微量Sr和高频磁场对AZ91D镁合金组织及性能的影响
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摘要
镁合金具有比重轻、高比强度、高比刚度以及良好的铸造性能、良好的电磁屏蔽能力和易于再生利用等一系列独特的优点，在汽车、飞机、计算机及通讯等设备上获得了日益广泛的应用，被认为是“21世纪最具发展潜力和前途的材料”。但镁合金密排六方的晶体结构决定了其塑性变形能力较差、成材率低、力学性能差等一系列问题，解决这些问题是镁合金进一步应用的关键。实践证明晶粒细化既能提高材料的强度，又能提高材料的塑性，所以晶粒细化在镁合金的研究中显得尤为重要。
本文以Mg-Al-Zn系中最具有代表性的AZ91D合金的组织细化作为研究方向，以溶质元素Sr和高频磁场对AZ91D的组织和性能的影响为主要研究内容，探讨AZ91D的化学成分、组织结构和性能变化之间的关系，以提高合金的综合性能。
本文通过添加微量Sr配制了四种合金。采用光学显微镜(OM)、X射线衍射仪(XRD)、差示扫描量热仪(DSC)、带能谱分析(EDS)的扫描电子显微镜(SEM)等分析手段，通过对合金的抗拉强度、伸长率、流动性等性能的测试，较系统和深入地研究了Sr对AZ91D合金组织及力学性能的影响及其作用机理。同时，在工艺方面，通过在合金熔液的凝固过程中施与高频磁场，研究了初生晶形态的演变过程和机制，以及高频磁场对合金显微组织的影响。
研究表明，铸态时，合金的显微组织主要是由α-Mg基体和离异共晶析出的化合物β-Mg_(17)Al_(12)相组成，添加0.2wt％Sr和0.5wt％Sr的合金中未发现存在不同于原始AZ91D合金组织的新相，而添加0.8wtSr％的合金中有新的Al_4Sr相生成。添加微量Sr元素，合金晶粒得到明显的细化，且随着Sr含量的增加，细化程度不断增加，晶粒大小由平均250μm减少到120μm。通过面分布分析发现合金中的Sr元素几乎都分布在晶界上，合金的其他元素如Mn、Zn和Al等也主要存在在晶界上。Sr以两种形式存在于合金中：一方面以固溶形式存在于合金中，影响Mg_(17)Al_(12)相的形态，作为表面活性元素细化晶粒；另一方面生成新的化合物Al_4Sr相，Al_4Sr相是高温稳定相，可以提高合金的共晶温度，从而细化晶粒。
由于晶粒细化的作用，合金的力学性能得到了一定程度的提高。AZ91D合金的抗拉强度是129MPa，而添加0.8wt％Sr以后，抗拉强度可达到160MPa，提高了23.6％。AZ91D的伸长率是1.1％，AZ91D-0.5wt％Sr、AZ91D-0.8wt％Sr的伸长率分别为1.95％和1.3％。铸态下AZ91D合金断裂总体上属于脆性断裂，从断口来看，具有解理特征，合金经Sr变质处理后，断口呈现一定的韧窝和撕裂棱，具有准解理断裂的特征，说明经Sr变质处理后，合金的韧性更好。
Sr的加入，对合金的固相线温度影响不大，但能明显降低合金的液相线温度。液相线温度从AZ91D合金的596℃下降到添加0.8wt％Sr后的566℃，固相线温度从AZ91D合金的435℃升高到添加0.8wt％Sr后的437℃，合金的结晶温度间隔减小了32℃。AZ91D合金流动性试验中螺旋型浇注试样长度为33mm，而当加入0．5wt％Sr后，其长度为40mm，合金的流动性比加入前提高了21％。
AZ91D镁合金在常规凝固条件下，由于成分过冷，α-Mg相为粗大的、明显的树枝晶，晶界上的共晶体形成连续的网状结构，且共晶组织较厚。经高频电磁搅拌后晶粒有所细化，晶粒变得圆整和细化，晶粒大小从180μm减小到120μm。用石英管作为加热容器会使石英管中的硅与镁反应生成Mg_2Si，离石英管壁越近，Mg_2Si越多。经热力学计算，证明反应2Mg(l)+SiO_2(s)→Mg_2Si(S)+O_2(g)在963K时可自发进行。电磁场对凝固过程中的合金的影响主要是促使枝晶破碎和提高合金元素在镁中的溶解度。
Magnesium alloy has the advantages of light-weight, high strength-to-weight ratio, high stiffness-to-weight ratio, good solidification, high electromagnetism shielding property and re-cyclability and so on, so it has bright promise for magnesium alloy to be widely used in vehicle and spaceflight, computer, communication, and is regarded as the most promising material of the 21 st century. However, for its h.c.p structure, it exhibits bad deformation ability, low efficiency, and bad mechanical properties. Solving these problems is the key to develop more application of magnesium alloy. It is found that grain refinement can increase the intensity and plasticity of materials, so it plays a very important role in the research of magnesium alloys.
Structural refinement during solidification of AZ91D alloy in Mg-AI-Zn system has been studied with a focus on the effects of solute elements Sr and high frequency electromagnetic field stirring on microstructures and mechanical properties. The relations of chemical composition, microstructures and properties are discussed to improve its mechanical properties.
Four kinds of new AZ91D alloys have been prepared by adding small amount of Sr in this dissertation. Using modem analysis and test facilities such as Optical Microscope (OM), X-ray Diffraction (XRD), Differential Scanning Calorimetric (DSC), Scanning Electron Microscopy (SEM) with Energy Dispersive Spectrometer (EDS) and the test of their tensile strength, specific elongation and fluidity, effects and mechanism of Sr addition on the microstructures and properties have been systemically and deeply investigated. In the meanwhile, by using high frequency electromagnetic field stirring in the solidification of alloy melt, the evolution process and mechanism of initial crystal structure have been investigated, and the effects of high-frequency electromagnetic field on microstructure have been studied.
