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It is highly desirable to undercool titanium based alloy melts and modulate their dendritic solidification process due to the relevant applications in aerospace engineering. But the serious chemical reactivities of this category of alloys result in potent heterogeneous nucleation and suppress remarkable undercoolings in the course of normal material processing. This paper shows that such a challenge can be solved by containerless processing approach. Liquid Ti-25 wt.%Al alloy is highly undercooled and rapidly solidified under containerless state by both electromagnetic levitation and drop tube techniques. Its metastable undecoolability, crystal nucleation mechanism and dendrite growth process are examined experimentally and analyzed theoretically. Those heterogeneous nuclei with wetting angles above 60 are found to be quite difficult to eliminate even during levitation processing, thus reducing the undercoolability of this alloy. The maximum undercooling of bulk alloy melt reaches 210 K (0.11 TL). The thermodynamic driving force to initiate the nucleation of -Ti phase increases almost linearly with the enhancement of undercooling. The phase dendrite displays a growth velocity up to 11.2 m/s, indicating that the rapid solidification is realized at the relatively slow cooling rate of levitated alloy melt. With the increase of undercooling, phase dendrite experiences a kinetic transition from solute diffusion controlled to thermal diffusion controlled growth. Once undercooling exceeds 100 K, the nonequilibrium solute trapping effect brings about the practically desirable segregationless solidification. Nevertheless, the single condition of substantial undercooling is insufficient to suppress the solid state transformation of phase. It is decomposed into 2-Ti3Al phase plus a small amount of -TiAl compound after containerless solidification at levitated state. A more efficient approach to controlling and modulating the solidification microstructures is to utilize the coupled effects of high undercooling and rapid quenching, which proves to be feasible through the rapid solidification of alloy droplets inside drop tube. For those alloy droplets with diameters ranging from 77 to 1048 m, their cooling rates attain a maximum of 1.05105 K/s, and the predicted maximum undercooling is 227-778 K. In this case, phase dendrites are well refined and kept in a metastable state until ambient temperature. The heat transfer calculations indicate that the thermal radiation is the dominant cooling mechanism for the large alloy droplets above 690 m, whereas thermal convection becomes the major cooling mechanism for the small alloy droplets below 690 m. The microgravity condition during free falling does not show apparent effect on the microstructural formation of these alloy droplets.
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Keywords:
- liquid alloy /
