电脉冲作用下铝铜合金铸造织构转变及其对耐蚀性的影响

发布时间：2018-05-04 03:03

本文选题：电脉冲处理 + 铝铜合金　；参考：《辽宁工业大学》2015年硕士论文

【摘要】：Al-Cu合金以其铸态下优良的耐热性，及良好的机械性能与工艺性能在生产中广泛应用。但其存在晶间耐蚀性较差的缺点，会使金属的物理性能急剧下降，造成严重的安全隐患。因此，研究电脉冲作用下Al-Cu合金铸造织构的转变机理及其对耐蚀性的影响，揭示其作用本质，对于该类材料的使用以及提高材料的性能有着极为重要的意义。本文以Al-5%Cu合金为研究对象，分别进行熔体电脉冲处理和液固两相区电脉冲处理，观察和分析合金的宏观组织，使用X-射线衍射仪检测其织构，研究电脉冲对其铸态织构的影响，最后采用电化学工作站检测其耐蚀性，通过铸态织构的变化探讨熔体电脉冲处理对耐蚀性的间接影响。通过分析实验现象，解释了脉冲电磁场和温度场对柱状晶生长的影响机理。实验结果表明，（1）熔体电脉冲处理时，随着脉冲电压的升高，宏观组织内柱状晶的出现与否具有周期性；随着脉冲频率的增大，柱状晶区域逐渐减小，当频率为15Hz时，柱状晶消失，试样组织中全部为细小的等轴晶。（2）液固两相区电脉冲处理主要有两方面影响：一方面会使表层晶粒平整；另一方面，电脉冲会缩小柱状晶区，并降低内部等轴晶的尺度。（3）熔体电脉冲处理会对Al-5%Cu合金的铸造织构产生重要影响，在温度场与脉冲电磁场的耦合作用下，常温金属型冷却条件下，，电脉冲对柱状晶生长的抑制效果显著，而500℃条件下，其抑制效果消失。整体来看，随着温度场的减弱，织构的总体积分数逐渐减小。（4）电脉冲对Al-5%Cu合金耐蚀性的影响显著，通过改善Cu原子的偏析，显著改善合金的耐蚀性；随着温度场作用的减弱，电脉冲对合金耐蚀性的改善效果逐渐增强。
[Abstract]:Al-Cu alloy is widely used in production for its excellent heat resistance and good mechanical and technological properties in its cast state. However, the poor corrosion resistance of the alloys will lead to a sharp decline in the physical properties of metals and cause serious safety problems. Therefore, the study of the transformation mechanism of the Al-Cu alloy casting texture and its pair is studied. The influence of corrosion resistance reveals the nature of its action, which is of great importance for the use of such materials and the improvement of the properties of materials.
In this paper, the Al-5%Cu alloy was taken as the research object, the melt electric pulse treatment and the liquid solid two phase region electric pulse processing respectively, the macroscopic microstructure of the alloy was observed and analyzed, the texture of the alloy was detected by the X- ray diffractometer, and the influence of the electric pulse on its as cast texture was studied. Finally, the corrosion resistance of the alloy was detected by the electrochemical workstation. The indirect effect of melt electric pulse treatment on corrosion resistance was discussed.
By analyzing the experimental phenomena, the influence mechanism of pulsed electromagnetic field and temperature field on columnar crystal growth is explained. The experimental results show that (1) when the melt electric pulse is treated, with the increase of the pulse voltage, the appearance of the columnar crystal in the macrostructure is periodic. With the increase of the pulse frequency, the columnar crystal gradually decreases, when the frequency is 15Hz When the columnar crystal disappears, the specimen microstructure is all fine equiaxed grains. (2) the electrical pulse treatment in the liquid solid two phase region has two main effects: on one hand it will make the surface grain smooth; on the other hand, the electric pulse will narrow the columnar crystal region and reduce the scale of the internal equiaxed grains. (3) the melt electrical pulse treatment will produce the casting texture of Al-5%Cu alloy. Under the interaction of temperature field and pulsed electromagnetic field, under the condition of metal cooling at normal temperature, the inhibition effect of electric pulse on columnar crystal growth is remarkable, and the inhibition effect is disappearing at 500. As a whole, the overall integral number of the texture decreases with the decrease of temperature field. (4) the corrosion resistance of Al-5%Cu alloy by electric pulse The corrosion resistance of the alloy was greatly improved by improving the segregation of Cu atoms. With the weakening of the temperature field, the effect of electric pulse on the corrosion resistance of the alloy was gradually improved.

【学位授予单位】：辽宁工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG290

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