由於金屬具有高強度、高韌性、高抗疲勞強度、抗腐蝕性、可塑性、加工性與高經濟性等優點，於西元1895年時，金屬已開始作為醫療用植入物，用於固定骨折的骨頭。目前常見的金屬生醫材料包含不銹鋼合金、鈷鉻合金、鈦及鈦合金等，這些材料植入人體後並不會於人體內降解，因此當傷口復原後需做二次手術將其移除。
可降解金屬生醫植入材料最大優點在於可以避免二次手術造成的危險及傷害，使復原能力較差的年老患者避免二次手術，同時解決植入永久植入材的患者可能需要之長期藥物控制。
本研究利用目前主流研究方向的可降解性金屬：鐵、鎂以及鋅作為研究材料，希望將此合金應用在骨科植入材。現今可降解性金屬所需要的降解速率與市面上可見之材料差距過大，如鐵的降解速率過慢，而鎂的降解速率則過快。本研究藉由將鐵、鋅、鎂三種金屬混合，由鐵提供植入材所需要的機械強度、鎂與鋅提供植入材所需要的降解速率。
由於鐵與鎂之間不會形成化合物，藉由添加鋅來與鎂進行化合，使鎂能留在以鐵為基底的材料中，期望生成鐵-鋅與鋅-鎂的合金。並調控燒結熱處理的溫度與時間，藉此達到材料較佳的腐蝕速率。
本實驗以利用冷壓成形並施加不同熱處理的鐵鎂鋅合金為主要研究對象，並與純鐵、純鎂和純鋅進行比較。評估材料經過不同製程處理後的微結構、腐蝕性質等，分析並歸納出成分、製程與性質之間的相依性，並對製程條件加以改進，供未來作為可降解金屬植入材研究參考。

SUMMARY
In recent years, the research of degradable metallic material is substantial because elderly patients with poor resilience will be able to avoid the second surgery, while addressing the long-term drug control implant material permanently implanted in the patient may be required.
In part 1, we use magnesium and zinc powder to form MgZn_2 and then mix it with iron powder to produce the Fe-Zn-Mg alloy. We compare the microstructure, composition and phase with different sintering conditions. In part 2, we directly mix three kinds of powder, which are iron, magnesium and zinc to produce the Fe-Zn-Mg alloy. We compare the microstructure, composition, porosity and corrosion rate of different proportions of iron and MgZn_2 powder.
We change the sintering temperature and sintering time to obtain purer MgZn_2, and find out that after sintering at T2℃ and lasting for t4 hours can obtain MgZn_2 with less remaining zinc. In the process of three-powder mixing sintering, we find out that we can have the corrosion rate 20 times faster than pure iron when the weight ratio is about ratio5.
Key words: Fe-Zn-Mg alloy, bio-degradable, corrosion

INTRODUCTION
In 1895, because of its high strength, high toughness, corrosion resistance, workability and high economic advantages, metal had started as a medical implant for fracture fixation of bone. Common metallic biomaterials such as stainless steel alloys are not degradable, therefore when the metals are implanted, they must be removed by second surgery after bone healing. The biggest advantage of biodegradable metallic materials is avoiding the second surgery and the injuries caused by this dangerous process. Elderly patients with poor resilience are able to avoid the second surgery, while addressing the long-term drug control implant material permanently implanted in the patient may be required. In this study, we use iron, zinc and magnesium powder as materials and apply different heat treatments on Fe-Zn-Mg alloy, trying to find the most appropriate corrosion rate which can be applied to the orthopedic implant materials.

MATERIALS AND METHODS
In part 1, we use magnesium and zinc powder to form MgZn_2 and then mix it with iron powder to produce the Fe-Zn-Mg alloy. We compare the microstructure, composition and phase between different sintering conditions. In part 2, we directly mix three kind of powder, iron, magnesium and zinc to produce the Fe-Zn-Mg alloy. We compare the microstructure, composition, porosity and corrosion rate of pure iron, zinc and magnesium.

