Effects of electric pulse modification on liquid structure of Al-5%Cu alloy

The electric pulse modification （EP, EPM） of liquid metal is a novel method for grain refinement. The structure of EP-modified Al-5%Cu melt was characterized by high-temperature X-ray diffractometry. The results show that the Cu-containing Al clusters remarkably increase in the EP-modified melt, furthermore, these clusters in that case tend to contract due to the decrease of relevant atomic radius and the co-ordination number. This kind of liquid-phase structure leads to a more homogeneous Cu-rich phase distribution in the final solidification structure. Differential scanning calorimetry （DSC） tests indicate that the solidification super-cooling degree of the EP-modified liquid phase is 2.36 times that of the unmodified. These facts suggest that the atom cluster changes in EP-modified Al-5%Cu melt would disagree with that by EPM model previously proposed in liquid pure metal.

Heredity of Aluminum Melt Caused by Electric Pulse Modification (Ⅰ)

The heredity of aluminum melt under the action of pulse electric field was investigated by means of the remelt experiment. A new hereditary criterion under this condition was proposed; in the meantime, the differential transferability of genetic carrier in activated melt among filial generations was validated with the aid of DSC.

Heredity of Aluminum Melt by Electric Pulse Modification (Ⅱ)

Heredity of high pure aluminum melts under different pulse electric field was investigated by means of repetitious remelt experiment. The results indicate that the genetic coefficient by measurement of grain size of cast structure has a close relation with pulse voltage. Moreover, the hereditary law accords with the function of In = 1＋ e^-an＋β. The stability of genetic carrier （cluster） comprises in the competition between repetitious cooling and heating impulse and the effect of electric pulse modification.

Casting structure of pure aluminum by electric pulse modification at different superheated temperatures

Electric pulse modification （EPM） is a novel technique that reduces grain size by altering the structure of a melt. It was investigated that the response of the casting structure of high pure aluminum to EPM in different superheated melts. The results indicate that the grain refining effect of a given pulse electric field holds an optimal temperature range, moreover, a lower or higher superheated temperature will both disadvantage the improvements of casting structure. It essentially lies in the cooperative action between the distorted absorption of clusters and the activated capability of atoms in the aluminum melt.

Further study on heredity of liquid aluminum modified by electric pulse

The remarkable heredity of liquid aluminum modified by electric pulse (EP, EPM) has been uncovered. For better understanding from all aspects on the hereditary properties, the present research deals with the heredity destruction and the secondary EPM procedure. It is shown that the secondary EPM is capable of preventing the heredity reduction of EP-modified liquid aluminum, and that the final refining effect has a close relationship with technique parameters of the secondary EPM. Furthermore, at a certain superheated temperature depending on the initial EPM technique parameters, the heredity relationship of EP-modified liquid aluminum can be cut off during remelting. High temperature X-ray diffraction combining with the DSC tests also indicates that the EP-induced structure changes have almost disappeared at an elevated remelting temperature.

Influences of electric pulse on solidification structure of LM-29 Al-Si alloy

The metallographic structure of LM-29 aluminum-silicon alloy modified by electric pulse treatment has been investigated and compared with those untreated.The solidification structure of LM-29 alloy has been analyzed by means of M1AP3 Quantimet image processing and analysis system,and then the solidification process has been analyzed by means of differential scanning calorimetry(DSC).The results indicate that the primary silicon phase was refined remarkably by electric pulse while the tensile strength and elongation properties increased accordingly.Electric pulse treatment can also increase the binding power between silicon clusters and alloy melt matrix,as a result,the precipitation of primary silicon phase is suppressed to meet the demand of supercooling degree for nucleating,correspondingly.The electric pulse modification has great influence on the size of silicon atomic cluster as well as its distribution in the melt,subsequently,leads to the refinement of solidification structure.