Experimental results showed that the microstructure of AZ91D casting magnesium alloy was made up ofα-Mg phase andβ-Mg_(17)Al_(12) phase, and the new phases which were different from the primary were not found in the AZ91D alloys which 0.2%Sr and 0.5%Sr were added to. But the new A14Sr phase was gained by adding 0.8Sr% to the alloy. The alloy grains were effectively refined by the addition of small amount of Sr. And the degreeof refinement was deeper and the grain size was decreased from 250μm to 120μm with the increase of the content of Sr. It is found that the Sr in the alloys almost existed in the grain boundary and the Mn, Zn and A1 also existed in the grain boundary by the analysis of surface scan. Sr exists in the alloys with two forms: one dissolves in the alloys which influence the configuration of Mg_(17)Al_(12) phase, as the surface activation element to refine the grain, the other is one element of new compound which is Al_4Sr phase. Al_4Sr phase is a high temperature steady phase which can increase the alloy eutectic temperature. The result is that the grains were refined.
The mechanical properties of alloys were increased gradually because of the refined grains. The tensile strength of as-cast alloy with 0.8wt%Sr addition was 23.6% higher than AZ91D alloy, from 129MPa to 160MPa. The rates of elongation of alloys with 0.5%Sr and 0.8%Sr addition were 1.95%, 1.3%, and the one without Sr was 1.1%. With an h.c.p structure, the failure of AZ91D alloy is usually brittle through cleavage fracture. The fracture of AZ91D with Sr additions obvioused features the combination of quasi-cleavage and local gliding fracture, and the ductility of AZ91D became better.
The addition of Sr made small influence to the solidus temperature, but could obviously decrease the liquidus temperature and reduce the interval of crystalloid temperature. When the liquidus temperature of AZ91D alloy which is 596℃reduced into 566℃after adding 0.5Sr, the solidus temperature increased from 435℃to 437℃, the interval of crystalloid temperature decreased for 32℃. The length of AZ91D fluidity sample was 33mm. But it became to 40mm after the 0.5wt%Sr was added. Then the fluidity was increased 21% before the 0.5wt%Sr addition.
Because of the composition super-cooling,α-Mg phase of AZ91D magnesium alloy presents thick and obvious dendritic crystal. At the crystal boundary, the eutectic presents continuous, reticular and thick structure. After the high frequency electromagnetic stirring, the grains became smaller and near spherical, and the size of grains was reduced from 180μm to 120μm. Si and Mg can make a reaction into Mg_2Si in the quartz pipe used as a heating container. Much closer to the wall of the quartz pipe, much more Mg_2Si will be produced. By thermodynamic calculation, we know that the reaction 2Mg(1)＋SiO_2(s) Mg2Si(s)＋O_2(g) can be spontaneously achieved. The effects of electromagnetic field to alloys in the solidification is breaking up the dendritic crystal and increasing the solubility of the alloy elements in the magnesium.
本文以Mg-Al-Zn系中最具有代表性的AZ91D合金的组织细化作为研究方向，以溶质元素Sr和高频磁场对AZ91D的组织和性能的影响为主要研究内容，探讨AZ91D的化学成分、组织结构和性能变化之间的关系，以提高合金的综合性能。
本文通过添加微量Sr配制了四种合金。采用光学显微镜(OM)、X射线衍射仪(XRD)、差示扫描量热仪(DSC)、带能谱分析(EDS)的扫描电子显微镜(SEM)等分析手段，通过对合金的抗拉强度、伸长率、流动性等性能的测试，较系统和深入地研究了Sr对AZ91D合金组织及力学性能的影响及其作用机理。同时，在工艺方面，通过在合金熔液的凝固过程中施与高频磁场，研究了初生晶形态的演变过程和机制，以及高频磁场对合金显微组织的影响。
研究表明，铸态时，合金的显微组织主要是由α-Mg基体和离异共晶析出的化合物β-Mg_(17)Al_(12)相组成，添加0.2wt％Sr和0.5wt％Sr的合金中未发现存在不同于原始AZ91D合金组织的新相，而添加0.8wtSr％的合金中有新的Al_4Sr相生成。添加微量Sr元素，合金晶粒得到明显的细化，且随着Sr含量的增加，细化程度不断增加，晶粒大小由平均250μm减少到120μm。通过面分布分析发现合金中的Sr元素几乎都分布在晶界上，合金的其他元素如Mn、Zn和Al等也主要存在在晶界上。Sr以两种形式存在于合金中：一方面以固溶形式存在于合金中，影响Mg_(17)Al_(12)相的形态，作为表面活性元素细化晶粒；另一方面生成新的化合物Al_4Sr相，Al_4Sr相是高温稳定相，可以提高合金的共晶温度，从而细化晶粒。
由于晶粒细化的作用，合金的力学性能得到了一定程度的提高。AZ91D合金的抗拉强度是129MPa，而添加0.8wt％Sr以后，抗拉强度可达到160MPa，提高了23.6％。AZ91D的伸长率是1.1％，AZ91D-0.5wt％Sr、AZ91D-0.8wt％Sr的伸长率分别为1.95％和1.3％。铸态下AZ91D合金断裂总体上属于脆性断裂，从断口来看，具有解理特征，合金经Sr变质处理后，断口呈现一定的韧窝和撕裂棱，具有准解理断裂的特征，说明经Sr变质处理后，合金的韧性更好。
Sr的加入，对合金的固相线温度影响不大，但能明显降低合金的液相线温度。液相线温度从AZ91D合金的596℃下降到添加0.8wt％Sr后的566℃，固相线温度从AZ91D合金的435℃升高到添加0.8wt％Sr后的437℃，合金的结晶温度间隔减小了32℃。AZ91D合金流动性试验中螺旋型浇注试样长度为33mm，而当加入0．5wt％Sr后，其长度为40mm，合金的流动性比加入前提高了21％。
AZ91D镁合金在常规凝固条件下，由于成分过冷，α-Mg相为粗大的、明显的树枝晶，晶界上的共晶体形成连续的网状结构，且共晶组织较厚。经高频电磁搅拌后晶粒有所细化，晶粒变得圆整和细化，晶粒大小从180μm减小到120μm。用石英管作为加热容器会使石英管中的硅与镁反应生成Mg_2Si，离石英管壁越近，Mg_2Si越多。经热力学计算，证明反应2Mg(l)+SiO_2(s)→Mg_2Si(S)+O_2(g)在963K时可自发进行。电磁场对凝固过程中的合金的影响主要是促使枝晶破碎和提高合金元素在镁中的溶解度。
Magnesium alloy has the advantages of light-weight, high strength-to-weight ratio, high stiffness-to-weight ratio, good solidification, high electromagnetism shielding property and re-cyclability and so on, so it has bright promise for magnesium alloy to be widely used in vehicle and spaceflight, computer, communication, and is regarded as the most promising material of the 21 st century. However, for its h.c.p structure, it exhibits bad deformation ability, low efficiency, and bad mechanical properties. Solving these problems is the key to develop more application of magnesium alloy. It is found that grain refinement can increase the intensity and plasticity of materials, so it plays a very important role in the research of magnesium alloys.