RESULTS
In part 1, we mix the magnesium and zinc powder in the molar ratio 1:2 and sinter at T2℃. As the sintering time is longer, the less internal residual zinc content exists. When the sintering time reaches t4 hours, we can obtain higher purity of the MgZn_2. Mixing the Iron and the MgZn_2 powder in the weight ratio of ratio1 and sintering at T1℃, which is in close proximity to the melting point of MgZn_2, the MgZn_2 will outwardly evaporate. It makes the content of MgZn_2 decreased in the specimen. When the sintering time reaches t3 hours, there’s almost no residual MgZn_2 left in the specimen. The MgZn_2 vapor in the process will be decomposed into magnesium and zinc. The zinc has lower vapor pressure so that the peripheral specimen’s zinc content is very small and magnesium remains in the specimen. After mixing the iron and the MgZn_2 powder with weight ratio of ratio7 and sintering at a lower temperature(T2℃) for t4 hours, the MgZn_2 particles successfully remain in the specimen and they are surrounded by the iron. In the absence of magnesium and zinc vapor, the sintering result under T2℃ is better than that of T1℃.
In part 2, Three kinds of powder, iron, zinc and magnesium, are mixed uniformly and sintering at T2℃ for t4 hours, and the specimen inside will produce MgZn_2. With the increase in the weight ratio of iron, the MgZn_2 amount will gradually decrease. Internal specimen will also generate the Fe_4 Zn_9. Because the zinc and magnesium inside the specimen will evaporate, there are some holes generated inside the specimen. The surrounding zinc particles generate Fe_4 Zn_9. When the weight ratio of iron rises, the porosity will increase slightly because of the evaporation of the magnesium which influences the sintering of iron, resulting in incomplete sintering area in the internal specimen. The Fe-Zn-Mg alloy’s corrosion rate is faster than that of the pure iron and magnesium because of the evaporation of zinc and magnesium during the sintering process. The MgZn_2 preferential corrosion and the evaporation of the magnesium influence iron sintering, so that the specimen has many internal voids, resulting in pitting phenomenon. When the weight ratio of iron increases, less magnesium and zinc content exist in the specimen and the corrosion rate can be reduced.

CONCLUSIONS
1. Sintering at T2℃ and lasting for t4 hours can obtain the MgZn_2 with less remaining zinc.
2. Sintering in close proximity to the melting point of the MgZn_2 will form a diffusion layer inside the specimen due to the evaporation of MgZn_2. If sintered at T2℃ instead, it can avoid the MgZn_2 to evaporate and make the iron sintered preferably compared to T1℃.
3. Mixing the iron, zinc and magnesium powder by the weight ratio and sintering, in addition to forming the MgZn_2 inside the specimen, it will also form the Fe_4 Zn_9. These compounds increase the corrosion rate of the specimen.

1. Mazzocca, A.D., DeAngelis, J.P., Caputo, A.E., Browner, B.D., Mast, J.W., Mendes, M.W., Principles of internal fixation, in: B.D. Browner (Ed.), Skeletal Trauma, W.B. Saunders Company, Philadelphia, 2008.

2. Brandes, E.A. & Brook, G.B. (1992). Smithells Metals Reference Book. 7th ed. Oxford, Butterworth-Heinemann.

3. Cristian Covarrubias, Matías Mattmann, Alfredo Von Marttens, Pablo Caviedesc,Cristián Arriagada, Francisco Valenzuela, Juan Pablo Rodríguez, Camila Corral, Osseointegration properties of titanium dental implants modifiedwith a nanostructured coating based on ordered porous silicaand bioactive glass nanoparticles, 2015

4. Chen, Q., Liu, L. & Zhang, S.-M. (2010). The potential of Zr-based bulk metallic glasses as biomaterials. Front Mater Sci China, 4, 34.

5. Chiba, A., Lee, S.-H., Matsumoto, H. & Nakamura, M. (2009). Construction of processing map for biomedical Co28Cr6Mo0.16N alloy by studying its hot deformation behavior using compression tests. Mater Sci Eng A, 513-514, 286.

6. Dalibor VOJTĚCH, Jiří KUBÁSEK, Jaroslav ČAPEK, Iva POSPÍŠILOVÁ, Magnesium, Zinc and Iron alloys for medical applications in biodegradable implants, Metal, 2014

7. Habibovic, P., Barrere, F., Blitterswijk, C.A.V., Groot, K.D. & Layrolle, P. (2002). Biomimetic hydroxyapatite coating on metal implants. J Am Ceram Soc, 83, 517.

8. Hermawan, H. & Mantovani, D. (2009). Degradable metallic biomaterials: The concept, current developments and future directions. Minerv Biotecnol, 21, 207.

9. Hermawan, H., Alamdari, H., Mantovani, D. & Dube, D. (2008). Iron-manganese: New class of degradable metallic biomaterials prepared by powder metallurgy. Powder Metall, 51, 38.

