Please wait a minute...
金属学报  2018, Vol. 54 Issue (2): 339-346    DOI: 10.11900/0412.1961.2017.00420
  本期目录 | 过刊浏览 |
LZ91 Mg-Li合金分流模挤压成形过程数值模拟与实验研究
陈良, 赵国群(), 陈高进, 梁赵青, 张存生
山东大学液固结构演变与加工教育部重点实验室 济南 250061
Numerical Simulation and Experimental Study on Porthole Die Extrusion Process of LZ91 Mg-Li Alloy
Liang CHEN, Guoqun ZHAO(), Gaojin CHEN, Zhaoqing LIANG, Cunsheng ZHANG
Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jinan 250061, China
全文: PDF(6394 KB)   HTML
摘要: 

建立了LZ91 Mg-Li合金分流模挤压过程的有限元模拟模型,研究了挤压比对型材挤压过程中温度、应变、流动速度等物理场量的影响规律,采用J准则对型材的焊合质量进行了定量分析,并开展了不同挤压比条件下的分流模挤压实验,研究了铸造态、均热态、挤压态LZ91 Mg-Li合金的微观组织特点。结果表明,在分流桥表面及其下部的材料处于大变形区,分流孔内部的材料处于小变形区,且随挤压比增加,材料的应变整体上升。受塑性变形热和型材冷却散热等因素的影响,分流桥上端材料的温度升高,但越靠近模具出口处,材料的温度越低。焊合质量受多种因素的影响,焊缝中心位置处的焊合质量低于焊缝边缘处,而随着挤压比的增大,焊合质量得到改善。焊缝区由于应变较大,其再结晶形核数量多,生成的晶粒较细小,而基体区因动态再结晶不够充分,其晶粒比较粗大。当挤压比增大时,由于温度升高,还发生了晶粒长大现象。

关键词 Mg-Li合金分流模挤压比焊合质量    
Abstract

Porthole die extrusion is the dominant process to produce hollow profiles due to its high productivity and capacity in producing complex profiles. In this study, the finite element simulation model of porthole die extrusion of LZ91 Mg-Li alloy was established. The effects of extrusion ratio on strain, temperature and flow velocity were studied, and the welding quality was quantitatively evaluated by means of J criterion. The experiments of porthole die extrusion were carried out by varying extrusion ratios. The microstructures of as-cast, homogenized and extruded LZ91 Mg-Li alloy were examined. The results show that the materials near the bridge surface and at the bottom of the bridge have large deformation, while the materials inside the portholes have small deformation. Moreover, with the increase of extrusion ratio, the effective strain of material is increased. Due to the heat generated by plastic deformation and the heat dissipation caused by profile cooling, the temperature of the material on the top of bridge is increased, while that of the material near the die exit becomes lower. The welding quality in the central area of weld seam is lower than that in the edge area of weld seam. With the increase of extrusion ratio, the welding quality is improved. More nucleation is generated in welding zone due to its large strain, resulting in the formation of fine grains. However, the dynamic recrystallization is not complete in the matrix zone, and some coarse grains still remain. Moreover, the material temperature becomes higher with high extrusion ratio, and the phenomenon of grain growth is observed.

Key wordsMg-Li alloy    porthole die    extrusion ratio    welding quality
收稿日期: 2017-10-10      出版日期: 2017-11-09
基金资助:国家自然科学基金项目Nos.51405268和51375270及山东大学交叉学科培育项目No.2017JC005
作者简介:

作者简介 陈 良,男,1985年生,副教授,博士

引用本文:

陈良, 赵国群, 陈高进, 梁赵青, 张存生. LZ91 Mg-Li合金分流模挤压成形过程数值模拟与实验研究[J]. 金属学报, 2018, 54(2): 339-346.
Liang CHEN, Guoqun ZHAO, Gaojin CHEN, Zhaoqing LIANG, Cunsheng ZHANG. Numerical Simulation and Experimental Study on Porthole Die Extrusion Process of LZ91 Mg-Li Alloy. Acta Metall Sin, 2018, 54(2): 339-346.

