固溶温度对Mn-N型双相不锈钢拉伸变形行为的影响
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摘要
在Gleeble-3800热模拟试验机上进行了一种新型Mn-N合金化双相不锈钢的拉伸变形实验,获得了不同固溶温度下(1000～1200℃)不锈钢的力学性能及加工硬化规律。利用OM、SEM和EBSD等手段研究了固溶温度对钢的形变亚结构及断裂特征的影响,探讨了固溶温度影响加工硬化的机理。结果表明,随着固溶温度的升高,Mn-N合金化双相不锈钢屈服强度与抗拉强度均逐渐降低,而延伸率(均匀延伸率和断裂延伸率)则先升高后降低。其中,1100℃固溶时不锈钢的塑性最佳,均匀延伸率可达46.7%,且综合力学性能优异,强塑积达44.6 GPa·%。不同固溶温度下,不锈钢的加工硬化率随应变的增加均表现为开始时迅速下降,经再次升高后再下降的"三阶段"特征,但随着固溶温度的升高,加工硬化率升高的趋势减弱。Mn-N合金化双相不锈钢中奥氏体相发生了形变诱导马氏体相变,主要表现为γ→ε→α′和γ→α′2种演化机制,从而形成TRIP效应,使得加工硬化率升高、塑性增加,但较高的固溶温度会使马氏体转变受到抑制。不同固溶温度下,铁素体与形变诱导马氏体均表现出解理断裂特征,而残余奥氏体则主要为韧性断裂。经计算,随着固溶温度增加(1000～1200℃),奥氏体相的M_(d30)值从81℃降到38℃,即奥氏体稳定性增加,减弱了TRIP效应,进而导致不锈钢加工硬化和增塑效果降低。
Advanced duplex stainless steels(DSSs) in which Ni is mostly or completely replaced by Mn and N have been developed in recent years. Such Mn-N bearing DSSs can readily achieve exceptional room-temperature tensile properties through the transformation-induced plasticity(TRIP) effect of metastable austenite. During the processing of DSSs, solution treatment is a critical step that tailors the phase fraction and the overall properties. In particular, the phase chemistry can change due to different element partitioning between two constituents, resulting in a different TRIP kinetics, when DSS is solution treated at different temperature. In this work, the effect of solution temperature on tensile deformation behavior of a new Mn-N bearing DSS was studied. The mechanical properties and work-hardening characteristic of the steels solution treated at different solution temperature(1000～1200 ℃) were investigated by thermal modeling test, and the effects of solution temperature on the deformation substructure and fracture characteristics were analyzed by OM, SEM and EBSD. The results show that as the solution temperature increases, the yield strength and tensile strength of the steels decrease, while the elongation(uniform elongation and total elongation) increases firstly and then decreases. The steel solution treated at 1100 ℃shows the optimum uniform elongation of 46.7%, and a better combination of ultimate tensile strength and ductility of approximately 44.6 GPa ·%. The work-hardening rate of the steel shows a three-stage characteristic, namely it declines firstly and then increases and subsequently declines again as the strain increases. However, the increasing extent of the work-hardening rate decreases as the solution temperature increases. The strain-induced martensitic transformation(SIMT) of metastable austenite which causes the TRIP effect has two evolution mechanisms of γ → ε → α' and γ → α'. But SIMT can be suppressed when the solution temperature increases. The fracture surfaces of specimens solution treated at different temperatures show a quasi-cleavage mode, in which both ferrite and strain-induced martensite exhibit cleavage fracture while the residual austenite displays a dimple-mode fracture. Furthermore, the M_(d30) which can characterize the stability of metastable austenite was calculated, which decreases from81 ℃ to 38 ℃ as the solution temperature increases from 1000 ℃ to 1200 ℃, indicating that the TRIP effect gets weakening at a higher solution temperature, and the work-hardening and plasticity therefore decrease.