Structural refinement during solidification of AZ91D alloy in Mg-AI-Zn system has been studied with a focus on the effects of solute elements Sr and high frequency electromagnetic field stirring on microstructures and mechanical properties. The relations of chemical composition, microstructures and properties are discussed to improve its mechanical properties.
Four kinds of new AZ91D alloys have been prepared by adding small amount of Sr in this dissertation. Using modem analysis and test facilities such as Optical Microscope (OM), X-ray Diffraction (XRD), Differential Scanning Calorimetric (DSC), Scanning Electron Microscopy (SEM) with Energy Dispersive Spectrometer (EDS) and the test of their tensile strength, specific elongation and fluidity, effects and mechanism of Sr addition on the microstructures and properties have been systemically and deeply investigated. In the meanwhile, by using high frequency electromagnetic field stirring in the solidification of alloy melt, the evolution process and mechanism of initial crystal structure have been investigated, and the effects of high-frequency electromagnetic field on microstructure have been studied.
Experimental results showed that the microstructure of AZ91D casting magnesium alloy was made up ofα-Mg phase andβ-Mg_(17)Al_(12) phase, and the new phases which were different from the primary were not found in the AZ91D alloys which 0.2%Sr and 0.5%Sr were added to. But the new A14Sr phase was gained by adding 0.8Sr% to the alloy. The alloy grains were effectively refined by the addition of small amount of Sr. And the degreeof refinement was deeper and the grain size was decreased from 250μm to 120μm with the increase of the content of Sr. It is found that the Sr in the alloys almost existed in the grain boundary and the Mn, Zn and A1 also existed in the grain boundary by the analysis of surface scan. Sr exists in the alloys with two forms: one dissolves in the alloys which influence the configuration of Mg_(17)Al_(12) phase, as the surface activation element to refine the grain, the other is one element of new compound which is Al_4Sr phase. Al_4Sr phase is a high temperature steady phase which can increase the alloy eutectic temperature. The result is that the grains were refined.
The mechanical properties of alloys were increased gradually because of the refined grains. The tensile strength of as-cast alloy with 0.8wt%Sr addition was 23.6% higher than AZ91D alloy, from 129MPa to 160MPa. The rates of elongation of alloys with 0.5%Sr and 0.8%Sr addition were 1.95%, 1.3%, and the one without Sr was 1.1%. With an h.c.p structure, the failure of AZ91D alloy is usually brittle through cleavage fracture. The fracture of AZ91D with Sr additions obvioused features the combination of quasi-cleavage and local gliding fracture, and the ductility of AZ91D became better.
The addition of Sr made small influence to the solidus temperature, but could obviously decrease the liquidus temperature and reduce the interval of crystalloid temperature. When the liquidus temperature of AZ91D alloy which is 596℃reduced into 566℃after adding 0.5Sr, the solidus temperature increased from 435℃to 437℃, the interval of crystalloid temperature decreased for 32℃. The length of AZ91D fluidity sample was 33mm. But it became to 40mm after the 0.5wt%Sr was added. Then the fluidity was increased 21% before the 0.5wt%Sr addition.
Because of the composition super-cooling,α-Mg phase of AZ91D magnesium alloy presents thick and obvious dendritic crystal. At the crystal boundary, the eutectic presents continuous, reticular and thick structure. After the high frequency electromagnetic stirring, the grains became smaller and near spherical, and the size of grains was reduced from 180μm to 120μm. Si and Mg can make a reaction into Mg_2Si in the quartz pipe used as a heating container. Much closer to the wall of the quartz pipe, much more Mg_2Si will be produced. By thermodynamic calculation, we know that the reaction 2Mg(1)＋SiO_2(s) Mg2Si(s)＋O_2(g) can be spontaneously achieved. The effects of electromagnetic field to alloys in the solidification is breaking up the dendritic crystal and increasing the solubility of the alloy elements in the magnesium.
