The growing demand for fuel-efficient vehicles to reduce energy consumption and air pollution has made the substitution of conventional materials, such as steel, cast iron and Cu, with lightweight metals a top priority in a variety of applications, including aerospace, automotive and construction industries [91]. The high specific strength of aluminum alloys combined with their good corrosion resistance, and their reasonable cost have made these lightweight materials the most promising candidates to replace heavier alloys [92-94]. For conventional aluminum alloys, age-hardening effects are widely used to improve their strength. Owing to the precipitation-strengthened microstructures after thermo-mechanical treatments, the age-hardened aluminum alloys have relatively high yield strength; for example, the high-strength 2014 and 7075 alloys have tensile yield strength of 441 and 523 MPa, respectively [95]. However, a survey of property-performance space for a wide range of aluminum alloys indicates that the upper yield strength limit for precipitation-strengthened wrought aluminum alloys is around 700 MPa [96], which is still too low to satisfy the most recent application requirements.
In the last decades, it has been found that the strength of Al-based alloys can be significantly improved by producing them in the amorphous state, i.e. Al-based metallic glasses
Table 1.2 Mechanical properties of Al-based metallic glasses (ribbons) in tension. Composition
(at.%)
Structure Yield strength (MPa) Fracture strain (%) Reference Al85Ni5Y10 Amorphous 920 1.4 [97] Al87Y8Ni5 Amorphous 1140 - [98] AlYNi Amorphous 1150 - [99] Al85Ni5Y8Co2 Amorphous 1250 1.7 [97] Al88Ni9Ce2Fe1 Amorphous +fcc-Al 1560 - [100]
Table 1.3 Mechanical properties of Al-based metallic glasses (cast rods) in compression.
Composition (at.%)
Structure Yield strength (MPa) Fracture strain (%) Reference Al86Ni7Y4.5Co1La1.5 amorphous 1050 - [101] Al84.5Ni5.5Y10 partially amorphous 1090 2.2 [102] A85.5Ni9.5La5 partially amorphous 950 3 [134]
Al-based metallic glass ribbons have tensile strength reaching the GPa level; for example, it was reported that the tensile strength of Al85Ni5Y8Co2 can reach 1250 MPa [97-99]. For these
ribbons, the strength can be further improved by precipitating NC particles into the amorphous matrix. In this case, the tensile strength can reach 1560 MPa, which is the highest strength among the Al-based alloys reported until now [100]. Recently, Al-based bulk metallic glasses (BMGs) with 1 mm in diameter and 30 mm in length have been produced by injection casting [101]. The compression strength of these Al-based BMGs also can reach the GPa level: for example, a yield strength of 1090 MPa was reported for the Al84.5Ni5.5Y10 BMG [101-103].
Table 1.4 Mechanical properties of bulk NC and UFG aluminum in compression (MA: mechanical alloying, HP: hot pressing, SPS: spark plasma sintering, HE: hot extrusion, CIP: cold isostatic pressing).
Composition (at.%) Processing Yield strength (MPa) Ultimate strength (MPa) Fracture strain (%) Theoretical density (g/cm3)) Reference Al85Cu9Si6 casting 800 1047 19.7 3.09 [111] Al90Ni4Y6 casting 810 1150 ˃ 150 3.07 [117] Al81Cu13Si6 casting 890 1149 11.4 3.28 [111] Al87La1.5Ni7Co1Y3.5 casting - 1100 10.6 [119] Al83Cu17 casting 1000 1200 2 3.50 [111] Al85Ni4Ag6Y5 casting 1020 1240 26 3.50 [120] Al87La1.5Ni7Co1Y3.5 casting 1290 1290 0 3.26 [119] Al85.2Zn10.0Mg3.0Cu1.8 SPS - 632 45 [121] Al93Fe3Cr2Ti2 HE 562 665 ˃ 45 2.92 [116, 122] Al–7.5 (wt.%) Mg HE 628 640 17 2.60 [123] Al96Cu4 MA/HP 750 - 2 2.89 [106] Al85.2Zn10.0Mg3.0Cu1.8 SPS/aging - 900 20 [121] Al85Y8Ni5Co2 SPS 800 1050 3.7 3.162 [114] Al95Fe5 SPS 992 1045 30 2.9 [124] Al95Fe5 MA/SPS ˃1000 ˃1200 20 2.9 [125] 5083 Al+10 wt.% B4C cryomilling /CIP/HE 1065 - 0.8 2.65 [126] Al85Ni10La5 SPS 1140 1240 0.43 3.49 [127] 5083 Al+B4C cryomilling /CIP/HE 1145 1145 3 2.65 [108] Al85Ni10La5 SPS/aging 1320 1341 0.21 3.49 [127] Al85Ni5Y8Co2 HP - 1420 1 3.162 [104] Al65Cu20Ti15 HP - 1490 0 3.77 [128]
