Rapid Cooling and Solidification Microstructure of Argon Atomized Ti-48Al Alloy Droplets
BAO Ying1,2, LUO Lin1, YU Ze-min1, YANG Dong-ye2, LIU Na3, ZHANG Guo-qing3, SUN Jian-fei2
1. School of Material Science and Engineering, Harbin University of Science and Technology, Harbin 150080, China;
2. School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China;
3. Science and Technology on Advanced High Temperature Structural Materials Laboratory, AECC Beijing Institute of Aeronautical Materials, Beijing 100095, China
Abstract：An analytical approach was developed to investigate nucleation and growth of Ti-48Al (atom fraction/%) alloy droplets during their flight in an argon atomization process. Evolution of microstructure of the solidified powders was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron back-scatter diffraction (EBSD). Newton cooling model based on the initial number of nuclei, liquid/solid interface velocity, cooling rate and size of droplets was established. The results show that statistical nucleation events increase exponentially with the increase of powders size, and the growth of nuclei is transformed from a twinned spherical segment into a concentric liquid/solid interface geometry. Temperature of atomized droplets decreases rapidly with the cooling rate of 105-106K·s-1.Then temperature increases sharply to near the liquidus temperature during recalescence. When the recalescence is completed, the droplet solidifies at a relatively slower rate. Afterwards the cooling rate of the fully solid phase decreases to about 105K·s-1.
 KIM Y W. Strength and ductility in TiAl alloys[J]. Intermetallics, 1998, 6(7/8):623-628.
 王艳晶,柳乐,宋玫锦. Y微合金化高铌TiAl基合金微观组织研究[J]. 材料工程, 2015,43(1):66-71. WANG Y J, LIU L, SONG M J. Microstructure of Y micro-alloying TiAl based alloy with high Nb content[J]. Journal of Materials Engineering,2015,43(1):66-71.
 RAO K P, PRASAD Y, SURESH K. Hot working behavior and processing map of a γ-TiAl alloy synthesized by powder metallurgy[J]. Materials & Design,2011,32(10):4874-4881.
 马李,何录菊,邵先亦,等. 电子束沉积TiAl合金的微观形貌及组织结构稳定性[J]. 材料工程, 2016, 44(1):89-95. MA L,HE L J,SHAO X Y,et al. Micro-morphology and microstructure stability of TiAl alloy deposited by electronic beam[J]. Journal of Materials Engineering,2016,44(1):89-95.
 阚文斌,林均品. 增材制造技术制备钛铝合金的研究进展[J]. 中国材料进展, 2015, 34(2):111-119. KAN W B,LIN J P. Research progress on fabrication of TiAl alloys fabricated by additive manufacturing[J]. Materials China,2015, 34(2):111-119.
 刘咏,黄伯云,贺跃辉,等. 热压反应合成TiAl合金的密度及孔隙分布[J]. 中南工业大学学报, 1998, 29(5):446-449. LIU Y, HUANG B Y, HE Y H, et al. Densification and porosity distribution of TiAl based alloy prepared by reactive hot pressing[J]. Journal of Central South University, 1998, 29(5):446-449.
 SUN J F, CAO F Y, CUI C C, et al. Dynamic behaviors of gas velocity field during metal atomization[J]. Powder Metallurgy Technology, 2002, 20(2):79-81.
 MATHUR P,APELIAN D,LAWLEY A. Analysis of the spray deposition process[J]. Acta Metallurgica,1989, 37(2):429-433.
 GRANT P S,CANTOR B,KATGERMAN L. Modelling of droplet dynamic and thermal histories during spray forming-Ⅰ individual droplet behaviour[J]. Acta Metallurgica et Materialia,1993,41(11):3097-3108.
 LEVI C G, MEHRABIAN R. Heat flow during rapid solidification of undercooled metal droplets[J]. Metallurgical and Materials Transactions A,1982,13(2):221-234.
 TRIVEDI R,JIN F,ANDERSON I E. Dynamical evolution of microstructure in finely atomized droplets of Al-Si alloys[J]. Acta Materialia,2003,51(2):289-300.
 JABBAR H, MONCHOUX J P, THOMAS M, et al. Improvement of the creep properties of TiAl alloys densified by spark plasma sintering[J]. Intermetallics,2014,46(1):1-3.
 SUN Y,KULKARNI K,SACHDEV A K,et al. Synthesis of γ-TiAl by reactive spark plasma sintering of cryomilled Ti and Al powder blend:part Ⅱ:effects of electric field and microstructure on sintering kinetics[J].Metallurgical and Materials Transactions A,2014,45(6):2759-2767.
 LEVI C G, MEHRABIAN R. Microstructures of rapidly solidified aluminum alloy submicron powders[J]. Metallurgical and Materials Transactions A,1982,13(1):13-23.
 AISSA A,ABDELOUAHAB M,NOUREDDINE A,et al. Ranz and Marshall correlations limits on heat flow between a sphere and its surrounding gas at high temperature[J]. Thermal Science,2015,19(5):1521-1528.
 RANZ W E, MARSHALL W R J. Evaporation from drops:part Ⅰ[J]. Chemical Engineering Progress,1952,48(3):141-146.
 LEE E S, AHN S. Solidification progress and heat transfer analysis of gas-atomized alloy droplets during spray forming[J]. Acta Metallurgica et Materialia,1994,42(9):3231-3243.
 SHUKLA P,MANDAL R K,OJHA S N.Non-equilibrium solidification of undercooled droplets during atomization process[J]. Bulletin of Materials Science,2001,24(5):547-554.
 MARASLI N,HUNT J D. Solid-liquid surface energies in the Al-CuAl2,Al-NiAl3 and Al-Ti systems[J]. Acta Materialia,1996,44(3):1085-1096.
 HARDING R A,BROOKS R F,POTTACHER G,et al. Thermo-physical properties of a Ti-44Al-8Nb-1B alloy in the solid and molten conditions[C]//Gamma Titanium Aluminides 2003.Warrendale,US:The Minerals,Metals & Materials Society, 2003:75-82.
 LI B, LIANG X, EARTHMAN J C, et al. Two dimensional modeling of momentum and thermal behavior during spray atomization of γ-TiAl[J]. Acta Materialia,1996,44(6):2409-2420.
 FRANZEN S F, KARLSSON J. γ-titanium aluminide manufactured by electron beam melting[D]. Chalmers,Sweden:Chalmers University of Technology, 2010.