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Acta Metall Sin  2017, Vol. 53 Issue (5): 583-591    DOI: 10.11900/0412.1961.2016.00502
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Effects of Direct Current on Microstructure and Properties of Ti-48Al-2Cr-2Nb Alloy
Zhanxing CHEN,Hongsheng DING,Shiqiu LIU,Ruirun CHEN,Jingjie GUO,Hengzhi FU
National Key Laboratory for Precision Hot Processing of Metals, School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
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TiAl based alloys have been widely used as promising aerospace structural materials, which benefit from their unique combination of mechanical properties. However, they yield poor plasticity and low process ability, thus restricting the wide application. In this work, an efficient way was proposed by which direct current (DC) was imposed on the solidification process of TiAl-based alloy. Influences of DC on the microstructure and properties of directionally solidified Ti-48Al-2Cr-2Nb alloy using water cold crucible directional solidification equipment has been investigated. The changes of solidification microstructure, phase structure and composition of the alloy and γ/α2 interlamellar structures were characterized by OM, XRD, SEM and TEM. The effect of DC on the size of eutectoid colony, interlamellar spacing and relative content of α2 phase had been studied by Image Pro Plus. Furthermore, the mechanical properties of the directionally solidified Ti-48Al-2Cr-2Nb alloy at 800 ℃ were performed. The results revealed that the DC can evidently promote the homogeneity of the solidification component and refiner the structure, and the segregation in lamellar colonies can be efficiently reduced or eliminated to a certain extent. With the increasing of the current density, the grain size and lamellar spacing decreased first and then increased, however, the α2 phase content showed a totally different trend. Moreover, the microhardness, compression yield strength and the fracture strength of the alloy also revealed a trend of decrease after the first increase too. With the current density increasing, the average grain size and interlamellar spacing declined to the lowest of 0.46 mm and 0.19 μm, respectively, and the content of α2 phase increased from 18.5% to 39.4%. The microhardness of sample reached 542 HV, the compression yield strength and the fracture strength were remarkably improved, and the maximum values reached 1200 and 1365 MPa, respectively. DC can cause a reduction of the supercooling in front of the liquid phase during the solidification process. The results can be seen as the peritectic reaction L→β+L→α+β moving a tiny drift to the direction of the Al-rich side in TiAl binary phase diagram, consequently, the primary β-phase increased, and the content of α2 phase, microstructure under room temperature, increased evidently.

Key words:  TiAl alloy      direct current      solidification      microstructure      microhardness      high temperature compression     
Received:  11 November 2016     
Fund: Supported by National Natural Science Foundation of China (Nos.51171053 and 51471062)

Cite this article: 

Zhanxing CHEN,Hongsheng DING,Shiqiu LIU,Ruirun CHEN,Jingjie GUO,Hengzhi FU. Effects of Direct Current on Microstructure and Properties of Ti-48Al-2Cr-2Nb Alloy. Acta Metall Sin, 2017, 53(5): 583-591.