Beside metallic glasses, bulk NC and ultrafine-grained (UFG) aluminum alloys have also been of significant interest because of their high strength and hardness [18]. Their mechanical properties are summarized in Tables 1.4 and 1.5. The yield strength of these materials is generally above 1 GPa and some of the m also display good ductility at room temperature. High compression strength of 1.420 MPa and tensile yield strength of 1 GPa have been reported for bulk NC aluminum alloys produced by crystallization of amorphous powders and by high
Table 1.5 Mechanical properties of bulk NC and ultrafine grain aluminum in tension (ECAE: equal channel angular extrusion, HIP: hot isostatic pressing, HPT: high pressure torsion).
Composition (at.%) Processing Yield strength (MPa) Ultimate strength (MPa) Fracture strain (%) Theoretical density (g/cm3)) Reference Pure Al ECAE 170 177 3 2.71 [129] Pure Al cryomilling /CIP/HE 345 363 28 2.71 [130] Al93Fe3Cr2Ti2 HE 440 - 0 2.92 [122] Al91.1Y4.0Ni4.0Co0.9 HE/hot rolling 551 586 7.1 3.04 [115] 5083 Al MA/HIP/HE 334 462 8.4 2.66 [131] 5083 Al cryomilling /CIP/HE 713 can 0.3 2.66 [107] Al–7.5 (wt.%) Mg HIP 554 734 5.4 2.60 [110] Al–7.5 (wt.%) Mg HIP 641 847 1.4 2.60 [110] Al95Mg5 consolidation 620 742 8.5 2.64 [105] Al88.5Y3.5Ni8 HE - 930 - - [132] Al85Y7.5Ni7.5 HE - 880 - - [132] Al88.5Mm3.5Ni8 HE 845 940 - 3.18 [133] 7075 HPT 1000 - 9 2.81 [96]
The microstructure of NC and UFG aluminum alloys can be classified into the three types: monomorphic or simple, bimodal and complex structure [42,106-112,115-118]. As discussed previously, the significant improvement of strength in NC aluminum alloys can be explained by the increased volume fraction of grain boundaries in these alloys, whi ch effectively block the dislocation movement, as described by the Hall-Petch relationship. Monomorphic structures have simple phases and their grain size is smaller than the micrometer. They show high strength: for example, NC Al–Mg (5 at.%) has compressive yield strength of 620 MPa [105], NC Al–Cu (4 wt.%) has compressive yield strength of 750 MPa [106], and 5083 Al has tensile yield strength of 713 MPa [107]. All these alloys are produced by P/M methods. However, due to the lack of strain hardening, they have very limited ductility. In order to get NC and UFG aluminum alloys with high strength and good ductility, bimodal structures, consisting of nano- and micron-sized grains, have been developed recently [108-111]. For example, the Al85Cu9Si6 alloy, which has micron-sized dendrites distributed in an UFG matrix, has yield
strength of 800 MPa combined with 25 % strain in compression [111]. The strain increases with increasing the volume fraction of the coarse grains [112]. It has been pointed out that the high strength comes from the UFG matrix and the improved plasticity is due to the plastic deformation within the coarse grains [111, 113]. The NC and UFG aluminum alloys which have complex structures display even higher strength [104, 114-117]. Most of them consist of a nano- sized fcc-Al matrix and distributed hard intermetallic particles. The high strength is mostly due to the high strength nanoscale matrix combined with the very hard intermetallic compounds [ 18, 96]. Figure 1.15 shows the yield strength vs. density for Al-based bulk metallic glasses (Al BMGs), Al-based NC and UFG alloys and conventional metals and alloys. It can be seen that Al BMGs and Al-based NC and UFG alloys have low density and high yield strength and, therefore, a high specific strength.
