低温回火对超大形变冷拔珠光体钢丝显微组织和力学性能的影响
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摘要
采用力学分析、SEM、TEM、3DAP和DSC技术研究了低温回火对超大应变冷拔珠光体钢丝微观组织和力学性能的影响。结果表明:应变ε≤4的钢丝,在120～170℃范围内进行低温回火能有效提高钢丝的强度,同时塑性略有下降;ε=3.0的钢丝,在150℃回火8 min后,钢丝强度提高约150 MPa;ε=4.5的钢丝,在170℃回火后,钢丝强度和塑性同时下降。钢丝经超大应变(ε=4.5)变形后,渗碳体发生分解。冷拔钢丝在150～170℃之间存在明显的放热峰,TEM衍射斑分析发现了衍射斑点拖尾的现象,这主要是由于在150℃热处理后,C原子在位错处偏聚引起的;而HRTEM分析表明,在170℃处理后,渗碳体由非晶转变为纳米晶,有效地钉扎和阻碍位错运动,这2种现象共同导致了钢丝的低温回火强化。
Ultra-heavy cold-drawn pearlite wires provide an excellent combination of ductility and strength. Therefore, they have been widely used in engineering applications, such as suspension bridge cables, automotive tyre cords and cutting wires. In this work, the effects of low temperature annealing on the microstructure and mechanical properties of ultra-heavy cold-drawn pearlitic steel wires were investigated. The mechanical properties have been determined by tensile testing and the structures analyzed by TEM and HRTEM. The overall carbon contents in the detected volumes as well as the carbon concentrations in ferrite and cementite were measured by 3DAP. Experimental results show that, for the steel wires with strain(ε) less than 4, annealing in the range of 120～170 ℃ could effectively increase the strength of steel wires and remain most of the plastic performance. The tensile strength of wire with a strain of 3.0 can be increased about 150 MPa after annealing at 150 ℃ for 8 min. However, both of strength and toughness of steel wires with a strain 4.5 decreased after annealed at 170 ℃. After the steel wire is deformed by excessive strain(ε=4.5), the cementite decomposed obviously. DSC analysis showed that there is an obviously exothermic peak between 150 ℃ and 170 ℃ in the DSC curve. The TEM diffraction pattern analysis reveal the phenomenon of tailing at diffraction pattern, which is mainly caused by segregation of carbon atom at the dislocation after annealed at 150 ℃. However, HRTEM images show that annealing temperature as low as 170 ℃ could result in the transformation of partial cementite from amorphous state to nano-crystalline state. It could effectively pin and hinder the movement of dislocations. The underlying mechanism responsible for changes in microstructure and mechanical properties after annealing at low temperature are closely related to C-segregation and "crystal-amorphous" cementite transformation in heavy cold-drawn pearlitic steel wires.
Ultra-heavy cold-drawn pearlite wires provide an excellent combination of ductility and strength. Therefore, they have been widely used in engineering applications, such as suspension bridge cables, automotive tyre cords and cutting wires. In this work, the effects of low temperature annealing on the microstructure and mechanical properties of ultra-heavy cold-drawn pearlitic steel wires were investigated. The mechanical properties have been determined by tensile testing and the structures analyzed by TEM and HRTEM. The overall carbon contents in the detected volumes as well as the carbon concentrations in ferrite and cementite were measured by 3DAP. Experimental results show that, for the steel wires with strain(ε) less than 4, annealing in the range of 120～170 ℃ could effectively increase the strength of steel wires and remain most of the plastic performance. The tensile strength of wire with a strain of 3.0 can be increased about 150 MPa after annealing at 150 ℃ for 8 min. However, both of strength and toughness of steel wires with a strain 4.5 decreased after annealed at 170 ℃. After the steel wire is deformed by excessive strain(ε=4.5), the cementite decomposed obviously. DSC analysis showed that there is an obviously exothermic peak between 150 ℃ and 170 ℃ in the DSC curve. The TEM diffraction pattern analysis reveal the phenomenon of tailing at diffraction pattern, which is mainly caused by segregation of carbon atom at the dislocation after annealed at 150 ℃. However, HRTEM images show that annealing temperature as low as 170 ℃ could result in the transformation of partial cementite from amorphous state to nano-crystalline state. It could effectively pin and hinder the movement of dislocations. The underlying mechanism responsible for changes in microstructure and mechanical properties after annealing at low temperature are closely related to C-segregation and "crystal-amorphous" cementite transformation in heavy cold-drawn pearlitic steel wires.
