碱金属氟化物润湿和溶解废铝表层氧化膜的行为与机理
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摘要
应用纳米扫描俄歇系统、分子动力学模拟和聚合实验,研究A356铝屑表面氧化膜的结构及含碱金属氟化物的熔剂润湿和溶解该氧化膜的行为,并探讨铝屑在熔剂中的聚合机理。结果表明:等摩尔NaCl-KCl熔剂及添加NaF或Na_3AlF_6后都可以与Al_2O_3润湿,而添加AlF_3的熔剂与Al_2O_3不润湿。添加氟化物的等摩尔NaCl-KCl熔剂可以溶解氧化膜,并使铝屑聚合为铝球,其中NaF和Na_3AlF_6对促进聚合的效果最显著,而AlF_3效果较差。聚合机理分析表明,熔融熔剂中的自由F-是铝屑聚合的前提条件,熔剂与Al_2O_3良好的润湿性可以提高氧化膜的溶解程度。氧化膜溶解后被其包裹的铝液滴可以自发地聚合成大的铝球,熔剂与铝液的不润湿性有利于铝液滴的聚合,但加入Na_3AlF_6后会比较显著提高熔剂黏度,阻碍细小铝球的聚合。
Nano scanning auger system, molecular dynamics simulations and coalescence experiments were employed to study the oxide film structure of A356 alloy chips and the behaviors of salt fluxes containing alkali fluorides wetting and melting oxide films. Moreover, the coalescence mechanism was discussed. The results show that equimolar Na Cl-KCl with addition of Na F or Na_3AlF_6 wetted well with Al_2O_3 inclusions but addition of AlF_3. Eequimolar Na Cl-KCl containing alkali fluorides can melt oxide film and promote the coalescence of wrapped aluminum droplets in molten fluxes. The effects of Na F and Na_3AlF_6 on coalescence are more significant than that of Al F_3. The coalescence mechanism analysis results show that free F-ions are the premise for chips coalescence and the wetting between fluxes and Al_2O_3 inclusions improve the coalescence degree. Aluminum droplets can coalesce spontaneously in molten fluxes and the non-wetting between fluxes and aluminum liquid is benefit for the coalescence, but the improvement of fluxes viscosity by Na_3AlF_6 will resist the coalescence of small aluminum droplets.
Nano scanning auger system, molecular dynamics simulations and coalescence experiments were employed to study the oxide film structure of A356 alloy chips and the behaviors of salt fluxes containing alkali fluorides wetting and melting oxide films. Moreover, the coalescence mechanism was discussed. The results show that equimolar Na Cl-KCl with addition of Na F or Na_3AlF_6 wetted well with Al_2O_3 inclusions but addition of AlF_3. Eequimolar Na Cl-KCl containing alkali fluorides can melt oxide film and promote the coalescence of wrapped aluminum droplets in molten fluxes. The effects of Na F and Na_3AlF_6 on coalescence are more significant than that of Al F_3. The coalescence mechanism analysis results show that free F-ions are the premise for chips coalescence and the wetting between fluxes and Al_2O_3 inclusions improve the coalescence degree. Aluminum droplets can coalesce spontaneously in molten fluxes and the non-wetting between fluxes and aluminum liquid is benefit for the coalescence, but the improvement of fluxes viscosity by Na_3AlF_6 will resist the coalescence of small aluminum droplets.
引文
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[2]CUI J,ROVEN H J.Recycling of automotive aluminum[J].Transactions of Nonferrous Metals Society of China,2010,20(11):2057-2063.
[3]XIAO Y,REUTER M A,BOIN U D O.Aluminium recycling and environmental issues of salt slag treatment[J].Journal of Environmental Science and Health,2005,40(10):1861-1875.
[4]谭喜平,郑开宏,宋东福,张新明.Al-3B中间合金添加量对再生铸造铝合金中杂质铁含量的影响[J].中国有色金属学报,2014,24(6):1401-1407.TAN Xi-ping,ZHANG Kai-hong,SONG Dong-fu,ZHANG Xin-ming.Effects of Al-3B master alloy addition on impurity iron content of recycled casting aluminum alloy[J].The Chinese Journal of Nonferrous Metals,2014,24(6):1401-1407.
[5]孙德勤,戴国洪,徐越.熔剂法去除废铝熔体中镁的试验研究[J].轻合金加工技术,2015,43(12):23-27.SUN De-qin,DAI Guo-hong,XU Yue.Study on the Mg element removing technology from Al slag melts by fluxing technology[J].Light Metal Fabrication Technology,2015,43(12):23-27.
