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Mg-Al alloys are the most widely used Mg-based industrial alloys, but their composition rules behind the apparent industrial specifications are largely unknown, which hinders the development of new alloys. As is well known, industrial alloys often undergo the process of a high-temperature solution treatment, and the final structures originate from the single-phase solid solution parent state. Since solid solutions are characterized by short-range chemical orders, necessarily the optimum alloy composition should be related to the presence of a certain short-range chemical structure unit. In the present paper, by introducing our cluster-resonance model for short-range-order structure description of solid solutions, a chemical structure unit of Mg-Al binary solid solution is established,[Al-Mg12]Mg1, which represents the characteristic short-range-order structure, with the bracketed part being the nearest-neighbor cluster centered by Al and shelled by 12Mg and with one glue atom Mg located between the clusters. Because of the existence of other alloying elements besides Al, a general formula[(Al, A)1-Mg12]-(Mg, B) is then proposed, where A represents the elements showing a negative mixing enthalpy with Mg, while B showing a positive one. This formula is used to explain the multi-component Mg-Al industrial alloys. Based on this chemical formula, typical Mg-Al industrial alloy specifications in ASTM handbook are well explained. For instance, cast AZ63A alloy is formulated as[Al0.78Zn0.16-Mg12]Mg1.04Mn0.02, cast AZ81A as[Al0.97Zn0.03-Mg12]Mg0.98Mn0.02, and wrought AZ80A as[Al1.02n0.03-Mg12]Mg0.94Mn0.01. The deviations from the ideal chemical structure unit in different Mg-Al alloys are well correlated to their corresponding alloy performances. Those alloys, where the numbers of center atoms are close to ones in their cluster formulas, exhibit excellent comprehensive mechanical performances in both strength and plasticity. While the alloy with less than one center atom only shows good plastic performance with a relatively poor strength, and the one with more than one center atom shows just the reverse tendency. Among cast Mg-Al alloys, AZ81A, whose cluster formula completely matches the stable chemical structure unit, exhibits the optimized combination of strength (275 MPa) and plasticity (elongation 15%). Among wrought Mg-Al alloys, AZ61A and AZ80A, whose cluster formulas show minor deviations of -0.11 and 0.05 in the center site from the ideal chemical structure unit, also have good comprehensive mechanical properties, respectively with the strengths of 310 MPa and 380 MPa, and the elongations of 16% and 7%. Based on the results in the present paper, the simple composition rule behind the complex industrial alloy specifications as unveiled here, can be a powerful approach to the development of Mg-Al alloys.
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Keywords:
- Mg-Al alloy /
- cluster-resonance model /
- chemical structure unit /
- composition interpretations
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[2] Cahn R W 1978 Nature 271 407
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[4] Friedel J 1954 Adv. Phys. 3 446
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[10] Chen H, Wang Q, Wang Y, Qiang J, Dong C 2010 Philos. Mag. 90 3935
[11] Chen H, Qiang J, Wang Q, Wang Y, Dong C 2011 Isr. J. Chem. 51 1226
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[13] Zhu C L, Wang Q, Li F W, Li Y H, Wang Y M, Dong C, Zhang W, Inoue A 2009 J. Phys.:Conference Series (London:IOP Publishing) 144 p012048
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[16] Yuan L, Pang C, Wang Y, Wang Q, Qiang J, Dong C 2010 Intermetallics 18 1800
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[24] Wang Q, Li Q, Li X, Zhang R, Gao X, Dong C, Liaw P K 2015 Metall. Mater. Trans. A 46 3924
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[28] Zhang J, Wang Q, Wang Y M, Wen L S, Dong C 2010 J. Alloys Compd. 505 179
[29] Hong H L, Wang Q, Dong C, Liaw P K 2014 Sci. Rep. 4 7065
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[31] Pang C 2015 Cluster Structure Model for BCC Substitutional Solid Solutions and the Application for Alloy Composition Design (Dalian:Dalian University of Technology) (in Chinese)[庞厰 2015 体心立方置换固溶体的团簇结构模型及其在合金成分设计中的应用 (大连:大连理工大学)]
[32] Dong D D 2017 Composition Origin of Metallic Glasses and Solid Solution Alloys:Short-range-order Structural Unit (Dalian:Dalian University of Technology) (in Chinese)[董丹丹 2017 金属玻璃和固溶体合金的成分根源:近程序结构单元 (大连:大连理工大学)]
[33] Takeuchi A, Inoue A 2005 Mater. Trans. 46 2817
[34] Pearson W B, Villars P, Calvert L D 1985 American Society for Metals 1985 3258
[35] Fiepke J W 1992 ASM Handbook, Properties and Selection:Nonferrous Alloys and Special-Purpose Materials.