References
[1] W. Klement, R.H. Willens, P. Duwez, Non-crystalline structure in solidified gold-silicon alloys, Nature, 187 (1960) 869.
[2] W.H. Wang, C. Dong, C.H. Shek, Bulk metallic glasses, Materials Science and Engineering R, 44 (2004) 45.
[3] P. Chaudhari, D. Turnbull, Structure and properties of metallic glasses, Science, 199 (1978) 11.
[4] R.W. Chan, A.L. Greer, Metastable states of alloys, in: R.W. Chan, P. Haasen (Eds.) Physical metallurgy, North-Holland, Oxford, 1996, pp. 1723.
[5] E.J. Lavernia, J.D. Ayers, T.S. Srivatsan, Rapid solidification processing with specific application to aluminum-alloys, International Materials Review, 37 (1992) 1.
[6] T.R.S. Anantharaman, C., Rapidly solidified metals - a technological overview, Trans Tech Publications, Aedermannsdorf, Switzerland, 1987.
[7] C.C.K. C. Suryanarayana, Non-equilibrium processing of materials, Pergamon materials series, 2 (1999) 313.
[8] A.L. Greer, Metallic Glasses, Science, 267 (1995) 1947.
[9] C.I. Suryanarayana, A. Inoue, Bulk metallic glasses, CRC Press Taylor & Francis Group, 2011.
[10] F. Cardellini, G. Mazzone, M.V. Antisari, Solid state reactions and microstructural evolution of Al---Ni powders during high-energy ball milling, Acta Materialia, 44 (1996) 1511.
[11] C. Suryanarayana, Mechanical alloying and milling, Progress in Materials Science, 46 (2001) 1.
[12] C.C. Koch, J.D. Whittenberger, Mechanical milling/alloying of intermetallics, Intermetallics, 4 (1996) 339.
[13] J. Sun, J.X. Zhang, Y.Y. Fu, G.X. Hu, Microstructural evolution of an Al67Mn8Ti24Nb1
alloy during mechanical milling and subsequent annealing process, Materials Science and Engineering A, 329–331 (2002) 703.
[14] Z. Zhang, Y. Zhou, E.J. Lavernia, Amorphization and crystallization in Al-Ni-La during mechanical milling, Journal of Alloys and Compound, 466 (2008) 189.
[15] T. Alonso, H. Yang, Y. Liu, P.G. Mccormick, De-mixing of Nd2Fe14B during mechanical
milling, Applied Physics Letters, 60 (1992) 833.
[16] S. Shukla, A. Banas, R.V. Ramanujan, Atomistic mechanism of cyclic phase transitions in Nd-Fe-B based intermetallics, Intermetallics, 19 (2011) 1265.
[17] C.C. Koch, Amorphization of single composition powders by mechanical milling, Scripta Materialia, 34 (1996) 21.
[19] L. Schultz, Bildung amorpher metalle durch festkörperreaktion, Physikalische Blaetter, 44 (1988) 244.
[20] L. Schultz, J. Eckert, Mechanically alloyed glassy metals, in: Glassy Metals III, Springer, (1994) 69.
[21] J. Eckert, M. Seidel, N. Schlorke, A. Kubler, L. Schultz, Solid state processing of bulk metallic glass forming alloys, synthesis and properties of mechanically alloyed and nanocrystalline materials, Pts 1 and 2 - Ismanam-96, 235 (1997) 23.
[22] Y.S. Cho, C.C. Koch, Mechanical milling of ordered intermetallic compounds - the role of defects in amorphization, Journal of Alloys and Compound, 194 (1993) 287.
[23] Y. He, G.J. Shiflet, S.J. Poon, Ball milling-induced nanocrystal formation in aluminum- based metallic glasses, Acta Metallurgica and Materialia, 43 (1995) 83.
[24] M. Sherif El-Eskandarany, K. Aoki, K. Sumiyama, K. Suzuki, Cyclic phase transformations of mechanically alloyed Co75Ti25 powders, Acta Materialia, 50 (2002)
1113.
