脉冲电流对疲劳后30CrMnSiA钢组织结构的影响

对在应力控制下预疲劳卸载的热轧态30CrMnSiA钢样品进行高密度脉冲电流处理后，得到了细小均匀的等轴晶组织，晶粒尺寸远小于热轧样品的晶粒尺寸．处理后样品的疲劳寿命显著提高．高密度脉冲电流使疲劳形成的位错产生运动，当刃型位错的距离达到临界距离时，位错发生湮灭，使局部的位错密度梯度增大，在位错密度低的地方发生再结晶形核，使钢发生再结晶．     

脉冲电流处理对冷轧态GH3030合金再结晶组织性能的影响

目的 探究不同工艺参数下脉冲电流处理对冷轧态GH3030合金静态再结晶组织的影响.方法 利用电子背散射衍射(EBSD),探究脉冲电流处理(EPT)和常规退火处理(CHT)对GH3030合金静态再结晶的影响.探究了两种热处理方式下不同退火温度和时间对冷轧态GH3030合金静态再结晶体积分数、晶粒尺寸以及硬度的影响,计算两种热处理方式下不同工艺参数的静态再结晶动力学方程与激活能.结果 与常规退火处理相比,脉冲电流处理可以快速提高冷轧态GH3030合金的静态再结晶体积分数,并且得到了尺寸更加均匀的晶粒,而脉冲电流处理的合金其硬度值均小于相同条件下常规退火处理的合金.根据静态再结晶动力学方程的结果可知,脉冲电流处理的合金再结晶激活能低于常规退火处理的合金,脉冲电流处理下发生完全再结晶所需时间远远少于常规退火处理下所需时间.结论 脉冲电流处理促进了冷轧GH3030合金静态再结晶行为,并且加速了再结晶晶粒的成核和长大,但脉冲电流处理对改善GH3030合金的硬度效果不明显.     

高密度脉冲电流处理后冷轧H59黄铜的超细晶结构

将H59双相多晶黄铜冷轧变形后,进行高密度脉冲电流处理.在透射电镜下观察发现,α β'双相粗晶组织均已发生超细晶化转变,而且在α相晶粒中伴有大量的孪晶.经过预应变处理后,α相在脉冲电流作用下发生再结晶细化,并在随后的α→β相变中进一步发生相变细化;β'相在预应变处理后发生再结晶细化.再结晶细化的原因是,预应变处理使晶体中产生大量的缺陷,极大的增加了形核率,而脉冲电流作用时间短,加热速度快,使晶核长大不充分;相变细化的原因是,高密度脉冲电流改变了相变势垒,促进了高电导率相的形核并抑制其长大.     

脉冲电流处理对X70管线钢腐蚀性能的影响

测量了X70管线钢在NS4溶液中的极化曲线，研究了高密度脉冲电流处理对其腐蚀性能的影响，结果表明，高密度脉冲电流处理导致X70管线钢的晶粒细化，使其内部活性区减少，提高了管线钢的耐局部腐蚀能力，X70管线钢的耐局部腐蚀能力随着脉冲电流密度的提高而增强，腐蚀产物的分布也更加均匀细密。     

Ti及TiAl合金的电致增塑性

TiAl合金和Ti合金由于缺少滑移系,是典型的难变形材料.本文探索应用高密度脉冲电流改善其成形性.所选择的材料是TiAl合金 (Ti₂AlNb)、TC4合金(Ti-6Al-4V)、TA15合金和TA1-A.研究了脉冲电流处理对变形损伤的影响,研究结果表明,在一定条件下因塑性变形而产生的微裂纹可以被治愈,并形成局部的再结晶组织,预塑性变形试样的塑性可以被完全恢复,极限变形量得到提高.对退火态的板材进行了高密度电流脉冲处理试验分析,试验结果表明,电流脉冲处理显著地改变了板材的力学性能:均匀延伸率提高、屈服应力和屈强比下降.这对改善钛合金板材成形性具有重要的意义.选用冷轧态板材进行了脉冲电流处理实验,研究结果表明,脉冲电流处理可以大幅度地提高冷轧钛合金板材的塑性,同时材料强度不降低,由于晶粒的细化作用,强韧性得到改善.本文的研究结果表明高密度脉冲电流是改善难变形合金成形性的一种有效方法.     

脉冲电流对冷加工黄铜的组织及性能的影响

研究了脉冲电流对一种冷加工黄铜再结晶组织和力学性能的影响，结果表明，利用脉冲电流作为形变黄铜的再结晶处理手段，可以得到比常规退火处理更细更均匀的再结晶晶粒，从而使该材料的综合力学性能提高，脉冲电流作用时间短，加热速度快、促进再结晶形核和抑制随后晶粒长大是得到细晶粒的原因。     

脉中电流对2091铝锂合金动态再结晶动力学的影响

研究了脉冲电流对2091铝锂合金超塑变形中动态再结晶及动力学的影响结果表明,脉冲电流加速动态再结晶,减小形核时的平均晶粒直径.脉冲电流能加快位错墙的形成并使其角度增大,使再结晶形核率提高.脉冲电流加快位错在晶界上的攀移及消失、减小形核界面两边的能量差,降低形核界面的迁移速率及再结晶形核的长大速率分析了脉冲电流作用下的动态再结晶动力学行为     

