Deformation Behavior and Microstructure Evolution of 9Cr18 Alloy During Semi-Solid Compression
Yongjin WANG1,2, Renbo SONG1(), Renfeng SONG3
1 School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China 2 Institute of Industrial Science, The University of Tokyo, Tokyo 1538505, Japan 3 Ansteel Mining Engineering Corporation, Anshan 114004, China
Cite this article:
Yongjin WANG, Renbo SONG, Renfeng SONG. Deformation Behavior and Microstructure Evolution of 9Cr18 Alloy During Semi-Solid Compression. Acta Metall Sin, 2018, 54(1): 39-46.
The compression behavior during semi-solid state is a fundamental basis for the following rheoforming or thixoforming. Coexist of solid/liquid phase leads to the unique deformation behavior. The chemical composition at each phase is different from conventional forming process. Deformation behavior and microstructure evolution are determined by various effects such as initial state, heating, cooling, etc. In this work, the semi-solid compression tests of 9Cr18 as hot-rolled material and semi-solid billet were conducted, respectively. Microstructure evolution during heating, semi-solid state, deformation and cooling was investigated by OM and SEM. Solid/liquid flow behavior and the relationship of stress-strain were analyzed. The results showed the preparation of semi-solid billet is essential for the uniformity of solid particle and liquid phase, which would help to demonstrate the flow behavior. Only heating the as hot-rolled material to semi-solid led to the banded precipitation of liquid phase. The banded melting of as hot-rolled material made it hard for liquid phase to connect with each other. Liquid flow only happened in partial area and plastic deformation of solid particles was the main deformation behavior. The stress increased at the final stage. As for semi-solid billet, solid particles and liquid film coexisted uniformly. Macro separation of solid/liquid occurred as deformation came into thixotropic stage. Liquid flew towards outside and solid particles rotated, thus leading to the decrease of stress. Microstructure evolution at semi-solid state was different from conventional heat treatment. Solid austenite particles at semi-solid state could dissolve more alloying elements than normal austenization (1050 ℃). This phenomenon would help to improve the stability of austenite and over-saturated meta-austenite was obtained after cooling. The special microstructure evolution during semi-solid state might provide a possible way to design a new heat treatment procedure.
Fig.2 Initial microstructures of as hot-rolled state (a) and semi-solid billet (b)
Fig.3 Thermo-Calc results of Fe-C-Cr alloy(a) pseudo-binary cut (b) property diagram of phases
Fig.4 Microstructures after rapid cooling from semi-solid state(a) as hot-rolled material (b) semi-solid billet
Fig.5 True stress-true strain curves of 9Cr18 as hot-rolled material at 1 s-1 (a) and 1300 ℃ (b)
Fig.6 True stress-true strain curves of 9Cr18 semi-solid billet at 1 s-1 (a) and 1300 ℃ (b)
Fig.7 Microstructures in the center of 9Cr18 as hot-rolled material at 1300 ℃, 1 s-1 after the semi-solid reduction rates of 20% (a), 40% (b) and 60% (c) (Insets show the configurations of compressed specimens)
Fig.8 Microstructures in the center (a~c) and at the edge (d~f) of 9Cr18 semi-solid billet at 1300 ℃, 1 s-1 after the semi-solid reduction rates of 20% (a, d), 40% (b, e) and 60% (c, f) (Insets show the configurations of compressed specimens)
Fig.9 Inverse pole figures of 9Cr18 traditional heat treatment specimen (a) and semi-solid billet after deformation (b)
Fig.10 EDS results of 9Cr18 traditional martensite lath (a) and semi-solid particles (b) (Insets show the microstructures of related area, E—energy)
Fig.11 Illustration of microstructure evolution for different initial states
[1]
Flemings M C.Behavior of metal alloys in the semisolid state[J]. Metall. Trans., 1991, 22: 957
[2]
Midson S P.Industrial applications for aluminum semi-solid castings[J].Solid State Phenom., 2014, 217-218: 487
[3]
Liu Z, Zhang J Y, Luo H L, et al.Research on morphology evolution of primary phase in semisolid A356 alloy under chaotic advection[J]. Acta Metall. Sin., 2016, 52: 177(刘政, 张嘉艺, 罗浩林等. 混沌对流下的半固态A356铝合金初生相形貌演变研究[J]. 金属学报, 2016, 52: 177)