引文
[1]Li Y J,Choi P,Borchers C,et al.Atomic-scale mechanisms of deformation-induced cementite decomposition in pearlite[J].Acta Mater.,2011,59:3965
[2]Languillaume J,Kapelski G,Baudelet B.Cementite dissolution in heavily cold drawn pearlitic steel wires[J].Acta Mater.,1997,45:1201
[3]Embury J D,Fisher R M.The structure and properties of drawn pearlite[J].Acta Metall.,1966,14:147
[4]Li Y J,Choi P,Borchers C,et al.Atom probe tomography characterization of heavily cold drawn pearlitic steel wire[J].Ultramicroscopy,2011,111:628
[5]Borchers C,Al-Kassab T,Goto S,et al.Partially amorphous nanocomposite obtained from heavily deformed pearlitic steel[J].Mater.Sci.Eng.,2009,A502:131
[6]Zhou L C,Hu X J,Ma C,et al.Effect of pearlitic lamella orientation on deformation of pearlite steel wire during cold drawing[J].Acta Metall.Sin.,2015,51:897(周立初,胡显军,马驰等.珠光体层片取向对冷拔珠光体钢丝形变的影响[J].金属学报,2015,51:897)
[7]Bang C W,Seol J B,Yang Y S,et al.Atomically resolved cementite dissolution governed by the strain state in pearlite steel wires[J].Scr.Mater.,2015,108:151
[8]Li Y J,Choi P,Goto S,et al.Atomic scale investigation of redistribution of alloying elements in pearlitic steel wires upon colddrawing and annealing[J].Ultramicroscopy,2013,132:233
[9]Zhang X D,Hansen N,Godfrey A,et al.Dislocation-based plasticity and strengthening mechanisms in sub-20 nm lamellar structures in pearlitic steel wire[J].Acta Mater.,2016,114:176
[10]Li Y J,Raabe D,Herbig M,et al.Segregation stabilizes nanocrystalline bulk steel with near theoretical strength[J].Phys.Rev.Lett.,2014,113:106104
[11]Fang F,Zhou L C,Hu X J,et al.Microstructure and mechanical properties of cold-drawn pearlitic wires affect by inherited texture[J].Mater.Des.,2015,79:60
[12]Fang F,Zhao Y F,Zhou L C,et al.Texture inheritance of cold drawn pearlite steel wires after austenitization[J].Mater.Sci.Eng.,2014,A618:505
[13]Borchers C,Kirchheim R.Cold-drawn pearlitic steel wires[J].Prog.Mater.Sci.,2016,82:405
[14]Zhang X D,Godfrey A,Huang X X,et al.Microstructure and strengthening mechanisms in cold-drawn pearlitic steel wire[J].Acta Mater.,2011,59:3422
[15]Danoix F,Julien D,Sauvage X,et al.Direct evidence of cementite dissolution in drawn pearlitic steels observed by tomographic atom probe[J].Mater.Sci.Eng.,1998,A250:8
[16]Gavriljuk V G.Decomposition of cementite in pearlitic steel due to plastic deformation[J].Mater.Sci.Eng.,2003,A345:81
[17]Fang F,Zhao Y F,Liu P P,et al.Deformation of cementite in cold drawn pearlitic steel wire[J].Mater.Sci.Eng.,2014,A608:11
[18]Hono K,Ohnuma M,Murayama M,et al.Cementite decomposition in heavily drawn pearlite steel wire[J].Scr.Mater.,2001,44:977
[19]Fang F,Hu X J,Chen S H,et al.Revealing microstructural and mechanical characteristics of cold-drawn pearlitic steel wires undergoing simulated galvanization treatment[J].Mater.Sci.Eng.,2012,A547:51
[20]Li Y J,Choi P,Goto S,et al.Evolution of strength and microstructure during annealing of heavily cold-drawn 6.3 GPa hypereutectoid pearlitic steel wire[J].Acta Mater.,2012,60:4005
[21]Zhou L C,Fang F,Zhou X F,et al.Cementite nano-crystallization in cold drawn pearlitic wires instigated by low temperature annealing[J].Scr.Mater.,2016,120:5
[22]Lamontagne A,Massardier V,Sauvage X,et al.Evolution of carbon distribution and mechanical properties during the static strain ageing of heavily drawn pearlitic steel wires[J].Mater.Sci.Eng.,2016,A667:115
