Please wait a minute...
金属学报  2019, Vol. 55 Issue (2): 202-212    DOI: 10.11900/0412.1961.2018.00053
  本期目录 | 过刊浏览 |
Mg-14.61Gd合金的定向凝固组织及生长取向
杨燕, 杨光昱(), 罗时峰, 肖磊, 介万奇
西北工业大学凝固技术国家重点实验室 西安 710072
Microstructures and Growth Orientation of Directionally Solidification Mg-14.61Gd Alloy
Yan YANG, Guangyu YANG(), Shifeng LUO, Lei XIAO, Wanqi JIE
State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China
全文: PDF(10964 KB)   HTML
摘要: 

采用电子背散射衍射(EBSD)和元胞自动机有限元(CAFE)方法研究了Mg-14.61Gd合金在温度梯度G=30 K/mm和抽拉速率v=10~200 μm/s条件下的定向凝固组织和生长取向。研究发现,Mg-14.61Gd合金纵向凝固组织呈单一方向的α-Mg枝晶生长形貌,随着v的增加,枝晶界面生长方式由凸前生长向平齐生长转变,枝晶间距减小。当v从10 μm/s增至100 μm/s时,α-Mg枝晶的生长取向由<1120>和<1010>转变为<1120>,其与凝固热流的偏离角(θ)由11.0°减小至5.7°,热流是影响生长取向的主导因素;当v从100 μm/s增至200 μm/s时,α-Mg枝晶的生长取向仍为<1120>,但θ却逐渐增大至10.6°,此时,晶体的各向异性占主导。研究表明,CAFE模型可以合理预测定向凝固镁合金的晶粒组织和生长取向。

关键词 Mg-14.61Gd合金定向凝固EBSDCAFE模型生长取向    
Abstract

As one of the most promising heat-resistant magnesium alloys, Mg-Gd series alloy has a wide application prospect in the industrial fields of aerospace, cars, and rail transit. There have been extensive researches on the performance improvement of Mg-Gd series alloys. As known, dendrites are the common solidification microstructures of castings of magnesium alloys, and solidification conditions have a significant effect on dendrite morphologies and growth orientation, which could strongly affect the mechanical properties of castings, thus it is critical to study the grain growth regularity for predicting the performance of magnesium castings. However, there are few studies on numerical simulation of dendrite growth process and growth orientation of magnesium alloys. Solidification behavior of magnesium alloys can be scientifically studied via directional solidification technology, and cellular automaton finite element (CAFE) method should be effective to simulate the dendrite growth process of magnesium alloys. In present work, microstructures and growth orientation of directionally solidified Mg-14.61Gd alloy under the temperature gradient G=30 K/mm and the withdrawal rate v=10~200 μm/s were investigated by EBSD measurement method and CAFE numerical simulation method. It was found that α-Mg primary phase presented unidirectional dendritic morphologies on longitudinal cross-section. The growth interface appearance of α-Mg changed from the protruding forward growth to the flat growth gradually and the dendritic arm spacing decreased gradually with the increasing v. when v increased from 10 μm/s to 100 μm/s, the main growth orientation of α-Mg changed from <1120> and <1010> to <1120>, and the deviation angle (θ) from solidification heat flow direction reduced from 11.0° to 5.7°, the reason for this lied mainly in the change of the heat flux. Further increasing v up to 200 μm/s, the main growth direction of α-Mg was still in <1120>, but the value of θ increased to 10.6°, and the anisotropy of the crystal was the dominant factor then. It was proved that the CAFE numerical simulation model could predict the grain structure and growth orientation reasonably for Mg alloy.

Key wordsMg-14.61Gd alloy    directional solidification    EBSD    CAFE model    growth orientation
收稿日期: 2018-02-05      出版日期: 2018-08-21
ZTFLH:  TG113.1  
基金资助:资助项目 国家自然科学基金项目Nos.51771152、51227001,国家重点研发计划项目No.2018YFB1106800及凝固技术国家重点实验室自主研究课题项目No.138-QP-2015
作者简介:

作者简介 杨 燕,女,1992年生,硕士生

引用本文:

杨燕, 杨光昱, 罗时峰, 肖磊, 介万奇. Mg-14.61Gd合金的定向凝固组织及生长取向[J]. 金属学报, 2019, 55(2): 202-212.
Yan YANG, Guangyu YANG, Shifeng LUO, Lei XIAO, Wanqi JIE. Microstructures and Growth Orientation of Directionally Solidification Mg-14.61Gd Alloy. Acta Metall Sin, 2019, 55(2): 202-212.