Advanced duplex stainless steels(DSSs) in which Ni is mostly or completely replaced by Mn and N have been developed in recent years. Such Mn-N bearing DSSs can readily achieve exceptional room-temperature tensile properties through the transformation-induced plasticity(TRIP) effect of metastable austenite. During the processing of DSSs, solution treatment is a critical step that tailors the phase fraction and the overall properties. In particular, the phase chemistry can change due to different element partitioning between two constituents, resulting in a different TRIP kinetics, when DSS is solution treated at different temperature. In this work, the effect of solution temperature on tensile deformation behavior of a new Mn-N bearing DSS was studied. The mechanical properties and work-hardening characteristic of the steels solution treated at different solution temperature(1000～1200 ℃) were investigated by thermal modeling test, and the effects of solution temperature on the deformation substructure and fracture characteristics were analyzed by OM, SEM and EBSD. The results show that as the solution temperature increases, the yield strength and tensile strength of the steels decrease, while the elongation(uniform elongation and total elongation) increases firstly and then decreases. The steel solution treated at 1100 ℃shows the optimum uniform elongation of 46.7%, and a better combination of ultimate tensile strength and ductility of approximately 44.6 GPa ·%. The work-hardening rate of the steel shows a three-stage characteristic, namely it declines firstly and then increases and subsequently declines again as the strain increases. However, the increasing extent of the work-hardening rate decreases as the solution temperature increases. The strain-induced martensitic transformation(SIMT) of metastable austenite which causes the TRIP effect has two evolution mechanisms of γ → ε → α' and γ → α'. But SIMT can be suppressed when the solution temperature increases. The fracture surfaces of specimens solution treated at different temperatures show a quasi-cleavage mode, in which both ferrite and strain-induced martensite exhibit cleavage fracture while the residual austenite displays a dimple-mode fracture. Furthermore, the M_(d30) which can characterize the stability of metastable austenite was calculated, which decreases from81 ℃ to 38 ℃ as the solution temperature increases from 1000 ℃ to 1200 ℃, indicating that the TRIP effect gets weakening at a higher solution temperature, and the work-hardening and plasticity therefore decrease.
引文
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[13]Chen L,Zhang Y J,Li F,et al.Effect of solution temperature on TRIP/TWIP behavior of a lean duplex stainless steel[J].Iron Steel,2017,52(4):55(陈雷,张英杰,李飞等.固溶温度对节约型双相不锈钢TRIP/TWIP行为的影响[J].钢铁,2017,52(4):55)
[14]Guo B F,Zhang Q F,Chen L,et al.Influence of annealing temperature on the strain-hardening behavior of a lean duplex stainless steel[J].Mater.Sci.Eng.,2018,A722:216
[15]Tang Z Y,Wu Z Q,Zan N,et al.Microstructure evolution and deformation behavior of high manganese TRIP/TWIP symbiotic effect steels under high-speed deformation[J].Acta Metall.Sin.,2011,47:1426(唐正友,吴志强,昝娜等.高锰TRIP/TWIP效应共生钢高速变形过程中的组织演变及变形行为[J].金属学报,2011,47:1426)
[16]Choi J Y,Ji J H,Hwang S W,et al.Effects of nitrogen content on TRIP of Fe-20Cr-5Mn-x N duplex stainless steel[J].Mater.Sci.Eng.,2012,A534:673
[17]Choi J Y,Ji J H,Hwang S W,et al.Strain induced martensitic transformation of Fe-20Cr-5Mn-0.2Ni duplex stainless steel during cold rolling:Effects of nitrogen addition[J].Mater.Sci.Eng.,2011,A528:6012
[18]Wang M M,Tasan C C,Ponge D,et al.Spectral TRIP enables ductile 1.1 GPa martensite[J].Acta Mater.,2016,111:262