引文
[1] 刘世友，镁工业生产应用与发展，上海有色金属，Vol．16，No．6(1995)，353-357；
[2] J.Abthoff, W.Gelseand J.Lang, Proc.3'd International Magnesium Conference,10-11 April 1996, Institute of Materials, London. 1997, p 193;
[3] 张诗昌，段汉桥，蔡启舟等。主要合金元素对镁合金组织和性能的影响[J]。铸造，2001，50(6)：310-314；
[4] 刘小川，王辅忠。镁合金材料研究[J]。锦州师范学院学报(自然科学版)，2002，23(2)：527；
[5] 黄乃瑜，罗吉荣。面向21世纪的消失模铸造技术。特种铸造及有色合金，1998(4)：37-402；
[6] 曾小勤，王渠东。镁合金应用新进展。铸造，1998(11)：39-43；
[7] 王祝堂。世界原镁产能将大幅增长[J]。有色金属世界，1999，(10)：51-54；
[8] 董春明，郭继东。1999年镁工业的基本现状与展望[J]。中国镁业，2000，(3)：13-24；
[9] Adolph Beck. The Technology of Magnesium and Its Alloys[M]. London: F A Hughes and Co. Limited, 1940;
[10] Ruden T J, Albright DL. High Ductility Magnesium Alloys in Automotive Applications[J]. Advanced Mater & Processes, 1999, 145(6):28-32:
[11] Demmier A. Europe's Automotive Components Business [J]. 1997, (1):102-117;
[12] [美]约翰J．伯克，沃克．威斯 著。王燕文，张永昌译。超细晶粒金属[M]。北京：国防工业出版社，1982：2-6；
[13] Kubota K, Mabuchi M, Higashi K. Review processing and mechanical properties of fine-grained magnesium alloys[J].Journal of Materials Science, 1999,34(10): 4311-4320;
[14] В．И．邦达列夫，В．И．那帕尔科夫，В．И．塔拉雷什金 著。王永海，张发明，高革 译。变形铝合金的细化处理[M]。北京：冶金工业出版社，1988；
[15] 刘峰，冯可芹，杨屹。镁合金晶粒细化的研究现状及发展。铸造技术，2004，25(6)：450-452；
[16] 陈平昌、朱六妹、李赞。材料成形原理。北京：机械工业出版社：2001．8；
[17] 张世军，黎文献，余琨等。添加含碳熔剂细化镁合金晶粒的方法[J]。特种铸造及有色合金，2002 (4)：64-65；
[18] 刘红梅，李鸿义，卫爱丽，赵浩峰。MgCO_3对镁铝系合金性能的影响。铸造设备研究，2003，(1)：23-27；
[19] 黎文献等。镁合金晶粒细化工艺[J]。铸造，2000，39(1)：1-3；
[20] 吴安如，夏长清，古一。镁-稀土合金的显微组织和力学性能研究。金属热处理，2005，30(8)：21-24；
[21] 刘生发，范晓明，王仲范。钙在铸造镁合金中的作用。铸造，2003，52(4)：246-248；
[22] 赵云虎，曾小勤，丁文江等。Be和Ca对Mg—9A1—0.5Zn合金表面氧化行为的影响[J]。中国有色金属学报，2000，10(6)：847-852；
[23] You B S, Park W W, Chung I S.The effect of calcium additions on the oxidation behavior in magnesium alloys[J].ScriptaMater, 2000, 42: 1089-1094;
[24] 郭学锋，黄正华，张忠明。Ce／Ca对AZ91D镁合金组织与力学性能的影响。西安理工大学学报，2003，19(3)：201-205；
[25] 杨明波，潘复生，李忠盛，张静。镁合金铸态晶粒细化技术的研究进展。铸造，2005，54(4)：314-319；
[26] Kinji Hirai, Hidetoshi Somekawa, Yorinobu Takigawa. Effects of Ca and Sr addition on mechanical properties of a cast AZ91 magnesium alloy at room and elevated temperature. Materials Science and Engineering,2005,A 403:276-280;
[27] 刘子利。镁合金消失模铸造工艺的应用基础研究[D]。上海：上海交通大学博士学位论文，2002；
[28] Aliravci A A, Gruzleski J E.Effect of Strontium on the shrinkage microporosity in magnesium sand castings [J.AFS Transactions, 1992, (100):353-362;
[29] 徐萍。Ce、Nd、Sr对AZ91镁合金显微组织和腐蚀性能的影响[D]。武汉：武汉理工大学硕士论文，2005；
[30] Nussbau Gm,Bribot P,Warner T J,et al. New Mg-Al based alloys with improved casting and corrosion properties [A.Mordike B L,Hehmann. Magnesium Alloys and Their Application [C] ,Oberursed Germany, 1992:351-358;
[31] 刘子利，沈以赴，李子全等。铸造镁合金的晶粒细化技术[J]。材料科学与工程学报，2004，22(1)：146-139；
[32] Lee Y C, Dahle A K, Sbjohn D H。 The Role of solute in grain refinement of magnesium[J]。 Metallurgical and Materials Transaction, 2000, 31A: 2895-29061
[33] Lee Y C, Dahle A K, StJohn D H. Grain refinement of magnesium [A].Magnesium Technology 2000 [C]. Nashville Tennessee, 2000.211-218;
[34] Lee Y C, Dahle A K, StJohn D H. The Role of solute in grain refinement of magnesium [J]. Metallurgical and Materials Transaction, 2000, 31A:2895-2906;
[35] 张世军，黎文献，余琨等。镁合金的晶粒细化工艺[J]。铸造，2001，150(17)：373-375；
[36] 陈晶阳，王利国，关绍康等。热速处理对AZ70镁合金显微组织和力学性能的影响[J]。铸造，2005，54(10)：963-966；
[37] Tetsuichi, Motegi. Grain-refining mechanisms of superheat-treatment of and carbon addition to Mg-Al-Zn alloys[J].Materials Science and Engineering A, 2005, 413-414:408-411;
[38] Aghion E, Bronfin B.Magnesium alloys development towards the 21st century [J].Materials Science Forum, 2000,350-351:19-28;
[39] 翟秋亚，袁森，蒋百灵。AZ91镁合金的SIMA法半固态组织特征。中国有色金属学报。2005，15(1)：123-128；
[40] 谢水生，李兴刚。半固态加工技术在镁合金零部件生产中的应用[J]。世界有色金属，2005，(2)：39-48；
[41] 刘生发。Mg—9Al基合金组织细化技术及性能研究。武汉理工大学博士学位论文。2004，11，01：151-155：
[42] Yoshiki Mizutani, Takuya Tamura, Kenji Miwa. Microstructural refinement process of pure magnesium by electromagnetic vibrations[J].Materials Science and Engineering A, 2005,413-414: 205-210.