链接本文:

http://www.ams.org.cn/CN/10.11900/0412.1961.2018.00053      或      http://www.ams.org.cn/CN/Y2019/V55/I2/202

图1  Bridgman定向凝固装置及试样模型网格示意图
Interface heat transfer coefficient Temperature Process condition
Wm-2K-1
Alloy/Mold: 1000[22,23] Alloy: 740 Heat zone enclosure temperature: 740 ℃
Alloy/Pull rod: 500[22,23] Mold: 740 Heat zone enclosure emissivity: 0.9[23]
Mold/Pull rod: 500[22,23] Graphite heater: 740 Cooling zone enclosure temperature: 20 ℃
Mold/Liquid Ga-In-Sn alloy: 2000 Pull rod: 20 Cooling zone enclosure emissivity: 0[23]
Mold emissivity: 0.7[23,24]
表1  Bridgman定向凝固装置及试样模型的边界条件
Parameter Symbol Value Unit
Slope of liquidus line m -2.513 K%-1 (mass fraction)
Melting point Tm 629
Enthalpy ΔH 883.6 kJkg-1
Thermal conductivity κ 39 Wm-1K-1
Partition coefficient k 0.101
Diffusion coefficient D 1.233×10-9 cm2s-1
Gibbs-Thomson coefficient Γ 1.1×10-7 mK
表2  Mg-14.61Gd合金的热物性参数
Parameter Symbol Value Unit
Critical value of average nucleation supercooling degree ΔTˉ 6 K
Total supercooling degree ΔT 1 K
Maximum nucleation density nmax 5×107 m-2
Fitting polynomial coefficient a2 8.145×10-7 ms-1K-2
Fitting polynomial coefficient a3 5.871×10-7 ms-1K-3
表3  形核及简化KGT模型计算所用参数
图2  不同换热系数下Mg-14.61Gd合金在温度梯度G=30 K/mm和抽拉速率v=100 μm/s生长条件时的冷却曲线和凝固温度梯度
图3  G=30 K/mm、不同v下定向凝固Mg-14.61Gd合金的XRD谱
图4  G=30 K/mm、不同v下定向凝固Mg-14.61Gd合金横向及纵向显微组织的OM像
图5  G=30 K/mm、v=10 μm/s时定向凝固Mg-14.61Gd合金的晶粒组织、EBSD像及α-Mg相的反极图与极图
图6  G=30 K/mm、v=100 μm/s时定向凝固Mg-14.61Gd合金的晶粒组织、EBSD像及α-Mg相的反极图与极图
图7  G=30 K/mm、v=200 μm/s时定向凝固Mg-14.61Gd合金的晶粒组织、EBSD像及α-Mg相的反极图与极图
v Growth orientation of θ
μms-1 α-Mg dendrite
10 [112?0], [101?0] 11.0°
100 [112?0] 5.7°
200 [112?0] 10.6°
表4  采用EBSD方法测定的G=30 K/mm和不同v下定向凝固Mg-14.61Gd合金的α-Mg枝晶生长取向
图8  采用CAFE方法模拟得到的G=30 K/mm和不同v下定向凝固Mg-14.61Gd合金的晶粒组织和α-Mg相的<100>极图
v (φ1, Φ, φ2) Growth orientation of α
μms-1 α-Mg dendrite
10 (22.6, 148.3, 145.1) [2?111?] 10.886°
(283.9, 6.3, 284.8) [01?10]
40 (91.5, 73.8, 166.7) [1?1?20] 8.016°
(115.7, 141.9, 224.5) [3?122]
100 (261.9, 78.7, 277.4) [12?10] 6.709°
(87.2, 158.3, 86.1) [12?10]
150 (275.7, 90.8, 273.8) [12?10] 8.835°
(261.8, 78.7, 277.3) [12?10]
200 (277.8, 62.2, 95.8) [12?10] 10.167°
(52.56, 8.6, 303.2) [12?10]
表5  采用CAFE方法模拟得到的G=30 K/mm时不同v下定向凝固Mg-14.61Gd合金的α-Mg枝晶生长取向
图9  Mg-14.61Gd合金晶粒生长取向偏差随v的变化曲线
图10  枝晶生长取向、最优长大方向与热流方向之间的关系示意图
[1] Mordike B L, Ebert T.Magnesium: Properties-applications-potential[J]. Mater. Sci. Eng., 2001, A302: 37
[2] Gao L, Chen R S, Han E H.Effects of rare-earth elements Gd and Y on the solid solution strengthening of Mg alloys[J]. J. Alloys Compd., 2009, 481: 379
doi: 10.1016/j.jallcom.2009.02.131
[3] Jie Y, Wang L D, Wang L M, et al.Microstructures and mechanical properties of the Mg-4.5Zn-xGd (x=0, 2, 3 and 5) alloys[J]. J. Alloys Compd., 2008, 459: 274
doi: 10.1016/j.jallcom.2007.05.044