[25] D.A. Porter, K.E. Easterling, Phase transformations in metals and alloys, CRC PressI Lc, 1992.
[26] J.C. Fisher, J.H. Hollomon, D. Turnbull, Nucleation, Journal of Applied Physics, 19 (1948) 775.
[27] D. Turnbull, Under what conditions can a glass be formed, Contemporary Physics, 10 (1969) 473.
[28] J. Burke, The kinetics of phase transformation in metals, Pergamon Press, Oxford, 1965. [29] D.M. Herlach, Willnecker, R., Undercooling and solidification, in: H.H. Liebermann
(Ed.) Rapidly solidified alloys, Marcel Dekker Inc, New York, 1993.
[30] D. Porter, K. Easterling, M. Sherif, Phase transformations in metals and alloys. 2009, UK: Van Nostrnad Reinhold Co. Ltd, (1991) 203.
[31] D.M. Herlach, Nonequilibrium solidification of undercooled metallic melts, Materials Science and Engineering R, 12 (1994) 177.
[32] B.A. Legg, J. Schroers, R. Busch, Thermodynamics, kinetics, and crystallization of Pt57.3Cu14.6Ni5.3P22.8 bulk metallic glass, Acta Materialia, 55 (2007) 1109.
[33] M. Avrami, Kinetics of phase change. I: General theory, Journal of Chemical Physics, 7 (1939) 1103.
[34] M. Avrami, Kinetics of phase change. II: Transformation-time relations for random distribution of nuclei, Journal of Chemical Physics, 8 (1940) 212.
[35] M. Avrami, Granulation, phase change, and microstructure kinetics of phase change. III, Journal of Chemical Physics, 9 (1941) 177.
[36] H.E. Kissinger, Reaction kinetics in differential thermal analysis, Analytical Chemistry, 29 (1957) 1702.
[37] D.L. Peng, M. Yan, J.F. Sun, J. Shen, Y.Y. Chen, D.G. McCartney, Enhanced thermal stability by pre-charged hydrogen of a Zr-based bulk metallic glass, Journal of Alloys and Compound., 400 (2005) 197.
[38] J. Málek, Kinetic analysis of crystallization processes in amorphous materials, Thermochimca Acta, 355 (2000) 239.
[39] S. Venkataraman, E. Rozhkova, J. Eckert, L. Schultz, D.J. Sordelet, Thermal stability and crystallization kinetics of Cu-reinforced Cu47Ti33Zr11Ni8Si1 metallic glass composite
powders synthesized by ball milling: the effect of particulate reinforcement, Intermetallics, 13 (2005) 833.
[40] U. Köster, P. Weiss, Crystallization and decomposition of amorphous silicon-aluminium films, Journal of Non-Crystalline Solids, 17 (1975) 359.
[41] Y.T. Zhu, X.Z. Liao, X.L. Wu, Deformation twinning in nanocrystalline materials, Progress in Materials Science, 57 (2012) 1.
[42] C. C. Koch, I. A. Ovid’ko, S. Seal, S. Veprek, Structural nanocrystalline materials: fundamentals and applications, Cambridge university press, New York, 2007.
[43] T.T. Sasaki, T. Mukai, K. Hono, A high-strength bulk nanocrystalline Al–Fe alloy processed by mechanical alloying and spark plasma sintering, Scripta Materialia, 57 (2007) 189.
[44] Y. Kawamura, H. Mano, A. Inoue, Nanocrystalline aluminum bulk alloys with a high strength of 1420 MPa produced by the consolidation of amorphous powders, Scripta Materialia, 44 (2001) 1599.
[45] Y. Saito, H. Utsunomiya, N. Tsuji, T. Sakai, Novel ultra-high straining process for bulk materials-development of the accumulative roll-bonding (ARB) process, Acta Materialia, 47 (1999) 579.
[46] R. Valiev, Nanostructuring of metals by severe plastic deformation for advanced properties, Nature Materials, 3 (2004) 511.
[47] J.R. Groza, Nanostructured materials (Processing, properties and potential applications), Noyes Publications/William Andrew Publishing, Norwich, New York, 2002.
[48] K.S. Kumar, H. Van Swygenhoven, S. Suresh, Mechanical behavior of nanocrystalline metals and alloys, Acta Materialia, 51 (2003) 5743.