[43] 甄子胜，毛卫民，陈洪涛等。电磁搅拌工艺参数对半固态AZ91D镁合金组织的影响。北京科技大学学报，2003，25(4)：341-345：
[44] Zenji Horita, Takayoshi Fajinami, Langdon T G.The Potential for Scaling ECAP: Effect of Sample Size on Grain Refinement and Mechanical Properties [J]. Materials Science and Engineering, 2001 (A318) :34241;
[45] Bowen J R, Gholinia A, Roberts S M. etc. Analysis of the Billet Deformation Behavior in Equal Channel Angular Extrusion [J].Materials Science and Engineering, 2000(A287): 87299;
[46] Wa S D, Wang I G, Jing C B,etc. The Formation of PSB- like sheer Bands in Cyclically Deformed Ultrafine Grained Copper Processed by ECAP [J].Scripta Materialia, 2003 (48): 160521609;
[47] Yamashita A , Horita I , Langdon T G. Improving the Mechanical Properties of Magnesium and A Magnesium Alloy through Severe Plastic Deformation[J]. Mater.Sci. Eng, 2001 (A300) : 1422147;
[48] 陈振华，严红革，陈吉华等。镁合金[M]。北京：化学工业出版社，2004．1；
[49] K. Xia, J.T. Wang, X. Wua, et al. Equal channel angular pressing of magnesium alloy AZ31[J] .Materials Science and Engineering A, 2005,410-411:324-327;
[50] W.J.Kim,C.W.An,Y.S.Kim,et al.Mechanical properties and microstructures of an AZ61 Mg Alloy produced by equal channel angular pressing[J]. Scripta Materialia, 2002,47(1):39-44;
[51] Hiroyuki Watanabe, Toshiji Mukai, Koichi Ishikawa,et al. Low temperature superplasticity of a fine-grained ZK60 magnesium alloy processed by equal-channel-angular extrusion [J]. Scripta Materialia, 2002, 46(12): 851-856;
[52] 王怀国，张景新，张奎，徐骏，石力开。AZ91D镁合金的半固态加工研究。特种铸造及有色合金。2003，(4)：10-13；
[53] 王立世，段汉桥。混合稀土对AZ91镁合金组织和性能的影响。特种铸造及有色合金，2002(3)：12-15；
[54] 余琨，黎文献，李松瑞等。含稀土镁合金的研究与开发。特种铸造及有色合金，2001(1)：41-44；
[55] 张永忠，赵浩峰。AZ91D镁合金的晶粒细化。理化检验2物理分册。2004，40(2)：68-70;
[56] Polmear L J.Magnesium Alloys and Applications [J].Materials Science and Technology, 1994,10 (1): 38-42;
[57] Celotto S.Acta mater .2000,48,1775-1787;
[58] Clark J.B.Acta metal. 1968,16,141-152;
[59] Duly D.Cheynet M.C.and Brehet Y.,Acta metal .mater, 1994,42,3843-3854;
[60] Crawley A.F.and Lagowski B.Metall .Trans, 1974,5,949-951;
[61] Gjonnes J. and Ostmore T,Z,Metallkd, 1970.61.604-606;
[62] Maitej ean S .Veron M.and Brechet Y.et al. Scr.Mater, 1999.41.1235-1240;
[63] Von Buch F.Lietzau J.and Mordike B.L.Mater ,Scr.Mater., 1999,A263,1-7;
[64] Sanschagrin A.Tremblay R.and Angers R.et al .Mater Sci.Eng, 1996.A220.69-77;
[65] Sakkinen D,J,SAE Technical Paper No.940779,SAE.Detroit .MI. 1994;
[66] Haferkamp H.Holzkamp U.and Juchmann Pet al,SAE.Technical Paper NO.982376. SAE.Detroit,MI, 1998;
[67] Pekguleryuz M O, Avedesian M M. Magnesium Alloy-ing, Some Potentials for Alloy Development [J]。轻金属，1992, 42(12): 25-29;
[68] 张诗昌，段汉桥，蔡启舟等。主要合金元素对镁合金组织和性能的影响[J]，铸造，2001，50(6)：310-315；
[69] I.A.Anyanwu, S.Kamado, T.Honda et al. Heat Resistance of Mg-Zn-Al-Ca Alloy Castings [J]. Materials Science Forum, 2000, (350-351): 73-78;
[70] Pekguleryuz O. Magnesium Alloys, Some Potentials for Alloy Development[J]. Light Metal, 1992, (12): 679-686;
[71] 刘宏伟。铝锌比以及稀土和钇对镁铝锌合金组织与性能的影响[D]。广州：华南理工大学博士论文，2003；
[72] 轻金属材料加工手册编写组。轻金属材料加工手册[M]。北京：冶金工业出版社，1979：143-166：
[73] 杨武。金属的局部腐蚀[M]。北京：化学工业出版社，1995；
[74] Easton M ,Stjohn D .Grain refinement of aluminum alloys:part 1[J].Metal Mater Trans A,1996,3 0A: 1613-1621;
[75] Easton M, Stohn D .Grain refinement of aluminum alloys :part 11[J].Metal Mater Trans A, 1996,30A: 1625-1633;
[76] 曾荣昌，柯伟，徐永波等。Mg合金的最新发展及应用前景[J]。金属学报，2001，37(7)：673-685；
[77] LIN Gao-yong, Peng Da-shu, ZHANG Hui. Influence of chemical composition on corrosion resistance of AZ91D magnesium alloy ingots[J]. Trans Nonferrous Met Soc China, 2001, 11(S1): 79-82;
[78] 刘正，张奎，曾小琴等。镁基轻质合金理论基础及其应用[M]。北京：机械工业出版社，2002；
[79] 国家标准局。GB 6397-86，金属拉伸试验试样[S]，1986；