链接本文:

http://www.ams.org.cn/CN/10.11900/0412.1961.2017.00420      或      http://www.ams.org.cn/CN/Y2018/V54/I2/339

图1  LZ91 Mg-Li合金分流模挤压过程数值建模
Material Young's modulus Poisson's ratio Thermal conductivity Heat capacity
Pa Wm-1-1 Jkg-1-1
LZ91 42 0.29 80.0 1340
H13 210 0.30 28.4 460
表1  LZ91合金和H13钢的物理参数
图2  模具型腔内材料的应变分布
图3  型材不同位置处的等效应变分布
图4  模具型腔内材料的温度分布
图5  焊合面上的静水压力分布
图6  焊合面上的流动速度分布
图7  焊缝不同位置的J值计算结果
图8  LZ91 Mg-Li合金显微组织OM像
图9  铸造态和均热态LZ91 Mg-Li合金XRD谱
图10  挤压态LZ91 Mg-Li合金基体区与焊合区的微观组织
[1] Li R H, Pan F S, Jiang B, et al.Effect of Li addition on the mechanical behavior and texture of the as-extruded AZ31 magnesium alloy[J]. Mater. Sci. Eng., 2013, A562: 33
[2] He J J, Jiang B, Yu X W, et al.Strain path dependence of texture and property evolutions on rolled Mg-Li-Al-Zn alloy possessed of an asymmetric texture[J]. J. Alloys Compd., 2017, 698: 771
[3] Yang Y, Peng X D, Ren F J, et al.Constitutive modeling and hot deformation behavior of duplex structured Mg-Li-Al-Sr alloy[J]. J. Mater. Sci. Technol., 2016, 32: 1289
[4] Ahn K, Lee H J, Yoon J.Material model for dynamic recrystallization of Mg-8Al-0.5Zn alloy under uni-axial compressive deformation with variation of forming temperatures[J]. Mater. Sci. Eng., 2016, A651: 1010
[5] Fatemi-Varzaneh S M, Zarei-Hanzaki A, Beladi H. Dynamic recrystallization in AZ31 magnesium alloy[J]. Mater. Sci. Eng., 2007, A456: 52
[6] Zhang Z R, Yang X Y, Xiao Z Y, et al.Dynamic recrystallization behaviors of a Mg-4Y-2Nd-0.2Zn-0.5Zr alloy and the resultant mechanical properties after hot compression[J]. Mater. Des., 2016, 97: 25
[7] Kim S H, You B S, Park S H.Effect of billet diameter on hot extrusion behavior of Mg-Al-Zn alloys and its influence on microstructure and mechanical properties[J]. J. Alloys Compd., 2017, 690: 417
[8] He X, Zhou J, Li L X, et al.FE analysis and solution of wall thickness attenuation during extrusion to produce a complex hollow magnesium profile[J]. J. Plast. Eng., 2010, 17(2): 62(何芯, 周佳, 李落星等. 镁合金薄壁空心型材挤压壁厚减薄问题的有限元分析及解决方案[J]. 塑性工程学报, 2010, 17(2): 62)
[9] Zhang B J, Yang H, Guo L G, et al.Numerical simulation of effect rules of porthole axial angle on extrusion process of AZ31 Mg alloy thin-walled tube[J]. Chin. J. Nonferrous Met., 2012, 22: 2713(张保军, 杨合, 郭良刚等. AZ31镁合金薄壁管挤压分流孔轴向倾角影响规律的仿真模拟[J]. 中国有色金属学报, 2012, 22: 2713)
[10] Liu G, Zhou J, Duszczyk J.FE analysis of metal flow and weld seam formation in a porthole die during the extrusion of a magnesium alloy into a square tube and the effect of ram speed on weld strength[J]. J. Mater. Process. Technol., 2008, 200: 185
[11] Hsiang S L, Lin Y W. Investigation of the influence of process parameters on hot extrusion of magnesium alloy tubes [J]. J. Mater. Process. Technol., 2007, 192-193: 292
[12] Huang D N, Zhang Z H, Li J Y, et al.Influences of welding chamber depth and welding angle on forming quality of extrusion of square tube by porthole die[J]. Chin. J. Nonferrous Met., 2010, 20: 954(黄东男, 张志豪, 李静媛等. 焊合室深度及焊合角对方形管分流模挤压成形质量的影响[J]. 中国有色金属学报, 2010, 20: 954)