- substantial undercooling /
- rapid solidification /
- dendritic growth
[1] Brillo J, Pommrich A I, Meyer A 2011 Phys. Rev. Lett. 107 165902
[2] Wang N, Wei B 2002 Appl. Phys. Lett. 80 3515
[3] Hartmann H, Galenko P K, Holland-Moritz D, Kolbe M, Herlach D M 2008 J. Appl. Phys. 103 073509
[4] Huang Q S, Liu L, Wei X X, Li J F 2012 Acta Phys. Sin. 61 166401 (in Chinese) [黄起森, 刘礼, 韦修勋, 李金富 2012 61 166401]
[5] Liu Y C, Lin X, Guo X F, Yang G C, Zhou Y H 2000 J. Cryst. Growth 217 211
[6] Kurz W, Fisher D J 1998 Fundamentals of Solidification (Switzerland: Trans. Tech. Publications Ltd) pp22-23
[7] Spaepen F, Meyer R B 1976 Scr. Metall. 10 257
[8] Jackson K A 2004 J. Cryst. Growth 264 519
[9] Anderson C D, Hofmeister W H, Bayuzick R J 1992 Metall. Trans. A 23 2699
[10] Shuleshora O, Woodcock T G, Lindenkreuz H G, Hermann R, Loeser W, Buechner B 2007 Acta Mater. 55 681
[11] Hu L, Li L H, Yang S J, Wei B 2015 Chem. Phys. Lett. 621 91
[12] McDaniel J G, Holt R G 2000 Phys. Rev. E 61 R2204
[13] Kidkhunthod P, Skinner L B, Barnes A C, Klystun W, Fisher H 2014 Phys. Rev. B 90 094206
[14] Yang S J, Wang W L, Wei B B 2015 Acta Phys. Sin. 64 056401 (in Chinese) [杨尚京, 王伟丽, 魏炳波 2015 64 056401]
[15] Mondal K, Kumar A, Gupta G, Murty B S 2009 Acta Mater. 57 3422
[16] Liu L X, Hou Z Y, Liu R S 2012 Acta Phys. Sin. 61 056101 (in Chinese) [刘丽霞, 侯兆阳, 刘让苏 2012 61 056101]
[17] Clopet C R, Cochrame R F, Mullis A M 2013 Appl. Phys. Lett. 102 031906
[18] Chang J, Wang H P, Wei B 2008 Phil. Mag. Lett. 88 821
[19] Lipton J, Kurz W, Trivedi R 1987 Acta Metall. 35 957
[20] Aziz M J 1982 J. Appl. Phys. 53 1158
[21] Boettinger W J, Coriell S R, Trevidi R 1987 in: Mehrabian R (Eds), Proceedings of the Fourth International Conference on Rapid Solidification Processing, Principles and Technologies Claitors, Baton Rouge 13-20
[22] Chen R, Xu Q Y, Liu B C 2014 Acta Phys. Sin. 63 188102 (in Chinese) [陈瑞, 许庆彦, 柳百成 2014 63 188102]
[23] Pan S Y, Zhu M F 2009 Acta Phys. Sin. 58 S278 (in Chinese) [潘诗琰, 朱鸣芳 2009 58 S278]
[24] Zghal S, Thomas M, Naka S, Finel A, Coret A 2005 Acta Mater. 53 2653
[25] Liu Z G, Chai L H, Chen Y Y, Kong F T 2008 Acta Metall. Sin. 44 569 (in Chinese) [刘志华, 柴丽华, 陈玉勇, 孔凡涛 2008 金属学报 44 569]
[26] Kartavykh A V, Tcherdyntsev V V, Gorshenkov M V, Kaloshkin S D 2014 J. Alloys Compd. 586 S180
[27] Wang H, Wariken N, Reed R C 2010 Mater. Sci. Eng. A 528 622
[28] Fan J L, Li X Z, Su Y Q, Guo J J, Fu H Z 2010 J. Alloys Compd. 504 60
[29] Zhou K, Wang H P, Wei B 2012 Chem. Phys. Lett. 521 52
[30] Masslaski T B 1986 Binary Alloy Diagrams ASM, Metals Park, Ohio 175
[31] Turnbull D 1952 J. Chem. Phys. 20 411
[32] Dubey K S, Ramachandrarao 1984 Acta Metall. 32 91
[33] Gale W F, Totemeir T C 2004 Smithells Metals Reference Book (8th Ed) (Elsevier Publishers Ltd) p14-1
[34] Wu K 2011 Transport Principles of Metallurgical Processes (Beijing: Metallurgical Industry Press) 169-178 (in Chinese) [吴铿 2011 冶金传输原理 (北京: 冶金工业出版社) 第167-178页]
