Investigation For Solidified Growth And Electrochemical Behavior Of Pure Al Under Electric Pulse

Effects of the changes of metallic solidification process governed by electric pulse modification(EPM)technology have been cognized and investigated gradually.Moreover,EPM technology has been applied in the industrial production further.Therein,it is an essential part to study the solidified growth of crystal governed by EPM after nucleation.In addition,the texture analysis is the frequently used method to characterize the orientation rotation of crystal planes.Thus,the crystal plane evolution during solidification growth of EP-modified metal can be unraveled by the texture analysis.The electrochemical properties versus various texture components can also be studied further.In this work,the pure aluminum melt was modified by EPM at various pulse voltages and melt temperatures.The X-ray reflection test was employed to study the function of the texture evolution in the EP-modified Al castings.The electrochemical properties of various main texture were investigated by electrochemical impedance spectroscopy and potentiodynamic polarization tests.The solidified growth behaviour of Al melt can be changed by EPM.After applying the EPM of various pulse voltages,the height and width of Al columnar crystals increased,and their growth orientation rotated.Moreover,the equiaxed crystals formed at a relatively high site.In the temperature region between 700 and 800 ?,with the melt temperature rising during EPM,the width of columnar crystals increased in Al directionally-solidified macrostructure and those columnar crystals grew more continuously.Due to the changes of EP-modified Al melt structure,Al(110)planes had a weakened growth tendency.Thereby,Al(111)and Al(100)planes with lower atomic planar density formed.After Al melt was applied EPM,intensity of texture with ? orientation strengthened within the space surrounded by ? and ? fibers.This leaded to an increase of the width of Al columnar crystals during the directional solidification of EP-modified Al melt.Additionally,the directionally-solidified texture components rotated away ? orientation in the Al solidified structure modified by EPM of 500 V pulse voltage.EPM of 100 and 500 V pulse voltage resulted in the solidified nucleation temperature decreasing to a minimum value.And the crystallization time of Al melt applied 100 V-pulse-voltage EPM increased to the maximum.When the Al melt temperature was at 700 and 750 ?,EPM caused that Al met had a lower nucleation temperature.Moreover,the solidified crystallization time increased to the maximum for the Al melt modified by EPM at 700 ?.The crystal plane orientation will be changed by EPM of various pulse voltage during the solidification process.This causes that the as-casting Al texture can be controlled.With the melt temperature rising,the crystal plane evolution is not continuous during the solidified growth process of EP-modified Al melt.Furthermore,its obvious differences of solidified growth process do not stem from the rotation of massive crystal planes,but the changes of primary crystal planes.For the hybrid {201}<100>&{110}<1-18> texture component contain low-index crystal planes,its Ra was much higher than other hybrid texture components.Furthermore,with a decrease of atomic planar density on the crystal plane,the Ca values had a gradually decreased tendency.The surface state of Al electrode with hybrid {441}<-1-18>&{552} <115> texture component can be changed obviously during the cathodic polarization process,which resulted in the positive shift of Ecorr.The larger average atomic planar density that the hybrid Al texture component had can lead to a decrease of icorr.Therefore,the hybrid texture on Al surface with the increased average atomic planar density had an improved corrosion resistance.