EET research on the Al-22%Si alloy under the action of electric pulses

Based on the empirical electron theory of solids and molecules (EET), the phase valence electron structure parameters of Al-22%Si alloy are calculated, and the sensitivity of the bond network of Al-Si alloy melt to temperature (energy) and the effect of the sensitivity on the morphology are studied. The results show that the Si-Si clusters with larger nA in the slightly superheated Al-Si alloy melt supply the nucleation core to the primary silicon phase in the hypereutectic Al-22%Si alloy, and strongly generate the drag-like effect for the Al-Si clusters around them; that the variation of temperature significantly affects the stability of bonds of the core so that the solidified structure is changed; that the electric pulse applied to the alloy melt can irrecoverably alter the stability of Si-Si clusters, then the modifica- tion of the solidified structure morphology of alloys is generated; that the higher the energy of the electric pulse, the less stable the Si-Si clusters, and the more significant the electric pulse modification.

变质剂与电脉冲复合处理对Al7SiMg合金组织与性能的影响

通过调整变质剂含量和电脉冲峰值电压和脉冲频率,研究了变质剂与电脉冲复合处理对Al7SiMg共晶相生长分布的影响。试验结果表明:适当参数的电脉冲处理Al7SiMg合金熔体时,α相的晶体形貌尺寸减小,共晶硅β相长针状形貌得到抑制,晶体形貌不再尖锐;并且脉冲电压的作用大于脉冲频率;0.01%Sr与电脉冲复合处理时,能改善树枝晶分支之间产生的硅溶质偏析,细化硅晶体形貌;复合处理后的拉伸断口合金韧窝数量进一步增多,解理面减少,抗拉强度提高。

电脉冲孕育处理对方坯连铸09CuPCrNi钢凝固组织的影响

在鞍钢工业生产中进行了利用电脉冲孕育技术改善和细化连铸坯凝固组织的探索性实验研究,实验钢种为09CuPCrNi,连铸坯的尺寸规格为150mm×150mm,实验结果表明,在连铸中间罐内对09CuPCrNi钢水进行电脉冲孕育处理可以明显细化连铸坯的凝固组织,与未经电脉冲孕育处理的连铸坯相比,经电脉冲孕育处理后,连铸坯的柱状晶长度明显缩短,一次枝晶臂间距明显减小;连铸坯的中心等轴晶区扩大,中心缩孔得到明显改善,轧材性能达到了技术要求。

过热度对电脉冲孕育处理Al-5%Cu合金凝固组织的影响

研究了不同的过热度对电脉冲孕育处理Al-5%Cu合金凝固组织的影响。实验结果表明:不同的过热度下对Al-5%Cu合金进行电脉冲处理,合金凝固组织均得到一定程度的细化,但过热度不同时细化效果不同。一定温度范围内,熔体温度为740℃时,电脉冲孕育处理细化的效果最好,并分析了过热度影响电脉冲孕育处理Al-5%Cu合金凝固组织的机制。

脉冲电场的非热效应及在液态食品处理中的应用

系统地阐述了脉冲电场对微生物非热效应的机理、影响因素 ,结合国内外研究现状 。

ZL102合金的电脉冲变质及其与硼砂细化处理的复合作用

研究了脉冲电流对ZL10 2合金凝固组织的影响 ,以及与硼砂细化处理的复合作用。实验表明 :在电脉冲作用下 ,凝固组织中粗大α Al枝晶得到明显细化 ,共晶硅片的尺寸减小 ;硼砂变质细化和电脉冲细化的复合作用使α Al枝晶成为球状晶。振荡的电磁收缩力和电流的热效应是电脉冲细化和均匀化凝固组织的主要原因。

电脉冲作用下Al-22%Si合金凝固组织的变化机制

研究了在过热Al-22%Si合金熔体中施加电脉冲对其凝固组织的影响,考察了电脉冲频率、作用时间对初生相形态的影响规律。结果表明,经电脉冲孕育的合金凝固组织明显细化,初生硅相由花瓣状向块状转变;示差扫描量热法(DSC)曲线发生变化,初生相凝固点下降了16.78℃,反应焓值降低了4.1J/kg。理论分析表明外场作用下铝硅合金熔体中的大尺度硅团簇发生裂解,从而提高了熔体均匀程度。