[49] P.V. Liddicoat, X.Z. Liao, Y. Zhao, Y. Zhu, M.Y. Murashkin, E.J. Lavernia, R.Z. Valiev, S.P. Ringer, Nanostructural hierarchy increases the strength of aluminium alloys, Nat ure Communications, 1 (2010) 63.
[50] R.Z. Valiev, I.V. Alexandrov, Y.T. Zhu, T.C. Lowe, Paradox of strength and ductility in metals processed bysevere plastic deformation, Journal of Materials Resesearch, 17 (2002) 5.
[51] R. Valiev, Y. Estrin, Z. Horita, T. Langdon, M. Zechetbauer, Y. Zhu, Producing bulk ultrafine-grained materials by severe plastic deformation, JOM, 58 (2006) 33.
[53] I.A. Ovid'ko, Deformation and diffusion modes in nanocrystalline materials, International Materials Review, 50 (2005) 65.
[54] E.O. Hall, The deformation and ageing of mild steel, Proceedings of Physical Society London, 64 (1951) 747.
[55] N.J. Petch, The cleavage strength of polycrystals, Journal of the Iron and Steel Institute, 174 (1953) 25.
[56] N. Hansen, Hall-Petch relation and boundary strengthening, Scripta Materialia, 51 (2004) 801.
[57] J. Schiotz, F.D. Di Tolla, K.W. Jacobsen, Softening of nanocrystalline metals at very small grain sizes, Nature, 391 (1998) 561.
[58] Y.M. Wang, E. Ma, Three strategies to achieve uniform tensile deformation in a nanostructured metal, Acta Materialia, 52 (2004) 1699.
[59] Z. Shan, E.A. Stach, J.M.K. Wiezorek, J.A. Knapp, D.M. Follstaedt, S.X. Mao, Grain boundary-mediated plasticity in nanocrystalline nickel, Science, 305 (2004) 654.
[60] Y. Champion, C. Langlois, S. Guerin-Mailly, P. Langlois, J.L. Bonnentien, M.J. Hytch, Near-perfect elastoplasticity in pure nanocrystalline copper, Science, 300 (2003) 310. [61] M.W. Chen, E. Ma, K.J. Hemker, H.W. Sheng, Y.M. Wang, X.M. Cheng, Deformation
twinning in nanocrystalline aluminum, Science, 300 (2003) 1275.
[62] Y.T. Chou, Dislocation pile-ups against a locked dislocation of a different burgers vector, Journal of Applied Physics, 38 (1967) 2080.
[63] R.L. Coble, A model for boundary diffusion controlled creep in polycrystalline materials, Journal of Applied Physics, 34 (1963) 1679.
[64] A.H. Chokshi, A. Rosen, J. Karch, H. Gleiter, On the validity of the Hall -Petch relationship in nanocrystalline materials, Scripta Metallurgica and Materialia, 23 (1989) 1679.
[65] H. Van Swygenhoven, Polycrystalline materials-grain boundaries and dislocations, Science, 296 (2002) 66.
[66] M.Y. Gutkin, I.A. Ovid'ko, Nanocracks at grain boundaries in nanocrystalline materials, Philosophical Magazine Letters, 84 (2004) 655.
[67] R. Valiev, Materials science: Nanomaterial advantage, Nature, 419 (2002) 88.
[68] L. Lu, Y.F. Shen, X.H. Chen, L.H. Qian, K. Lu, Ultrahigh strength and high electrical conductivity in copper, Science, 304 (2004) 422.
[69] K. Lu, L. Lu, S. Suresh, Strengthening materials by engineering coherent internal boundaries at the nanoscale, Science, 324 (2009) 349.
[70] O. Kraft, Crystalline materials twin behaviour and size, Nat Mater., 9 (2010) 295-296. [71] W. Han, G. Cheng, S. Li, S. Wu, Z. Zhang, Deformation induced microtwins and
[72] I.S. Howard, Powder metal technologies and application, in: Powder metal technologies and applications, ASM Handbook, Vol. 7, American Society of Metals, 1998.
[73] F. Thümmler, R. Oberacker, An introduction to powder metallurgy, Oxford Science Publications, 1993.
