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金属学报  2016, Vol. 52 Issue (5): 632-640    DOI: 10.11900/0412.1961.2015.00492
  论文 本期目录 | 过刊浏览 |
基于Thermo-Calc和微观偏析统一模型对Al-6.32Cu-25.13Mg合金凝固路径的预测*
闫二虎1,2(),孙立贤1,徐芬1,徐达鸣2
1 桂林电子科技大学材料科学与工程学院, 桂林 541004
2 哈尔滨工业大学材料科学与工程学院, 哈尔滨 150001
PREDICTION OF THE SOLIDIFICATION PATH OF Al-6.32Cu-25.13Mg ALLOY BY A UNIFIED MICROSEGREGATION MODEL COUPLED WITH THERMO-CALC
Erhu YAN1,2(),Lixian SUN1,Fen XU1,Daming XU2
1 School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, China
2 School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China
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摘要: 

采用微观偏析统一模型并耦合Thermo-Calc研究了Al-6.32Cu-25.13Mg (质量分数, %)合金在不同冷却速率Rf和固相反扩散系数Φ下的凝固路径. 结果表明: 冷却速率对合金的凝固路径影响较小, 即不同冷却速率下合金的凝固路径均为: (L+α)→(L+α+T)→(L+α+β+T); 固相反扩散系数对合金的凝固路径影响较大, 当Φ由0逐渐增大至1时, 合金的凝固路径由(L+α)→(L+α+T)→(L+α+β+T)逐渐过渡为(L+α)→(L+α+T); 随着Rf的降低, 显微组织中初生相体积分数Vα基本不变, 两相共晶体积分数V2E增大而三相共晶体积分数V3E减少, 上述参数满足: V2E=-2.5lgRf+64.9, V3E=2.5lgRf+22.12, Φ的增加使得显微组织中的VαV2E变大而V3E变小. 结合实验研究了Al-6.32Cu-25.13Mg合金在上述不同冷却速率下的凝固路径及各相体积分数, 结果显示, 实验结果与模拟结果吻合较好.

关键词 Al-Cu-Mg三元共晶合金凝固路径微观偏析统一模型Thermo-Calc    
Abstract

The solidification path of alloy reveals the detailed relationship between the solute concentration in liquid and the temperature during the solidification process. The best and most accurate method to predict the solidification path of multicomponent/multiphase alloys is to establish proper microsegregation modeling coupled with phase diagram calculations according to the CALPHAD method. Recently, several alloy systems such as Al-Cu, Al-Mg and Cu-Mg have been developed, which have aroused the interest of many researchers. Up to now, the research about Al-Cu-Mg ternary alloy, especially containing higher Mg content, is relatively rare. The purpose of the present work is to investigate the solidification path of Al-6.32Cu-25.13Mg (mass fraction, %) ternary eutectic alloy at different cooling rates and solid back diffusion coefficients by an extended unified microsegregation model coupled with Thermo-Calc. Solidification experiments and subsequent microstructural characterization are combined with numerical calculation of solidification paths. It was shown that the cooling rates Rf had no obvious effect on the solidification path which was (L+α)→(L+α+T)→(L+α+β+T); but the solid back diffusion coefficient Φ had a great effect on the solidification path, which evolved gradually from (L+α)→(L+α+T)→(L+α+β+T) into (L+α)→(L+α+T) when Φ increased from 0 to 1. The volume fractions of primary α phase Vα, binary eutectic V2E and ternary eutectic V3E at each solidification path were calculated. It was shown that V2E decreased with the increase of Rf whereas V3E increased and Vα was almost invariant. The dependence of V2E, V3E and Rf were determined by linear regression analysis given as: V2E=-2.5lgRf+64.9, V3E=2.5lgRf+22.12. The increase in Φ led to increases in Vα and V2E and decrease in V3E. The predicted solidification paths and volume fractions of Al-6.32Cu-25.13Mg ternary eutectic alloy at different cooling rates were in good agreement with experimental results.

Key wordsAl-Cu-Mg ternary alloy    solidification path    microsegregation model    Thermo-Calc
收稿日期: 2015-09-18      出版日期: 2016-03-16
基金资助:*国家自然科学基金项目51361005, 广西自然科学基金项目2015GXNSFBA139208, 2014GXNSFDA118005和UF14023Y及广西信息材料重点实验室项目1210908-217-Z资助

引用本文:

闫二虎,孙立贤,徐芬,徐达鸣. 基于Thermo-Calc和微观偏析统一模型对Al-6.32Cu-25.13Mg合金凝固路径的预测*[J]. 金属学报, 2016, 52(5): 632-640.
Erhu YAN,Lixian SUN,Fen XU,Daming XU. PREDICTION OF THE SOLIDIFICATION PATH OF Al-6.32Cu-25.13Mg ALLOY BY A UNIFIED MICROSEGREGATION MODEL COUPLED WITH THERMO-CALC. Acta Metall, 2016, 52(5): 632-640.

链接本文:

http://www.ams.org.cn/CN/10.11900/0412.1961.2015.00492      或      http://www.ams.org.cn/CN/Y2016/V52/I5/632

图1  Al-Cu-Mg三元合金相图[25]及Al-6.32Cu-25.13Mg合金在相图中的位置
图2  微观偏析数值模型示意图
图3  不同冷却速率下Al-6.32Cu-25.13Mg合金凝固路径的计算结果
Parameter Value Literature
Solidification shrinkage 0.043 [19]
Distance of secondary dendrite / mm 0.1 Calculated
DCuα/ (mm2s-1) 29exp(-15600/T) [20]
DMgα/ (mm2s-1) 37exp(-14900/T) [20]
Rf 0.08 Calculated
Step length of α ΔfS 0.0025 Initial value
Step length of binary eutectic ΔT / ℃ 0.25 Initial value
表1  凝固路径模拟计算中所用参数
图4  两相共晶组织体积分数和三相共晶组织体积分数与凝固速率关系曲线
图5  不同固相反扩散系数Φ下Al-6.32Cu-25.13Mg合金凝固路径的计算结果
图6  Al-6.32Cu-25.13Mg三元合金凝固过程中CL-fS曲线
图7  Al-6.32Cu-25.13Mg三元合金在4种不同铸型中的凝固冷却曲线
图8  Al-6.32Cu-25.13Mg合金在4种冷却速率下显微组织的SEM像
Mold Cooling rate
℃s-1
Primary phase α-Al Binary eutectic Ternary eutectic
Calculated Measured Calculated Measured Calculated Measured
Graphite mold 0.1 13.2 15.1 66.8 68.2 20.0 16.7
Sand mold 0.06 13.3 14.7 69.6 70.1 17.1 15.2
Insulated mold 0.005 13.2 14.5 71.6 72.8 15.2 12.7
Constant temperature mold 0.0007 13.2 14.1 75.1 76.7 11.7 9.2
表2  不同冷却速率下Al-6.32Cu-25.13Mg合金初生相、两相共晶及三相共晶体积分数对比
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