[23]Joung S W,Kang U G,Hong S P,et al.Aging behavior and delamination in cold drawn and post-deformation annealed hypereutectoid steel wires[J].Mater.Sci.Eng.,2013,A586:171
[24]WattéP,Van Humbeeck J,Aernoudt E,et al.Strain ageing in heavily drawn eutectoid steel wires[J].Scr.Mater.,1996,34:89
[25]Lamontagne A,Kleber X,Massardier-Jourdan V,et al.Identification of the mechanisms responsible for static strain ageing in heavily drawn pearlitic steel wires[J].Philos.Mag.Lett.,2014,94:495
[26]Takahashi J,Kosaka M,Kawakami K,et al.Change in carbon state by low-temperature aging in heavily drawn pearlitic steel wires[J].Acta Mater.,2012,60:387
[27]Park D B,Lee J W,Lee Y S,et al.Effects of the annealing temperature and time on the microstructural evolution and corresponding the mechanical properties of cold-drawn steel wires[J].Met.Mater.Int.,2008,14:59
[28]Kirchheim R.Reducing grain boundary,dislocation line and vacancy formation energies by solute segregation.I.Theoretical background[J].Acta Mater.,2007,55:5129
[29]Borchers C,Chen Y,Deutges M,et al.Carbon-defect interaction during recovery and recrystallization of heavily deformed pearlitic steel wires[J].Philos.Mag.Lett.,2010,90:581
[30]Ivanisenko Y,Wunderlich R K,Valiev R Z,et al.Annealing behaviour of nanostructured carbon steel produced by severe plastic deformation[J].Scr.Mater.,2003,49:947
[31]Taylor K A,Olson G B,Cohen M,et al.Carbide precipitation during stage I tempering of Fe-Ni-C martensites[J].Metall.Trans.,1989,20A:2749
[32]Guo W,Meng Y F,Zhang X,et al.Extremely hard amorphouscrystalline hybrid steel surface produced by deformation induced cementite amorphization[J].Acta Mater.,2018,152:107
[2]Languillaume J,Kapelski G,Baudelet B.Cementite dissolution in heavily cold drawn pearlitic steel wires[J].Acta Mater.,1997,45:1201
[3]Embury J D,Fisher R M.The structure and properties of drawn pearlite[J].Acta Metall.,1966,14:147
[4]Li Y J,Choi P,Borchers C,et al.Atom probe tomography characterization of heavily cold drawn pearlitic steel wire[J].Ultramicroscopy,2011,111:628
[5]Borchers C,Al-Kassab T,Goto S,et al.Partially amorphous nanocomposite obtained from heavily deformed pearlitic steel[J].Mater.Sci.Eng.,2009,A502:131
[6]Zhou L C,Hu X J,Ma C,et al.Effect of pearlitic lamella orientation on deformation of pearlite steel wire during cold drawing[J].Acta Metall.Sin.,2015,51:897(周立初,胡显军,马驰等.珠光体层片取向对冷拔珠光体钢丝形变的影响[J].金属学报,2015,51:897)
[7]Bang C W,Seol J B,Yang Y S,et al.Atomically resolved cementite dissolution governed by the strain state in pearlite steel wires[J].Scr.Mater.,2015,108:151
[8]Li Y J,Choi P,Goto S,et al.Atomic scale investigation of redistribution of alloying elements in pearlitic steel wires upon colddrawing and annealing[J].Ultramicroscopy,2013,132:233
[9]Zhang X D,Hansen N,Godfrey A,et al.Dislocation-based plasticity and strengthening mechanisms in sub-20 nm lamellar structures in pearlitic steel wire[J].Acta Mater.,2016,114:176
[10]Li Y J,Raabe D,Herbig M,et al.Segregation stabilizes nanocrystalline bulk steel with near theoretical strength[J].Phys.Rev.Lett.,2014,113:106104
[11]Fang F,Zhou L C,Hu X J,et al.Microstructure and mechanical properties of cold-drawn pearlitic wires affect by inherited texture[J].Mater.Des.,2015,79:60
