摘要
本文在对氟化钪、氧化钪金属热还原的还原反应进行了热力学计算和分析的基础上,提出了采用ScF_3-MF-Mg(Al)热还原法制备Al-Mg-Sc中间合金的新思路;利用热分析技术结合相图资料方法研究了ScF_3-MF-Mg热还原反应机理,采用Freeman-Carrol法和Kissinger法计算了反应级数与反应活化能,并在此基础上进行了还原反应熔盐体系优选;对ScF_3-MF-Mg(Al)热还原法制备Al-Mg-Sc中间合金的新工艺实验条件进行了优化,制备出了含钪量为2%的Al-Mg-Sc中间合金,制备新工艺中钪回收率达80%;利用研制的中间合金制备了Al-5Mg-Sc系列合金,通过对加钪和不加钪的合金组织与性能的对比研究,对Al-5Mg-Sc合金的应用进行了评价。
其热力学计算结果表明,ScF_3与Mg之间的还原反应在热力学上是可行的,而Sc_2O_3与Mg及ScF_3与Al之间的反应是不可行的。制备Al-Mg-Sc中间合金时应采用ScF_3为原料,Mg为还原剂,在过量Al熔体中进行。还原产生的初生态Sc与Al形成稳定的Al_3Sc金属间化合物,从而使金属热还原的Δ_rG_m~0(T)减少了138KJ/mol,由此增加了反应体系的熵变值,大大提高了金属热还原进行的趋势。在温度为1100K的Al熔体中Mg热还原制备Al-Mg-Sc中间合金,当使用ScF_3为原料且在氟化物熔盐体系中进行时,还原反平衡常数计算值可达6.6×10~9。
研究了Sc_2O_3-NH_4HF_2固相氟化及ScF_3-Mg热还原机理,利用DTA分析方法研究了ScF_3-Mg热还原反应的热力学及动力学机理。研究结果表明Sc_2O_3与NH_4HF_2分解产生的HF反应生成ScF_3。ScF_3-Mg体系590℃发生ScF_3-Mg(s)固-固还原反应;740℃发生ScF_3-Mg(1)固-液还原反应;ScF_3-LiF-Mg体系在496℃发生ScLiF_4(s)-Mg(s)固-固还原反应;650℃发生(ScF_3-LiF)-Mg(1)液-液还原反应。计算了Mg热还原的动力学参数,其反应活化能E=48.62KJ/mol,反应级数n=1.03。
研究制定了ScF_3-MX熔盐在Al熔体中Mg热还原制备Al-Mg-Sc中间合金的新工艺,研究结果表明新工艺能制备Sc含量大于1.5wt%的Al-Mg-Sc中间合金,最佳的还原反应温度为1100℃,还原时间40min;二次还原后,Sc收率大于80%。
微量Sc在Al和Al-Mg合金中,除少量固溶在基体中。主要以两种析出的Al_3Sc金属间化合物的形式存在。其中一种为合金凝固过程中析出的一次Al_3Sc粒子,起非均质晶核的作用,可强烈细化合金的铸态晶粒组织,并由于细晶强化作用可使Al-Mg合金的强度大大提高。由于在Sc含量较低时,Sc与Mg并不形成金属间化合物,在研究的成分范围内Sc在Mg合金中多以固溶体形式存在。
利用研制的Al-Mg-Sc中间合金制成Al-5Mg-Sc合金,当Sc含量为0.2%时,合金晶粒细化效果不明显;当Sc含量大于0.4%时,铸态合金晶粒得到明显细化,当Sc含量为1.45%时,铸态合金晶粒最细小。表明研制的中间合金是Al-Mg合金的变质剂。
Based on thermodynamics calculation and analysis about the reduction reaction of ScF3, 80203 metallic thermoreduction, the paper put forward to a new preparation method of Al-Mg-Sc master alloys by means of ScF3-Mx-Mg (Al) metallic thermoreduction; It studied the mechanism of ScF3-MF-Mg thermoreduction reaction using DTA and phase diagram analysis and computed reaction progression and reaction activation energy using the Freeman-Carrol method and the Kissinger method, and then on the basis of these results chose the most suitable molten salt system of the thermoreduction reaction. It also optimized the experimental conditions of the new technics preparing Al-Mg-Sc master alloys in which the recovery of Sc is 80% and got the Al-Mg-Sc master alloys with 2% Sc content; And then a sheet of Al-Mg alloys with and without Sc was manufactured by using these Al-Mg-Sc master alloys, whose microstructure and properties were studied contrastively and whose application was valued.