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Fig.1  Macrostructures of directionally solidified Ti-48Al-2Cr-2Nb alloy without direct current (DC) (a) and with the DC densities of 32 mA/mm2 (b), 64 mA/mm2 (c) and 96 mA/mm2 (d) (Zone A—original as-cast zone, zone B—heat affected zone, zone C—transition zone, zone D—columnar crystal zone, zone E—equiaxed crystal zone)
Fig.2  OM images of microstructures of Ti-48Al-2Cr-2Nb alloys solidified without DC (a) and with the DC densities of 32 mA/mm2 (b), 64 mA/mm2 (c) and 96 mA/mm2 (d)
Fig.3  SEM images of microstructures of Ti-48Al-2Cr-2Nb alloy solidified without DC (a) and with the DC densities of 32 mA/mm2 (b), 64 mA/mm2 (c) and 96 mA/mm2 (d)
Fig.4  XRD spectra of Ti-48Al-2Cr-2Nb alloy solidified with and without DC
Fig.5  TEM images of lamella structures of Ti-48Al-2Cr-2Nb alloy solidified without DC (a) and with the DC densities of 32 mA/mm2 (b), 64 mA/mm2 (c) and 96 mA/mm2 (d)
Fig.6  Volume fraction of α2 phase in Ti-48Al-2Cr-2Nb alloy solidified with and without DC
Fig.7  Grain size and lamella width of Ti-48Al-2Cr-2Nb alloy with and without DC
Fig.8  Microhardness in various zones of directionally solidified Ti-48Al-2Cr-2Nb alloy with and without DC current
Fig.9  True stress-true strain curves of Ti-48Al-2Cr-2Nb alloy solidified with and without DC
Fig.10  Schematic of equivalent binary phase diagram of TiAl system with direct current
[1] Dimiduk D M.Gamma titanium aluminide alloys—An assessment within the competition of aerospace structural materials[J]. Mater. Sci. Eng., 1999, A263: 281
[2] Appel F, Brossmann U, Christoph U, et al.Recent progress in the development of gamma titanium aluminide alloys[J]. Adv. Eng. Mater., 2000, 2: 699
[3] Appel H F, Paul J D H, Oehring M. Gamma Titanium Aluminide Alloys: Science and Technology[M]. Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2011: 1
[4] Wu X H.Review of alloy and process development of TiAl alloys[J]. Intermetallics, 2006, 14: 1114
[5] Kim Y W.Ordered intermetallic alloys, part III: Gamma titanium aluminides[J]. JOM, 1994, 46(7): 30
[6] Asai S.Electromagnetic Processing of Materials[M]. Netherlands: Springer, 2012: 87
[7] Conrad H.Enhanced phenomena in metals with electric and magnetic fields: I electric fields[J]. Mater. Trans., 2005, 46: 1083
[8] Liao X L, Zhai Q J, Luo J, et al.Refining mechanism of the electric current pulse on the solidification structure of pure aluminum[J]. Acta Mater., 2007, 55: 3103
[9] Li X B, Lu F G, Cui H C, et al.Migration behavior of solidification nuclei in pure Al melt under effect of electric current pulse[J]. Trans. Nonferrous Met. Soc. China, 2014, 24: 192
[10] Barnak J P, Sprecher A F, Conrad H.Colony (grain) size reduction in eutectic Pb-Sn castings by electroplusing[J]. Scr. Metall. Mater., 1995, 32: 879
[11] Nakada M, Shiohara Y, Flemings M C.Modification of solidification structures by pulse electric discharging[J]. ISIJ Int., 1990, 30: 27
[12] Misra A K.Effect of electric potentials on solidification of near eutectic Pb-Sb-Sn alloy[J]. Mater. Lett., 1986, 4: 176
[13] Liao X L, Zhai Q J, Song C J, et al.Effects of electric current pulse on stability of solid/liquid interface of Al-4.5wt.% Cu alloy during directional solidification[J]. Mater. Sci. Eng., 2007, A466: 56
[14] R?biger D, Zhang Y H, Galindo V, et al.The relevance of melt convection to grain refinement in Al-Si alloys solidified under the impact of electric currents[J]. Acta Mater., 2014, 79: 327
[15] Vashchenko K I, Chernega D F, Vorobev S L, et al.Effect of electric current on the solidification of cast iron[J]. Met. Sci. Heat Treat., 1974, 16: 261
[16] Feng X H, Yang Y S, Li Y J, et al.Effect of DC field on mechanical property of a Ni-based single crystal superalloy[J]. Acta Metall. Sin., 2006, 42: 947
[16] (冯晓辉, 杨院生, 李应举等. 直流电场对一种镍基单晶高温合金力学性能的影响[J]. 金属学报, 2006, 42: 947)
[17] Jiang H X, Zhao J Z, Wang C P, et al.Effect of electric current pulses on solidification of immiscible alloys[J]. Mater. Lett., 2014, 132: 66
[18] Zhou B L.Nonequilibrium processes in materials processing[J]. Chin. J. Mater. Res., 1997, 11: 576
[18] (周本濂. 材料制备中的非平衡过程 [J]. 材料研究学报, 1997,11: 576)
[19] Nie G.Microstructure and properties of electromagnetic cold crucible directionally solidified α2/γ laminar TiAl-based billets [D]. Harbin: Harbin Institute of Technology, 2012
[19] (聂革. 电磁冷坩埚定向凝固α2/γ片层TiAl基坯锭组织与性能 [D]. 哈尔滨: 哈尔滨工业大学, 2012)
[20] Yang J R.Heat transfer and microstructures and properties of high Nb containing TiAl alloys direction solidified by cold crucible [D]. Harbin: Harbin Institute of Technology, 2013
[20] (杨劼人. 高Nb-TiAl合金冷坩埚定向凝固传热特性及组织与性能 [D]. 哈尔滨: 哈尔滨工业大学, 2013)
[21] McNelley T R, Swaminathan S, Su J Q. Recrystallization mechanisms during friction stir welding/processing of aluminum alloys[J]. Scr. Mater., 2008, 58: 349
[22] Jung I S, Kim M C, Lee J H, et al.High temperature phase equilibria near Ti-50 at% Al composition in Ti-Al system studied by directional solidification[J]. Intermetallics, 1999, 7: 1247
[23] Jung I S, Jang H S, Oh M H, et al. Microstructure control of TiAl alloys containing β stabilizers by directional solidification [J]. Mater. Sci. Eng., 2002, A329-331: 13
[24] Fu H Z, Guo J J, Liu L, et al.Directional Solidification and Processing of Advanced Materials [M]. Beijing: Science Press, 2008: 16
[24] (傅恒志, 郭景杰, 刘林等. 先进材料定向凝固 [M]. 北京: 科学出版社, 2008: 16)
[25] Su Y Q, Liu C, Li X Z, et al.Microstructure selection during the directionally peritectic solidification of Ti-Al binary system[J]. Intermetallics, 2005, 13: 267
[26] Li X, Fautrelle Y, Ren Z M.Influence of thermoelectric effects on the solid-liquid interface shape and cellular morphology in the mushy zone during the directional solidification of Al-Cu alloys
[26] under a magnetic field[J]. Acta Mater., 2007, 55: 3803
[27] Hansen N.Hall-Petch relation and boundary strengthening[J]. Scr. Mater., 2004, 51: 801
[28] Yamamoto Y, Takeyama M.Physical metallurgy of single crystal gamma titanium aluminide alloys: orientation control and thermal stability of lamellar microstructure[J]. Intermetallics, 2005, 13: 965
[29] Ashby M F, Jones D R H. Engineering Materials [M]. Oxford: Pergamon Press, 1980: 105
[30] Sato Y S, Urata M, Kokawa H, et al.Hall-Petch relationship in friction stir welds of equal channel angular-pressed aluminium alloys[J]. Mater. Sci. Eng., 2003, A354: 298
[31] Pfann W G, Wagner R S.Principles of field freezing[J]. Trans. Metall. Soc. AIME, 1962, 224: 1139
[32] Prodhan A, Sivaramakrishnan C S, Chakrabarti A K.Solidification of aluminum in electric field[J]. Metall. Mater. Trans., 2001, 32B: 372
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