The Casting Texture Transformation For Al-Cu Alloy Modified By Electric Pulse And Its Effect On The Corrosion Resistance

The casting Al-Cu alloy has a wide application in production for its good heat resistant,mechanical properties and process performance in the as-cast condition. But its intergranularcorrosion resistance is so poor which will make the physical properties of metal decreasessharply, causing serious security hidden danger. Therefore, it’s very significant for the useand the improvement of the performance of this material to study on the transition mechanismof Al-Cu alloy casting texture under the electrical pulse modification (EP,EPM) and itsinfluence on corrosion resistance, as well as reveal its essential function.In this paper, Al-5%Cu alloy is used as experimental samples, which were modifiedrespectively by electric pulse in melt and mushy zone. And then the macrostructure of thisalloy was observed and its texture polarization was also tested by XRD to study the effect ofelectric pulse on its texture. Finally, its corrosion resistance was tested by theelectronchemical workstation to investigate the indirect effect of electric pulse on corrosionresistance by changing the texture of melt.Through the analysis of the experimental phenomenon, the influence mechanism of thepulse electromagnetic field and temperature field on the growth of columnar crystal wasexplained. The results show that,(1) With the increase of pulse voltage,when the alloy ismodificated in melt, the columnar crystalsin macrostructure appears periodically. With theincrease of frequency, the columnar region gradually decreases, when the frequency is15Hz,the columnar crystal disappears and the macrostructure is full of fine equiaxed grains.(2)Electric pulse modification in mushy zone mainly has two aspects, on one hand, it makes thesurface of grain flat; on the other hand, electric pulse will narrow columnar crystal zone, andreduce the equiaxed grain scale internal.(3) The electric pulse modification influencesAl-5%Cu alloy casting texture significantly. On the condition of the coupling action oftemperature field and the pulse electromagnetic field, on condition of normal temperature mold,electric pulse inbibites the growth of columnar crystal significantly. While on condition of500℃, theinhibiting effect disappears.Overall, with the weakness of temperature field, the total volumefraction decreases gradually.(4) The effect of electric pulse on the corrosion resistance ofAl-5%Cu alloy is significant, which improves the Cu atoms segregation to enhance theintergranular corrosion resistance. With the weakness of temperature field, the improvementeffect of electric pulse on alloy corrosion resistance increases gradually.