脉冲电流对5052铝合金铸轧板材组织的影响

在传统铸轧过程中施加脉冲电流,生产5052铝合金板材,通过显微观察,研究了铸轧工艺对板材显微组织的影响。结果表明:与传统铸轧相比,施加脉冲电流的铸轧能细化5052铝合金板材组织,抑制枝晶生长。当脉冲电流参数:占空比20%、峰值电流200 A、电流频率50 Hz时,5052铝合金铸轧板组织的细化效果最好。     

脉冲电流对过共晶铝硅合金凝固组织及力学性能的影响

将脉冲电流应用于过共晶铝硅合金的凝固过程中,通过改变脉冲电流参数(如峰值电流、脉冲占空比、脉冲频率),研究了各个参数对过共晶铝硅合金凝固组织及性能的影响。实验结果表明,脉冲电流对过共晶铝硅合金凝固组织的细化效果明显;经过脉冲电流处理后,合金试样的显微硬度、布氏硬度均得到很大提高,力学性能明显改善。     

脉冲电流对Zn-42%Al合金定向凝固行为的影响

采用Zn-42%Al合金作为试验材料,研究不同电流强度和脉冲频率下脉冲电流对合金定向凝固组织的影响.结果表明,随着脉冲电流强度的增大,组织得到更加明显的细化;脉冲电流细化组织的作用对脉冲频率存在一个极限响应,当脉冲振荡频率过高,脉冲电流的细化组织效果会被削弱.     

高频脉冲电流对HT150灰铸铁凝固组织的影响

采用频率高于1000Hz的高频脉冲电流,在不同的电流参数下,对HT150灰铸铁进行脉冲电流处理.实验结果表明,在高频脉冲电流作用下铸铁石墨片细化,石墨片变得卷曲,共晶团尺寸减小.电流参数对电流的作用效果有显著影响.     

脉冲电流频率对2219铝合金焊缝组织性能的影响

采用超快速变换复合高频脉冲方波变极性TIG电弧焊接方法进行2219-T87高强铝合金焊接,研究脉冲方波电流频率对焊缝组织性能的影响.结果表明,加入脉冲方波电流后,焊缝组织明显细化,焊缝区由粗大柱状晶向细小等轴晶转变.当脉冲电流频率达超音频段时,在焊缝中部还存在一种呈带状分布的细小等轴非枝晶组织,并与等轴树枝晶组织交替分布.与未加入脉冲电流相比,当脉冲电流频率为60kHz时,接头抗拉强度和断后伸长率分别增加约17.6%和66%.在一定范围内提高脉冲电流频率,可显著减小焊缝熔合区宽度,改善接头硬度分布,明显提高接头塑性,但对接头强度的影响作用并不明显.     

中频低压脉冲电流对纯铝凝固组织的影响

通过调整脉冲电流峰值和脉冲频率，研究了中频低压脉冲电流对纯铝凝固组织的影响。试验结果表明：中频低压脉冲电流可使纯铝的凝固组织由柱状晶转变为等轴晶，电流峰值在500～6000A、脉冲频率在100～1000Hz范围内，随着脉冲电流峰值和脉冲频率的提高，等轴晶不断细化，等轴晶晶区面积增大。     

低压脉冲电流对Al- 4.5Cu合金凝固组织的影响

研究了低压脉冲电流作用下Al-4．5Cu合金凝固组织的变化，考察了冷却速度、脉冲电压和处理时间对合金晶粒大小的影响。试验结果表明：在低压脉冲电流的作用下，Al-4.5Cu合金的凝固组织显著细化，其初生相由发达的树枝晶转变为均匀细小的蔷薇状晶体。合金的晶粒尺寸随着冷却速度的增加而逐渐减小。随着脉冲电压的提高，合金的晶粒尺寸逐渐减小；当脉冲电压达到400V时，晶粒尺寸略有回弹。随着处理时间的增加，合金的晶粒尺寸逐渐减小；当处理时间大于10min时，晶粒尺寸随着处理时间的增加而略有增大。     

脉冲铸轧5052铝合金板坯的组织及性能

将不同频率的脉冲电流引入铸轧工艺中,生产出质量良好的三组5052铝合金板坯。通过观察显微组织,详细地对比了不同频率的脉冲电流铸轧对板坯的显微组织及力学性能的影响。结果表明:在浇铸温度为690℃下,与传统铸轧成形的板材相比,施加300 A脉冲峰值电流和50 Hz频率的脉冲电流生产的5052铝合金板坯的枝晶生长受到抑制,组织得到一定程度细化,但晶粒大小并不均匀;施加300 A峰值电流和30 Hz频率的铸轧方式,产生较强的电磁振荡效果,组织中心部位呈现较大范围的等轴晶组织。多次拉伸试验表明,施加300 A脉冲峰值电流和30 Hz频率的脉冲电流调控的铸轧板坯的平均强度值最高,其平均屈服强度和平均抗拉强度分别为119 N/mm~2和239N/mm~2。     