[4] Zheng X W, Luo A A, Zhang C, et al.Directional solidification and microsegregation in a magnesium-aluminum-calcium alloy[J]. Metall. Mater. Trans., 2012, 43A: 3239
doi: 10.1007/s11661-012-1159-8
[5] Asta M, Beckermann C, Karma A, et al.Solidification microstructures and solid-state parallels: Recent developments, future directions[J]. Acta Mater., 2009, 57: 941
doi: 10.1016/j.actamat.2008.10.020
[6] Zou M Q, Huang C Q, Xia W J, et al.Study on the crystal orientations and mechanical properties of AZ31 magnesium alloy produced by directional solidification[J]. Foundry, 2006, 55: 890(邹敏强, 黄长清, 夏伟军等. 定向凝固AZ31镁合金晶粒取向及力学性能研究[J]. 铸造, 2006, 55: 890)
doi: 10.3321/j.issn:1001-4977.2006.09.004
[7] Pettersen K, Ryum N.Crystallography of directionally solidified magnesium alloy AZ91[J]. Metall. Trans., 1989, 20A: 847
doi: 10.1007/BF02651651
[8] Jing T, Shuai S S, Wang M Y, et al.Research progress on 3D dendrite morphology and orientation selection during the solidification of Mg alloys: 3D experimental characterization and phase field modeling[J]. Acta Matell. Sin., 2016, 52: 1279(荆涛, 帅三三, 汪明月等. 镁合金凝固过程三维枝晶形貌和生长取向研究进展: 三维实验表征和相场模拟[J]. 金属学报, 2016, 52: 1279
doi: 10.11900/0412.1961.2016.00323
[9] Wang M Y, Xu Y J, Jing T, et al.Growth orientations and morphologies of α-Mg dendrites in Mg-Zn alloys[J]. Scr. Mater., 2012, 67: 629
doi: 10.1016/j.scriptamat.2012.07.031
[10] Yang X L, Dong H B, Wang W, et al.Microscale simulation of stray grain formation in investment cast turbine blades[J]. Mater. Sci. Eng., 2004, A386: 129
doi: 10.1016/j.msea.2004.07.007
[11] Ramirez A, Carrillo F, Gonzalez J L, et al.Stochastic simulation of grain growth during continuous casting[J]. Mater. Sci. Eng. 2006, A421: 208
doi: 10.1016/j.msea.2006.01.077
[12] Rappaz M, Gandin C A.Probabilistic modelling of microstructure formation in solidification processes[J]. Acta Metall. Mater., 1993, 41: 345
doi: 10.1179/imr.1989.34.1.93
[13] Gandin C A, Rappaz M.A coupled finite element-cellular automaton model for the prediction of dendritic grain structures in solidification processes[J]. Acta Metall. Mater., 1994, 42: 2233
doi: 10.1016/0956-7151(94)90302-6
[14] Kermanpur A, Mehrara M, Varahram N, et al.Improvement of grain structure and mechanical properties of a land based gas turbine blade directionally solidified with liquid metal cooling process[J]. Mater. Sci. Technol., 2008, 24: 100
doi: 10.1179/174328407X239109
[15] Takatani H, Gandin C A, Rappaz M.EBSD characterisation and modelling of columnar dendritic grains growing in the presence of fluid flow[J]. Acta Mater., 2000, 48: 675
doi: 10.1016/S1359-6454(99)00413-9
[16] Carozzani T, Digonnet H, Gandin C.3D CAFE modeling of grain structures: Application to primary dendritic and secondary eutectic solidification[J]. Modell. Simul. Mater. Sci. Eng., 2012, 20: 15010
