α+β两相钛合金元素再分配行为及其对显微组织和力学性能的影响
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摘要
研究了两相区固溶温度及固溶后冷速对Ti-6Al-4V (TC4)合金元素再分配行为的影响,利用EPMA技术表征了初生α相(α_p)以及β转变区域(β_t)的元素浓度,考察了β_t显微组织尺寸随固溶温度及元素浓度的变化。结果表明:随着固溶温度升高,β_t区域元素浓度变化显著,表现为Al含量升高、V含量降低,而αp晶粒中元素浓度变化较小,导致两区域元素浓度差异减小;同一固溶温度下,以不同冷却方式(水冷、空冷及炉冷)冷却的显微组织及元素分布显示,冷却速率越低,α_p比例越高,α_p与β_t之间元素浓度差异越明显。合金经固溶水冷、空冷后,β_t分别为淬火马氏体、次生α相(α_s)+残余β相,2种冷速下β_t的显微组织尺寸均与高温β相内的元素浓度水平有关,即β_t内部显微组织尺寸受固溶温度的显著影响。利用纳米压痕技术表征了不同固溶温度下微区域(α_p、β_t)的力学特征,结果表明,密排六方(hcp)晶格α_p本身呈现的力学行为的各向异性对其纳米压痕性能起决定性作用,而β_t的弹性模量及硬度主要受α_s片层尺寸的影响。最后讨论了"固溶温度-微区元素浓度-微区显微组织-微区力学性能"之间的关系。
During the thermal treatments of α+β titanium alloys in(α+β) phase field, alloying element partitioning effect takes place accompanying with the α?β transformation, which results in the segregation of α stabilizing elements(Al, O) and β stabilizing elements(V, Mo, etc.) into the corresponding phases respectively. The element partitioning effect will further affect the microstructure characteristics(phase constitution, microstructure size), plastic deformation modes and the final mechanical properties of the alloy. In this work, the influences of solution temperature and cooling rate on the element partitioning behavior during solution process of Ti-6 Al-4 V alloy in(α+β) phase field were investigated. The element concentrations in primary α phase(α_p) and β transformed region(β_t) were characterized by EPMA technique. The microstructural variation of βtwith respect to solution temperature was analyzed. It was found that βt showed an obvious increase of Al content and decrease of V content with the increasing of solution temperature, while the αpexhibited less noticeable change, which led to the reduction of concentration difference between the two phases. Under the same solution temperature, the microstructures and element distributions at different cooling rates(water quenching, air cooling, furnace cooling) were exhibited. The slow cooling processing especially furnace cooling would induce higher volume fraction of αpphase and more pronounced element partitioning. The microstructural characteristics of β_t cooled from different solution temperatures were further analyzed. During the water or air cooling process, the transformations of β→matensite/α_s happened, and the sizes of martensite or α_s were postulated to be dependent on the element concentration of β phase. The properties of local microstructure(α_p, β_t) were further measured by nanoindentation. It indicates that the intrinsically anisotropic character of the hexagonal crystal structure(hcp) of the α_p phase has decisive consequences for the properties, while the elastic modulus and hardness of β_t calculated by nanoindentation are mainly dominated by the width of αslamellas. On the basis of the above results, the relationship between solution temperature, element concentration of local microstructure, microstructure size and mechanical properties of local microstructure was finally discussed.