高能脉冲电源及其在铸造中的应用研究

介绍自行研制的一款电压在1～3 kV、最大峰值电流可达1.7MA的脉冲发生装置--XJDMC型高能脉冲电源。电源的电压、输出能量可以调节,能够对充电电压、储能电容、充放电时间进行设置。研究了电压在1、2 kV,电流脉冲峰值为1.7MA时对Al-4wt%Cu合金铸造组织的影响。分析了Al-4wt%Cu合金组织的晶粒尺寸和脉冲电流、电压、冲击频率以及电路自振荡频率之间的相关性。结果表明：脉冲电压2kV、电容的冲击频率为0.5 Hz、电路的振荡频率为50 Hz时,脉冲电流对Al-4wt%Cu合金作用后,晶粒尺寸由1.5mm减小到0.2 mm。在合金凝固过程中施加脉冲电流能够有效细化晶粒尺寸,提高合金的力学性能。     

高密度脉冲电流作用下LY12铝合金的凝固组织

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。     

Refining mechanism of the electric current pulse on the solidification structure of pure aluminum

The refining mechanism of the electric current pulse (ECP) on the solidification structure of pure aluminum is systematically investigated by properly designed experiments. The experiment results show that the solidification structure cannot be refined by exerting an ECP on the high temperature liquid phase, indicating that the ECP has no inoculation effect on the liquid metal. The ECP has also no obvious influence on the solidification structure when it is applied during crystal growth, showing that the ECP cannot cause melting or break off the growing crystal. However, the very fine macrostructure is obtained by applying an ECP during the nucleation of the melt. The reason is that the ECP makes the crystal nuclei formed on the wall of the mould fall off and move freely in the molten metal, promoting the multiplication of crystal nuclei.     

高密度脉冲电流对A356铝合金低温熔体凝固组织的影响

研究了高密度脉冲电流的A356铝合金低温熔体凝固组织的影响。实验中对680和630℃的低温熔体施加脉冲电流处理。对比试验和凝固曲线测试结果表明。低温熔体中施加脉冲电流有利于增大凝固过冷度，提高冷却速率。缩短凝固时间。细化凝固组织。同时，经脉冲电流处理后，随熔体的保温时间延长。凝固组织逐渐粗化。分析认为，低温熔体结构比凝固过程本身更能影响最终凝固组织。     

金属凝固组织的脉冲磁场细化技术

介绍了脉冲磁场对纯会属、低熔点合金和高熔点铁基材料凝固组织的影响.认为脉冲磁场细化纯铝、1Cr18Ni9Ti奥氏体不锈钢的凝固组织时,存在一个最佳磁场强度值;而脉冲频率对纯铝凝固组织的细化效果影响较小;随着磁场强度的增大,纯铜的凝固组织逐渐细化;脉冲磁场能使灰铸铁凝固组织细化,石墨片的宽度减少.指出脉冲磁场细化凝固组织的机理尚无统一认识,在一定程度上限制了该技术的工业应用.     

脉冲电流对Al-4.5Cu合金定向凝固组织的影响

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。     

Effect of temperature field on solidification structure of pure Al under pulse magneto-oscillation

This article discusses the effect of temperature field on the Pulse Magneto-Oscillation (PMO) induced solidification refinement of pure aluminiurn to provide more information for the industrial application of the PMO solidification technology. The temperature field is altered mainly by applied variable cooling conditions and pulse parameters. Experimental results show that the refinement effect in the case of full sand mould applied is weakened with the decreasing of cooling rate, however, in the alternative case, the sand mould whose sand bottom was replaced by a graphite block is favorable to the survival of equiaxed nucleus. The refinement mechanism is discussed in terms of the relationship between temperature field and the formation process of solidified structure.The formation or survival of nucleus depends on both temperature field and Joule heat produced by PMO, both low pulse frequency and high pulse current were experimentally confirmed to be effective; and PMO was demonstrated high potential in industrial application.     

脉冲电流作用下金属凝固研究现状评述

脉冲电流作用于金属材料的凝固过程已逐渐发展为一种新的细化金属凝固组织的技术。作者从脉冲电流的施加方式、凝固材料选择、电流参数选择和机理探讨四个方面综述了脉冲电流细化金属凝固组织的研究状况,并阐述其研究的新进展。最后就脉冲电流细化金属凝固组织的研究趋势进行了展望。     

Effect of pulse magnetic field on solidification structure and properties of pure copper

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.     

Improving the carbon macrosegregation in high-carbon steel by an electric current pulse

Thus far, the relationship between the macrosegregation and refinement of solidification structures in metals is not clearly understood. In this paper, the effect of an electric current pulse (ECP) on the refinement of the solidification structure as well as carbon macrosegregation in high-carbon steel was investigated. The experimental results revealed that if central porosity exists in the solidification structure, the carbon macrosegregation in high-carbon steel cannot be improved by applying an ECP, although increased equiaxed dendrites and a reduced primary dendritic arm in a solidification structure were obtained after an ingot was exposed to an ECP. In contrast, after central porosity was eliminated, carbon macrosegregation was improved through the refinement of the solidification structure in high-carbon steel through the use of an ECP.     

电极和保温剂对脉冲电流细化晶粒的影响

在实际的铸造过程中应用脉冲电流要求电极插入熔体中并在熔体的上面覆盖保温剂.为了探明这两个因素对脉冲电流细化组织的影响,采用不同电极或不同保温剂进行了3组实验.通过比较不同条件下得到的凝固组织,发现在脉冲电流作用下电极和保温剂都对凝固组织的细化有明显的影响.进一步的分析表明,液面在凝固组织的细化中起到了关键性的作用,而且结果也支持了在脉冲电流作用下等轴晶主要来自液面的观点.