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氣體釋壓誘引金屬發泡之研究

Producing metal foams by pressure-induced phase separation

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[[abstract]]本研究的目的乃是將PIPS的發泡技術應用到金屬發泡上,並探討其製程條件,包括熔融金屬溫度、氣體壓力,以及氣體種類等對合金發泡及凝固組織的影響。合金試樣首先置入高壓高溫爐中,然後加熱至其固相線之上的溫度,同時高壓高溫爐可視氣體壓力使用範圍選擇性地由管狀爐、熱油壓機或儲槽罐組合而成,將CO2或H2氣體加壓進入高壓高壓爐中。熔融合金在高溫高壓狀態下持續一小時後,予以急速洩壓並淬冷至冷水中以嘗試獲得金屬發泡體。在研究當中發現,氣泡在5Sec之內便已大致完全停止成長,隨著時間的增長,其密度會些微上升;推論是因為氣泡結構體的崩解或排液所造成。Pb-Sn合金使用CO2氣體時,在180℃下,發現壓力越大(100bar?300Bar),則密度越低,孔洞越多,孔徑越大;推論是因為加壓之後可增加CO2在液態金屬中的溶解度所致。然而在190℃之下,孔徑隨壓力的變化並不顯著。微觀組織的觀察進一步發現,富錫相的孔洞較多,顯示富錫相與CO2的親和力較高。然而Pb-Sn合金在205℃與210℃使用H2氣體時,隨壓力增加(2Bar?10Bar)其密度並沒有顯著變化,而微觀結構的觀察也沒有顯著的泡孔產生。推論是因為在低壓的情況下,H2的溶解度並不足以產生大量泡孔。當Zn合金在375℃?400℃,使用H2氣體(2Bar?10Bar),其密度的變化也不顯著。但本研究另外發現其共晶組織的直徑會隨壓力的增大而變小,是一值得進一步研究的課題。

[[abstract]]The purpose of this study is to employ the technique of PIPS (pressure-induced phase separation) in foaming metallic alloys. The effects of the temperature of the molten metal, the gas pressure, and the various kinds of gases on the density and the microstructure of the solidified metal are investigated. The metal sample is loaded into a high-pressure furnace, which could be optionally made of stainless tube, hot press, or pressure vessel, and heated up to their solidus. In the meanwhile, either the pressurized carbon dioxide or hydrogen gas is purged into the high-pressure furnace. After the molten metal is hold at the designed pressure and temperature for one hour, the gas in the furnace is rapidly depressurized. Then, the alloy is quenched into in cold water to study the feasibility in the production of metal foam by the PIPS. It is presumed that the bubbles, created after depressurization, in the liquid molten stops growing within five seconds. It is found that extending the growing time leads to bubble’s merge and collapse and/or drainage, which results in the decrease of the density of the solidified alloys. When carbon dioxide is applied to Pb-Sn alloy at 180℃, the number and the size of the bubbles increases and the density of the solidified alloys decreases while the gas pressure increased from 100 to 300bar. It is presumed that the solubility of carbon dioxide in the molten alloys increases with gas pressure. However, the change of density, bubble size, and number of bubble with gas pressure at 190℃ is not significant as that found in 180℃. This temperature effect needs further study. From their microstructure observed in SEM, it is found that much of the bubbles is located in the Tin-rich phase. It is presumed that the interaction between carbon dioxide and Tin is much stronger than that of Lead. When hydrogen is applied to Pb-Sn alloy at 205 and 210℃, the density of the solidified alloys is not affected by the gas pressure in the range of 2 to 10bar, and no significant bubbles is observed in their microstructure. It is presumed that the solubility of hydrogen gas in this pressure range is too low to create significant number of gas bubbles in the molten metal. This is confirmed by replacing Pb-Sn alloy by Zinc alloy, which also shows that the density of Zinc alloy is not affected by the pressure of the hydrogen gas in the same range of pressure. Interestingly, it is observed that the size of the eutectic structure of the Zinc alloy decreases while the pressure of the hydrogen gas increases. This observation is worth further study.

