电脉冲孕育处理对Al-5%Cu合金液态结构的影响

利用高温X射线衍射仪对经电脉冲孕育处理的Al?5%Cu合金液态结构进行表征。结果表明：在经电脉冲孕育处理的熔体中,含 Cu 的铝团簇数量明显增加,由于相关原子半径和配位数的减小而使这些团簇呈现某种热收缩状态。这种液相结构将使最终的凝固组织中富Cu相更趋于均匀分布。DSC测试表明,经电脉冲孕育处理的液相在结晶过程中,其过冷度是未处理液相的2.36倍。可以确定,电脉冲处理后的Al?5%Cu熔体中原子团簇的变化与先前提出的纯金属电脉冲孕育处理机理模型存在明显差异。     

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。     

电脉冲对金属铝箔的作用

通过对金属铝箔施加高密度脉冲电流的方法 ,从实验和理论上研究了电脉冲对金属铝箔的作用机制。实验结果表明 ,电脉冲对铝箔能够产生收缩作用 ,铝箔的收缩率与电脉冲充电电压和充电电容以及放电次数有关 ,充电电压越高 ,充电电容越高 ,放电次数越多 ,铝箔的收缩率就越大。分析认为 ,脉冲电流在铝箔中产生的电磁力是导致铝箔收缩的主要原因 ,而脉冲电流产生的焦耳热则不会导致铝箔熔化收缩。     

电脉冲孕育处理对Al-Cu-Mn合金时效过程的影响

考察了不同电脉冲孕育处理参数对Al-Cu-Mn合金时效过程的影响，结果表明：电脉冲孕育处理加速了A1．5％Cu-0．8％Mn合金时效进程，缩短了时效时间，使合金最大显微硬度较未处理试样提高了13％～17％；但不同的电脉冲参数影响时效过程的程度不同，一定范围内，500V电压，30s处理时间，频率为3Hz的电脉冲参数在740℃处理时，合金时效后的显微硬度最高。     

电脉冲处理对纯铝形变织构及加工性能的影响

利用X-射线Schulz背反射法及拉伸试验等研究了电脉冲处理对纯铝冷轧带材的织构及加工性能的影响.结果表明:经电脉冲处理的纯铝冷轧带材织构与未经电脉冲处理有明显不同,这主要是因为经过电脉冲处理后,纯铝冷轧带材的晶粒得到细化,相对均匀的取向分布使各向同性程度提高,塑性变形相对均匀,各部位的塑性流动速度接近相同,其产生的剪...     

电脉冲作用下铜铝合金的凝固行为模型

利用电磁学理论并结合电脉冲处理细化机制推算出凝固过程中结晶雨产生及激冷层形成时的脉冲电压临界值。对结晶雨出现时等效电流及其影响因素进行模型研究,分析电脉冲作用下合金凝固行为的特点,指出电脉冲处理组织细化时域应处于结晶雨产生与激冷层形成之间。此外,以该条件下Al-5%Cu合金的凝固组织特点对模型进行了验证。     

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.     

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.     

Noise wavelet-suppressing on electric signals in meso-spray process of pulse MIG welding of aluminum

An analysis with Fourier series on electric signals of meso-spray process of pulse MIG welding of aluminum shows many harmonic waves of different frequency in the signals,including the inherent high,low frequency elementary waves of short circuit and the harmonic waves from pulse current besides the noise signals of high frequency.The wavelet filtering with adjustable threshold is applied to study and handle the electric signals from meso-spray process of pulse MIG welding of aluminum,displaying a good solution on suppressing the noise in the signals.     

电脉冲处理对热镀锌镀层组织和生长的影响

研究了电脉冲处理对热镀锌镀层组织和生长影响。采用冷轧钢板在460℃条件下得到不同电脉冲处理参数不同浸镀时间的镀层组织,结果表明,未经电脉冲处理试样铁锌互扩散较快,δ相和ζ相同时生长,且随时间延长ζ相呈起伏式生长,合金层的组织变得不连续且存在疏松。电脉冲处理后试样合金层的生长均受到抑制,生长比较稳定。在180 s浸镀时间内,δ相层的组织晶粒度均匀致密,ζ相的连绵式生长消失,与δ相和η相相界面变得非常连续,厚度明显减薄,由83.5μm减薄到70μm以内。经电脉冲处理后,合金层的生长由扩散和界面反应联合控制转变为仅受扩散控制。     

磷酸改性处理后氢氧化铝的热稳定性

研究磷酸改善氢氧化铝粉体热稳定性的工艺及修饰处理对粉体形貌与物相的影响，并探讨磷酸提高氢氧化铝热稳定性的机理。结果表明：反应温度的提高、反应时间的延长及磷酸浓度的加大均有利于氢氧化铝热稳定性的提高，当磷酸浓度为10％、反应温度与时间分别取90℃与75min时，可使氢氧化铝中结晶水的初始失去温度由192℃提高到211℃；磷酸提高氢氧化铝热稳定性的原因可能是磷酸与氢氧化铝反应所生成的耐热铝盐包覆在氢氧化铝颗粒的表面；所研究的修饰工艺没有改变粉体的三水铝石结构，但磷酸处理会使粉体颗粒长大，并且还会有大尺寸团聚粒子的出现。     

用电解原铝液生产高精6063铝合金圆铸锭的工艺研究

针对国外客户对高精6063铝合金圆铸锭的质量要求,主要在电解原铝液熔体处理、炉内精炼、晶粒细化、炉外在线净化、均匀化处理和生产设备等方面进行了试验研究.现在我公司利用电解原铝液能够稳定生产出高精6063铝合金圆铸锭,满足了客户的需求.     