[19]Masumura T,Nakada N,Tsuchiyama T,et al.The difference in thermal and mechanical stabilities of austenite between carbonand nitrogen-added metastable austenitic stainless steels[J].Acta Mater.,2015,84:330
[20]Kim E Y,Woo W C,Heo Y U,et al.Effect of kinematic stability of the austenite phase on phase transformation behavior and deformation heterogeneity in duplex stainless steel using the crystal plasticity finite element method[J].Int.J.Plast.,2016,79:48
[21]Lin Y C,Chen M S,Zhong J.Static recrystallization behaviors of deformed 42CrMo steel[J].J.Cent.South Univ.(Sci.Technol.),2009,40:411(蔺永诚,陈明松,钟掘.42CrMo钢形变奥氏体的静态再结晶[J].中南大学学报(自然科学版),2009,40:411)
[22]Gutierrez-Urrutia I,Raabe D.Multistage strain hardening through dislocation substructure and twinning in a high strength and ductile weight-reduced Fe-Mn-Al-C steel[J].Acta Mater.2012,60:5791
[23]Lu F Y,Yang P,Meng L,et al.Microstructure,mechanical properties and crystallography analysis of Fe-22Mn TRIP/TWIP steel after tensile deformation[J].Acta Metall.Sin.,2013,49:1(鲁法云,杨平,孟利等.Fe-22Mn TRIP/TWIP钢拉伸过程组织、性能及晶体学行为分析[J].金属学报,2013,49:1)
[24]Yen H W,Ooi S W,Eizadjou M,et al.Role of stress-assisted martensite in the design of strong ultrafine-grained duplex steels[J].Acta Mater.,2015,82:100
[25]Bian H X.The research of plastic instability on austenitic stainless steel during hot deformation[D].Lanzhou:Lanzhou University of Technology,2014(边红霞.奥氏体不锈钢热变形过程中的塑性失稳研究[D].兰州:兰州理工大学,2014)
[26]Sun P L,Cerreta E K,Bingert J F,et al.Enhanced tensile ductility through boundary structure engineering in ultrafine-grained aluminum[J].Mater.Sci.Eng.,2007,A464:343
[27]Chen J H,Cao R.Micromechanism of cleavage fracture of weld metals[J].Acta Metall.Sin.,2017,53:1427(陈剑虹,曹睿.焊缝金属解理断裂微观机理[J].金属学报,2017,53:1427)
[28]Moallemi M,Zarei-Hanzaki A,Baghbadorani H S.Evolution of microstructure and mechanical properties in a cold deformed nitrogen bearing TRIP-assisted duplex stainless steel after reversion annealing[J].Mater.Sci.Eng.,2017,A683:83
[29]Zhang W,Hu J C.Effect of annealing temperature on transformation induced plasticity effect of a lean duplex stainless steel[J].Mater.Charact.,2013,79:37
[2]Badji R,Bacroix B,Bouabdallah M.Texture,microstructure and anisotropic properties in annealed 2205 duplex stainless steel welds[J].Mater.Charact.,2011,62:833
[3]Jiang L Z,Zhang W,Wang Z Y.Research and development of lean duplex stainless steels[J].J.Iron Steel Res.,2013,25(4):1(江来珠,张伟,王治宇.经济型双相不锈钢的研发进展[J].钢铁研究学报,2013,25(4):1)
[4]Du C F,Zhan F,Yang Y H,et al.Research progress in nickelsaving duplex stainless steel[J].Met.Funct.Mater.,2010:17(5):63(杜春风,詹凤,杨银辉等.节镍型双相不锈钢的研究进展[J].金属功能材料,2010:17(5):63)
[5]Herrera C,Ponge D,Raabe D.Design of a novel Mn-based 1 GPa duplex stainless TRIP Steel with 60%ductility by a reduction of austenite stability[J].Acta Mater.,2011,59:4653
[6]Wang J,Uggowitzer P J,Magdowski R,et al.Nickel-free duplex stainless steels[J].Scr.Mater.,1998,40:123
[7]Ran Q X,Xu Y L,Li J,et al.Effect of heat treatment on transformation-induced plasticity of economical Cr19 duplex stainless steel[J].Mater.Des.,2014,56:959
[8]Choi J Y,Ji J H,Hwang S W,et al.TRIP aided deformation of a near-Ni-free,Mn-N bearing duplex stainless steel[J].Mater.Sci.Eng.,2012,A535:32
[9]Kang J Y,Kim H,Kim K I,et al.Effect of austenitic texture on tensile behavior of lean duplex stainless steel with transformation induced plasticity(TRIP)[J].Mater.Sci.Eng.,2017,A681:114
[10]Zhang W N,Liu Z Y,Wang G D.Martensitic transformation induced by deformation and work-hardening behavior of high manganese TRIP steels[J].Acta Metall.Sin.,2010,46:1230(张维娜,刘振宇,王国栋.高锰TRIP钢的形变诱导马氏体相变及加工硬化行为[J].金属学报,2010,46:1230)
