奥氏体析出相激发形核的原位TEM研究
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摘要
利用原位透射电镜(TEM)观察双相不锈钢中奥氏体析出相变过程,发现了端-面连接的奥氏体激发形核现象。定量表征结果表明,激发形核奥氏体和先驱奥氏体与母相铁素体的位向关系都接近N-W,但属于不同的位向关系,且在不同的Bain环上。基于弹性相互作用能和界面能解释了激发形核奥氏体的择优晶体学取向,计算结果表明,先驱奥氏体与不同Bain环上激发形核奥氏体的弹性相互作用能为负值,且相邻奥氏体之间可以形成孪晶取向关系及共格孪晶界。
Duplex stainless steels(DSSs) are widely used for chemical industry, marine construction and power plants, due to the beneficial combination of ferrite and austenite properties: high strength with a desirable toughness and good corrosion resistance. The sympathetic nucleation(SN) of intragranular austenite precipitates has been frequently observed in DSS. This type of nucleation, which occurs in a considerable variety of steels and titanium alloys, has a great effect on the morphological arrangement of precipitates and hence the mechanical properties of metallic materials. Therefore, understanding the SN mechanism of austenite precipitates is essential to knowledge based material design of the microstructure in DSS. Three types of morphological arrangement, i.e., face-to-face, edge-to-edge and edge-to-face SN of austenite precipitates, have been identified in previous investigations on DSS. The adjacent grains of face-to-face and edge-to-edge sympathetically nucleated austenite have approximately the identical orientations, with a small-angle boundary between two austenite crystals. However, as regards to the edge-to-face SN, the lacking of crystallographic features of adjacent austenite precipitates obstructs the understanding of the mechanism for the edge-to-face SN. Moreover, it is usually difficult to distinguish between SN and hard impingement following nucleation at separate sites in conventional experimental observations. Thus, in the present work, the typical morphology of edge-to-face SN of austenite precipitates was directly observed at 725 ℃ in a DSS using in situ TEM. The orientation relationship(OR) between the sympathetically nucleated austenite precipitate and ferrite matrix is determined through analysis of Kikuchi lines. Since the long axes of austenite precipitates parallel to the invariant line are restricted in the thin TEM foil, there are only four types of austenite with different near N-W ORs and cystallographically inequivalent long axes. This work reveals that the ORs of sympathetically nucleated austenite grains belong to different Bain groups with those of the pre-formed austenites. The explanation for the OR selection is provided based on two factors favoring SN, namely the reduction of elastic interaction strain energy and the interfacial energy. The local stress generated by the semi-coherent pre-formed austenite was calculated by Eshelby inclusion method. The local stress field accompanying with the pre-formed austenite assists the subsequent nucleation and growth of sympathetically nucleated austenite. It shows that the elastic interaction energy for the sympathetically nucleated austenite of particular OR is negative. In addition, the pre-formed austenite and the sympathetically nucleated austenite grain are twin related. This indicates that the nucleation barrier associated with SN of austenite with selected OR is comparably lower than other candidates. Hence, the austenite precipitate with a specific OR is preferred during SN.
Duplex stainless steels(DSSs) are widely used for chemical industry, marine construction and power plants, due to the beneficial combination of ferrite and austenite properties: high strength with a desirable toughness and good corrosion resistance. The sympathetic nucleation(SN) of intragranular austenite precipitates has been frequently observed in DSS. This type of nucleation, which occurs in a considerable variety of steels and titanium alloys, has a great effect on the morphological arrangement of precipitates and hence the mechanical properties of metallic materials. Therefore, understanding the SN mechanism of austenite precipitates is essential to knowledge based material design of the microstructure in DSS. Three types of morphological arrangement, i.e., face-to-face, edge-to-edge and edge-to-face SN of austenite precipitates, have been identified in previous investigations on DSS. The adjacent grains of face-to-face and edge-to-edge sympathetically nucleated austenite have approximately the identical orientations, with a small-angle boundary between two austenite crystals. However, as regards to the edge-to-face SN, the lacking of crystallographic features of adjacent austenite precipitates obstructs the understanding of the mechanism for the edge-to-face SN. Moreover, it is usually difficult to distinguish between SN and hard impingement following nucleation at separate sites in conventional experimental observations. Thus, in the present work, the typical morphology of edge-to-face SN of austenite precipitates was directly observed at 725 ℃ in a DSS using in situ TEM. The orientation relationship(OR) between the sympathetically nucleated austenite precipitate and ferrite matrix is determined through analysis of Kikuchi lines. Since the long axes of austenite precipitates parallel to the invariant line are restricted in the thin TEM foil, there are only four types of austenite with different near N-W ORs and cystallographically inequivalent long axes. This work reveals that the ORs of sympathetically nucleated austenite grains belong to different Bain groups with those of the pre-formed austenites. The explanation for the OR selection is provided based on two factors favoring SN, namely the reduction of elastic interaction strain energy and the interfacial energy. The local stress generated by the semi-coherent pre-formed austenite was calculated by Eshelby inclusion method. The local stress field accompanying with the pre-formed austenite assists the subsequent nucleation and growth of sympathetically nucleated austenite. It shows that the elastic interaction energy for the sympathetically nucleated austenite of particular OR is negative. In addition, the pre-formed austenite and the sympathetically nucleated austenite grain are twin related. This indicates that the nucleation barrier associated with SN of austenite with selected OR is comparably lower than other candidates. Hence, the austenite precipitate with a specific OR is preferred during SN.