[4]
Rassili A.A Review on thixoforming of high melting point alloys[J]. Solid State Phenom., 2016, 256: 228
[5]
Lu Y L, Ji Z S, Hong Y, et al.Overview and research prospect of semisolid steel & iron[J]. Heat Treat. Met., 2006, 31(8): 27(逯允龙, 吉泽升, 洪艳等. 钢铁材料半固态研究现状及展望[J]. 金属热处理, 2006, 31(8): 27)
[6]
Hu K, Phillion A B, Maijer D M, et al.Constitutive behavior of as-cast magnesium alloy Mg-Al3-Zn1 in the semi-solid state[J]. Scr. Mater., 2009, 60: 427
[7]
Pan H P, Ding Z Y, Dong Y S, et al.Study of the constitutive model for thixo-forming of semi-solid AlSi7Mg alloy[J]. Acta Metall. Sin., 2003, 39: 369(潘洪平, 丁志勇, 董原生等. 半固态AlSi7Mg合金的触变力学模型研究[J]. 金属学报, 2003, 39: 369)
[8]
Rogal ?.Semi-solid processing of the CoCrCuFeNi high entropy alloy[J]. Mater. Des., 2017, 119: 406
[9]
Rogal ?, Korpala G, Dutkiewicz J.Evolution of microstructure in 100Cr6 steel after cooling from a thixoforming temperature to bainitic transformation ranges[J]. Mater. Sci. Eng., 2015, A624: 291
[10]
Rogal ?, Dutkiewicz J.Deformation behavior of high strength X210CrW12 steel after semi-solid processing[J]. Mater. Sci. Eng., 2014, A603: 93
[11]
Rogal ?, Dutkiewicz J, Szklarz Z, et al.Mechanical properties and corrosion resistance of steel X210CrW12 after semi-solid processing and heat treatment[J]. Mater. Charact., 2014, 88: 100
[12]
Rogal ?, Dutkiewicz J.Heat treatment of thixo-formed hypereutectic X210CrW12 tool steel[J]. Metall. Mater. Trans., 2012, 43A: 5009
[13]
Püttgen W, Hallstedt B, Bleck W, et al.On the microstructure and properties of 100Cr6 steel processed in the semi-solid state[J]. Acta Mater., 2007, 55: 6553
[14]
Meng Y, Sugiyama S, Yanagimoto J.Microstructural evolution during RAP process and deformation behavior of semi-solid SKD61 tool steel[J]. J. Mater. Process. Technol., 2012, 212: 1731
[15]
Xiao H, Chen Z B, Li Y, et al.Microstructure evolution of semi-solid copper alloy billet during uniaxial compression[J]. Chin. J. Nonferrous Met., 2016, 26: 2537(肖寒, 陈泽邦, 李勇等. 单向压缩半固态铜合金的显微组织演变[J]. 中国有色金属学报, 2016, 26: 2537)
[16]
Wang Y J, Song R B, Li Y P.Flow mechanism of 9Cr18 steel during thixoforging and its properties for functionally graded material[J]. Mater. Des., 2015, 86: 41
[17]
Jirková H, David A, Bohuslav M.Unconventional structure of X210Cr12 steel obtained by thixoforming[J]. J. Alloys Compd., 2010, 504: S500
[18]
Gu G C, Pesci R, Langlois L, et al.Microstructure observation and quantification of the liquid fraction of M2 steel grade in the semi-solid state, combining confocal laser scanning microscopy and X-ray microtomography[J]. Acta Mater., 2014, 66: 118
[19]
Moradi M, Nili-Ahmadabadi M, Poorganji B, et al.Recrystallization behavior of ECAPed A356 alloy at semi-solid reheating temperature[J]. Mater. Sci. Eng., 2010, A527: 4113
[20]
Kang C G, Choi J S, Kim K H.The effect of strain rate on macroscopic behavior in the compression forming of semi-solid aluminum alloy[J]. J. Mater. Process. Technol., 1999, 88: 159
[21]
Gu G C, Pesci R, Langlois L, et al.Microstructure investigation and flow behavior during thixoextrusion of M2 steel grade[J]. J. Mater. Process. Technol., 2015, 216: 178
[22]
Zhang Y, Wu G H, Liu W C, et al.Microstructure and mechanical properties of rheo-squeeze casting AZ91-Ca magnesium alloy prepared by gas bubbling process[J]. Mater. Des., 2015, 67: 1
[23]
Püttgen W, Hallstedt B, Bleck W, et al.On the microstructure formation in chromium steels rapidly cooled from the semi-solid state[J]. Acta Mater., 2007, 55: 1033
[24]
Samantaray D, Borah U, Bhaduri A K, et al.Effect of semi-solid heat treatment on elevated temperature plasticity of 304L stainless steel[J]. J. Mater. Sci., 2016, 51: 4306
[25]
Meng Y, Sugiyama S, Yanagimoto J.Effects of heat treatment on microstructure and mechanical properties of Cr-V-Mo steel processed by recrystallization and partial melting method[J]. J. Mater. Process. Technol., 2014, 214: 87
[26]
Aisman D, Jirkova H, Kucerova L, et al.Metastable structure of austenite base obtained by rapid solidification in a semi-solid state[J]. J. Alloys Compd., 2011, 509: S312
