低频低压脉冲电流对纯铝凝固过程的影响

Effects of Low Voltage and Frequency Pulse Electric Current on Pure Aluminium Solidification Process

采用自行设计的低频低压脉冲电源对工业纯铝进行处理。脉冲电流处理的熔体宏观组织从外向内生长的长条柱状晶被碎断,外围粗大的树枝晶呈现变短变细趋势。随着脉冲电压不断增加,等轴晶面积不断加大,晶粒尺寸不断减小,影响程度呈现衰弱的趋势。当占空比不断增大时,等轴晶面积和晶粒尺寸的影响呈现先增大后减小的趋势,当占空比为60%时,熔体处理效果最佳。最佳件与未施加脉冲试样相比,布氏硬度、抗拉强度、屈服强度、伸长率分别提高10%、13.9%、9.3%、10.4%。试验表明,脉冲电流影响了铝熔体在凝固过程中的过冷度,使得晶粒细化程度出现波动。这种影响是多种参数共同作用的结果,但并不是线性关系。

Industrial pure Al was treated by a self-developed low voltage and low frequency pulsed apparatus.The long columnar crystals which grows up from the outside to the inside in macrostructure with melt pulsed current treatment were broken off,and the peripheral coarse dendrite exhibits fine and short trend.With the increase of the pulse voltage,the area of equiaxed crystal is increased with the decrease of equiaxed crystal grain＇s size to be stable.With increasing in duty,equiaxed area and grain size are increased firstly and then decreased,where with 60% duty,melting treating is desirable.Compared with those of the pure aluminum without pulsed treatment,the hardness,tensile strength,yield strength,elongation of pure aluminum with pulsed treatment are increased by 10%,13.9%,9.3%and 10.4%,respectively.The experimental results reveal that the super-cooled degree of liquid Al during solidification process is affected by pulsed current,leading to the fluctuation of grain refinement.This role is attributed to combined effect of various parameters,however it is not belong linear relationship.