引文
[1]Jiao H S,Aindow M,Pond R C.Precipitate orientation relationships and interfacial structures in duplex stainless steel Zeron-100[J].Philos.Mag.,2003,83:1867
[2]Qiu D,Zhang W Z.A TEM study of the crystallography of austenite precipitates in a duplex stainless steel[J].Acta Mater.,2007,55:6754
[3]Du J,Mompiou F,Zhang W Z.A TEM study of the crystallography of lath-shaped austenite precipitates in a duplex stainless steel[J].J.Mater.Sci.,2017,52:11688
[4]Shek C H,Lai J K L,Wong K W,et al.Early-stage Widmanstatten growth of theγphase in a duplex steel[J].Metall.Mater.Trans.,2000,31A:15
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[6]Chen C Y,Yen H W,Yang J R.Sympathetic nucleation of austenite in a Fe-22Cr-5Ni duplex stainless steel[J].Scr.Mater.,2007,56:673
[7]Chen T H,Yang J R.Microstructural characterization of simulated heat affected zone in a nitrogen-containing 2205 duplex stainless steel[J].Mater.Sci.Eng.,2002,A338:166
[8]Haghdadi N,Cizek P,Hodgson P D,et al.Effect of ferrite-toaustenite phase transformation path on the interface crystallographic character distributions in a duplex stainless steel[J].Acta Mater.,2018,145:196
[9]Magalh?es C H X M,De Faria G L,Lagoeiro L E,et al.Characterization of the austenite reformation mechanisms as a function of the initial ferritic state in a UNS S32304 duplex stainless steel[J].Mater.Res.,2017,20:1470
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[11]Phelan D,Dippenaar R.Widmanst?tten ferrite plate formation in low-carbon steels[J].Metall.Mater.Trans.,2004,35A:3701
[12]Spanos G,Fang H S,Aaronson H I.A mechanism for the formation of lower bainite[J].Metall.Trans.,1990,21A:1381
[13]Beladi H,Tari V,Timokhina I B,et al.On the crystallographic characteristics of nanobainitic steel[J].Acta Mater.,2017,127:426
[14]Fang H S,Wang J J,Yang Z G,et al.Formation of bainite in ferrous and nonferrous alloys through sympathetic nucleation and ledgewise growth mechanism[J].Metall.Mater.Trans.,1996,27A:1535
[15]Menon E S K,Aaronson H I.Morphology,crystallography and kinetics of sympathetic nucleation[J].Acta Metall.,1987,35:549
[16]Meng M,Fan X G,Yang H,et al.Precipitation of secondary alpha in competition with epitaxial growth of primary alpha in twophase titanium alloys[J].J.Alloys Compd.,2017,714:294
[17]Menon E S K,Krishnan R.Phase transformations in Ti-V alloys[J].J.Mater.Sci.,1983,18:375
[18]Tang B,Kou H C,Zhang X,et al.Study on the formation mechanism ofαlamellae in a nearβtitanium alloy[J].Prog.Nat.Sci.:Mater.Int.,2016,26:385
[19]Spanos G,Aaronson H I.Morphology,crystallography and mechanism of sympathetic nucleation of proeutectoid cementite plates[J].Scr.Metall.,1988,22:1537
[20]Ameyama K,Weatherly G C,Aust K T.A study of grain boundary nucleated widmanst?tten precipitates in a two-phase stainless steel[J].Acta Metall.Mater.,1992,40:1835
[21]Aaronson H I,Spanos G,Masamura R A,et al.Sympathetic nucleation:An overview[J].Mater.Sci.Eng.,1995,B32:107
[22]Lee J K,Johnson W C.Elastic strain energy and interactions of thin square plates which have undergone a simple shear[J].Scr.Metall.,1977,11:477
[23]Russell K C,Barnett D M,Altstetter C J,et al.Strain energy interactions,the Toconcept and sympathetic nucleation[J].Scr.Metall.,1977,11:485
[24]Qiu D,Shi R,Zhang D,et al.Variant selection by dislocations duringαprecipitation inα/βtitanium alloys[J].Acta Mater.,2015,88:218
[25]Shi R,Wang Y.Variant selection duringαprecipitation in Ti-6Al-4V under the influence of local stress-A simulation study[J].Acta Mater.,2013,61:6006
[26]Eshelby J D.The determination of the elastic field of an ellipsoidal inclusion,and related problems[J].Proc.R.Soc.London,1957,241A:376