doi: 10.1088/0965-0393/20/1/015010
[17] Wang M Y, Williams J J, Jiang L, et al.Dendritic morphology of α-Mg during the solidification of Mg-based alloys: 3D experimental characterization by X-ray synchrotron tomography and phase-field simulations[J]. Scr. Mater., 2011, 65: 855
doi: 10.1016/j.scriptamat.2011.07.040
[18] Böttger B, Eiken J, Ohno M, et al.Controlling microstructure in magnesium alloys: A combined thermodynamic, experimental and simulation approach[J]. Adv. Eng. Mater., 2006, 8: 241
[19] Yuan X F, Ding Y T, Guo T B, et al.Numerical simulation of dendritic growth of magnesium alloys using phase-field method under forced flow[J]. Chin. J. Nonferrous Met., 2010, 20: 1474(袁训锋, 丁雨田, 郭廷彪等. 强制对流作用下镁合金枝晶生长的相场法数值模拟[J]. 中国有色金属学报, 2010, 20: 1474)
[20] Liu Z Y, Xu Q Y, Liu B C.Modeling of dendrite growth for the cast magnesium alloy[J]. Acta Matell. Sin., 2007, 43: 367(刘志勇, 许庆彦, 柳百成. 铸造镁合金的枝晶生长模拟[J]. 金属学报, 2007, 43: 367)
doi: 10.3321/j.issn:0412-1961.2007.04.007
[21] Liu S J, Yang G Y, Jie W Q.Microstructure, microsegregation, and mechanical properties of directional solidified Mg-3.0Nd-1.5Gd Alloy[J]. Acta Metall. Sin.(Engl. Lett.), 2014, 27: 1134
doi: 10.1007/s40195-014-0151-2
[22] Matache G, Stefanescu D M, Puscasu C, et al.Investigation of solidification microstructure of single crystal CMSX-4 superalloy—Experimental measurements and modelling predictions[J]. Int. J. Cast Met. Res., 2015, 28: 323
doi: 10.1179/1743133615Y.0000000021
[23] ESI Software Inc.PROCAST User's Manual and Technical Reference. Version 3.1.1, 2008
[24] Elliott A J, Pollock T M.Thermal analysis of the Bridgman and liquid-metal-cooled directional solidification investment casting processes[J]. Metall. Mater. Trans., 2007, 38A: 871
doi: 10.1007/s11661-006-9085-2
[25] Pang R P, Wang F M, Zhang G Q, et al.Study of solidification thermal parameters of 430 ferrite stainless steel based on 3D-CAFE method[J]. Acta Metall. Sin., 2013, 49: 1234(庞瑞朋, 王福明, 张国庆等. 基于3D-CAFE法对430铁素体不锈钢凝固热参数的研究[J]. 金属学报, 2013, 49: 1234)
doi: 10.3724/SP.J.1037.2013.00288
[26] Wang J H, Yang G Y, Liu S J, et al.Microstructure and room temperature mechanical properties of directionally solidified Mg-2.35Gd magnesium alloy[J]. Trans. Nonferrous Met. Soc. China, 2016, 26: 1294
doi: 10.1016/S1003-6326(16)64231-0
[27] Ma J, Wang B, Zhao S L, et al.Incorporating an extended dendritic growth model into the CAFE model for rapidly solidified non-dilute alloys[J]. J. Alloys Compd., 2016, 668: 46
doi: 10.1016/j.jallcom.2016.01.210
[28] Kurz W, Giovanola B, Trivedi R.Theory of microstructural development during rapid solidification[J]. Acta Metall., 1986, 34: 823
doi: 10.1016/0001-6160(86)90056-8