During the thermal treatments of α+β titanium alloys in(α+β) phase field, alloying element partitioning effect takes place accompanying with the α?β transformation, which results in the segregation of α stabilizing elements(Al, O) and β stabilizing elements(V, Mo, etc.) into the corresponding phases respectively. The element partitioning effect will further affect the microstructure characteristics(phase constitution, microstructure size), plastic deformation modes and the final mechanical properties of the alloy. In this work, the influences of solution temperature and cooling rate on the element partitioning behavior during solution process of Ti-6 Al-4 V alloy in(α+β) phase field were investigated. The element concentrations in primary α phase(α_p) and β transformed region(β_t) were characterized by EPMA technique. The microstructural variation of βtwith respect to solution temperature was analyzed. It was found that βt showed an obvious increase of Al content and decrease of V content with the increasing of solution temperature, while the αpexhibited less noticeable change, which led to the reduction of concentration difference between the two phases. Under the same solution temperature, the microstructures and element distributions at different cooling rates(water quenching, air cooling, furnace cooling) were exhibited. The slow cooling processing especially furnace cooling would induce higher volume fraction of αpphase and more pronounced element partitioning. The microstructural characteristics of β_t cooled from different solution temperatures were further analyzed. During the water or air cooling process, the transformations of β→matensite/α_s happened, and the sizes of martensite or α_s were postulated to be dependent on the element concentration of β phase. The properties of local microstructure(α_p, β_t) were further measured by nanoindentation. It indicates that the intrinsically anisotropic character of the hexagonal crystal structure(hcp) of the α_p phase has decisive consequences for the properties, while the elastic modulus and hardness of β_t calculated by nanoindentation are mainly dominated by the width of αslamellas. On the basis of the above results, the relationship between solution temperature, element concentration of local microstructure, microstructure size and mechanical properties of local microstructure was finally discussed.
引文
[1] Wang F, Cui W C. Experimental investigation on dwell-fatigue property of Ti-6Al-4V ELI used in deep-sea manned cabin[J]. Mater. Sci. Eng., 2015, A642:136
[2] Boyer R R. An overview on the use of titanium in the aerospace industry[J]. Mater. Sci. Eng., 1996, A213:103
[3] Lütjering G. Property optimization through microstructural control in titanium and aluminum alloys[J]. Mater. Sci. Eng., 1999,A263:117
[4] Zhang Z Q, Dong L M, Yang Y, et al. Influences of quenching temperature on the microstructure and deformation behaviors of TC16titanium alloy[J]. Acta Metall. Sin., 2011, 47:1257(张志强,董利民,杨洋等.淬火温度对TC16钛合金显微组织及变形行为的影响[J].金属学报, 2011, 47:1257)
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[6] Barriobero-Vila P, Requena G, Buslaps T, et al. Role of element partitioning on theα-βphase transformation kinetics of a bi-modal Ti-6Al-6V-2Sn alloy during continuous heating[J]. J. Alloys Compd., 2015, 626:330
[7] Bruneseaux F, Aeby-Gautier E, Geandier G, et al. In situ characterizations of phase transformations kinetics in the Ti17 titanium alloy by electrical resistivity and high temperature synchrotron Xray diffraction[J]. Mater. Sci. Eng., 2008, A476:60
[8] Semiatin S L, Knisley S L, Fagin P N, et al. Microstructure evolution during alpha-beta heat treatment of Ti-6Al-4V[J]. Metall. Mater. Trans., 2003, 34A:2377