不同脉冲电场对铝熔体遗传行为的影响

近年来,采用电脉冲作用熔体进而细化金属凝固组织的技术日益引起人们的关注,探讨熔体在该条件下的异构现象是该技术的核心问题之一。采用不同脉冲电场孕育处理的高纯铝锭进行多次重熔试验,系统研究了其熔体结构的遗传行为。结果表明按晶粒度度量的遗传因子与脉冲电压直接相关,其遗传衰减规律符合In=1+e-αn+β方程;遗传载体—团簇的稳定性在于反复冷热激励与电脉冲孕育两因素的竞争。

脉冲电场作用下纯铝熔体的遗传机制

对处于熔点以上的纯铝施加电脉冲,通过对铝锭的多次重熔实验,研究了其熔体结构的遗传性。结果表明电脉冲孕育处理对试样凝固组织具有明显细化效果;基于该条件下熔体遗传规律的特异性,提出了一种按晶粒度度量的遗传判据。计算指出子一代遗传效应显著,其遗传信息保持率在80%以上;另一方面,遗传系数与脉冲电压直接相关,其衰减规律符合In=1+e-αn+β方程。差热分析实验揭示了脉冲场下熔体结构的变异性,一定程度上验证了遗传载体团簇在子代间的传递。

电脉冲处理对纯铜再结晶温度的影响

研究了脉冲电场作用对纯铜再结晶温度的影响,并对纯铜的显微组织、硬度-温度曲线进行了研究。结果表明:经电脉冲处理的纯铜再结晶过程向高温区推移,使纯铜的热稳定性、耐热性能得到了改善。

变频调速技术的发展及其在电力系统中的应用

从电力半导体、控制技术和主电路拓扑结构等方面综述了变频调速技术的发展历史和现状,并总结了在变频控制中的主要控制技术;分析了高压变频调速技术的发展动态和几种实现方案的技术特点对比情况;指出变频调速技术在未来的发展趋势。最后介绍了变频调速技术在电力系统中节能降耗、改善工艺和控制性能等方面的应用。

蛋白质物理改性的研究进展

蛋白质是食品中的重要组分之一,其功能特性对食品的品质至关重要。蛋白质改性主要包括化学法、酶法、物理法以及基因工程等。相对于其他改性方法,蛋白质的物理改性方法具有廉价、安全、处理时间短以及对产品营养性能影响较小等优点。而新兴的物理改性方法又具有低能耗、低温处理、产品品质高以及低消耗等优点。本文介绍了超高压、脉冲电场、超声、辐照、微波和射频处理等几种新的物理改性方法以及改性对蛋白功能性的影响,以及各种方法亟需解决的问题等。目前,新兴的物理改性方法还处于实验室阶段,未广泛应用于食品工业中,并且关于部分方法改性机理研究较少,研究材料种类较少,还需进一步扩展相关知识从而为蛋白质改性加工提供新思路。

电脉冲对HRB335螺纹钢凝固组织的影响

用不同的脉冲电流对HRB335螺纹钢进行孕育处理,研究了不同的电脉冲参数对其宏观组织和微观组织的影响。结果表明,将处理过的钢液在保温砖中冷却,晶粒明显得到了细化,枝晶大大减少,经过电脉冲处理后的HRB335螺纹钢的珠光体形态发生了显著的变化,片层间距明显缩短。

电脉冲对P510L钢的影响

用不同的脉冲电流对P510L钢进行了孕育处理,研究了不同的电脉冲参数对其宏观组织和微观组织的影响.结果表明,将处理过的钢液在空气中冷却,晶粒明显得到了细化、枝晶大大减少,经过电脉冲处理后的P510L钢的珠光体形态发生了显著的变化,片层间距明显缩短.