vol.15, 1999, pp.683-688.
27. Jien-wei Yeh, Shi-Ying Yuan, Chao-Hung Peng, "A reciprocating extrusion process for producing hypereutectic Al-20wt.% Si wrought alloys", Materials Science and Engineering A, vol.252, 1998, pp.212-221.
28. 劉國雄,林樹均,李勝隆,鄭晃忠,葉均蔚, "工程材料科學", 全華科技圖書股份有限公司, 1999, pp.556-558.
29. Serope Kalpakjian, "Manufacturing engineering and technology", Addison Wesley Publishing Company, 2001, pp16-43.
30. Robert F. Mehl, "Metals handbook eight edition", American Society for Metals, 1972, pp.340.
31. Z.M. El-Baradie, "Grain refining of Zn-22wt.%Al superplastic alloy", Materials Processing Technology, Vol.84, 1997, pp.73-78.
32. C.F. Yang, L.H. CHiu, Y.P.Sheu, "Effects of thermomechanical treatments on superplasticity of Zn-22%Al alloy", Materials and Manufacturing Processes, Vol.12, 1997, pp.199-214.
33. Minoru Furukawa, Zenji Horita, Minoru Nemoto, Ruslan Z. Valiev, T. G. Langdon, "Fabrication of submicrometer-grained Zn-22%Al by torsion straining", Materials Research, Vol.11, 1996, pp.2128-2130.
34. Minoru Furukawa, "Microstructual characteristics and superplastic ductility in a Zn-22%Al alloy with submicrometer grain size", Materials Science and Engineering, A241,1998, pp.122-128.
35. S. M. Lee, T.G. Langdon, "High strain rate superplasticity in a Zn-22%Al alloy after equal-channel angular pressing", Materials Science Forum, Vols.355-359, 2001, pp.321-326.
36. D. W. Livesey, N. Ridley, "Investigation of the stress-strain rate curve at low strain rates for superplastic Zn-22%Al Alloy", Scripta Metallurgica, Vol.16, 1982, pp.165-168.
37. F. A. Mohamed, T. G. Langdon, "Flow localization and neck formation in a superplastic metal", Acta Metallurgica, Vol.29, 1981, pp.911-920.
38. F. Porter, “Zinc handbook, properties, processing and use in design”, Marcel Dekker, 1991, pp.421-550.
39. H. Naziri, R. Pearce, "Effect of prestraining under hydrostatic pressure on the creep life of an Al-20%Zn alloy", J Aust Inst Metals, Vol.15, 1970, pp.206-211.
40. C. H. Caceres, D. S. Wilkinson, "Superplastic behavior of a Zn-22 pct Al-0.5 pec Cu alloy", Metallurgical Transactions A, Vol.17A, 1986, pp.1873-1875.
41. William D. Callister, "Materials science and engineering an introduction", Wiley, 1999, pp.251-255.
42. Preveen Kumar, Cheng Xu, Terence G. Langdon, "The significance of grain boundary sliding in the superplastic Zn-22%Al alloy after processing by ECAP", Materials Science and Engineering, 2005, pp.447-450.
43. M. T. Abou El-khair, A. Daoud, A. Ismail, "Effect of different Al contents on the microstructure, tensile and wear properties of Zn-based alloy", Materials Letters, Vol.58, 2003, pp.1754-1760.
44. Yuwei Xun, F. A. Mohamed, "Superplastic behavior of Zn-22%Al containing nano-scale dispersion particles", Acta Materialia, Vol.52, 2004, pp.4401-4412.
45. K. T. Park, D. Y. Hwang, Y. K. Lee, Y. K. Kim, D. H. Shin, "High strain rate superplasticity of submicrometer grained 5083 Al alloy containing scandium fabricated by severe plastic deformation", Materials Science and Engineering, A341, 2003, pp.273-281.
46. F. Musin, R. Kaibyshev, Y. Motohashi, G. Itoh, "High strain rate superplasticity in a commercial Al–Mg–Sc alloy", Scripta Materialia, vol.50, 2004, pp.511-516.
47. P. Malek, "Superplasticity in an Al-Zn-Mg-Cu alloy ", Materials Science and Engineering, A137, 1997, pp.21-26.