[80] 铸造工艺基础编写组。铸造工艺基础[M]。北京：北京出版社，1979；
[81] 徐宋兵，彭晓东，陈刚，谢卫东。Mg-8Sr中间合金对AZ91晶粒细化的研究。轻合金加工技术，2005，33(10)：29-32；
[82] Du Wenwen , Sun Yangshan, Min Xuegang, Xue Feng, Zhu Min, Wu Dengyun Microstructure and mechanical properties of Mg-A1 based alloy with calcium and rare earth additions.Materials Science and Engineering, 2003,A356: 1-7;
[83] Douin J, Dahmen U, Westmacott K H.Philos Mag, 1991; B63: 867;
[84] 肖晓玲，罗承萍，聂建峰。AZ91Mg-Al合金中β-(Mg_(17)Al_(12))析出相的形态及其晶体学特征。金属学报，2001，37(1)：1-7；
[85] 金鑫焱，李双寿，曾大本等。Sr对AM60B铸造镁合金晶粒细化的影响。铸造，2005，54(6)：566-569：
[86] 李元东，郝远，陈体军。AZ91D镁合金半固态挤压铸造的研究，热加工工艺，2004，(1)：7-11；
[87] 利歌等。微量Sr对轿车用铝镁硅基合金板材力学性能的影响。铸造技术，2005，26(1)：52-55；
[88] 裴利霞，张金山等。稀土元素镧对AZ91镁合金显微组织及硬度的影响。铸造设备研究，2005，(1)：20-22；
[89] 李培杰，郑伟超，汤彬，曾大本。Ca和Sr对AZ91D合金组织的细化作用。特种铸造及有色合金，2004(3)：8-10；
[90] 廖恒成，夏锦宏，孙国雄。Sr+B联合熔体处理对Al-Si-Mg合金组织和力学性能的 影响。中国有色金属学报，2003，13(1)：27-34；
[91] 韩富银，杨巧莲，高义斌，张金山。电磁搅拌对镁合金AZ91D初生相形貌的影响及机理。中国铸造装备与技术，(1)2005，11-13；
[92] Krista. Magnesium Automotive Application. Advanced Materials & Processcs, 2002,160(6): 62-67;
[93] ATAC. Advanced Materials & Processes, 1998, 153(1): 47-50;
[94] 师昌绪，李恒德，王淀佐等。加速我国金属镁工业发展的建议。材料导报，2001，15(4)：5-6：
[95] A L Alan. Magnesium: Ceurrent and Potential Automotive Applications. JOM, 2002, 54 (2): 42-45;
[96] 张永忠，张奎。AZ91D镁合金的压铸工艺及性能。铸造，2000，49(2)：74-78；
[97] 刘正，张奎，曾小勤。镁基轻质合金理论基础及其应用。北京：机械工业出版社，2002；
[98] 吉泽升，吕新宇，王国军等。镁合金半固态成形技术的研究进展。金属热处理，2003，28(5)：8-11；
[99] 李远东，郝远，陈体军等。镁合金半固态成形的现状及发展前景。特种铸造及有色合金，2001(2)：77-78；
[100] 陆文华。铸铁及其熔炼[M]。北京：机械工业出版社：1981；
[101] 王晓虎。旋转磁场下金属熔体的流动和高铬铸铁凝固组织的研究[D]。北京：北京科技大学：2003；
[102] Winandy C D.Magnesium Die-Casting Motor Vehicles. In:Smith D.S. Magnesium-the Light weight solution-automotive sourcing special report, 1998.8-9;
[2] J.Abthoff, W.Gelseand J.Lang, Proc.3'd International Magnesium Conference,10-11 April 1996, Institute of Materials, London. 1997, p 193;
[3] 张诗昌，段汉桥，蔡启舟等。主要合金元素对镁合金组织和性能的影响[J]。铸造，2001，50(6)：310-314；
[4] 刘小川，王辅忠。镁合金材料研究[J]。锦州师范学院学报(自然科学版)，2002，23(2)：527；
[5] 黄乃瑜，罗吉荣。面向21世纪的消失模铸造技术。特种铸造及有色合金，1998(4)：37-402；
[6] 曾小勤，王渠东。镁合金应用新进展。铸造，1998(11)：39-43；
[7] 王祝堂。世界原镁产能将大幅增长[J]。有色金属世界，1999，(10)：51-54；
[8] 董春明，郭继东。1999年镁工业的基本现状与展望[J]。中国镁业，2000，(3)：13-24；
[9] Adolph Beck. The Technology of Magnesium and Its Alloys[M]. London: F A Hughes and Co. Limited, 1940;
[10] Ruden T J, Albright DL. High Ductility Magnesium Alloys in Automotive Applications[J]. Advanced Mater & Processes, 1999, 145(6):28-32:
[11] Demmier A. Europe's Automotive Components Business [J]. 1997, (1):102-117;
[12] [美]约翰J．伯克，沃克．威斯 著。王燕文，张永昌译。超细晶粒金属[M]。北京：国防工业出版社，1982：2-6；
[13] Kubota K, Mabuchi M, Higashi K. Review processing and mechanical properties of fine-grained magnesium alloys[J].Journal of Materials Science, 1999,34(10): 4311-4320;
[14] В．И．邦达列夫，В．И．那帕尔科夫，В．И．塔拉雷什金 著。王永海，张发明，高革 译。变形铝合金的细化处理[M]。北京：冶金工业出版社，1988；
[15] 刘峰，冯可芹，杨屹。镁合金晶粒细化的研究现状及发展。铸造技术，2004，25(6)：450-452；
[16] 陈平昌、朱六妹、李赞。材料成形原理。北京：机械工业出版社：2001．8；
[17] 张世军，黎文献，余琨等。添加含碳熔剂细化镁合金晶粒的方法[J]。特种铸造及有色合金，2002 (4)：64-65；
[18] 刘红梅，李鸿义，卫爱丽，赵浩峰。MgCO_3对镁铝系合金性能的影响。铸造设备研究，2003，(1)：23-27；
[19] 黎文献等。镁合金晶粒细化工艺[J]。铸造，2000，39(1)：1-3；
[20] 吴安如，夏长清，古一。镁-稀土合金的显微组织和力学性能研究。金属热处理，2005，30(8)：21-24；
[21] 刘生发，范晓明，王仲范。钙在铸造镁合金中的作用。铸造，2003，52(4)：246-248；
[22] 赵云虎，曾小勤，丁文江等。Be和Ca对Mg—9A1—0.5Zn合金表面氧化行为的影响[J]。中国有色金属学报，2000，10(6)：847-852；
[23] You B S, Park W W, Chung I S.The effect of calcium additions on the oxidation behavior in magnesium alloys[J].ScriptaMater, 2000, 42: 1089-1094;
[24] 郭学锋，黄正华，张忠明。Ce／Ca对AZ91D镁合金组织与力学性能的影响。西安理工大学学报，2003，19(3)：201-205；
[25] 杨明波，潘复生，李忠盛，张静。镁合金铸态晶粒细化技术的研究进展。铸造，2005，54(4)：314-319；
