累积叠轧TC4钛合金的组织演化与力学性能
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摘要
采用累积叠轧技术制备具有超细晶组织的TC4钛合金,考察了叠轧工艺对界面结合和微观组织的影响规律以及该过程中α/β两相钛合金的变形机制,分析了叠轧工艺对TC4合金力学性能的影响。结果表明,TC4合金累积叠轧过程中需要足够的加热温度(近于720℃)、防氧化处理以及多层数大下压量的轧制工艺,才能获得良好的界面结合,但是界面处存在O含量较高的硬化层。随着叠轧温度和叠轧层数的增加,TC4板材的结合界面逐渐消失并具有较高的结合强度。累积叠轧过程是协同变形和剪切变形综合作用的结果,即变形初期晶界β相由长条状转变为短片状且晶界发生滑移,而在变形程度较高时组织中有大量的剪切带,此过程存在大量局部变形以适应大塑性变形过程。变形组织中存在局部等轴组织(约300 nm)和拉长的变形结构(约400 nm),其中等轴组织是由于变形温度、局部剪切变形和局部过热作用而发生再结晶形成的。叠轧板材在厚度方向存在组织性能不均匀现象,在结合界面处硬度较高,随着叠轧层数的增加硬度逐渐趋于一致。同时随着叠轧层数的增加,TC4合金的抗拉强度逐渐增加,在叠轧16层后抗拉强度达到1325 MPa,塑性降低为5.4%。在叠轧层数较少时,断裂过程表现为韧性断裂,随着叠轧层数的增加,断口形貌逐渐转变为韧窝断口和准解理断口的综合形貌。
TC4 titanium alloy is highly promising for aerospace and medical implant applications due to its low density,high strength,corrosion resistance and biocompatibility,and the ultra-fine grains of TC4 alloy by accumulative roll bonding(ARB) can efficiently improve the low temperature super-plasticity and biocompatibility for its widespread applications.However,the ARB process for TC4 alloy has been limited due to the high deformation resistance and low anti-oxidant ability.In this work,ARB was conducted for the ultra-fine grains of TC4 titanium alloy,and the effects of ARB temperatures and layer numbers on the bonding interface and microstructure were investigated as well as the deformation mechanism of the mixed α/β phase structure,and the influences of ARB processing on the mechanical properties were studied.The good interface bonding could be fabricated by the proper ARB temperature(near 720 ℃),the anti-oxidation treatment and the multilayer with the high deformation,which always takes on the hardened interface with the high oxidation contents,and the interface bonding strength increases with the increase of the ARB layers and temperature through the process of the diffusion and the necking fracture.The deformation process is composed by the cooperation deformation of α/β structure and the shear deformation during ARB processed TC4 alloy,during which the β phase at the grain boundary changes from the long strips to the short bands to deform with hcp a phase,while the shear bands with severe local-deformation is used to adapt the severe plastic deformation.The deformed microstructure is composed of the equiaxed structure(about 300 nm spacing) and the elongated deformation structure(about 400 nm spacing),in which the equiaxed structure comes from the function of the deformation temperature,loca shear deformation and the local overheat.Additionally,the inhomogeneous microstructure and properties along the thickness direction can be observed,and the high hardness can be obtained at the bonding interface,which gradually distributes homogeneous with the increase of ARB layers.The strength of ARB processed TC4 sheets increases with the increase of ARB layers,which can get to 1325 MPa after 16 ARB layers,and simultaneously the plasticity decreases to 5.4%.The ductile fracture can be observed with the low ARB layers,while the mixed structure of the quasi-cleavage and ductile fracture is obtained with the increase of ARB layers.