[12]Fang F,Zhao Y F,Zhou L C,et al.Texture inheritance of cold drawn pearlite steel wires after austenitization[J].Mater.Sci.Eng.,2014,A618:505
[13]Borchers C,Kirchheim R.Cold-drawn pearlitic steel wires[J].Prog.Mater.Sci.,2016,82:405
[14]Zhang X D,Godfrey A,Huang X X,et al.Microstructure and strengthening mechanisms in cold-drawn pearlitic steel wire[J].Acta Mater.,2011,59:3422
[15]Danoix F,Julien D,Sauvage X,et al.Direct evidence of cementite dissolution in drawn pearlitic steels observed by tomographic atom probe[J].Mater.Sci.Eng.,1998,A250:8
[16]Gavriljuk V G.Decomposition of cementite in pearlitic steel due to plastic deformation[J].Mater.Sci.Eng.,2003,A345:81
[17]Fang F,Zhao Y F,Liu P P,et al.Deformation of cementite in cold drawn pearlitic steel wire[J].Mater.Sci.Eng.,2014,A608:11
[18]Hono K,Ohnuma M,Murayama M,et al.Cementite decomposition in heavily drawn pearlite steel wire[J].Scr.Mater.,2001,44:977
[19]Fang F,Hu X J,Chen S H,et al.Revealing microstructural and mechanical characteristics of cold-drawn pearlitic steel wires undergoing simulated galvanization treatment[J].Mater.Sci.Eng.,2012,A547:51
[20]Li Y J,Choi P,Goto S,et al.Evolution of strength and microstructure during annealing of heavily cold-drawn 6.3 GPa hypereutectoid pearlitic steel wire[J].Acta Mater.,2012,60:4005
[21]Zhou L C,Fang F,Zhou X F,et al.Cementite nano-crystallization in cold drawn pearlitic wires instigated by low temperature annealing[J].Scr.Mater.,2016,120:5
[22]Lamontagne A,Massardier V,Sauvage X,et al.Evolution of carbon distribution and mechanical properties during the static strain ageing of heavily drawn pearlitic steel wires[J].Mater.Sci.Eng.,2016,A667:115
[23]Joung S W,Kang U G,Hong S P,et al.Aging behavior and delamination in cold drawn and post-deformation annealed hypereutectoid steel wires[J].Mater.Sci.Eng.,2013,A586:171
[24]WattéP,Van Humbeeck J,Aernoudt E,et al.Strain ageing in heavily drawn eutectoid steel wires[J].Scr.Mater.,1996,34:89
[25]Lamontagne A,Kleber X,Massardier-Jourdan V,et al.Identification of the mechanisms responsible for static strain ageing in heavily drawn pearlitic steel wires[J].Philos.Mag.Lett.,2014,94:495
[26]Takahashi J,Kosaka M,Kawakami K,et al.Change in carbon state by low-temperature aging in heavily drawn pearlitic steel wires[J].Acta Mater.,2012,60:387
[27]Park D B,Lee J W,Lee Y S,et al.Effects of the annealing temperature and time on the microstructural evolution and corresponding the mechanical properties of cold-drawn steel wires[J].Met.Mater.Int.,2008,14:59
[28]Kirchheim R.Reducing grain boundary,dislocation line and vacancy formation energies by solute segregation.I.Theoretical background[J].Acta Mater.,2007,55:5129
[29]Borchers C,Chen Y,Deutges M,et al.Carbon-defect interaction during recovery and recrystallization of heavily deformed pearlitic steel wires[J].Philos.Mag.Lett.,2010,90:581
[30]Ivanisenko Y,Wunderlich R K,Valiev R Z,et al.Annealing behaviour of nanostructured carbon steel produced by severe plastic deformation[J].Scr.Mater.,2003,49:947
[31]Taylor K A,Olson G B,Cohen M,et al.Carbide precipitation during stage I tempering of Fe-Ni-C martensites[J].Metall.Trans.,1989,20A:2749
[32]Guo W,Meng Y F,Zhang X,et al.Extremely hard amorphouscrystalline hybrid steel surface produced by deformation induced cementite amorphization[J].Acta Mater.,2018,152:107