The results of thermodynamics calculation indicated that ScF3 can be reduced to scandium by magnesium, but Sc2O3 can not be reduced to scandium by magnesium and aluminum .If reduction reaction are proceeded in aluminum bath, the entropy of system will be increased because of the formation of the stable intermetallic compound Al3Sc whose standard Gibbs formation free energy is estimated to be about -138KJ/mol. Owing to the sequent formation of Al3Sc, thermodynamics tendency of reduction will be greatly enhanced and equilibrium constants and conversion ration of reduction will be greatly enlarged. Therefore Al-Mg-Sc master alloy can be gained well by reducing ScF3 using magnesium in aluminum bath. At 1100K ,the empirical equilibrium constants of ScF3-MX-Mg(Al) reduction system is 6.6 109 .
Principles of scandium oxide solid fluorinating and ScF3-Mg thermoreduction reaction were researched by thermal analysis (DTA). The results indicated that scandium oxide was fluorinated by the reaction with hydrogen fluoride gas coming from NH4HF2 decomposing and ScF3-Mg system starts ScF3(s)-Mg(s) solid-solid phase reduction at 590 C, ScF3(s)-Mg(l) solid-liquid phase reduction at 740 C, ScF3-LiF-Mg system starts ScLiF4(s)-Mg(s) solid-solid phase reduction at 496 C ,(ScF3-LiF)(l)-Mg(l) liquid-liquid phase reduction at 650 C .The kinetics parameters of ScF3-Mg reaction were calculated. The activation energy E=48.62KJ/mol, reaction progression n=1.03.
The optimum reduction temperature of ScF3-MX-Mg(Al) to manufacture Al-Mg-Sc master alloy is 1100 C,time is 40 min, the concentration of scandium in
Sc-bearing master is more than 1.99%. All recovery can be up to 91.9% after
fluoridating and reduction secondly.
Most part of minor scandium in pure Al and Al-Mg alloys exists in form of primary of secondly A13Sc,only a few of then stayed in a (Al) based solid solution .The primary AlsSc particles precipitating from melt of alloy during cooling act as inhomogeneous nuclei and fining grain size effectively. Most part of scandium stayed in magnesium based solid solution in our composition because magnesium and scandium don't act each other to form intermetallic compound when scandium concentration is low.
Al-5Mg-Sc ingots were manufactured by mixing Al-Mg-Sc master alloy with metals needed. When scandium concentration is about 0.2%, the effect of grain fining of master alloy prepared was not remarkably. When scandium concentration is about 0.4%, the effect of grain fining of master alloy prepared was remarkably. The effect of grain fining of master alloy prepared was most remarkably, when scandium concentration is about 1.45%.
引文
[1] 易宪武。钪[M] 。北京:科学出版社,1992。
[2] Spedding EH., Croat J.J. Magnetic properties of high purity scandium and the effect of impurities on these properties [J] o chem..Phys., 1973, 58 (12): 5514
[3] 18-19 1994.[A].Moscow: 1994, 13: 9.
[4] 徐进修。高新技术用材料钪的提取冶金(一)[J] 。广西冶金,1993,(1):1-11。
[5] 张玉学,何其光,邵树勋等。铝土矿钪的地球化学[J] 。地质地球化学,1999,27(2):55-62。
[6] 黄机炎。钪资源开发与工业应用简况[J] 。稀土,1988,(2):49-54。
[7] 李汉广,尹志民,刘竟安。含钪铝合金的开发应用前景[J] 。铝加工,1996,19(1):45-48。
[8] 林肇奇,马宏声,赵刚。铝钪合金的发展概况[J] 。轻金属,1992,(1):54-58。
[9] 潘青林,高拥政等。Sc对Al-Mg合金组织与性能的影响[J] 。材料科学与工艺,19975(4):9~13
[10] 孙志臣。钪的应用[J] 。湖南稀土,1991(3):9。
[11] 刘世友。钪的资源、生产、应用与开发[J] 。稀有金属与硬合金,1995,121(2):57-61。
[12] 姜锋 尹志民 李汉广。铝钪合金的制备方法[J] 。稀土,2001,22(1):21~24。
[13] 廖春生,徐刚,贾江涛等。新世纪的战略资源.钪的提取与应用[J] 。中国稀土学报,2001,19(4):289-297。
[14] 李正安,利用钛白粉生成的废酸提取高纯氧化钪[J] 。河南化工,1996,(2):32-33。
[15] 杨健张湛惠。从钛白用液中提取钪的研究[J] 。金属矿山,1991,(12)52-54。
[16] 李勇明,陈建军。对钛白用液中提取钪工艺流程的改进研究[J] 。稀有金属与硬质合金,1997,128:1-2。
[17] 张湛惠。浅谈综合回收钪的意义[J] 。金属矿山,1990,(9):43-47。
[18] 赵杰,马国杰,李义辉。黑钨矿渣的综合利用[J] 。化学世界,1990,(10):472-475。
[19] 徐进修。高新技术用材料钪的提取冶金(二)[J] 。广西冶金,1993,(2):35-42。
[20] 袁茂林。稀土火法冶金工艺学[M] 。中国有色金属工业总公司:北京,1986。
[21] 陆庆桃,倪福生。钪的应用及其提取冶金的进展[J] 。上海有色金属,1995,16(3):160-165。
[22] 李汉广,尹志民。钪的发展动态与发展战略[J] 。稀有金属与硬质合金,1996,19(1)45-48。
[23] 高拥政,尹志民,潘青林等。用微量钪合金化的新型铝钪合金[J] 。兵器材料与工程,1998,21(1):24-26.
