共查询到18条相似文献,搜索用时 125 毫秒
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不同电压下脉冲电流对纯铝凝固组织的影响 总被引:12,自引:5,他引:7
采用储能电容为3640μF的脉冲电源,在不同的充电电压下,对纯铝的凝固过程进行电脉冲处理。结果表明:脉冲电流能够扩大纯铝铸锭的等轴晶区、缩小柱状晶区,并使晶粒尺寸细化。在一定的脉冲电流参数范围内,电流密度增大和脉冲频率升高都有利于金属凝固组织的细化和改善。 相似文献
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采用自制的脉冲电源,通过调节脉冲电流峰值,研究了脉冲电流峰值对亚共晶Al-Si合金凝固组织的影响。结果表明;随着脉冲电流峰值的增大,合金的的宏观组织愈加细化;微观组织中,先析出相α-Al枝晶形态趋于向等轴晶转变,而共晶Si组织逐渐粗化。 相似文献
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纯铝定向凝固过程加以高密度脉冲电流处理,研究了脉冲峰值电流密度对定向凝固组织的影响。随着脉冲电流密度的增大,定向凝固组织经历了由柱状晶→胞状晶→发达的枝晶→柱状晶3个演化阶段。基于感应磁场与脉冲电流的耦合作用,从电磁流体力学方面分析了高密度脉冲电流对凝固组织形成的作用机制。高密度脉冲电流在金属熔体内感生高频振荡磁场,并感生动态径向电磁压力,影响凝固界面上方金属液流场分布与金属凝固前沿的温度梯度,并对枝晶臂有冲刷作用,从而改变凝固组织形态。 相似文献
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《特种铸造及有色合金》2016,(1)
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。 相似文献
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从脉冲电流内在因素(如脉冲电流类型、脉冲电流参数选择等)和电流外在因素(如脉冲电流施加方式、通电时间控制等)两方面介绍了脉冲电流影响纯铝凝固组织的研究现状。从促进形核因素,如脉冲磁力作用、团簇结构理论、过冷度的影响、降低形核势垒;抑制晶粒生长因素,如焦耳热效应和Peltier热效应、枝晶断裂等多方面探讨了脉冲电流影响纯铝凝固组织的机理。并指出在机理方面尚未形成定论,将该项技术应用于工业生产存在一定的困难。但随着对其研究深入,必将成为未来先进的绿色凝固技术。 相似文献
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研究了脉冲电流对Al-4.5Cu合金定向凝固过程及组织的影响。结果表明,随着脉冲电流峰值和频率的增大,Al—4.5Cu合金柱状晶被熔断,形态由细条状变为不连续,失去其定向凝固的取向性;且柱状晶间距随电流峰值和频率的增大而减小。由脉冲电流的引入而产生的脉冲磁压力及焦耳热效应在固液界面处造成的强烈扰动是定向凝固组织失去取向性的主要原因。 相似文献
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通过调节脉冲电流峰值电压,研究了脉冲电流峰值电压对AZ91镁合金凝固组织和力学性能的影响,并与MgCO3变质处理进行了对比。结果表明,随着脉冲电流峰值电压的增大,合金的凝固组织愈加细化,力学性能不断提高;当脉冲电流峰值电压达到2000V时,脉冲电流处理试样的抗拉强度比未处理试样提高了25%、伸长率提高了128%,比变质处理的抗拉强度提高了4%、伸长率提高了14%。 相似文献
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The combined effects of direct current pulsed magnetic field (DC-PMF) and inoculation on pure aluminum were investigated, the grain refinement behavior of DC-PMF and inoculation was discussed. The experimental results indicate that the solidification micro structure of pure aluminum can be greatly refined under DC-PMF. Refinement of pure aluminum is attributed to electromagnetic undercooling and forced convection caused by DC-PMF. With single DC-PMF, the grain size in the equiaxed zone is uneven. However, under DC-PMF, by adding 0.05% (mass fraction) Al–5Ti–B, the grain size of the sample is smaller, and the size distribution is more uniform than that of single DC-PMF. Furthermore, under the combination of DC-PMF and inoculation, with the increase of output current, the grain size is further reduced. When the output current increases to 100 A, the average grain size can decrease to 113 μm. 相似文献
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Zhen-Xing Yin Yong-Yong Gong Bo Li Yu-Feng Cheng Dong Liang Qi-Jie Zhai 《Journal of Materials Processing Technology》2012,212(12):2629-2634
A technique termed surface pulsed magneto-oscillation (SPMO) was developed for refining the solidification structure of metals and alloys. Its working principles are to allow an electropulse to pass through a cookie-like induction coil mounted on the top of a mold to produce pulsed electromagnetic fields (EMFs) which are expected to modify the solidification process and structure of ingots. The experimental results showed that an electropulse flowing in the induction coil can make pure aluminum cast structures transform radically from the columnar to equiaxed grains. In order to examine the origin of equiaxed grains, the steel gauze was applied to the mold to hinder the migration of free grains induced by the pulsed electromagnetic fields. Through comparison of cast structures it was showed that the equiaxed grains should originate from the upper surface of the melt and/or top mold wall. And the forced convection induced by the pulsed magneto-oscillation plays a vital role in the formation of cast structure. 相似文献
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高密度脉冲电流作用下LY12铝合金的凝固组织 总被引:28,自引:6,他引:22
研究了高密度脉冲电流作用下LY12铝合金的凝固组织,试验结果表明嵩密度的脉冲电流可明显地改善该合金凝固组织。和未经电流处理的样品相比,其组织明显细化和等轴化,且脉冲电流愈强,且脉冲电流愈强,这种效果愈显著。 相似文献
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Effect of pulse magnetic field on solidification structure and properties of pure copper 总被引:1,自引:0,他引:1
The application of pulse magnetic field to metal solidification is an advanced technique which can remarkably refine solidification structure. In this paper, the effect of pulse magnetic field on solidification structure, mechanical properties and conductivity of pure copper was experimentally investigated. The results showed that the solidification structure transformed from coarse columnar crystal to fine globular crystal with increasing pulse voltage. Increasing pulse voltage also improved the tensile strength. However, with the increase of pulse voltage, the elongation and electrical resistivity firstly decreased, then increased when the pulse voltage beyond a critical value. Moreover, in some conditions, pulse magnetic field can simultaneously improve the conductivity and mechanical property of pure copper. 相似文献