[26] Kinji Hirai, Hidetoshi Somekawa, Yorinobu Takigawa. Effects of Ca and Sr addition on mechanical properties of a cast AZ91 magnesium alloy at room and elevated temperature. Materials Science and Engineering,2005,A 403:276-280;
[27] 刘子利。镁合金消失模铸造工艺的应用基础研究[D]。上海：上海交通大学博士学位论文，2002；
[28] Aliravci A A, Gruzleski J E.Effect of Strontium on the shrinkage microporosity in magnesium sand castings [J.AFS Transactions, 1992, (100):353-362;
[29] 徐萍。Ce、Nd、Sr对AZ91镁合金显微组织和腐蚀性能的影响[D]。武汉：武汉理工大学硕士论文，2005；
[30] Nussbau Gm,Bribot P,Warner T J,et al. New Mg-Al based alloys with improved casting and corrosion properties [A.Mordike B L,Hehmann. Magnesium Alloys and Their Application [C] ,Oberursed Germany, 1992:351-358;
[31] 刘子利，沈以赴，李子全等。铸造镁合金的晶粒细化技术[J]。材料科学与工程学报，2004，22(1)：146-139；
[32] Lee Y C, Dahle A K, Sbjohn D H。 The Role of solute in grain refinement of magnesium[J]。 Metallurgical and Materials Transaction, 2000, 31A: 2895-29061
[33] Lee Y C, Dahle A K, StJohn D H. Grain refinement of magnesium [A].Magnesium Technology 2000 [C]. Nashville Tennessee, 2000.211-218;
[34] Lee Y C, Dahle A K, StJohn D H. The Role of solute in grain refinement of magnesium [J]. Metallurgical and Materials Transaction, 2000, 31A:2895-2906;
[35] 张世军，黎文献，余琨等。镁合金的晶粒细化工艺[J]。铸造，2001，150(17)：373-375；
[36] 陈晶阳，王利国，关绍康等。热速处理对AZ70镁合金显微组织和力学性能的影响[J]。铸造，2005，54(10)：963-966；
[37] Tetsuichi, Motegi. Grain-refining mechanisms of superheat-treatment of and carbon addition to Mg-Al-Zn alloys[J].Materials Science and Engineering A, 2005, 413-414:408-411;
[38] Aghion E, Bronfin B.Magnesium alloys development towards the 21st century [J].Materials Science Forum, 2000,350-351:19-28;
[39] 翟秋亚，袁森，蒋百灵。AZ91镁合金的SIMA法半固态组织特征。中国有色金属学报。2005，15(1)：123-128；
[40] 谢水生，李兴刚。半固态加工技术在镁合金零部件生产中的应用[J]。世界有色金属，2005，(2)：39-48；
[41] 刘生发。Mg—9Al基合金组织细化技术及性能研究。武汉理工大学博士学位论文。2004，11，01：151-155：
[42] Yoshiki Mizutani, Takuya Tamura, Kenji Miwa. Microstructural refinement process of pure magnesium by electromagnetic vibrations[J].Materials Science and Engineering A, 2005,413-414: 205-210.
[43] 甄子胜，毛卫民，陈洪涛等。电磁搅拌工艺参数对半固态AZ91D镁合金组织的影响。北京科技大学学报，2003，25(4)：341-345：
[44] Zenji Horita, Takayoshi Fajinami, Langdon T G.The Potential for Scaling ECAP: Effect of Sample Size on Grain Refinement and Mechanical Properties [J]. Materials Science and Engineering, 2001 (A318) :34241;
[45] Bowen J R, Gholinia A, Roberts S M. etc. Analysis of the Billet Deformation Behavior in Equal Channel Angular Extrusion [J].Materials Science and Engineering, 2000(A287): 87299;
[46] Wa S D, Wang I G, Jing C B,etc. The Formation of PSB- like sheer Bands in Cyclically Deformed Ultrafine Grained Copper Processed by ECAP [J].Scripta Materialia, 2003 (48): 160521609;
[47] Yamashita A , Horita I , Langdon T G. Improving the Mechanical Properties of Magnesium and A Magnesium Alloy through Severe Plastic Deformation[J]. Mater.Sci. Eng, 2001 (A300) : 1422147;
[48] 陈振华，严红革，陈吉华等。镁合金[M]。北京：化学工业出版社，2004．1；
[49] K. Xia, J.T. Wang, X. Wua, et al. Equal channel angular pressing of magnesium alloy AZ31[J] .Materials Science and Engineering A, 2005,410-411:324-327;
[50] W.J.Kim,C.W.An,Y.S.Kim,et al.Mechanical properties and microstructures of an AZ61 Mg Alloy produced by equal channel angular pressing[J]. Scripta Materialia, 2002,47(1):39-44;
[51] Hiroyuki Watanabe, Toshiji Mukai, Koichi Ishikawa,et al. Low temperature superplasticity of a fine-grained ZK60 magnesium alloy processed by equal-channel-angular extrusion [J]. Scripta Materialia, 2002, 46(12): 851-856;
[52] 王怀国，张景新，张奎，徐骏，石力开。AZ91D镁合金的半固态加工研究。特种铸造及有色合金。2003，(4)：10-13；
[53] 王立世，段汉桥。混合稀土对AZ91镁合金组织和性能的影响。特种铸造及有色合金，2002(3)：12-15；
[54] 余琨，黎文献，李松瑞等。含稀土镁合金的研究与开发。特种铸造及有色合金，2001(1)：41-44；
[55] 张永忠，赵浩峰。AZ91D镁合金的晶粒细化。理化检验2物理分册。2004，40(2)：68-70;