[6]孙德勤,戴国洪,徐越.废铝熔体中去除Cr元素的试验研究[J].轻合金加工技术,2016,44(1):24-28.SUN De-qin,DAI Guo-hong,XU Yue.Experiments of removing Cr from waste Al slag melts[J].Light Metal Fabrication Technology,2016,44(1):24-28.
[7]KHOEI A R,MASTERS I,GETHIN D T.Design optimization of aluminium recycling processes using Taguchi technique[J].Journal of Materials Processing Technology,2002,127(1):96-106.
[8]ZHOU B,YANG Y,REUTER M A,BOIN U M J.Modeling of aluminium scrap melting in a rotary furnace[J].Minerals Engineering,2006,19(3):299-308.
[9]BUTNARIU I,BUTNARIU I,BUTNARIU D.Technological researches concerning a decrease in the losses due to the oxidation of remelted scrap from aluminium alloys[J].Materials Science Forum,2010,630:71-74
[10]MOLOODI A,AMINI H,KARIMI E Z V,GOLESTANIPOUR M.On the role of both salt flux and cold pressing on physical and mechanical properties of aluminum alloy scraps[J].Materials and Manufacturing Processes,2011,26(9):1207-1212.
[11]XIONG B,ZHANG X,LI F,HU H,LIU C.Recycling of aluminum A380 machining chips[C]//HYLAND M.Light Metals.New Jersey:TMS,2015:1011-1015.
[12]YE J,SAHAI Y.Interfacial behavior and coalescence of aluminum drops in molten salts[J].Materials Transactions,1996,37(2):175-180.
[13]XIAO Y,REUTER M A.Recycling of distributed aluminium turning scrap[J].Minerals Engineering,2002,15(11):963-970.
[14]ROY R R,SAHAI Y.Coalescence behavior of aluminum alloy drops in molten salts[J].Materials Transactions,1997,38(11):995-1003.
[15]ZHOLNIN A G,NOVICHKOV S B.About the coalescence mechanism of aluminum,the analysis of the recent conceptions[C]//KVANDE H.Light Metals.Pennsylvania:TMS,2005:1197-1202.
[16]SYDYKOV A,FRIEDRICH B,ARNOLD A.Impact of parameters changes on the aluminum recovery in a rotary kiln[C]//SCHNEIDER W.Light Metals.Washington:TMS,2002:1045-1052.
[17]MASSON D B,TAGHIEI M M.Interfacial reactions between aluminum alloys and salt flux during melting[J].Materials Transactions,1989,30(6):411-422.
[18]SUN H.COMPASS:An ab initio force-field optimized for condensed-phase applications overview with details on alkane and benzene compounds[J].The Journal of Physical Chemistry B,1998,102(38):7338-7364.
[19]YEH I C,LENHART J L,RINDERSPACHER B C.Molecular dynamics simulations of adsorption of catechol and related phenolic compounds to alumina surfaces[J].Journal of Physical Chemistry C,2015,119(14):7721-7731.
[20]CHEN C F,LI H Y,HONG C W.Molecular dynamics analysis of high-temperature molten-salt electrolytes in thermal batteries[J].CMC:Computers,Materials and Continua,2015,46(3):145-163.
[21]张亚楠.Na F-Al F3基电解质氧化铝溶解过程研究[D].北京:北京科技大学,2015:104-115.ZHANG Ya-nan.Study on dissolution process of alumina in Na F-Al F3-based melts[D].Beijing:University of Science and Technology Beijing,2015:104-115.
[22]徐宁,郭咏梅,邱竹贤.冰晶石-氧化铝熔体中的酸碱体系[J].东北大学学报(自然科学版),2000,21(1):63-65.XU Ning,GUO Yong-mei,QIU Zhu-xian.The acid&alkali system in cryolite-alumina melts[J].Journal of Northeastern University(Natural Science),2000,21(1):63-65.
[23]ROY R R,YE J,SAHAI Y.Viscosity and density of molten salts based on equimolar Na Cl-KCl[J].Materials Transactions,1997,38(6):566-570.
[24]TENORIO J A S,ESPINOSA D C R.Effect of salt/oxide interaction on the process of aluminum recycling[J].Journal of Light Metals,2002,2(2):89-93.