NbCr_2/Nb合金高温蠕变行为
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摘要
采用机械合金化+热压制备了成分为Nb-22.5at.%Cr的细晶NbCr_2/Nb合金。通过Gleeble 3500型热模拟机上的恒应力压缩试验,研究了合金的高温蠕变行为,并采用透射电子显微镜观察了合金变形前后的组织。结果表明:NbCr_2/Nb合金的稳态蠕变速率随应力的增加和变形温度的升高而加快,1000℃和200 MPa条件下,NbCr_2/Nb合金的稳态蠕变速率为9.0×10-5s-1,1000℃下的应力指数为4.36,而200 MPa下的蠕变激活能为510.7 kJ·mol-1。蠕变变形过程中,Nb基体中位错的滑移、攀移和Laves相NbCr_2中的同步剪切是蠕变变形的主要方式;随着变形温度升高,Nb基体颗粒有形成亚晶的趋势,且两相颗粒界面处应力增大,Laves相NbCr_2颗粒中层错/孪晶密度增加。
The fine-crystal NbCr_2/Nb alloy with composition Nb-22.5 at.% Cr was prepared by mechanical alloying and hot pressing.Then,the high temperature creep behaviors of NbCr_2/Nb alloy were studied by constant stress compression tests on Gleeble 3500 thermal simulator,and the microstructure of NbCr_2/Nb alloy before and after deformation was observed by transmission electron microscopy.The results show that the steady creep rate of NbCr_2/Nb alloy increases with the increase of stress and deformation temperature.The steady creep rate of NbCr_2/Nb alloy crept at 1000 ℃,200 MPa is 9.0×10-5 s-1.The stress exponent is 4.36 at 1000 ℃ and the creep activation energy is 510.7 kJ·mol-1 under 200 MPa.The dislocation slip and climb in the Nb matrix and the synchroshear in the Laves phase NbCr_2 are the main modes of creep deformation.With the increase of deformation temperature,Nb matrix particle tends to form subgrain,the stress at the interface of two phase particles increases and the density of stacking fault/twinning in the Laves phase NbCr_2 particle increases.
The fine-crystal NbCr_2/Nb alloy with composition Nb-22.5 at.% Cr was prepared by mechanical alloying and hot pressing.Then,the high temperature creep behaviors of NbCr_2/Nb alloy were studied by constant stress compression tests on Gleeble 3500 thermal simulator,and the microstructure of NbCr_2/Nb alloy before and after deformation was observed by transmission electron microscopy.The results show that the steady creep rate of NbCr_2/Nb alloy increases with the increase of stress and deformation temperature.The steady creep rate of NbCr_2/Nb alloy crept at 1000 ℃,200 MPa is 9.0×10-5 s-1.The stress exponent is 4.36 at 1000 ℃ and the creep activation energy is 510.7 kJ·mol-1 under 200 MPa.The dislocation slip and climb in the Nb matrix and the synchroshear in the Laves phase NbCr_2 are the main modes of creep deformation.With the increase of deformation temperature,Nb matrix particle tends to form subgrain,the stress at the interface of two phase particles increases and the density of stacking fault/twinning in the Laves phase NbCr_2 particle increases.
引文
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[3]CHEN C,ZHOU C G,GONG S K,et al.Deposition of Cr-modified silicide coatings on Nb-Si system intermetallics[J].Intermetallics,2007,15:805-809.
[4]QIAO Y Q,LI M Y,GU X P.Development of silicide coatings over Nb-NbCr2alloy and their oxidation behavior at 1250℃[J].Surface&Coatings Technology,2014,258:921-930.
[5]GUO B H,GUO X P.Effect of withdrawal rates on microstructures and room temperature fracture toughness in a directionally solidified Nb-Ti-Cr-Si based alloy[J].Materials Science and Engineering A,2014,617:39-45.
[6]SU L F,JIA L N,FENG Y B,et al.Microstructure and roomtemperature fracture toughness of directionally solidified Nb-Si-TiCr-Al-Hf alloy[J].Materials Science&Engineering A,2013,560:672-677.
[7]LIMA J C D,ALMEIDA T O,JERONIMO A R,et al.Reverse Monte Carlo simulations of an amorphous Cr25Nb75alloy produced by mechanical alloying[J].Journal of Non-Crystalline Solids,2006,352:109-115.
[8]肖璇.Laves相Cr2Nb合金的原位合成与室温增韧研究[D].南京:南京航空大学,2008.XIAO Xuan.Research on the in-situ synthesis and room-temperature toughening of Laves phase Cr2Nb based alloys[D].Nanjing:Nanjing University of Aeronautics and Astronautics,2008.
[9]肖璇,鲁世强,马燕青,等.机械合金化-热压制备Nb/NbCr2复合材料的组织与性能[J].中国有色金属学报,2007,17(11):1761-1766.XIAO Xuan,LU Shiqiang,MA Yanqing,et al.Microstructure and properties of Nb/NbCr2composites prepared by mechanical alloying followed by hot pressing[J].The Chinese Journal of Nonferrous Metals,2007,17(11):1761-1766.
[10]齐先胜,薛祥义,陈伟,等.表面塑性变形对高Nb-TiAl合金扩散连接界面组织演化的影响[J].塑性工程学报,2014,21(4):23-27.QI Xiansheng,XUE Xiangyi,CHEN Wei,et al.Influence of surface plastic deformation on the microstructure evolution of high Nb containing Ti Al alloy[J].Journal of Plasticity Engineering,2014,21(4):23-27.
[11]CHAN K S.Modeling creep behavior of niobium silicide in-situ composites[J].Materials Science and Engineering A,2002,337:59-66.
[12]XIA Z X,WANG C Y,LEI C,et al.Growth kinetics of Laves phase and its effect on creep rupture behavior in 9Cr heat resistant steel[J].Journal of Iron and Steel Research,International,2016,23(7):685-691.
[13]ZHANG X Z,WU X J,LIU R,et al.Influence of Laves phase on creep strength of modified 9Cr-1Mo steel[J].Materials Science&Engineering A,2017,706:279-286.
[14]KUHN B,TALIK M,NIEWOLAK L.Development of high chromium ferritic steels strengthened by intermetallic phases[J].Materials Science&Engineering A,2014,594:372-380.
[15]TIAN S G,SU Y,QIAN B J,et al.Creep behavior of a single crystal nickel-based superalloy containing 4.2%Re[J].Materials and Design,2012,37(9):236-242.
[16]LEE S,LIAW P K,LIU C T,et al.Cracking in Cr-Cr2Nb eutectic alloys due to thermal stresses[J].Materials Science and Engineering A,1999,268:184-192.
[17]KUMAR K S,LIU C T.Precipitation in a Cr-Cr2Nb alloy[J].Acta Materialia,1997,45(9):3671-3686.