[74] G.S. Upadhyaya, Powder metallurgy technology, Cambridge International Science Publishing, Cambridge, 2002.
[75] S. Scudino, G. Liu, M. Sakaliyska, K.B. Surreddi, J. Eckert, Powder metallurgy of Al- based metal matrix composites reinforced with beta-Al3Mg2 intermetallic particles:
Analysis and modeling of mechanical properties, Acta Materialia, 57 (2009) 4529.
[76] F.H. Froes, Advances in powder metallurgy applications, in: Powder metal technologies and applicationos, ASM Handbook, Vol. 7, American Society of Metals, 1998.
[77] І.W.G.W. Leander F. Pease, Fundamentals of powder metallurgy, Metal Powder Industries Federation 2002.
[78] Y. Trudel, Introduction to metal powder production and characterization, in: Powder metal technologies and applications, ASM Handbook, Vol. 7, American Society of Metals, 1998.
[79] G. Dowson, Powder metallurgy: The process and its products, Springer, Bristol, 1990. [80] S.-J. L.Kang, Sintering densification, grain growth, and microstructure, Elsevier
Butterworth-Heinemann, 2005.
[81] R.M. German, Sintering theory and practice, Wiley-Interscience, 1996.
[82] L. Berrin, D.L. Johnson, Precise diffusion sintering models for initial shrinkage and neck growth, (1967).
[83] J.M. Vieira, R.J. Brook, Kinetics of hot-pressing: The Semilogarithmic law, Journal of American Ceramic Society, 67 (1984) 245.
[84] H. Kuhn, Powder metallurgy processing: The techniques and analyses, Academic press, 1978.
[85] E.J. Felten, Hot-pressing of alumina powders at low temperatures, Journal of American Ceramic Society, 44 (1961) 381.
[86] C.J. Ting, H.Y. Lu, Hot-pressing of magnesium aluminate spinel—I. Kinetics and densification mechanism, Acta Materialia, 47 (1999) 817.
[87] D. Kalish, E.V. Clougher, Densification mechanisms in high-pressure hot-pressing of HfB2, Journal of American Ceramic Society, 52 (1969) 26.
[88] A.S. Rao, A.C.D. Chaklader, Plastic flow during hot-pressing, Journal of American Ceramic Society, 55 (1972) 596.
[89] J. Mackenzie, R. Shuttleworth, A phenomenological theory of sintering, Proceedings of the Physical Society: Section B, 62 (1949) 833.
[91] J.C. Williams, E.A. Starke, Progress in structural materials for aerospace systems, Acta Materialia, 51 (2003) 5775.
[92] J.G. Kaufman, Introduction to aluminum alloys and tempers, ASM International, 2000. [93] W.S. Miller, L. Zhuang, J. Bottema, A.J. Wittebrood, P. De Smet, A. Haszler, A.
Vieregge, Recent development in aluminium alloys for the automotive industry, Materials Science and Engineering A, 280 (2000) 37.
[94] A. Heinz, A. Haszler, C. Keidel, S. Moldenhauer, R. Benedictus, W.S. Miller, Recent development in aluminium alloys for aerospace applications, Materials Science and Engineering A, 280 (2000) 102.
[95] P.J.E. Forsyth, C.A. Stubbington, Directionality in structure-property relationships: aluminium and titanium alloys, Metals Technology, 2 (1975) 158.
[96] P.V. Liddicoat, X.Z. Liao, Y. Zhao, Y. Zhu, M.Y. Murashkin, E.J. Lavernia, R.Z. Valiev, S.P. Ringer, Nanostructural hierarchy increases the strength of aluminium alloys, Nat ure Communication, 1 (2010) 63.
[97] A. Inoue, N. Matsumoto, T. Masumoto, Al-Ni-Y-Co amorphous-alloys with high mechanical strengths, wide supercooled liquid region and large glass-forming capacity, Materials Transactions, JIM , 31 (1990) 493.
[98] A. Inoue, K. Ohtera, A.P. Tsai, T. Masumoto, Aluminum-based amorphous-alloys with tensile-strength above 980 MPa (100 kg/mm2), Japanese Journal of Applied Physics, 27 (1988) 479.
