臺灣博碩士論文加值系統

目前有許多的研究使用大量塑性變形法來進行鎂合金機械性質的改善。等徑轉角擠製為眾多大量塑性變形法中最為簡單方便的一種方法，而且運用此法在擠製後可以得到與試片在進行擠製前相同的橫截面。此外，ECAE所需的外力較小，並且可以藉由改變模具參數控制試片的顯微組織。文獻中指出，當溫度越低時晶粒細化的效果越好，但對於不同的材料與擠製模具，最低擠製溫度多半有所限制。而增加背壓有助於增加試片的應變量並且可以防止由張應力造成表面破裂，即代表增加背壓可降低成形溫度。
本研究將探討藉由增加背壓降低最低擠製溫度對鎂合金AZ80晶粒尺寸的影響。實驗結果顯示增加背壓確實有助於降低最低擠製溫度，而在同溫度下增加背壓將使的晶粒尺寸增大，但隨著溫度的降低，晶粒細化的效果越好。

Severe Plastic Deformation (SPD) is widely used to improve the mechanical properties of magnesium. The equal channel angular extrusion (ECAE) is the most simple and convenient technique in SPD. By using ECAE, we obtain a product which has the same cross section with original billet after extrusion .In addition, the force required in extrusion during ECAE process is usually not large, and we can control the microstructure of the billet by changing the die parameters. Our experiments show that low temperature extrusion can achieve in grain refinement, but the lowest extrusion temperature is limited by materials and dies. Imposing a back-pressure is useful for increasing the strain of billet to avoid the cracking on the billet surface by tensile stress. In order words, imposing a back-pressure is beneficial to compromise the extrusion temperature.
In this study, the effect on the microstructure of magnesium alloy AZ80 of imposing the back-pressure was investigated. As a result, we found that imposing the back-pressure is helpful in extending the lowest extrusion temperature. At the same temperature, it makes the grain size larger with increasing back-pressure.

中文摘要...........................................i
英文摘要...........................................ii
誌謝...............................................iii
目錄...............................................iv
表目錄.............................................vii
圖目錄.............................................viii
第一章 序論.......................................1
1-1 研究背景......................................1
1-2 研究動機與目的................................3
第二章 文獻回顧...................................5
2-1 鎂合金簡介....................................5
2-1-1 鎂合金的命名方式............................5
2-1-2 鎂合金的優點................................5
2-2 回復與再結晶..................................6
2-2-1 回復........................................6
2-2-2 再結晶......................................7
2-3 晶粒細化......................................8
2-4 大量塑性變形法................................9
2-4-1 等徑轉角擠製簡介............................10
2-4-2 等徑轉角擠製之晶粒細化原理..................11
2-4-3 擠製方位與剪應變幾何特性....................12
2-4-4 連續等徑轉角擠製............................13
2-4-5 背壓........................................13
第三章 實驗流程與材料.............................24
3-1 模具強化......................................24
3-2 背壓系統......................................25
3-3 實驗材料......................................25
3-4 實驗設備......................................26
3-5 實驗步驟......................................27
3-5-1 等徑轉角擠製................................27
3-5-2 金相實驗....................................28
3-5-3 金相分析....................................30
第四章 實驗結果與討論.............................41
4-1 最低擠製溫度測試與取樣........................41
4-2 試片在同溫度不同背壓下的晶粒尺寸..............42
4-3 試片在同背壓不同溫度下之晶粒尺寸..............42
4-4 晶粒尺寸之均勻度..............................43
第五章 結論與未來展望.............................57
5-1 結論..........................................57
5-2 未來展望......................................58
參考文獻...........................................60

[1] 郭哲良，「鎂合金薄板之熱間擠製加工之探討」，國立台灣科技大學，碩士論文，民國90年。
[2] H. Proffit, ”Magnesium and Magnesium Alloys”, ASM Handbook 9th edition, Vol. 2, ASM International, 1989.
[3] J. Humphreys, and M. Hatherly, “Recrystallization and Related Annealing Phenomena”, Pergamon, 1994.
[4] G. Neite, et al., Materials Science and Technology, Vol. 8 , pp.113, 1996.
[5] R.Z. Valiev, R.K. Islamgaliev and I.V. Alexandrov, ”Bulk nanostructured materials from severe plastic deforemation”, Progress in Materials Science, vol. 45, pp. 103-189, 2000.
[6] A. Korbel, and M. Richert, “Formation of shear bands during cyclic deformation of aluminum”, Acta Metall., vol. 33, pp. 1971-1978, 1985.
[7] M. Mabuchi, K. Kubota, and K. Higashi, “New recycling process by extrusion for machined chips of AZ91 magnesium and mechanical properties of extruded bar”, Mater Trans JIM, vol. 36, p. 1249, 1995.
[8] R.B. Schwarz, and W.L. Johnson, “Formation of an Amorphous Alloy by Solid-State Reaction of the Pure Polycrystalline Metals”, Phys. Rev. Lett., vol. 51, pp. 415-418, 1983.
[9] J.Y. Huang, Y.T. Zhu, and T.C. Lowe, “Microstructures and dislocation configurations in nanostructured Cu processed by repetitive corrugation and straightening”, Acta Mater., vol. 49, pp. 1497-1505, 2001.
[10] V.M. Segal, “Materials processing by simple shear”, Materials Science and Engineering A , vol. 197, p. 157, 1995.
[11] Y. Iwahashi, Z. Horita, M. Nemoto, and T.G. Langdon, “The process of grain refinement in equal-channel angular pressing”, Acta Mater., vol. 46, pp. 3317-3331, 1998.
[12] M. Furukawa, Y. Iwahashi, Z.Horita, M. Nemoto, and T.G. Langdon, ”The shearing characteristics associated with equal-channel angular pressing”, Materials Science and Engineering A, vol. 257, pp. 328-332, 1998.
[13] T. Mukai, H. Watanabe and K. Higashi, Materials Science Forum, Vol. 350-351, pp. 159-170, 2000.
[14] Yoshinori Nishida, Hiroaki Arima, Jin-Chun Kim, and Teiichi Ando, ” Superplasticity of SiCw/7075 composites processed by rotary-die equal-channel angular pressing”, JOURNAL OF THE JAPAN INSTITUTE OF METALS, vol 64, pp.1224-1229, 2000.
[15] M. Furukawa, Z. Horita, M. Nemoto, and T. G. Langdon, in Ultrafine Grained Materials, ed. R. S. Mishra et al., The Minerals, Metals ＆Materials Society, Warrendale, pp.125, 2000.
[16] M. Furukawa, Y. Iwahashi, Z. Horita, M. Nemoto, and T. G. Langdon, Materials Science and Engineering A257 ,pp.328-332, 1998.
[17] Y. Iwahashi, Z. Horita, M. Nemoto, T. G. Langdon, Acta Materialia, Vol.46, pp.3317-3331, 1998.
[18] K. Oh-ishi, Z. Horita, M. Furukawa, M. Nemoto, T. G. Langdon, Metall.Trans. A29, p.2245, 1998.
[19] Valiev R.Z., Alexandrov I.V., Lowe T.C., Zhu Y.T., Journal of Materials Research, 2002.
[20] Krasilnikov N.A., Russian Metall, 2005.
[21] Nakashima K, Horita Z, Nemoto M, Langdon TG. Materials Science & Engineerig 2000;A281,p.82.