[27]Wang J J,Ma X Q,Li Q,et al.Phase transitions and domain structures of ferroelectric nanoparticles:Phase field model incorporating strong elastic and dielectric inhomogeneity[J].Acta Mater.,2013,61:7591
[28]Jia N,Lin P R,Wang Y D,et al.Micromechanical behavior and texture evolution of duplex stainless steel studied by neutron diffraction and self-consistent modeling[J].Acta Mater.,2008,56:782
[29]Zhang M X.Crystallography of phase transformation in steels[D].Brisbane:University of Queensland,1997
[30]Wu J.Study on microstructure and transformation crystallography of lath martensite in Fe-20Ni-5.4Mn(wt%)alloy[D].Beijing:Tsinghua University,2011(吴静.Fe-20Ni-5.4Mn(wt%)合金中板条马氏体微结构和相变的研究[D].北京:清华大学,2011)
[31]Crosky A,Mcdougall P G,Bowles J S.The crystallography of the precipitation ofαrods fromβCu-Zn alloys[J].Acta Metall.,1980,28:1495
[32]Wayman C M.Introduction to the Crystallography of Martensitic Transformations[M].New York:MacMilla,1964:84
[33]Zhang W Z,Purdy G R.O-lattice analyses of interfacial misfit.Ⅱ.Systems containing invariant lines[J].Philos.Mag.,1993,68:291
[34]Du J.A TEM study on the austenite/ferrite interface migration in a duplex stainless steel[D].Beijig:Tsinghua University,2018.(杜娟.双相不锈钢中奥氏体/铁素体界面迁移的透射电镜研究[D].北京:清华大学,2018)
[35]Bowles J S,Mackenzie J K.The crystallography of martensite transformations I[J].Acta Metall.,1954,2:129
[36]Wechsler M S,Lieberman D S,Read T A.On the theory of the formation of martensite[J].Trans.Am.Inst.Min.Metall.Eng.,1953,197:1503
[37]Porter D A,Easterling K E,Sherig M Y,translated by Chen L,Yu Y N.Phase Transformations in Metals and Alloys[M].Beijing:High Education Press,2011:104(Porter D A,Easterling K E,Sherif M Y著,陈冷,余永宁译.金属和合金中的相变[M].北京:高等教育出版社,2011:104)
[38]Brandon D G.The structure of high-angle grain boundaries[J].Acta Metall.,1966,14:1479
[2]Qiu D,Zhang W Z.A TEM study of the crystallography of austenite precipitates in a duplex stainless steel[J].Acta Mater.,2007,55:6754
[3]Du J,Mompiou F,Zhang W Z.A TEM study of the crystallography of lath-shaped austenite precipitates in a duplex stainless steel[J].J.Mater.Sci.,2017,52:11688
[4]Shek C H,Lai J K L,Wong K W,et al.Early-stage Widmanstatten growth of theγphase in a duplex steel[J].Metall.Mater.Trans.,2000,31A:15
[5]Ohmori Y,Nakai K,Ohtsubo H,et al.Mechanism of Widmanst?tten austenite formation in aδ/γduplex phase stainless steel[J].ISIJ Int.,1995,35:969
[6]Chen C Y,Yen H W,Yang J R.Sympathetic nucleation of austenite in a Fe-22Cr-5Ni duplex stainless steel[J].Scr.Mater.,2007,56:673
[7]Chen T H,Yang J R.Microstructural characterization of simulated heat affected zone in a nitrogen-containing 2205 duplex stainless steel[J].Mater.Sci.Eng.,2002,A338:166
[8]Haghdadi N,Cizek P,Hodgson P D,et al.Effect of ferrite-toaustenite phase transformation path on the interface crystallographic character distributions in a duplex stainless steel[J].Acta Mater.,2018,145:196
[9]Magalh?es C H X M,De Faria G L,Lagoeiro L E,et al.Characterization of the austenite reformation mechanisms as a function of the initial ferritic state in a UNS S32304 duplex stainless steel[J].Mater.Res.,2017,20:1470
[10]Aaronson H I,Wells C.Sympathetic nucleation of ferrite[J].Trans.Am.Inst.Min.Metall.Eng.,1956,206:1216
[11]Phelan D,Dippenaar R.Widmanst?tten ferrite plate formation in low-carbon steels[J].Metall.Mater.Trans.,2004,35A:3701
[12]Spanos G,Fang H S,Aaronson H I.A mechanism for the formation of lower bainite[J].Metall.Trans.,1990,21A:1381
[13]Beladi H,Tari V,Timokhina I B,et al.On the crystallographic characteristics of nanobainitic steel[J].Acta Mater.,2017,127:426