[24] 谢燮揆译。用钪合金化的铝合金[J] 。轻金属,1993,(3):54-58。
[25] 夏德顺。含钪的铝和铝锂合金[J] ] 。航天工艺,1999,(4):37-42。
[26] 1965, (4)176-182.
[27] 1984, (4) 180-183.
[28] OkamotoHo J Phase Equilibria, 1991, 12 (5): 612
[29] Murray L J. J Phase Equilibria, 1998, 19 (5): 380
[30] Davydov V Go Scientific principes of making an alloying addition of Scandium to aluminum alloys [J]. Materials Science Engineering A, 2000, 280 (1): 30-36.
[31] Yu A, Filatovo New Al-Mg-Sc alloys [J]. Materials Science Engineering A, 2000, 289 (1): 97-101.
[32] Filatov Yu.A. Deformable Alloys Based on the Al-Mg-Sc System [J]. Met. Sci. & Heat Tr., 1996, (6): 271-274.
[33] 2002 (2): 96-104.
[34] 2001 (6) 117-123.
[35] Shogo Komura, Zenji Horita et alo Influence of scandium on superplastic ductilities in an Al-Mg-Sc alloys [J]. J. Mater. Res., 2000, 15 (11): 2571-2576.
[36] Yin, Qinglin Pan, Yonghong Zhang, Feng Jiango Efeect of minor Sc and Zr on the microstructure and mechanical properties Al-Mg based alloys [J]. Mater Sci. Eng A, 2000, 280 (1) 151.
[37] Elagin V. I., Zaharov V. V., Rostova T. D. o Scandium-alloyed aluminun alloys [J]. Met. Sci. Tret., 1992, 34:37-45
[38] Fukunaga K., Shouji T., Miura Y. Temperture dependence of dislocation structure of LI_2-Al_3Sc [J]. Mat. Sci. & Eng, 1997, A239-340: 202-205.
[39] Roder O., Wirtz T., Gysler A.o Fatigue properties of Al-Mg alloys with and without scandium [J]. Mat. Sci.Eng.1997, A234-36.. 181-184.
[40] John S. Vetron, Steve M., Bruemmer. Influence of the particle size on recrystallization and grain growth in Al-Mg-X alloys[J]. Mat. Sci. & Eng, 1997, A238: 101-107.
[41] Xu J. H., Freeman A. J. Phase stability and electronic structure OF ScAl_3 and ZrAl_3 and of So-stabilized cubic ZrAl_3 percipitates [J]. Physical review B, 1990, 41 (2): 12 556-12 561.
[42] http://www.study.ntun.nu/alsc-ref.htlm.
[43] Murray, et al. Method for the recovery of rare earth metal alloys [P]. US patent 4,
648, 901. 1987.
[44] 路贵民,刘学山。氧化钪在nNaF·AlF3-ScF3熔盐体系中的溶解[J] 。中国有色金属学报,1999,9(3):624-626。
[45] 孙志臣。钪在铝合金中的应用[J] 。湖南冶金,1991,(1):31-33。
[46] Tian Yanwen, Sun Benliang, Zhai Yuchuno Preparation of Al-Sc alloy in chloride system with molten salt electolysis [J]. Trans. Nonferrous Met. Soc.China, 1998, 8 (4): 626-631.