[99] M. Gögebakan, Mechanical properties of AlYNi amorphous alloys, Journal of Light Metals, 2 (2002) 271.
[100] A. Inoue, Y. Horio, Y.H. Kim, T. Masumoto, Elevated-temperature strength of an Al88Ni9Ce2Fe1 amorphous alloy containing nanoscale fcc-Al particles, Materials
Transactions, JIM, 33 (1992) 669.
[101] B.J. Yang, J.H. Yao, J. Zhang, H.W. Yang, J.Q. Wang, E. Ma, Al-rich bulk metallic glasses with plasticity and ultrahigh specific strength, Scripta Materialia, 61 (2009) 423. [102] H.M. Fu, J. Mu, A.M. Wang, H. Li, Z.Q. Hu, H.F. Zhang, Synthesis and compressive
properties of Al-Ni-Y metallic glass, Philosophical Magazine Letters, 89 (2009) 711. [103] B.J. Yang, J.H. Yao, Y.S. Chao, J.Q. Wang, E. Ma, Developing aluminum-based bulk
metallic glasses, Philosophical Magazine, 90 (2010) 3215.
[104] Y. Kawamura, H. Mano, A. Inoue, Nanocrystalline aluminum bulk alloys with a high strength of 1420 MPa produced by the consolidation of amorphous powders, Scripta Materialia, 44 (2001) 1599.
[105] K.M. Youssef, R.O. Scattergood, K.L. Murty, C.C. Koch, Nanocrystalline Al-Mg alloy with ultrahigh strength and good ductility, Scripta Materialia, 54 (2006) 251.
[106] T. Shanmugasundaram, M. Heilmaier, B.S. Murty, V.S. Sarma, On the Hall -Petch relationship in a nanostructured Al-Cu alloy, Materials Science and Engineering A, 527 (2010) 7821.
[107] B.Q. Han, J. Ye, F. Tang, J. Schoenung, E.J. Lavernia, Processing and behavior of nanostructured metallic alloys and composites by cryomilling, Journal of Materials Science, 42 (2007) 1660.
[108] Y. Li, Z. Zhang, R. Vogt, J.M. Schoenung, E.J. Lavernia, Boundaries and interfaces i n ultrafine grain composites, Acta Materialia, 59 (2011) 7206.
[109] A. Magee, L. Ladani, T.D. Topping, E.J. Lavernia, Effects of tensile test parameters on the mechanical properties of a bimodal Al-Mg alloy, Acta Materialia, 60 (2012) 5838. [110] D. Witkin, Z. Lee, R. Rodriguez, S. Nutt, E. Lavernia, Al-Mg alloy engineered with
bimodal grain size for high strength and increased ductility, Scripta Materialia, 49 (2003) 297.
[111] J.M. Park, K.B. Kim, D.H. Kim, N. Mattern, R. Li, G. Liu, J. Eckert, Multi-phase Al- based ultrafine composite with multi-scale microstructure, Intermetallics, 18 (2010) 1829. [112] B.Q. Han, J.Y. Huang, Y.T. Zhu, E.J. Lavernia, Strain rate dependence of properties of
cryomilled bimodal 5083 Al alloys, Acta Materialia, 54 (2006) 3015.
[113] G. He, J. Eckert, W. Loser, L. Schultz, Novel Ti-base nanostructure-dendrite composite with enhanced plasticity, Nature Materials, 2 (2003) 33.
[114] K.B. Surreddi, V.C. Srivastava, S. Scudino, M. Sakaliyska, V. Uhlenwinkel, J.S. Kim, J. Eckert, Production of high-strength Al85Y8Ni5Co2 bulk alloy by spark plasma sintering,
Journal of Physics Conference Series, 240 (2010) 1.
[115] Y. Wang, X.L. Shi, R.S. Mishra, T.J. Watson, Ductility improvement in devitrified ultrafine-grained Al-4.0Y-4.0Ni-0.9Co alloy via hot rolling, Scripta Materialia, 56 (2007) 923.
[116] L. Shaw, H. Luo, J. Villegas, D. Miracle, Compressive behavior of an extruded nanocrystalline Al-Fe-Cr-Ti alloy, Scripta Materialia, 50 (2004) 921.