[13] Donati L, Tomesani L. The effect of die design on the production and seam weld quality of extruded aluminum profiles [J]. J. Mater. Process. Technol., 2005, 164-165: 1025
[14] Jo H H, Jeong C S, Lee S K, et al.Determination of welding pressure in the non-steady-state porthole die extrusion of improved Al7003 hollow section tubes[J]. J. Mater. Process. Technol., 2003, 139: 428
[15] Jo H H, Lee S K, Jung C S, et al.A non-steady state FE analysis of Al tubes hot extrusion by a porthole die[J]. J. Mater. Process. Technol., 2006, 173: 223
[16] Zhang C S, Zhao G Q, Chen H, et al.Optimization of an aluminum profile extrusion process based on Taguchi's method with S/N analysis[J]. Int. J. Adv. Manuf. Technol., 2012, 60: 589
[17] Yu J Q, Zhao G Q, Chen L.Investigation of interface evolution, microstructure and mechanical properties of solid-state bonding seams in hot extrusion process of aluminum alloy profiles[J]. J. Mater. Process. Technol., 2016, 230: 153
[18] Yu J Q, Zhao G Q, Chen L.Analysis of longitudinal weld seam defects and investigation of solid-state bonding criteria in porthole die extrusion process of aluminum alloy profiles[J]. J. Mater. Process. Technol., 2016, 237: 31
[19] Chen G J, Chen L, Zhao G Q, et al.Investigation on longitudinal weld seams during porthole die extrusion process of high strength 7075 aluminum alloy[J]. Int. J. Adv. Manuf. Technol., 2017, 91: 1897
[20] Yu J Q, Zhao G Q, Zhang C S, et al.Dynamic evolution of grain structure and micro-texture along a welding path of aluminum alloy profiles extruded by porthole dies[J]. Mater. Sci. Eng., 2017, A682: 679
[21] Schikorra M, Donati L, Tomesani L, et al.The role of friction in the extrusion of AA6060 aluminum alloy, process analysis and monitoring[J]. J. Mater. Process. Technol., 2007, 191: 288
[22] Jia Y X, Huang J L, Feng J.Hot deformation behavior of Mg-8Li-2Al-1Zn alloy[J]. Trans. Mater. Heat Treat., 2014, 35(9): 210(贾玉鑫, 黄金亮, 冯剑. Mg-8Li-2Al-1Zn合金的热变形行为[J]. 材料热处理学报, 2014, 35(9): 210)
[23] Akeret R.Properties of pressure welds in extruded aluminium alloy sections[J]. J. Inst. Met., 1972, 10: 202
[24] Donati L, Tomesani L. The prediction of seam welds quality in aluminum extrusion [J]. J. Mater. Process. Technol., 2004, 153-154: 366
[25] Xu T C, Peng X D, Qin J, et al.Dynamic recrystallization behavior of Mg-Li-Al-Nd duplex alloy during hot compression[J]. J. Alloys Compd., 2015, 639: 79
[26] Gasior W, Moser Z, Zakulski W, et al.Thermodynamic studies and the phase diagram of the Li-Mg system[J]. Metall. Mater. Trans., 1996, 27A: 2419
[27] Chang T C, Wang J Y, Chu C L, et al.Mechanical properties and microstructures of various Mg-Li alloys[J]. Mater. Lett., 2006, 60: 3272
[1] 崔崇亮,朱天龙,冷哲,巫瑞智,张景怀,张密林. 复合添加Y和Nd对Mg-Li合金显微组织及室温压缩织构的影响[J]. 金属学报, 2012, 48(6): 725-732.