[9] Popov A A, Illarionov A G, Stepanov S I, et al. Effect of quenching temperature on structure and properties of titanium alloy:Structure and phase composition[J]. Phys. Met. Metallogr., 2014, 115:507
[10] Song M, Ma Y J, Wu J, et al. Effect of cooling rate on microstructure and properties of Ti-5.8Al-3Mo-1Cr-2Sn-2Zr-1V-0.15Si alloy[J]. Chin. J. Nonferrous Met., 2010, 20(suppl.):565(宋淼,马英杰,邬军等.冷却速率对Ti-5.8Al-3Mo-1Cr-2Sn-2Zr-1V-0.15Si合金组织及性能的影响[J].中国有色金属学报, 2010,20(增刊):565)
[11] Zeng L R, Chen H L, Li X, et al. Influence of alloy element partitioning on strength of primaryαphase in Ti-6Al-4V alloy[J]. J.Mater. Sci. Technol., 2018, 34:782
[12] Fitzner A, Prakash D G L, da Fonseca J Q, et al. The effect of aluminium on twinning in binary alpha-titanium[J]. Acta Mater.,2016, 103:341
[13] Xue Q, Ma Y J, Lei J F, et al. Mechanical properties and deformation mechanisms of Ti-3Al-5Mo-4.5V alloy with variedβphase stability[J]. J. Mater. Sci. Technol., 2018, 34:2507
[14] Xue Q, Ma Y J, Lei J F, et al. Evolution of microstructure and phase composition of Ti-3Al-5Mo-4.5V alloy with variedβphase stability[J]. J. Mater. Sci. Technol., 2018, 34:2325
[15] Chen Q, Ma N, Wu K S, et al. Quantitative phase field modeling of diffusion-controlled precipitate growth and dissolution in Ti-AlV[J]. Scr. Mater., 2004, 50:471
[16] Gao X X, Zeng W D, Zhang S F, et al. A study of epitaxial growth behaviors of equiaxed alpha phase at different cooling rates in near alpha titanium alloy[J]. Acta Mater., 2017, 122:298
[17] Elmer J W, Palmer T A, Babu S S, et al. Phase transformation dynamics during welding of Ti-6Al-4V[J]. J. Appl. Phys., 2004, 95:8327
[18] Elmer J W, Palmer T A, Babu S S, et al. In situ observations of lattice expansion and transformation rates ofαandβphases in Ti-6Al-4V[J]. Mater. Sci. Eng., 2005, A391:104
[19] Zhang Z, Wang Q J, Mo W. Metallurgy and Heat Treatment of Titanium Alloys[M]. Beijing:Metallurgical Industry Press, 2009:7(张翥,王群骄,莫畏.钛的金属学和热处理[M].北京:冶金工业出版社, 2009:7)
[20] Mishin Y, Herzig C. Diffusion in the Ti-Al system[J]. Acta Mater.,2000, 48:589
[21] Tarzimoghadam Z, Sandl?bes S, Pradeep K G, et al. Microstructure design and mechanical properties in a near-αTi-4Mo alloy[J].Acta Mater., 2015, 97:291
[22] Davis R, Flower H M, West D R F. Martensitic transformations in Ti-Mo alloys[J]. J. Mater. Sci., 1979, 14:712
[23] Srivastava D, Madangopal K, Banerjee S, et al. Self accomodation morphology of martensite variants in Zr2.5-wt%Nb alloy[J]. Acta Metall. Mater., 1993, 41:3445
[24] Grosdidier T, Combres Y, Gautier E, et al. Effect of microstructure variations on the formation of deformation-induced martensite and associated tensile properties in aβmetastable Ti alloy[J]. Metall.Mater. Trans., 2000, 31A:1095
[25] Peng C, Zhang S Y, Ren L, et al. Effect of cooling rate on microstructure and properties of a Cu-containing titanium alloy[J]. Acta Metall. Sin., 2017, 53:1377(彭聪,张书源,任玲等.冷却速率对含Cu钛合金显微组织和性能的影响[J].金属学报, 2017, 53:1377)
[26] Rugg D, Britton T B, Gong J, et al. In-service materials support for safety critical applications—A case study of a high strength Tialloy using advanced experimental and modelling techniques[J].Mater. Sci. Eng., 2014, A599:166
[2] Boyer R R. An overview on the use of titanium in the aerospace industry[J]. Mater. Sci. Eng., 1996, A213:103
[3] Lütjering G. Property optimization through microstructural control in titanium and aluminum alloys[J]. Mater. Sci. Eng., 1999,A263:117
[4] Zhang Z Q, Dong L M, Yang Y, et al. Influences of quenching temperature on the microstructure and deformation behaviors of TC16titanium alloy[J]. Acta Metall. Sin., 2011, 47:1257(张志强,董利民,杨洋等.淬火温度对TC16钛合金显微组织及变形行为的影响[J].金属学报, 2011, 47:1257)
[5] Lütjering G, Williams J C. Titanium[M]. 2nd Ed., Berlin Heidelberg:Springer, 2007:211