[14]Fang H S,Wang J J,Yang Z G,et al.Formation of bainite in ferrous and nonferrous alloys through sympathetic nucleation and ledgewise growth mechanism[J].Metall.Mater.Trans.,1996,27A:1535
[15]Menon E S K,Aaronson H I.Morphology,crystallography and kinetics of sympathetic nucleation[J].Acta Metall.,1987,35:549
[16]Meng M,Fan X G,Yang H,et al.Precipitation of secondary alpha in competition with epitaxial growth of primary alpha in twophase titanium alloys[J].J.Alloys Compd.,2017,714:294
[17]Menon E S K,Krishnan R.Phase transformations in Ti-V alloys[J].J.Mater.Sci.,1983,18:375
[18]Tang B,Kou H C,Zhang X,et al.Study on the formation mechanism ofαlamellae in a nearβtitanium alloy[J].Prog.Nat.Sci.:Mater.Int.,2016,26:385
[19]Spanos G,Aaronson H I.Morphology,crystallography and mechanism of sympathetic nucleation of proeutectoid cementite plates[J].Scr.Metall.,1988,22:1537
[20]Ameyama K,Weatherly G C,Aust K T.A study of grain boundary nucleated widmanst?tten precipitates in a two-phase stainless steel[J].Acta Metall.Mater.,1992,40:1835
[21]Aaronson H I,Spanos G,Masamura R A,et al.Sympathetic nucleation:An overview[J].Mater.Sci.Eng.,1995,B32:107
[22]Lee J K,Johnson W C.Elastic strain energy and interactions of thin square plates which have undergone a simple shear[J].Scr.Metall.,1977,11:477
[23]Russell K C,Barnett D M,Altstetter C J,et al.Strain energy interactions,the Toconcept and sympathetic nucleation[J].Scr.Metall.,1977,11:485
[24]Qiu D,Shi R,Zhang D,et al.Variant selection by dislocations duringαprecipitation inα/βtitanium alloys[J].Acta Mater.,2015,88:218
[25]Shi R,Wang Y.Variant selection duringαprecipitation in Ti-6Al-4V under the influence of local stress-A simulation study[J].Acta Mater.,2013,61:6006
[26]Eshelby J D.The determination of the elastic field of an ellipsoidal inclusion,and related problems[J].Proc.R.Soc.London,1957,241A:376
[27]Wang J J,Ma X Q,Li Q,et al.Phase transitions and domain structures of ferroelectric nanoparticles:Phase field model incorporating strong elastic and dielectric inhomogeneity[J].Acta Mater.,2013,61:7591
[28]Jia N,Lin P R,Wang Y D,et al.Micromechanical behavior and texture evolution of duplex stainless steel studied by neutron diffraction and self-consistent modeling[J].Acta Mater.,2008,56:782
[29]Zhang M X.Crystallography of phase transformation in steels[D].Brisbane:University of Queensland,1997
[30]Wu J.Study on microstructure and transformation crystallography of lath martensite in Fe-20Ni-5.4Mn(wt%)alloy[D].Beijing:Tsinghua University,2011(吴静.Fe-20Ni-5.4Mn(wt%)合金中板条马氏体微结构和相变的研究[D].北京:清华大学,2011)
[31]Crosky A,Mcdougall P G,Bowles J S.The crystallography of the precipitation ofαrods fromβCu-Zn alloys[J].Acta Metall.,1980,28:1495
[32]Wayman C M.Introduction to the Crystallography of Martensitic Transformations[M].New York:MacMilla,1964:84
[33]Zhang W Z,Purdy G R.O-lattice analyses of interfacial misfit.Ⅱ.Systems containing invariant lines[J].Philos.Mag.,1993,68:291
[34]Du J.A TEM study on the austenite/ferrite interface migration in a duplex stainless steel[D].Beijig:Tsinghua University,2018.(杜娟.双相不锈钢中奥氏体/铁素体界面迁移的透射电镜研究[D].北京:清华大学,2018)
[35]Bowles J S,Mackenzie J K.The crystallography of martensite transformations I[J].Acta Metall.,1954,2:129
[36]Wechsler M S,Lieberman D S,Read T A.On the theory of the formation of martensite[J].Trans.Am.Inst.Min.Metall.Eng.,1953,197:1503
[37]Porter D A,Easterling K E,Sherig M Y,translated by Chen L,Yu Y N.Phase Transformations in Metals and Alloys[M].Beijing:High Education Press,2011:104(Porter D A,Easterling K E,Sherif M Y著,陈冷,余永宁译.金属和合金中的相变[M].北京:高等教育出版社,2011:104)
[38]Brandon D G.The structure of high-angle grain boundaries[J].Acta Metall.,1966,14:1479