10. Hendra Hermawan,Biodegradable Metals From Concepts to Applications, Springer, 2012

11. Helsen, Jozef A., Missirlis, Yannis(2010), Biomaterials：A Tantalus Experience(1^st ed.), Berlin Heidelberg, Springer-Verlag

12. Hendra Hermawan,Biodegradable Metals From Concepts to Applications, Springer, 2012

13. Hollander, D.A., Von Walter, M., Wirtz, T., Sellei, R., Schmidt-Rohlfing, B., Paar, O. & Erli, H.-J. (2006). Structural, mechanical and in vitro characterization of individually structured Ti6Al4V produced by direct laser forming. Biomaterials, 27, 955.

14. Ik-Hyun Oh, Naoyuki Nomura *, Naoya Masahashi, Shuji Hanada, Mechanical properties of porous titanium compacts prepared by powder sintering, 2003

15. Park, J.B.,Lakes, R.S., Biomaterials: An Introduction, Springer, New York, 2007.

16. Hirschhorn, J. S.,Mcbeath, A. A.,Dustoor, M. R., Porous Titanium Surgical Implant Materials, Biomedical Materials Research Symposium, 1(1971) 49-67

17. Johnson, W.L. (1999). Bulk glass-forming metallic alloys:Science and technology. MRS Bull. 24(10):42-56.

18. J. Cheng, B. Liu, Y.H. Wu, Y.F. Zheng, Comparative in vitro Study on Pure Metals (Fe, Mn, Mg, Zn and W) as Biodegradable Metals, 2013

19. Kuroda, D., Niinomi, M., Morinaga, M., Kato, Y. & Yashiro, T. (1998). Design and mechanical properties of new [beta] type Ti alloys for implant materials. Mater Sci Eng A, 243, 244.

20. Li, Z., Gu, X., Lou, S. & Zheng, Y. (2008). The development of binary Mg-Ca alloys for use as biodegradable materials within bones. Biomaterials, 29, 1329.

21. Lahann, J., Klee, D., Thelen, H., Bienert, H., Vorwerk, D. & Hocker, H. (1999). Improvement of haemocompatibility of metallic stents by polymer coating. J Mater Sci Mater Med, 10, 443.

22. Lambotte, A. (1909). Technique et indication des protheses dans le traitement des fractures.Presse Med, 17, 321.

23. Lee, S.H., Nomura, N. & Chiba, A. (2008). Significant improvement in mechanical properties of biomedical CoCrMo alloys with combination of N addition and Cr-enrichment. Mater Trans, 49, 260.

24. Lopez-Heredia, M.A., Sohier, J., Gaillard, C., Quillard, S., Dorget, M. & Layrolle, P. (2008). Rapid prototyped porous Ti coated with calcium phosphate as a scaffold for bone tissue engineering. Biomaterials, 29, 2608.

25. Li, J.P., Habibovic, P., Van Den Doel, M., Wilson, C.E., De Wijn, J.R., Van Blitterswijk, C.A. & De Groot, K. (2007). Bone ingrowth in porous Ti implants produced by 3D fiber deposition. Biomaterials, 28, 2810.

26. Matsumoto, H., Watanabe, S. & Hanada, S. (2005). Beta TiNbSn alloys with low Young’s modulus and high strength. Mater Trans, 46, 1070.

27. M. Peuste,C. Hesse,T. Schloo,C. Fink,P. Beerbaum and C. Schnakenburg, Long-term biocompatibility of a corrodible peripheral iron stent in the porcine descending aorta, Biomaterials, 27(2006)4955-4962.

28. Schinhammer, M., Hanzi, A.C., Loffler, J.F. & Uggowitzer, P.J. (2010). Design strategy for biodegradable Fe-based alloys for medical applications. Acta Biomater, 6, 1705.

29. Nicolas Schiff, Brigitte Grosgogeat, Michele Lissac, Francis Dalard, Influence of fluoride content and pH on the corrosion resistance of titanium and its alloys, 2001

30. Narushima, T. (2010). New-generation metallic biomaterials. IN NIINOMI, M. (Ed.) Metals for Biomedical Devices. Cambrigde, Woodhead Publishing.

31. Peuster, M., Wohlsein, P., Brugmann, M., Ehlerding, M., Seidler, K., Fink, C., Brauer, H., Fischer, A. & Hausdorf, G. (2001). A novel approach to temporary stenting:Degradable cardiovascular stents produced from corrodible metal-results 6-18 months after implantation into New Zealand white rabbits. Heart, 86, 563.