[6] Barriobero-Vila P, Requena G, Buslaps T, et al. Role of element partitioning on theα-βphase transformation kinetics of a bi-modal Ti-6Al-6V-2Sn alloy during continuous heating[J]. J. Alloys Compd., 2015, 626:330
[7] Bruneseaux F, Aeby-Gautier E, Geandier G, et al. In situ characterizations of phase transformations kinetics in the Ti17 titanium alloy by electrical resistivity and high temperature synchrotron Xray diffraction[J]. Mater. Sci. Eng., 2008, A476:60
[8] Semiatin S L, Knisley S L, Fagin P N, et al. Microstructure evolution during alpha-beta heat treatment of Ti-6Al-4V[J]. Metall. Mater. Trans., 2003, 34A:2377
[9] Popov A A, Illarionov A G, Stepanov S I, et al. Effect of quenching temperature on structure and properties of titanium alloy:Structure and phase composition[J]. Phys. Met. Metallogr., 2014, 115:507
[10] Song M, Ma Y J, Wu J, et al. Effect of cooling rate on microstructure and properties of Ti-5.8Al-3Mo-1Cr-2Sn-2Zr-1V-0.15Si alloy[J]. Chin. J. Nonferrous Met., 2010, 20(suppl.):565(宋淼,马英杰,邬军等.冷却速率对Ti-5.8Al-3Mo-1Cr-2Sn-2Zr-1V-0.15Si合金组织及性能的影响[J].中国有色金属学报, 2010,20(增刊):565)
[11] Zeng L R, Chen H L, Li X, et al. Influence of alloy element partitioning on strength of primaryαphase in Ti-6Al-4V alloy[J]. J.Mater. Sci. Technol., 2018, 34:782
[12] Fitzner A, Prakash D G L, da Fonseca J Q, et al. The effect of aluminium on twinning in binary alpha-titanium[J]. Acta Mater.,2016, 103:341
[13] Xue Q, Ma Y J, Lei J F, et al. Mechanical properties and deformation mechanisms of Ti-3Al-5Mo-4.5V alloy with variedβphase stability[J]. J. Mater. Sci. Technol., 2018, 34:2507
[14] Xue Q, Ma Y J, Lei J F, et al. Evolution of microstructure and phase composition of Ti-3Al-5Mo-4.5V alloy with variedβphase stability[J]. J. Mater. Sci. Technol., 2018, 34:2325
[15] Chen Q, Ma N, Wu K S, et al. Quantitative phase field modeling of diffusion-controlled precipitate growth and dissolution in Ti-AlV[J]. Scr. Mater., 2004, 50:471
[16] Gao X X, Zeng W D, Zhang S F, et al. A study of epitaxial growth behaviors of equiaxed alpha phase at different cooling rates in near alpha titanium alloy[J]. Acta Mater., 2017, 122:298
[17] Elmer J W, Palmer T A, Babu S S, et al. Phase transformation dynamics during welding of Ti-6Al-4V[J]. J. Appl. Phys., 2004, 95:8327
[18] Elmer J W, Palmer T A, Babu S S, et al. In situ observations of lattice expansion and transformation rates ofαandβphases in Ti-6Al-4V[J]. Mater. Sci. Eng., 2005, A391:104
[19] Zhang Z, Wang Q J, Mo W. Metallurgy and Heat Treatment of Titanium Alloys[M]. Beijing:Metallurgical Industry Press, 2009:7(张翥,王群骄,莫畏.钛的金属学和热处理[M].北京:冶金工业出版社, 2009:7)
[20] Mishin Y, Herzig C. Diffusion in the Ti-Al system[J]. Acta Mater.,2000, 48:589
[21] Tarzimoghadam Z, Sandl?bes S, Pradeep K G, et al. Microstructure design and mechanical properties in a near-αTi-4Mo alloy[J].Acta Mater., 2015, 97:291
[22] Davis R, Flower H M, West D R F. Martensitic transformations in Ti-Mo alloys[J]. J. Mater. Sci., 1979, 14:712
[23] Srivastava D, Madangopal K, Banerjee S, et al. Self accomodation morphology of martensite variants in Zr2.5-wt%Nb alloy[J]. Acta Metall. Mater., 1993, 41:3445
[24] Grosdidier T, Combres Y, Gautier E, et al. Effect of microstructure variations on the formation of deformation-induced martensite and associated tensile properties in aβmetastable Ti alloy[J]. Metall.Mater. Trans., 2000, 31A:1095
[25] Peng C, Zhang S Y, Ren L, et al. Effect of cooling rate on microstructure and properties of a Cu-containing titanium alloy[J]. Acta Metall. Sin., 2017, 53:1377(彭聪,张书源,任玲等.冷却速率对含Cu钛合金显微组织和性能的影响[J].金属学报, 2017, 53:1377)
[26] Rugg D, Britton T B, Gong J, et al. In-service materials support for safety critical applications—A case study of a high strength Tialloy using advanced experimental and modelling techniques[J].Mater. Sci. Eng., 2014, A599:166