[36] Quan G Z, Ku T W, Song W J, Kang B S 2011 Mater. Des. 32 2462
[37] L C, Liu T, Liu D, Jiang S, Zeng W 2012 Mater. Des. 33 529
[38] Zhao D, Wang Z, Zuo M, Geng H 2014 Mater. Des. 56 589
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[1] Hume-Rothery W, Smallman R E, Haworth C W 1969 The Structure of Metals and Alloys (London:The Institute of Metals)
[2] Cahn R W 1978 Nature 271 407
[3] Jones H 1980 Proc. R. Soc. London Ser. A 371 52
[4] Friedel J 1954 Adv. Phys. 3 446
[5] Dong D D, Zhang S, Wang Z R, Dong C 2015 J. Appl. Crystallogr. 48 2002
[6] Dong C, Wang Q, Qiang J B, Wang Y M, Jiang N, Han G, Li Y H, Wu J, Xia J H 2007 J. Phys. D:Appl. Phys. 40 273
[7] Han G, Qiang J B, Li F W, Yuan L, Quan S G, Wang Q, Wang Y M, Dong C, Hässlerc P 2011 Acta Mater. 59 5917
[8] Luo L J, Chen H, Wang Y M, Qiang J B, Wang Q, Dong C, Hässlerc P 2014 Philos. Mag. 94 2520
[9] Dong C 1995 Scripta Metal. Mater. 33 239
[10] Chen H, Wang Q, Wang Y, Qiang J, Dong C 2010 Philos. Mag. 90 3935
[11] Chen H, Qiang J, Wang Q, Wang Y, Dong C 2011 Isr. J. Chem. 51 1226
[12] Wang Q, Dong C, Qiang J, Wang Y 2007 Mater. Sci. Eng. A 449 18
[13] Zhu C L, Wang Q, Li F W, Li Y H, Wang Y M, Dong C, Zhang W, Inoue A 2009 J. Phys.:Conference Series (London:IOP Publishing) 144 p012048
[14] Luo L, Wu J, Wang Q, Wang Y, Han G, Dong C 2010 Philos. Mag. 90 3961
[15] Wang Y, Wang Q, Zhao J, Dong C 2010 Scripta Mater. 63 178
[16] Yuan L, Pang C, Wang Y, Wang Q, Qiang J, Dong C 2010 Intermetallics 18 1800
[17] Li F W, Qiang J B, Wang Q, Wang Y M, Dong X L, Dong C, Zhu S J 2012 Intermetallics 30 86
[18] Wang Z R, Dong D D, Qiang J B, Wang Q, Wang Y M, Dong C 2013 Sci. China:Phys. Mech. 56 1419
[19] Geng Y X, Han K M, Wang Y M, Qiang J B, Wang Q, Dong C, Zhang G F, Tegus O, H Hösslerc P 2015 Acta Metall. Sin. 51 1017 (in Chinese)[耿遥祥, 韩凯明, 王英敏, 羌建兵, 王清, 董闯, 张贵峰, 特古斯, Hässlerc P 2015 金属学报 51 1017]
[20] Zhang J, Wang Q, Wang Y M, Dong C 2009 Acta Metall. Sin. 45 1390 (in Chinese)[张杰, 王清, 王英敏, 董闯 2009 金属学报 45 1390]
[21] Ma R T, Hao C P, Wang Q, Ren M F, Wang Y M, Dong C 2010 Acta Metall. Sin. 46 1034 (in Chinese)[马仁涛, 郝传璞, 王清, 任明法, 王英敏, 董闯 2010 金属学报 46 1034]
[22] Chen J X, Qiang J B, Wang Q, Dong C 2012 Acta Phys. Sin. 61 046102 (in Chinese)[陈季香, 羌建兵, 王清, 董闯 2012 物理学报 61 046102]
[23] Wang Q, Zha Q F, Liu E X, Dong C, Wang X J, Tan Z X, Ji C J 2012 Acta Metall. Sin. 48 1201 (in Chinese)[王清, 查钱锋, 刘恩雪, 董闯, 王学军, 谭朝鑫, 冀春俊 2012 金属学报 48 1201]
[24] Wang Q, Li Q, Li X, Zhang R, Gao X, Dong C, Liaw P K 2015 Metall. Mater. Trans. A 46 3924
[25] Hong H, Wang Q, Dong C 2015 Sci. China:Mater. 58 355
[26] Zhang J, Wang Q, Wang Y, Li C, Wen L, Dong C 2010 J. Mater. Res. 25 328
[27] Zhang J, Wang Q, Wang Y M, Wen L S, Dong C 2010 J. Alloys Compd. 505 505
[28] Zhang J, Wang Q, Wang Y M, Wen L S, Dong C 2010 J. Alloys Compd. 505 179
[29] Hong H L, Wang Q, Dong C, Liaw P K 2014 Sci. Rep. 4 7065
[30] Reinhard L, Schönfeld B, Kostorz G, Bhrer W 1990 Phys. Rev. B 41 1727
[31] Pang C 2015 Cluster Structure Model for BCC Substitutional Solid Solutions and the Application for Alloy Composition Design (Dalian:Dalian University of Technology) (in Chinese)[庞厰 2015 体心立方置换固溶体的团簇结构模型及其在合金成分设计中的应用 (大连:大连理工大学)]
[32] Dong D D 2017 Composition Origin of Metallic Glasses and Solid Solution Alloys:Short-range-order Structural Unit (Dalian:Dalian University of Technology) (in Chinese)[董丹丹 2017 金属玻璃和固溶体合金的成分根源:近程序结构单元 (大连:大连理工大学)]
[33] Takeuchi A, Inoue A 2005 Mater. Trans. 46 2817
[34] Pearson W B, Villars P, Calvert L D 1985 American Society for Metals 1985 3258
[35] Fiepke J W 1992 ASM Handbook, Properties and Selection:Nonferrous Alloys and Special-Purpose Materials.
[36] Quan G Z, Ku T W, Song W J, Kang B S 2011 Mater. Des. 32 2462
[37] L C, Liu T, Liu D, Jiang S, Zeng W 2012 Mater. Des. 33 529
[38] Zhao D, Wang Z, Zuo M, Geng H 2014 Mater. Des. 56 589
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