[11]Chen L,Li F,Zhang Y J,et al.Calculation for the phase diagram and stability of metastable austenite in a TRIP/TWIP duplex stainless steel[J].J.Yanshan Univ.,2016,40:35(陈雷,李飞,张英杰等.一种TRIP/TWIP型双相不锈钢的相图及其亚稳奥氏体组织稳定性计算[J].燕山大学学报,2016,40:35)
[12]Li X F,Li Z B,Guo H S,et al.Influence of solution temperature on structure and properties of Ni-free type dual stainless steel00Cr21Mn5Ni1N[J].J.Iron Steel Res.,2007,19(10):44(李学锋,李正邦,郭海生等.固溶温度对00Cr21Mn5Ni1N节镍型双相不锈钢组织和性能的影响[J].钢铁研究学报,2007,19(10):44)
[13]Chen L,Zhang Y J,Li F,et al.Effect of solution temperature on TRIP/TWIP behavior of a lean duplex stainless steel[J].Iron Steel,2017,52(4):55(陈雷,张英杰,李飞等.固溶温度对节约型双相不锈钢TRIP/TWIP行为的影响[J].钢铁,2017,52(4):55)
[14]Guo B F,Zhang Q F,Chen L,et al.Influence of annealing temperature on the strain-hardening behavior of a lean duplex stainless steel[J].Mater.Sci.Eng.,2018,A722:216
[15]Tang Z Y,Wu Z Q,Zan N,et al.Microstructure evolution and deformation behavior of high manganese TRIP/TWIP symbiotic effect steels under high-speed deformation[J].Acta Metall.Sin.,2011,47:1426(唐正友,吴志强,昝娜等.高锰TRIP/TWIP效应共生钢高速变形过程中的组织演变及变形行为[J].金属学报,2011,47:1426)
[16]Choi J Y,Ji J H,Hwang S W,et al.Effects of nitrogen content on TRIP of Fe-20Cr-5Mn-x N duplex stainless steel[J].Mater.Sci.Eng.,2012,A534:673
[17]Choi J Y,Ji J H,Hwang S W,et al.Strain induced martensitic transformation of Fe-20Cr-5Mn-0.2Ni duplex stainless steel during cold rolling:Effects of nitrogen addition[J].Mater.Sci.Eng.,2011,A528:6012
[18]Wang M M,Tasan C C,Ponge D,et al.Spectral TRIP enables ductile 1.1 GPa martensite[J].Acta Mater.,2016,111:262
[19]Masumura T,Nakada N,Tsuchiyama T,et al.The difference in thermal and mechanical stabilities of austenite between carbonand nitrogen-added metastable austenitic stainless steels[J].Acta Mater.,2015,84:330
[20]Kim E Y,Woo W C,Heo Y U,et al.Effect of kinematic stability of the austenite phase on phase transformation behavior and deformation heterogeneity in duplex stainless steel using the crystal plasticity finite element method[J].Int.J.Plast.,2016,79:48
[21]Lin Y C,Chen M S,Zhong J.Static recrystallization behaviors of deformed 42CrMo steel[J].J.Cent.South Univ.(Sci.Technol.),2009,40:411(蔺永诚,陈明松,钟掘.42CrMo钢形变奥氏体的静态再结晶[J].中南大学学报(自然科学版),2009,40:411)
[22]Gutierrez-Urrutia I,Raabe D.Multistage strain hardening through dislocation substructure and twinning in a high strength and ductile weight-reduced Fe-Mn-Al-C steel[J].Acta Mater.2012,60:5791
[23]Lu F Y,Yang P,Meng L,et al.Microstructure,mechanical properties and crystallography analysis of Fe-22Mn TRIP/TWIP steel after tensile deformation[J].Acta Metall.Sin.,2013,49:1(鲁法云,杨平,孟利等.Fe-22Mn TRIP/TWIP钢拉伸过程组织、性能及晶体学行为分析[J].金属学报,2013,49:1)
[24]Yen H W,Ooi S W,Eizadjou M,et al.Role of stress-assisted martensite in the design of strong ultrafine-grained duplex steels[J].Acta Mater.,2015,82:100
[25]Bian H X.The research of plastic instability on austenitic stainless steel during hot deformation[D].Lanzhou:Lanzhou University of Technology,2014(边红霞.奥氏体不锈钢热变形过程中的塑性失稳研究[D].兰州:兰州理工大学,2014)
[26]Sun P L,Cerreta E K,Bingert J F,et al.Enhanced tensile ductility through boundary structure engineering in ultrafine-grained aluminum[J].Mater.Sci.Eng.,2007,A464:343
[27]Chen J H,Cao R.Micromechanism of cleavage fracture of weld metals[J].Acta Metall.Sin.,2017,53:1427(陈剑虹,曹睿.焊缝金属解理断裂微观机理[J].金属学报,2017,53:1427)
[28]Moallemi M,Zarei-Hanzaki A,Baghbadorani H S.Evolution of microstructure and mechanical properties in a cold deformed nitrogen bearing TRIP-assisted duplex stainless steel after reversion annealing[J].Mater.Sci.Eng.,2017,A683:83
[29]Zhang W,Hu J C.Effect of annealing temperature on transformation induced plasticity effect of a lean duplex stainless steel[J].Mater.Charact.,2013,79:37