[47] 孙本良,翟玉春,田彦文。氟盐体系中电解制取铝钪中间合金的研究[J] 。稀有金属,1998,22(3):191-193。
[48] Aleksandrovskij S, Zakharecivh A A, Kolesnikov V A, et al. Production feasibility of improved-quality scandium by sodium-thermic reduction of chloride aluminum-scandium master alloyso U. S. S. R. SU1812810Al 27Aug 1996.
[49] 姜锋,尹志民,李汉广等。氧化钪-氯化-铝镁热还原法制备钪中间合金新工艺研究[J] 。稀土,2001,22(3):34-36。
[50] 路贵民,刘学山。冰晶石熔体中Al热还原制备Al-Sc合金[J] 。中国有色金属学报,1999,9(1):171-174。
[51] 梁英教、牛荫星。无机物热力学数据手册[M] 。沈阳:东北大学出版社,1993。
[52] 1997。
[53] 1982, 356-357.
[54] Ratne A.H., Geilikman M.B., Aleksandrovski S.V., Jiang Feng, LiHanGuang, Yin ZhiMino Thermodynamic calculation on metallic thermoreduction during preparation of aluminum-rare earth master alloys [J]. Trans. Nonferrous Met. Soc. China, 2001, 11 (6): 18-21.
[55] 1998, 6:70-760
[56] E. W. DEWING. Thermodynamic Functions for LiF-AlF_3 Mixtures at 1293K [J]. METALLURGICAL TRANSACTIONS B, 1980, 11B (6): 245-249.
[57] E. W. DEWING. Thermodynamic of the system NaF-AlF_3 [J]. METALLURGICAL TRANSACTIONS B, 1972, 3 (2): 495-501.
[58] 许茜,邱竹贤。LiF-MgF2、NaF-MgF_2、KF-MgF_2系热力学性质及相图计算[J] 。有色金属,1994,46(3):48-52。
[59] 陈新民,陈启民。冶金热力学导论[M] 。北京:冶金工业出版社,1986。
[60] A. Pisch et al. Mg-rich Phase Equilibria and Thermodynamic Assessment of the Mg-Sc
System[J] , Z.Metallkd, 1998, 89 (7): 474-477.
[61] 陈镜泓,李传儒。热分析及其应用[M] 。北京:科学出版社,1985。
[62] 刘预知。无机物理化性质及重要反应方程式手册[M] 。成都:成都科技大学出版社,1992。
[63] 刘振海。热分析导论[M] 。北京:化学工业出版社,1991。
[64] 梁连科,车荫昌,杨怀,李宪文。冶金热力学及动力学[M] 。沈阳:东北工学院出版社,1990。
[65] 程兰征,章燕豪。物理化学[M] 。上海:上海科学技术出版社,1988。
[66] 余琨,黎文献,李松瑞,谭敦强。含稀土镁合金的研究与开发[J] 。特种铸造及有色合金,2001(1):41-43。
[67] 潘青林。Al-Mg-Sc和Al-Mg-Sc-Zr合金的性能与组织结构研究,中南工业大学博士论文[D] 。长沙,2000年3月。
[68] Alexander Pisch, Joachim Grobner, Rainer Schmid-Fetzer . Application of computation thermochemitry to Al and Mg alloy processing with Sc addition [J]. Materails Science Engineering , 2000, A298: 123-129.
[69] Jackson K.A..J. Crystal Growth [J]. 1967, (1): 1.
[70] Blake N., Hopkins M.A. Constitution and age hardening of Al-Sc Alloys [J]. J. Mater. Sci., 1985, (20): 2861-2867.
[71] 孙伟成,张淑荣,候爱芹。稀土在铝合金中的行为[M] 。北京:兵器工业出版社,1992。
[72] 毛裕文。冶金熔体[M] 。北京:冶金工业出版社,1994。
[73] 段淑贞等。熔盐化学:原理与应用[M] 。北京:冶金工业出版社,1990。
[74] 别略耶夫。熔盐物理化学[M] 。北京:中国工业出版社,1963。
[75] 刘刚,陈瑞亮,李生河等。熔盐.液体金属相互溶解度的规律[J] 。金属学报,1997,33(9):939-941。
[76] B.M.邦达列夫等著,王永海等译。变形铝合金的细化处理[M] 。北京:冶金工业出版社,1998。
[77] 尹志民,高拥政,潘青林等。微量Sc和zr对A1-Mg合金铸态组织的晶粒细化作用[J] 。中国有色金属学报,1997,7(4):75-78。
[78] 韩德伟。金属学实验指导书[M] 。长沙:中南工业大学出版社,1990。