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[1] Brillo J, Pommrich A I, Meyer A 2011 Phys. Rev. Lett. 107 165902
[2] Wang N, Wei B 2002 Appl. Phys. Lett. 80 3515
[3] Hartmann H, Galenko P K, Holland-Moritz D, Kolbe M, Herlach D M 2008 J. Appl. Phys. 103 073509
[4] Huang Q S, Liu L, Wei X X, Li J F 2012 Acta Phys. Sin. 61 166401 (in Chinese) [黄起森, 刘礼, 韦修勋, 李金富 2012 61 166401]
[5] Liu Y C, Lin X, Guo X F, Yang G C, Zhou Y H 2000 J. Cryst. Growth 217 211
[6] Kurz W, Fisher D J 1998 Fundamentals of Solidification (Switzerland: Trans. Tech. Publications Ltd) pp22-23
[7] Spaepen F, Meyer R B 1976 Scr. Metall. 10 257
[8] Jackson K A 2004 J. Cryst. Growth 264 519
[9] Anderson C D, Hofmeister W H, Bayuzick R J 1992 Metall. Trans. A 23 2699
[10] Shuleshora O, Woodcock T G, Lindenkreuz H G, Hermann R, Loeser W, Buechner B 2007 Acta Mater. 55 681
[11] Hu L, Li L H, Yang S J, Wei B 2015 Chem. Phys. Lett. 621 91
[12] McDaniel J G, Holt R G 2000 Phys. Rev. E 61 R2204
[13] Kidkhunthod P, Skinner L B, Barnes A C, Klystun W, Fisher H 2014 Phys. Rev. B 90 094206
[14] Yang S J, Wang W L, Wei B B 2015 Acta Phys. Sin. 64 056401 (in Chinese) [杨尚京, 王伟丽, 魏炳波 2015 64 056401]
[15] Mondal K, Kumar A, Gupta G, Murty B S 2009 Acta Mater. 57 3422
[16] Liu L X, Hou Z Y, Liu R S 2012 Acta Phys. Sin. 61 056101 (in Chinese) [刘丽霞, 侯兆阳, 刘让苏 2012 61 056101]
[17] Clopet C R, Cochrame R F, Mullis A M 2013 Appl. Phys. Lett. 102 031906
[18] Chang J, Wang H P, Wei B 2008 Phil. Mag. Lett. 88 821
[19] Lipton J, Kurz W, Trivedi R 1987 Acta Metall. 35 957
[20] Aziz M J 1982 J. Appl. Phys. 53 1158
[21] Boettinger W J, Coriell S R, Trevidi R 1987 in: Mehrabian R (Eds), Proceedings of the Fourth International Conference on Rapid Solidification Processing, Principles and Technologies Claitors, Baton Rouge 13-20
[22] Chen R, Xu Q Y, Liu B C 2014 Acta Phys. Sin. 63 188102 (in Chinese) [陈瑞, 许庆彦, 柳百成 2014 63 188102]
[23] Pan S Y, Zhu M F 2009 Acta Phys. Sin. 58 S278 (in Chinese) [潘诗琰, 朱鸣芳 2009 58 S278]
[24] Zghal S, Thomas M, Naka S, Finel A, Coret A 2005 Acta Mater. 53 2653
[25] Liu Z G, Chai L H, Chen Y Y, Kong F T 2008 Acta Metall. Sin. 44 569 (in Chinese) [刘志华, 柴丽华, 陈玉勇, 孔凡涛 2008 金属学报 44 569]
[26] Kartavykh A V, Tcherdyntsev V V, Gorshenkov M V, Kaloshkin S D 2014 J. Alloys Compd. 586 S180
[27] Wang H, Wariken N, Reed R C 2010 Mater. Sci. Eng. A 528 622
[28] Fan J L, Li X Z, Su Y Q, Guo J J, Fu H Z 2010 J. Alloys Compd. 504 60
[29] Zhou K, Wang H P, Wei B 2012 Chem. Phys. Lett. 521 52
[30] Masslaski T B 1986 Binary Alloy Diagrams ASM, Metals Park, Ohio 175
[31] Turnbull D 1952 J. Chem. Phys. 20 411
[32] Dubey K S, Ramachandrarao 1984 Acta Metall. 32 91
[33] Gale W F, Totemeir T C 2004 Smithells Metals Reference Book (8th Ed) (Elsevier Publishers Ltd) p14-1
[34] Wu K 2011 Transport Principles of Metallurgical Processes (Beijing: Metallurgical Industry Press) 169-178 (in Chinese) [吴铿 2011 冶金传输原理 (北京: 冶金工业出版社) 第167-178页]
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