TC4 titanium alloy is highly promising for aerospace and medical implant applications due to its low density,high strength,corrosion resistance and biocompatibility,and the ultra-fine grains of TC4 alloy by accumulative roll bonding(ARB) can efficiently improve the low temperature super-plasticity and biocompatibility for its widespread applications.However,the ARB process for TC4 alloy has been limited due to the high deformation resistance and low anti-oxidant ability.In this work,ARB was conducted for the ultra-fine grains of TC4 titanium alloy,and the effects of ARB temperatures and layer numbers on the bonding interface and microstructure were investigated as well as the deformation mechanism of the mixed α/β phase structure,and the influences of ARB processing on the mechanical properties were studied.The good interface bonding could be fabricated by the proper ARB temperature(near 720 ℃),the anti-oxidation treatment and the multilayer with the high deformation,which always takes on the hardened interface with the high oxidation contents,and the interface bonding strength increases with the increase of the ARB layers and temperature through the process of the diffusion and the necking fracture.The deformation process is composed by the cooperation deformation of α/β structure and the shear deformation during ARB processed TC4 alloy,during which the β phase at the grain boundary changes from the long strips to the short bands to deform with hcp a phase,while the shear bands with severe local-deformation is used to adapt the severe plastic deformation.The deformed microstructure is composed of the equiaxed structure(about 300 nm spacing) and the elongated deformation structure(about 400 nm spacing),in which the equiaxed structure comes from the function of the deformation temperature,loca shear deformation and the local overheat.Additionally,the inhomogeneous microstructure and properties along the thickness direction can be observed,and the high hardness can be obtained at the bonding interface,which gradually distributes homogeneous with the increase of ARB layers.The strength of ARB processed TC4 sheets increases with the increase of ARB layers,which can get to 1325 MPa after 16 ARB layers,and simultaneously the plasticity decreases to 5.4%.The ductile fracture can be observed with the low ARB layers,while the mixed structure of the quasi-cleavage and ductile fracture is obtained with the increase of ARB layers.
引文
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[23]Saito Y,Utsunomiya H,Tsuji N,et al.Novel ultra-high straining process for bulk materials——Development of the accumulative roll-bonding(ARB)process[J].Acta Mater.,1999,47:579
[24]Huang X,Tsuji N,Hansen N,et al.Microstructural evolution during accumulative roll-bonding of commercial purity aluminum[J].Mater.Sci.Eng.,2003,A340:265
[25]Terada D,Inoue M,Kitahara H,et al.Change in mechanical properties and microstructure of ARB processed Ti during annealing[J].Mater.Trans.,2008,49:41
[26]Wu H J,Rong Y,Li X D,et al.Rolling process of wide titanium sheet ply[J].Chin.J.Nonferrous Met.,2010,20:807(吴慧娟,容耀,李向东等.宽幅纯钛薄板的叠轧工艺[J].中国有色金属学报,2010,20:807)
[27]Xing C.Processing and properties of ultrafine grained titanium prepared by accumulative roll bonding[D].Harbin:Harbin Engineering University,2014(邢超.超细晶纯钛累积叠轧制备工艺与性能研究[D].哈尔滨:哈尔滨工程大学,2014)
[2]Wang M,Yang Y Q,Luo X.Research status in preparation and properties of ultra-fine grained Ti alloys[J].Mater.Rev.,2013,27(7):94(王苗,杨延清,罗贤.超细晶钛合金的制备及性能研究现状[J].材料导报,2013,27(7):94)
[3]Valiev R Z,Estrin Y,Horita Z,et al.Producing bulk ultrafinegrained materials by severe plastic deformation[J].JOM,2006,58:33
[4]Tsuji N,Saito Y,Lee S H,et al.ARB(accumulative roll-bonding)and other new techniques to produce bulk ultrafine grained materials[J].Adv.Eng.Mater.,2003,5:338
