Formation and Controlling of Central-Line Segregation in Magnesium Alloy Cast-Rolled Strip
摘 要
采用光学显微镜、扫描电镜等分析了镁合金铸轧板坯中心线偏析区域的显微组织与微区成分;用有限差分法模拟了镁合金铸轧过程中的凝固传热与流动过程;在此基础上分析了镁合金铸轧板坯中心线偏析的形成原因与抑制方法。结果表明:中心线偏析区域的铝、锌溶质元素富集,锰元素在该区域内贫化,该区域的显微组织由细小均匀的等轴晶组成;在铸轧过程中,镁合金熔体在轧辊表面形核,并沿传热方向形成发达的柱状晶,凝固界面发生溶质再分配,溶质在凝固前沿特别是在全凝固点富集,在后续轧制变形过程中形成中心线偏析;铸轧速度显著影响铸轧凝固传热与流动过程,调整铸轧速度将全凝固点位置控制在合理位置时,可利用供液端过热镁合金熔体引起的强迫流动,改善镁合金铸轧凝固过程中的溶质扩散条件,从而抑制中心线偏析的形成。
Abstract
The microstructure and micro-area chemical composition of central-line segregation in magnesium alloy cast-rolled strip were investigated by optical microscopy, scanning electron microscopy, etc. The heat transfer in solidification process and flow process were analyzed by finite difference method. Based on the above, the forming reasons and control method of central-line segregation in magnesium alloy cast-rolled strip were analyzed. The results indicate that solute elements of Al and Zn were enriched and Mn was diluted in the central-line segregation area. The area's microstructure was composed of equiaxed grains with fine size. During the casting and rolling process, magnesium alloy melt nucleated on the roll surface and formed developed columnar crystals along the heat transfer direction. Solute redistribution occurred at the solidification interface. The solute was enriched at the solidification front, particularly at the freezing point. Central-line segregation was formed during the subsequent rolling deformation process. The casting and rolling speed markedly affected the heat transfer and flow in solidification process. The central-line segregation could be controlled by adjusting casting and rolling speed to control the freezing point in a proper location because the overheated melts supplied by feed tip could caused the re-melt of the solidification front and the forced convection, and thus improved the diffusion condition of solute elements during the casting and rolling process.
中图分类号 TG292 DOI 10.11973/jxgccl201703015
所属栏目 物理模拟与数值模拟
基金项目 国家自然科学基金资助项目(51204115);江苏省自然科学基金资助项目(BK20151221)
收稿日期 2015/12/3
修改稿日期 2016/12/23
网络出版日期
作者单位点击查看
备注翁文凭(1978-),男,湖北仙桃人,副教授,博士。
引用该论文: WENG Wen-ping,QU Tian-peng,SHENG Min-qi,JI-fang,ZHOU Wei,WANG Jing. Formation and Controlling of Central-Line Segregation in Magnesium Alloy Cast-Rolled Strip[J]. Materials for mechancial engineering, 2017, 41(3): 73~78
翁文凭,屈天鹏,盛敏奇,许继芳,周巍,王璟. 镁合金铸轧板坯中心线偏析的形成与抑制[J]. 机械工程材料, 2017, 41(3): 73~78
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【2】WALDE T, RIEDEL H. Modeling texture evolution during hot rolling of magnesium alloy AZ31[J]. Materials Science and Engineering A, 2007, 443:277-284.
【3】刘龙飞, 姜炳春, 赵俊, 等. 冲击载荷下AZ31镁合金的变形行为和组织演变[J]. 机械工程材料, 2015, 39(1):24-28.
【4】LIANG D, COWLEY C B. The twin-roll strip casting of magnesium[J]. Journal of the Minerals, Metal & Materials Society, 2004, 56(5):26-28.
【5】孙述利, 张敏刚, 周俊琪, 等. AZ31镁合金在热压缩过程中的变形行为[J]. 机械工程材料, 2010, 34(8):88-90.
【6】HUANG M H, LI X Q, MAO D H, et al. Research and development of transnormal twin-roll casting technology[J]. Trans Nonferrous Met Soc China, 2003, 13(7):532-540.
【7】YUCEL B. Analysis of macro segregation in twin-roll cast aluminium strips via solidification curves[J]. Journal of Alloys and Compounds, 2009, 486:168-172.
【8】JIN I, MORRIS L R, HUNT J D. Centerline segregation in twin-roll-cast aluminum alloy slab[J]. Journal of Metals, 1982, 6:70-75.
【9】GRAS C, MEREDITH M, HUNT J D. Microstructure and texture evolution after twin roll casting and subsequent cold rolling of Al-Mg-Mn aluminium alloys[J]. Journal of Materials Processing Technology, 2005, 169:156-163.
【10】WATARI H, HAGA T, KOGA N, et al. Feasibility study of twin roll casting process for magnesium alloys[J]. Journal of Materials Processing Technology, 2007, 192/193:300-305.
【11】唐宁, 汪明朴, 娄花芬, 等. 双辊铸轧AZ31镁合金板坯的物相分析[J]. 中国有色金属学报, 2009, 19(3):433-438.
【12】黄志权, 黄庆学, 马立峰, 等. 宽幅AZ31B镁合金铸轧板显微组织和性能研究[J]. 材料研究学报, 2013, 27(3):292-298.
【13】翁文凭, 邓康, 任忠鸣, 等. 镁合金铸轧过程中表面点状偏析形成机制[J]. 稀有金属材料及工程, 2013, 42(10):2093-2096.
【14】HADADZADEH A,WELLS M A, JUNG I H. Scale-up modeling of the twin roll casting process for AZ31 magnesium alloy[J]. Journal of Manufacturing Processes, 2014, 16:468-478.
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