[56] Polmear L J.Magnesium Alloys and Applications [J].Materials Science and Technology, 1994,10 (1): 38-42;
[57] Celotto S.Acta mater .2000,48,1775-1787;
[58] Clark J.B.Acta metal. 1968,16,141-152;
[59] Duly D.Cheynet M.C.and Brehet Y.,Acta metal .mater, 1994,42,3843-3854;
[60] Crawley A.F.and Lagowski B.Metall .Trans, 1974,5,949-951;
[61] Gjonnes J. and Ostmore T,Z,Metallkd, 1970.61.604-606;
[62] Maitej ean S .Veron M.and Brechet Y.et al. Scr.Mater, 1999.41.1235-1240;
[63] Von Buch F.Lietzau J.and Mordike B.L.Mater ,Scr.Mater., 1999,A263,1-7;
[64] Sanschagrin A.Tremblay R.and Angers R.et al .Mater Sci.Eng, 1996.A220.69-77;
[65] Sakkinen D,J,SAE Technical Paper No.940779,SAE.Detroit .MI. 1994;
[66] Haferkamp H.Holzkamp U.and Juchmann Pet al,SAE.Technical Paper NO.982376. SAE.Detroit,MI, 1998;
[67] Pekguleryuz M O, Avedesian M M. Magnesium Alloy-ing, Some Potentials for Alloy Development [J]。轻金属，1992, 42(12): 25-29;
[68] 张诗昌，段汉桥，蔡启舟等。主要合金元素对镁合金组织和性能的影响[J]，铸造，2001，50(6)：310-315；
[69] I.A.Anyanwu, S.Kamado, T.Honda et al. Heat Resistance of Mg-Zn-Al-Ca Alloy Castings [J]. Materials Science Forum, 2000, (350-351): 73-78;
[70] Pekguleryuz O. Magnesium Alloys, Some Potentials for Alloy Development[J]. Light Metal, 1992, (12): 679-686;
[71] 刘宏伟。铝锌比以及稀土和钇对镁铝锌合金组织与性能的影响[D]。广州：华南理工大学博士论文，2003；
[72] 轻金属材料加工手册编写组。轻金属材料加工手册[M]。北京：冶金工业出版社，1979：143-166：
[73] 杨武。金属的局部腐蚀[M]。北京：化学工业出版社，1995；
[74] Easton M ,Stjohn D .Grain refinement of aluminum alloys:part 1[J].Metal Mater Trans A,1996,3 0A: 1613-1621;
[75] Easton M, Stohn D .Grain refinement of aluminum alloys :part 11[J].Metal Mater Trans A, 1996,30A: 1625-1633;
[76] 曾荣昌，柯伟，徐永波等。Mg合金的最新发展及应用前景[J]。金属学报，2001，37(7)：673-685；
[77] LIN Gao-yong, Peng Da-shu, ZHANG Hui. Influence of chemical composition on corrosion resistance of AZ91D magnesium alloy ingots[J]. Trans Nonferrous Met Soc China, 2001, 11(S1): 79-82;
[78] 刘正，张奎，曾小琴等。镁基轻质合金理论基础及其应用[M]。北京：机械工业出版社，2002；
[79] 国家标准局。GB 6397-86，金属拉伸试验试样[S]，1986；
[80] 铸造工艺基础编写组。铸造工艺基础[M]。北京：北京出版社，1979；
[81] 徐宋兵，彭晓东，陈刚，谢卫东。Mg-8Sr中间合金对AZ91晶粒细化的研究。轻合金加工技术，2005，33(10)：29-32；
[82] Du Wenwen , Sun Yangshan, Min Xuegang, Xue Feng, Zhu Min, Wu Dengyun Microstructure and mechanical properties of Mg-A1 based alloy with calcium and rare earth additions.Materials Science and Engineering, 2003,A356: 1-7;
[83] Douin J, Dahmen U, Westmacott K H.Philos Mag, 1991; B63: 867;
[84] 肖晓玲，罗承萍，聂建峰。AZ91Mg-Al合金中β-(Mg_(17)Al_(12))析出相的形态及其晶体学特征。金属学报，2001，37(1)：1-7；
[85] 金鑫焱，李双寿，曾大本等。Sr对AM60B铸造镁合金晶粒细化的影响。铸造，2005，54(6)：566-569：
[86] 李元东，郝远，陈体军。AZ91D镁合金半固态挤压铸造的研究，热加工工艺，2004，(1)：7-11；
[87] 利歌等。微量Sr对轿车用铝镁硅基合金板材力学性能的影响。铸造技术，2005，26(1)：52-55；
[88] 裴利霞，张金山等。稀土元素镧对AZ91镁合金显微组织及硬度的影响。铸造设备研究，2005，(1)：20-22；
[89] 李培杰，郑伟超，汤彬，曾大本。Ca和Sr对AZ91D合金组织的细化作用。特种铸造及有色合金，2004(3)：8-10；
[90] 廖恒成，夏锦宏，孙国雄。Sr+B联合熔体处理对Al-Si-Mg合金组织和力学性能的 影响。中国有色金属学报，2003，13(1)：27-34；
[91] 韩富银，杨巧莲，高义斌，张金山。电磁搅拌对镁合金AZ91D初生相形貌的影响及机理。中国铸造装备与技术，(1)2005，11-13；
[92] Krista. Magnesium Automotive Application. Advanced Materials & Processcs, 2002,160(6): 62-67;
[93] ATAC. Advanced Materials & Processes, 1998, 153(1): 47-50;
[94] 师昌绪，李恒德，王淀佐等。加速我国金属镁工业发展的建议。材料导报，2001，15(4)：5-6：
[95] A L Alan. Magnesium: Ceurrent and Potential Automotive Applications. JOM, 2002, 54 (2): 42-45;
[96] 张永忠，张奎。AZ91D镁合金的压铸工艺及性能。铸造，2000，49(2)：74-78；
[97] 刘正，张奎，曾小勤。镁基轻质合金理论基础及其应用。北京：机械工业出版社，2002；
[98] 吉泽升，吕新宇，王国军等。镁合金半固态成形技术的研究进展。金属热处理，2003，28(5)：8-11；
[99] 李远东，郝远，陈体军等。镁合金半固态成形的现状及发展前景。特种铸造及有色合金，2001(2)：77-78；
[100] 陆文华。铸铁及其熔炼[M]。北京：机械工业出版社：1981；
[101] 王晓虎。旋转磁场下金属熔体的流动和高铬铸铁凝固组织的研究[D]。北京：北京科技大学：2003；
[102] Winandy C D.Magnesium Die-Casting Motor Vehicles. In:Smith D.S. Magnesium-the Light weight solution-automotive sourcing special report, 1998.8-9;