[5]Karimi M,Toroghinejad M R.An alternative method for manufacturing high-strength CP Ti-Si C composites by accumulative roll bonding process[J].Mater.Des.,2014,59:494
[6]Gashti S O,Fattah-Alhosseini A,Mazaheri Y,et al.Effects of grain size and dislocation density on strain hardening behavior of ultrafine grained AA 1050 processed by accumulative roll bonding[J].J.Alloys Compd.,2016,658:854
[7]Duan J D,Quadir M Z,Xu W,et al.Texture balancing in a fcc/bcc multilayered composite produced by accumulative roll bonding[J].Acta Mater.,2017,123:11
[8]Mishin O V,Zhang Y B,Godfrey A.The influence of multiscale heterogeneity on recrystallization in nickel processed by accumulative roll bonding[J].J.Mater.Sci.,2017,52:2730
[9]Saito Y,Utsunomiya H,Tsuji N,et al.Novel ultra-high straining process for bulk materials-development of the accumulative rollbonding(ARB)process[J].Acta Mater.,1999,47:579
[10]Xing Z P,Kang S B,Kim H W.Softening behavior of 8011 alloy produced by accumulative roll bonding process[J].Scr.Mater.,2001,45:597
[11]Sergueeva A V,Stolyarov V V,Valiev R Z,et al.Advanced mechanical properties of pure titanium with ultrafine grained structure[J].Scr.Mater.,2001,45:747
[12]Ghafari-Gousheh S,Nedjad S H,Khalil-Allafi J.Tensile properties and interfacial bonding of multi-layered,high-purity titanium strips fabricated by ARB process[J].J.Mech.Behav.Biomed.,2015,51:147
[13]Matsumoto H,Yoshida K,Lee S H,et al.Ti-6Al-4V alloy with an ultrafine-grained microstructure exhibiting low-temperature-highstrain-rate superplasticity[J].Mater.Lett.,2013,98:209
[14]Leyens C,Peters M,translated by Chen Z H.Titanium and Titanium Alloys[M].Beijing:Chemical Industry Press,2005:22(Leyens C,Peters M著,陈振华译.钛与钛合金[M].北京:化学工业出版社,2005:22)
[15]Seagle S R,Yu K O,Giangiordano S.Considerations in processing titanium[J].Mater.Sci.Eng.,1999,A263:237
[16]Song H W,Zhang S H,Cheng M,et al.Flow softening mechansim of a Ti alloy with lamellar structure during subtransus deformation[J].Acta Metall.Sin.,2011,47:462(宋鸿武,张士宏,程明等.钛合金片层组织两相区变形时的流动软化机理分析[J].金属学报,2011,47:462)
[17]Milner J L,Bunget C,Abu-Farha F,et al.Modeling tensile strength of materials processed by accumulative roll bonding[J].J.Manuf.Process.,2013,15:219
[18]Zherebtsov S V,Salishchev G A,Galeyev R M,et al.Production of submicrocrystalline structure in large-scale Ti-6Al-4V billet by warm severe deformation processing[J].Scr.Mater.,2004,51:1147
[19]Pachla W,Kilczyk M,Przybysz S,et al.Effect of severe plastic deformation realized by hydrostatic extrusion and rotary swaging on the properties of CP Ti grade 2[J].J.Mater.Process.Technol.,2015,221:255
[20]Terada D,Inoue S,Tsuji N.Microstructure and mechanical properties of commercial purity titanium severely deformed by ARB process[J].J.Mater.Sci.,2007,42:1673
[21]Milner J L,Abu-Farha F,Bunget C,et al.Grain refinement and mechanical properties of CP-Ti processed by warm accumulative roll bonding[J].Mater.Sci.Eng.,2013,A561:109
[22]Saito Y,Tsuji N,Utsunomiya H,et al.Ultra-fine grained bulk aluminum produced by accumulative roll-bonding(ARB)process[J].Scr.Mater.,1998,39:1221
[23]Saito Y,Utsunomiya H,Tsuji N,et al.Novel ultra-high straining process for bulk materials——Development of the accumulative roll-bonding(ARB)process[J].Acta Mater.,1999,47:579
[24]Huang X,Tsuji N,Hansen N,et al.Microstructural evolution during accumulative roll-bonding of commercial purity aluminum[J].Mater.Sci.Eng.,2003,A340:265
[25]Terada D,Inoue M,Kitahara H,et al.Change in mechanical properties and microstructure of ARB processed Ti during annealing[J].Mater.Trans.,2008,49:41
[26]Wu H J,Rong Y,Li X D,et al.Rolling process of wide titanium sheet ply[J].Chin.J.Nonferrous Met.,2010,20:807(吴慧娟,容耀,李向东等.宽幅纯钛薄板的叠轧工艺[J].中国有色金属学报,2010,20:807)
[27]Xing C.Processing and properties of ultrafine grained titanium prepared by accumulative roll bonding[D].Harbin:Harbin Engineering University,2014(邢超.超细晶纯钛累积叠轧制备工艺与性能研究[D].哈尔滨:哈尔滨工程大学,2014)