本研究主要目的是分析數種含鉬高矽球墨鑄鐵的顯微組織與機械性質的特性及其間的關連性。研究的進行是利用熔煉時調整矽與鉬的添加量，澆鑄成Y形塊後再車製出試片，供金相觀察與機械性質測試。室溫機械性質測試包括硬度、拉伸及衝擊試驗，而在高溫650℃的機械性質測試是拉伸及衝擊試驗；並利用EPMA分析元素的分佈以探討偏析的特性。
實驗結果顯示：(1)高矽球墨鑄鐵中添加鉬，會在晶胞間處偏析出含鉬的共晶碳化物，並在其外圍區域出現顆粒狀析出碳化物，該析出碳化物區域的鉬含量超過2wt%；(2) 高矽球墨鑄鐵的高溫抗拉強度隨鉬含量而增強，這應與肥粒鐵基底的鉬含量及晶胞間共晶碳化物的增加有關；(3)矽含量增加，會對肥粒鐵基底產生固溶強化的效果，提高材料的室溫硬度和抗拉強度，但也使之脆化；(4)共晶碳化物隨鉬含量增加而增多，並形成網狀結構，相對上其對室溫機械性質並不比矽來的顯著。

In this research it is aimed to investigate the characteristics of the microstructures and mechanical properties of high silicon ductile irons with alloying molybdenum. The study was carried with adjusting the silicon and molybdenum contents during melting, then the casting of Y-blocks and machining the testing specimens for metallographic examination and testing of mechanical properties. Mechanical testing in room temperature included hardness, tensile and impact testing; mechanical testing in 650C high temperature included tensile and impact testing; The EPMA was used to analyze the elements distribution to study the mechanism of segregation.
The results show that: (1) For high silicon ductile irons with molybdenum alloying, eutectic carbide containing molybdenum existed in the intercellular regions together with fine particles of carbide precipitated along its outer vicinity, those fine particles precipitated areas have a molybdenum concentration over 2.0wt.%; (2) The high temperature tensile strength of high silicon ductile irons increase with the increasing of molybdenum content, that strengthening effect could be attributed to the strengthening in the ferrite matrix from molybdenum and intercellular eutectic carbide ; (3) The solid-solution strengthening effect on the ferrite matrix by increasing of silicon content did increase the room temperature strength but impair its toughness; (4) The amount of intercellular eutectic carbide increased with the increasing of molybdenum content, and then tended to form network structure. Relatively, these intercellular eutectic carbides did not have strong effect on the mechanical properties in room temperature when comparing to the influence of silicon.

參考文獻

1. 王信義，「高矽低合金球墨鑄鐵偏析現象之研究」，碩士論文，國立台灣科技大學，台北(2004)。
2. 潘永寧，「耐高溫球狀石墨鑄鐵」，機械月刊，第10卷，第8期，第95~101頁，民國73年八月(1984)。
3. 吳慶郎，「球墨鑄鐵的凝固模擬」，碩士論文，台灣工業技術學院，台北(1988)。
4. Schissler J.M. and J. Saverna, “The Effect of Segregation on the Formation of Austempered Ductile Iron”, J. Heat Treating, Vol.4, No.2, pp.167~176(1985).
5. 陳興時、黃瀛珍、洪敏雄、吳正棕，「矽含量與鑄件大小對肥粒鐵系球墨鑄鐵機械性質的影響」，鑄工，第33期，第1~11頁，民國71年六月(1982)。
6. 潘國桐 等譯，球墨鑄鐵手冊，中華民國鑄造學會，民國83年11月(1994)。
7. Walton,C.F., Iron Casting Handbook, Iron Casting Society, pp.358~374 (1981).
8. 林本源，「合金元素對球墨鑄鐵沃斯回火相轉變的影響」，博士論文，台灣工業技術學院，台北(1995)。
9. Shubat G. J., Metals Handbook 8th edition Vol.8 – Metallography, Structure and Phase Diagrams, ASM (1973).
10. Black B., Burger G., Logan R., Perrin R., Gundlach R., “Microstructure and Dimensional Stability in Si-Mo Ductile Irons for Elevated Temperature Applications”, SAE 2002-01-2115, SAE, Warrendale PA.(2002).
11. 岩渕義孝、小林勳、成田英記、竹之內朋夫，「肥粒鐵基地球狀石墨鑄鐵之高溫粒界脆性」，日本鑄造工學，第68卷，第3號，pp.209~215(1996)。
12. 林宏茂、呂傳盛、陳立輝，「鎂元素及鉬元素對高矽球墨鑄鐵熱循環誘發沿晶脆性破壞之影響」，鑄造工程學刊，第32卷，第1期，民國九十五年三月(2006)。
13. Park S. H., Kim J. M., Kim H. J., Ko S. J., Park H. S., Lim J. D., ”Development of a Heat Resistant Cast Iron Alloy for Engine Exhaust Manifolds”, SAE 2005-01-1688, SAE, Warrendal PA.(2005).
14. 式田昌弘、松本弘司，「各種石墨型態鑄鐵在高溫範圍的拉伸特性」，日本鑄造工學，第70卷，第9號，pp.629~634，(1998)。
15. CHENG, C.P., S.M. CHEN, T.S. LUI, and L.H. CHEN, ” High- Temperature Tensile Deformation and Thermal Cracking of Ferritic Spheroidal Graphite Cast Iron”, Metallurgical and Materials Trans. A, Vol.28A , pp.325~333(1997).
16. Park, Y.J., R.B. Gundlach, R.G. Thoas, and J.F. Janowak, “Thermal Fatigue Resistance of Gray and Compacted Graphite Iron”, AFS Trans., Vol. 93, pp.415~422(1985)
17. Roehring, K., ”Thermal Fatigue of Gray and Ductile Irons”, AFS Trans., Vol. 86, PP.75~88 (1978).
18. 中華民國國家標準CNS 5536 ，「鋼鐵及耐熱合金之高溫拉伸試驗法」，經濟部中央標準局，民國86年10月(1997)。
19. ASTM E21-92, Standard Test Methods for Elevated Temperature Tension Tests of Metallic Materials, (1998).
20. ASTM E8-96, Standard Test Methods for Tension Testing of Metallic Materials, (2003).
21. ASTM E23-96, Standard Test Methods for Notched Bar Impact Testing of Metallic Materials, (2003).