[[note]][1] 施希弦,“超臨界二氧化碳在高分子發泡之應用面面觀”,化工技術,卷6,期八,頁116-121,1998. [2] 梁明在,戴宏哲,吳昭燕,“超臨界流體於塑膠發泡之應用”,化工技術,頁180-187,10月,民國87年. [3] C. Kőrner, R. F. Singer,“Processing of Metal Foams - Challenges and Opportunities”, Advanced Engineering Materials, Volume 2, Issue 4, pp. 159-165, 2000. [4] J. Banhart,“Foam metal: The recipe”, Europhysical News, pp.17-20, January/February, 1999. [5] T.Mukai,H.Kanahshi,.Yamada,K.Shimojima,M.Mabuchi,T.G.Nie,K.Higashi,“Dynamic compressive behavior of an ultra-lightweight magnesium foam”, Scripta Materialia, volume. 41, No. 4, pp.365-371, 1999. [6] Y.Yamada,K.Shimojima,Y.Sakaguchi,M.Mabuchi,M.Nakamura,T.Asahina, “Processing Of An Open- celllular AZ91 Magnesium Alloy With A Low Density Of 0.05g/cm3”,Journal of materials Science letters 18 ,pp.1477 - 1480, 1999. [7] Y. Yamada, K. Shimojima, Y. Sakaguchi, M. Mabuchi, M. Nakamura, T. Asahina, T. Mukai, H. Kanahashi, K. Higashi, “Processing of Cellular Magnesium Materials”, Advanced Engineering Materials, Volume 2, Issue 4, pp. 184-187, 2000. [8] 劉建偉,宋敏安,周更生,陳信文,呂世源,“以鹽粒子製備低密度多孔金屬鋁之研究”,中國材料科學年會,論文集,pp.49,2000. [9] E. Maine, M. F. Ashby, “Cost Estimation and the Viability of Metal Foams”, Advanced Engineering Materials, Volume 2, Issue 4, pp. 205-209, 2000. [10] 桂椿雄,沈桓儀,“超臨界流體層析儀之介紹”, 化工技術, 6, 140,1998. [11] 姚俊旭,“次臨界及超臨界狀態下二氧化碳對芳香烴、重正烷烴及重烷醇之等溫相平衡”,碩士論文,國立成功大學化學工程研究所,民國81年. [12] 張宏毅,“二氧化碳-水-正丁醇三成份系統高壓相平衡之研究”,碩士論文,國立成功大學化學工程研究所,民國89年. [13] T. J. Bruno, J. F. Ely supercritical fluid engineering science, CRC press, Inc, pp.78-79, 1993. [14] 陳辰昌,“超臨界流體原理及其應用”,製酒科技專論彙編, 期19, 頁276-286, 3月,民國86年. [15] 楊武勇,“超臨界流體在化學工程上之應用”,化工資訊, 卷10,期6, 頁23-30, 6月,民國85年. [16] M. A. Abraham, A. K. Sunol, Supercritical Fluids, American chemical society, pp.2-25, 1997. [17] 比重及密度測試,陶瓷實驗課本,義守大學材料工程系,一版,民國八十九年. [18] 陳道達,熱分析,國立編譯館出版. [19] R. J. Fruehan, Gases in Metals,volume 15,Metals handbook,9th,by American society for metals,pp82-87,1989. [20] 陳文照,曾春風,林淳傑,劉偉隆,物理冶金,3rd,全華出版社,pp.14-45?14-48,1996. [21] C. J. Smithells, Metal reference book, 5th,by Butterworths, pp.835-859, 1977. [22] 錢增源,低融點金屬的熱物性,科學出版社,pp.53,1985. [23] 黃禎烈,楊智超,林於隆,非鐵合金鑄造手冊,中華民國鑄造協會出版,pp.13-14,民國86年.