A taguchi experimental design study of twin-wire electric arc sprayed aluminum coatings

An experimental study was conducted on the twin- wire electric arc spraying of aluminum coatings. This aluminum wire system is being used to fabricate heater tubes that emulate nuclear fuel tubes for use in thermal-hydraulic experiments. Experiments were conducted using a Taguchi fractional factorial design parametric study. Operating parameters were varied around the typical process parameters in a systematic design of experiments to display the range of processing conditions and their effect on the resultant coating. The coatings were characterized by hardness tests, optical metallography, and image analysis. This article discusses coating hardness, roughness, deposition efficiency, and microstructure. The study attempts to correlate the features of the coatings with the changes in operating parameters. A numerical model of the process is presented, including gas, droplet, and coating dynamics.     

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.     

In-flight oxidation of aluminum in the twin-wire electric arc process

This paper examines the in-flight oxidation of aluminum sprayed in air using the twin-wire electric arc (TWEA) thermal spray process. Aerodynamic shear at the droplet surface increases the amount of in-flight oxidation by promoting entrainment of the surface oxides within the molten droplet and continually exposing fresh fluid available for oxidation. Mathematical predictions herein confirm experimental measurements that reveal an elevated, nearly constant surface temperature (∼2273 K) of the droplets during flight. The calculated oxide volume fraction of a “typical” droplet with internal circulation compares favorably to the experimentally determined oxide content (3.3–12.7%) for a typical TWEA-sprayed aluminum coating sprayed onto a room temperature substrate. It is concluded that internal circulation within the molten aluminum droplet is a significant source of oxidation. This effect produces an oxide content nearly two orders of magnitude larger than that of a droplet without continual oxidation.     

Ir-based refractory superalloys by pulse electric current sintering (PECS) process (II prealloyed powder)

Five prealloyed powder samples prepared from binary Ir-based refractory superalloys were sintered at 1800 °C for 4 h by Pulse Electric Current Sintering (PECS). No metal loss was observed during sintering. The relative densities of the sintered specimens all exceeded 90% T.D. The best one was Ir-13% Hf with the density of 97.82% T.D. Phases detected in sintered samples were in accordance with the phase diagram as expected. Fractured surfaces were observed in two samples (Ir-13% Hf and Ir-15% Zr). Some improvements obtained by using prealloyed powders instead of elemental powders, which were investigated in the previous studies, were presented.     

铝合金电流强化激光焊接焊缝组织及性能

采用电流强化激光焊接方法对3.0 mm厚的2219-T6铝合金板材进行堆焊,研究了电流对激光焊缝宏观和微观组织、气孔缺陷以及力学性能的影响.试验发现,引入电流后,焊缝区的晶粒发生明显细化,促使粗大的柱状晶转变为细小的等轴晶;而且消除了激光焊缝中央存在的羽毛状晶.与激光焊接相比,电流强化激光焊接焊缝中的气孔明显减少,接头...     

电脉冲处理对亚共晶铁碳合金珠光体组织的影响

研究了电脉冲（ECP）处理对亚共晶铁碳合金珠光体组织的影响。结果表明,亚共晶铁碳合金经ECP处理后,促进了石墨的生成,增加了铁素体的形核率,最终导致组织中铁素体相对含量增加,珠光体相对含量相应降低;ECP处理同样增加了共析转变的有效驱动力,且随着输出电压的升高,珠光体内的渗碳体层片逐渐变短、变薄,珠光体的显微硬度逐渐增加。     

Influences of pulse electric current treatment on solidification microstructures and mechanical properties of Al-Si piston alloys

Three kinds of Al-Si piston alloys were prepared and subjected to pulse electric current treatment (PECT) at different pouring temperatures. Some aspects of the solidification microstructures were examined including the morphology and the distribution of the matrix and the secondary phases by using of optical microscopy (OM), SEM and EDS methods. Results indicate that PECT can refine the grains of α-Al in the alloys as effectively as chemical modification by sodium salt. The processing parameters of PECT on the multi-component Al-Si alloys were then optimized through the testing of tensile strength, elongation and microhardness of the prepared alloys. A new theory was put forward to explain the mechanism of PECT.     

Effect of electric pulse treatment on solidification structure of an Al-15%Si alloy

1 IntroductionThe study of electric field (EF) modifying themetal microstructure has made some progress sinceAsoka applied electric current when a Pb-Sn alloysolidified [1-8]. Based on the different applying du-rations of EF to melt, there are two kinds o…