32. Qizhi Chen, George A. Thouas, Metallic implant biomaterials, 2014

33. Ryan, G., Pandit, A. & Apatsidis, D.P. (2006). Fabrication methods of porous metals for use in orthopaedic applications. Biomaterials, 27, 2651.

34. Ryan, G.E., Pandit, A.S. & Apatsidis, D.P. (2008). Porous Ti scaffolds fabricated using a rapid prototyping and powder metallurgy technique. Biomaterials, 29, 3625.

35. Sherman, W.O. (1912). Vanadium steel bone plates and screws. Surg Gynecol Obstet, 14, 629.

36. Stack, R. S., Califf, R. M., Phillips, H. R., Pryor, D. B., Quigley, P. J., Bauman, R. P., Tcheng, J. E. and Greenfield, J. C., Jr. (1988) Interventional cardiac catheterization at Duke Medical Center. Am J Cardiol, 62, 3F-24F.

37. Rhalmi, S.,Odin, M.,Assad, M.,Tabrizian, M.,Rivard, C. H. and Yahia, L. H., Bio-Medical Materials and Engineering, 9(1999)151–162.

38. Schroers, J., Kumar, G., Hodges, T., Chan, S. & Kyriakides, T. (2009). Bulk metallic glasses for biomedical applications. J Mater, 61, 21.

39. Volynova, T. F., Medov, I. B., and Sidorova, I. B., Mechaical properties and the fine structure of powdered Iron-Manganese alloys, Powder Metallurgy and Metal Ceramics, 25(1986)999-1006

40. Tsuji, T., Tamai, H., Igaki, K., Kyo, E., Kosuga, K., Hata, T., Okada, M., Nakamura, T., Komori, H., Motohara, S. and Uehata, H. (2001) Biodegradable polymeric stents. Curr Interv Cardiol Rep, 3, 10-7.

41. Vijay Krishna Raghunathan, Michael Devey, Sue Hawkins, Lauren Hails, Sean A. Davis, Stephen Mann, Isaac T. Chang, Eileen Ingham, Ashraf Malhas, David J. Vaux, Jon D. Lane, Charles P. Case, Influence of particle size and reactive oxygen species on cobalt chromenanoparticle-mediated genotoxicity, 2013

42. Van Der Giessen, W. J., Lincoff, A. M., Schwartz, R. S., Van Beusekom, H. M., Serruys, P. W., Holmes, D. R., Jr., Ellis, S. G. and Topol, E. J. (1996) Marked inflammatory sequelae to implantation of biodegradable and nonbiodegradable polymers in porcine coronary arteries. Circulation, 94, 1690-7.

43. Venkatraman, S., Poh, T. L., Vinalia, T., Mak, K. H. and Boey, F. (2003) Collapse pressures of biodegradable stents. Biomaterials, 24, 2105-11.

44. Wang, Y.B., Zheng, Y.F., Wei, S.C. & Li, M. (2011). In vitro study on Zr-based bulk metallic glasses as potential biomaterials. J Biomed Mater Res, 96B, 34.

45. Waksman, R. (2006) Update on bioabsorbable stents: From bench to clinical. J Interv Cardiol 19, 414-21.

46. Xue-Nan Gu,Yu-Feng Zheng,A review on magnesium alloys as biodegradable materials, Frontiers of Materials Science, 4(2010)111-115
47. Yang, K. & Ren, Y. (2010). Nickel-free austenitic stainless steels for medical applications. Sci Technol Adv Mater, 11, 1.

48. 王姿婷，鐵鎂複合材料製程及性質探討，國立成功大學碩士論文，2015

49. 王盈錦，生物醫學材料，合記圖書出版社，p.157-160，p.166-168，2002

50. 王繼敏，不鏽鋼與金屬腐蝕，科技圖書股份有限公司，p.136-156，1990

51. 宋信文，生醫材料簡介，2003

52. 高材，林康平、林峰輝、陳家進、生物醫學工程導論，中華民國生物醫學工程學會，2008

53. 徐仁輝，粉末冶金概論，新文京開發出版有限公司，2002

54. 黃坤祥，粉末冶金學，中華民國粉體及粉末冶金協會，p43-65，p.163-168，2014

55. 國人膳食營養素參考攝取量，第六版，2003