[117] Y. Li, K. Georgarakis, S.J. Pang, F. Charlot, A. LeMoulec, S. Brice-Profeta, T. Zhang, A.R. Yavari, Chill-zone aluminum alloys with GPa strength and good plasticity, Journal of Materials Research, 24 (2009) 1513.
[118] M.F. Ashby, Materials selection in mechanical design, MRS Bull., 30 (2005) 995.
[119] Z.P. Chen, H. Yu, Y. Wu, H. Wang, X.J. Liu, Z.P. Lu, Nano-network mediated high strength and large plasticity in an Al-based alloy, Materials Letters, 84 (2012) 59.
[120] L.C. Zhuo, E.H. Yin, H. Wang, T. Zhang, Hierarchical ultrafine-grained/nanocystalline Al-based bulk alloy with high strength and large plasticity, Intermetallics, 23 (2012) 199. [121] H.B. Chen, B. Yang, Effect of Precipitations on Microstructures and Mechanical
Properties of Nanostructured Al-Zn-Mg-Cu Alloy, Materials Transactions, 49 (2008) 2912.
[122] H. Luo, L. Shaw, L.C. Zhang, D. Miracle, On tension/compression asymmetry of an extruded nanocrystalline Al-Fe-Cr-Ti alloy, Materials Science and Engineering A, 409 (2005) 249.
[123] G.J. Fan, G.Y. Wang, H. Choo, P.K. Liaw, Y.S. Park, B.Q. Han, E.J. Lavernia, Deformation behavior of an ultrafine-grained Al-Mg alloy at different strain rates, Scripta Materialia, 52 (2005) 929.
[124] T.T. Sasaki, T. Mukai, K. Hono, A high-strength bulk nanocrystalline Al-Fe alloy processed by mechanical alloying and spark plasma sintering, Scripta Materialia, 57 (2007) 189.
[125] T.T. Sasaki, T. Ohkubo, K. Hono, Microstructure and mechanical properties of bulk nanocrystalline Al-Fe alloy processed by mechanical alloying and spark plasma sintering, Acta Materialia, 57 (2009) 3529.
[126] J. Ye, B.Q. Han, Z. Lee, B. Ahn, S.R. Nutt, J.M. Schoenung, A tri-modal aluminum based composite with super-high strength, Scripta Materialia, 53 (2005) 481.
[127] T.T. Sasaki, K. Hono, J. Vierke, M. Wollgarten, J. Banhart, Bulk nanocrystalline Al85Ni10La5 alloy fabricated by spark plasma sintering of atomized amorphous powders,
Materials Science and Engineering A, 490 (2008) 343.
[128] D. Roy, R. Mitra, T. Chudoba, Z. Witczak, W. Lojkowski, H.J. Fec ht, I. Manna, Structure and mechanical properties of Al65Cu20Ti15-based amorphous/nanocrystalline
alloys prepared by high-pressure sintering, Materials Science and Engineering A, 497 (2008) 93.
[129] C.Y. Yu, P.W. Kao, C.P. Chang, Transition of tensile deformation behaviors in ultrafine- grained aluminum, Acta Materialia, 53 (2005) 4019.
[130] R.W. Hayes, D. Witkin, F. Zhou, E.J. Lavernia, Deformation and activation volumes of cryomilled ultrafine-grained aluminum, Acta Materialia, 52 (2004) 4259.
[131] V.L. Tellkamp, A. Melmed, E.J. Lavernia, Mechanical behavior and microstructure of a thermally stable bulk nanostructured Al alloy, Metallurgical and Materials Transactions A, 32 (2001) 2335.
[132] K. Ohtera, A. Inoue, T. Masumoto, High mechanical strength of aluminum-based crystalline alloys produced by warm consolidation of amorphous powder, Materials Science and Engineering A, 134 (1991) 1212.
[133] K. Ohtera, A. Inoue, T. Terabayashi, H. Nagahama, T. Masumoto, Mechanical-properties of an Al88.5Ni8MM3.5 (MM, misch metal) alloy produced by extrusion of atomized
amorphous plus fcc-Al phase powders, Materials Transactions, JIM, 33 (1992) 775. [134] J. Mu, H. Fu, Z. Zhu, A. Wang, H. Li, Z. Hu, H. Zhang, Synthesis and properties of Al -