[29] Gandin C A, Rappaz M, Tintillier R.3-Dimensional simulation of the grain formation in investment castings[J]. Metall. Mater. Trans., 1994, 25A: 629
doi: 10.1007/BF02651604
[30] Wang Y N, Huang J C.Texture analysis in hexagonal materials[J]. Mater. Chem. Phys., 2003, 81: 11
doi: 10.1016/S0254-0584(03)00168-8
[31] Wang J A, Shi Y, Zhang J W.Microstructure and micro segregation of Mg-1.5Gd alloy under directional solidification station[J]. Heat Treat. Met., 2015, 40(7): 115(王甲安, 石岩, 张锦文. 定向凝固下Mg-1.5Gd合金的微观结构与微观偏析[J]. 金属热处理, 2015, 40(7): 115)
doi: 10.13251/j.issn.0254-6051.2015.07.027
[32] Peng Q M, Ma N, Li H.Gadolinium solubility and precipitate identification in Mg-Gd binary alloy[J]. J. Rare Earth, 2012, 30: 1064
doi: 10.1016/S1002-0721(12)60179-3
[33] Pettersen K, Lohne O, Ryum N.Dendritic solidification of magnesium alloy AZ91[J]. Metall. Trans., 1990, 21A: 221
doi: 10.1007/BF02656439
[34] Bei H, George E P, Kenik E A, et al.Directional solidification and microstructures of near-eutectic Cr-Cr3Si alloys[J]. Acta Mater., 2003, 51: 6241
doi: 10.1016/S1359-6454(03)00447-6
[35] Luo S F, Yang G Y, Liu S J, et al.Microstructure evolution and mechanical properties of directionally solidified Mg-xGd (x=0.8, 1.5, and 2.5) alloys[J]. Mater. Sci. Eng., 2016, A662: 241
doi: 10.1016/j.msea.2016.03.065
[36] Xiao Z X, Zheng L J, Yang L L, et al.Effects of temperature gradient on lamellar orientations of directional solidified TiAl-based alloy[J]. Acta Matell. Sin., 2010, 46: 1223(肖志霞, 郑立静, 杨莉莉等. 温度梯度对定向凝固TiAl基合金片层取向的影响[J]. 金属学报, 2010, 46: 1223)
doi: 10.3724/sp.j.1037.2010.00308
[1] 方辉,薛桦,汤倩玉,张庆宇,潘诗琰,朱鸣芳. 定向凝固糊状区枝晶粗化和二次臂迁移的实验和模拟[J]. 金属学报, 2019, 55(5): 664-672.
[2] 唐文书,肖俊峰,李永君,张炯,高斯峰,南晴. 再热恢复处理对蠕变损伤定向凝固高温合金γ′相的影响[J]. 金属学报, 2019, 55(5): 601-610.
[3] 刘晏宇, 毛萍莉, 刘正, 王峰, 王志. Schmid因子的理论计算及其在镁合金高速变形过程中的应用[J]. 金属学报, 2018, 54(6): 950-958.
[4] 鲍思前, 刘兵兵, 赵刚, 徐洋, 柯珊珊, 胡晓, 刘磊. Hi-B钢二次再结晶退火中异常长大Goss取向晶粒的三维形貌表征[J]. 金属学报, 2018, 54(6): 877-885.
[5] 康慧君, 李金玲, 王同敏, 郭景杰. 定向凝固Al-Mn-Be合金初生金属间化合物相生长行为及力学性能[J]. 金属学报, 2018, 54(5): 809-823.
[6] 侯渊, 任忠鸣, 王江, 张振强, 李霞. 纵向静磁场对定向凝固GCr15轴承钢柱状晶向等轴晶转变的影响[J]. 金属学报, 2018, 54(5): 801-808.
[7] 李言祥, 刘效邦. 定向凝固多孔金属研究进展[J]. 金属学报, 2018, 54(5): 727-741.
[8] 陈光, 郑功, 祁志祥, 张锦鹏, 李沛, 成家林, 张中武. 受控凝固及其应用研究进展[J]. 金属学报, 2018, 54(5): 669-681.
[9] 王锦程, 郭春文, 李俊杰, 王志军. 定向凝固晶粒竞争生长的研究进展[J]. 金属学报, 2018, 54(5): 657-668.
[10] 苏彦庆, 刘桐, 李新中, 陈瑞润, 郭景杰, 傅恒志. 籽晶法定向凝固TiAl基合金片层取向控制[J]. 金属学报, 2018, 54(5): 647-656.
[11] 吴国华, 陈玉狮, 丁文江. 高性能镁合金凝固组织控制研究现状与展望[J]. 金属学报, 2018, 54(5): 637-646.
[12] 刘林, 孙德建, 黄太文, 张琰斌, 李亚峰, 张军, 傅恒志. 高梯度定向凝固技术及其在高温合金制备中的应用[J]. 金属学报, 2018, 54(5): 615-626.
[13] 张洪伟,秦学智,李小武,周兰章. 一种高硼定向凝固合金的初熔行为及其对力学性能的影响[J]. 金属学报, 2017, 53(6): 684-694.
[14] 徐洋,鲍思前,赵刚,黄祥斌,黄儒胜,刘兵兵,宋娜娜. Hi-B钢二次再结晶退火初期不同取向晶粒的三维形貌表征[J]. 金属学报, 2017, 53(5): 539-548.
[15] 余建波, 侯渊, 张超, 杨志彬, 王江, 任忠鸣. 静磁场对新型Co-Al-W基高温合金定向凝固组织的影响[J]. 金属学报, 2017, 53(12): 1620-1626.