脉冲电流对2091铝锂合金动态再结晶动力学的影响

研究了脉冲电流对2091铝锂合金超塑变形中动态再结晶及动力学的影响,结果表明,脉冲电流加速动态再结晶,减少形核时的平均晶粒,脉冲电流能加快位错墙的形成并使其角度增大,使再结晶形核率提高,脉冲电流加快位错在晶界上的攀移及消失,减少形核界面两边的能量差,降低形核界面的迁移速率及再结晶形核的长大速率,分析了脉冲电流作用下的动态再结晶动力学行为。     

初次再结晶组织和渗氮量对低温渗氮取向硅钢二次再结晶行为的影响

通过控制初次再结晶工艺获得尺寸不同的低温渗氮取向硅钢初次再结晶组织,研究初次晶粒尺寸对二次再结晶行为和磁性能的影响,探索初次晶粒尺寸过大条件下合适的渗氮量,并分析初次再结晶组织中{411}〈148〉织构对二次再结晶行为的影响。结果表明:随着初次晶粒尺寸由10μm升高至15μm,二次再结晶温度升高,Goss织构更加锋锐,成品磁性能提高,当初次晶粒尺寸为28μm时,合适的渗氮量约为6×10-4。初次再结晶组织中{411}〈148〉取向晶粒生长能力更强,极易粗化,阻碍二次晶粒的异常长大,同时{411}〈148〉与黄铜晶粒之间为大于45°的低迁移率晶界,对黄铜晶粒异常长大的阻碍作用更为显著。     

高能量密度脉冲电流对Fe76Si12B12共晶合金凝固组织的影响

利用自行设计的高能量密度脉冲放电设备及高温坩埚炉研究脉冲电流对Fe76Si12B12共晶合金凝固组织的影响.结果表明,高能量密度脉冲电流处理可明显细化Fe76Si12B12共晶合金凝固组织,而且在脉冲电流宽度相同的条件下脉冲电流密度越大,晶粒尺寸越小;在脉冲电流密度相同的条件下,脉冲电流宽度越小,晶粒尺寸越小.     

6063T4铝合金脉冲电流辅助拉伸力学性能实验研究

为研究电流密度对材料力学性能的影响,对6063T4铝合金板材进行了脉冲电流辅助单向拉伸试验.理论分析了拉伸过程中电能转化温升的效率,探讨了脉冲电流辅助拉伸过程中材料的动态应变时效(DSA)现象及其机理,定量分析了电流密度与应力降之间的关系,并观察了试验前后试样的微观组织及断口形貌.结果表明,脉冲电流降低了材料流动应力,提高了材料塑性;电能转化为温升的效率约为60%;随着电流密度或脉冲数的增加,DSA现象越发显著;在给定的电流密度下,应力降值随着变形量的增加呈线性增加;光学微观组织表明,材料在相对较低的温度(165℃)下发生了动态再结晶;断口形貌分析显示电流辅助单向拉伸所获得的断口中韧窝数量以及撕裂棱增多,材料塑性提高.     

Effects of electropulsing on inclusion size and corrosion-resistance of 304 stainless steel

Electropulsing has been imposed on molten AISI 304 stainless steel and its effects on the inclusion size and corrosion properties have been investigated. The average size of inclusions in electropulsing-treated samples was finer than that in untreated ones. A theoretical analysis shows that the mobility of solute atoms increases with electropulsing treatment. This promotes the nucleation of inclusions. Owing to a smaller inclusion size, the electrochemical experiments reveal that the pitting corrosion resistance of the electropulsing-treated stainless steel is significantly improved. The beneficial effects of electropulsing on the refinement of inclusions and the resistance to pitting corrosion increase with an increase in current density. Electropulsing treatment, therefore, provides a promising means to improve pitting corrosion resistance.     

Effect of electropulsing treatment on static recrystallization behavior of cold-rolled magnesium alloy ZK60 with different reductions

Effect of electropulsing treatment (EPT) on recrystallization behavior of cold-rolled Mg alloy ZK60 strips was investigated. It was found that EPT significantly improved nucleation rate and migration ability of grain boundaries, leading to accelerated recrystallization of the deformed metals at relatively low temperature. After the recrystallization induced by EPT, the average grain size of 20% rolling reduction samples decreased from 113 μm to around 10 μm, meanwhile the typical basal-type texture of the cold-rolled sample was weakened. EPT was normally accompanied with a thermal and an athermal effects. The athermal effect played a dominated role in increasing nucleation rate, while the thermal effect promoted grain growth. A fewer recrystallized grains originated along the grain boundaries in the 10% reduction samples, while most of the recrystallization took place inside the twins in the 20% reduction samples.     

脉冲电流处理后低碳钢中的局域纳米结构

用透射电镜观察经过高密度脉冲电流处理后的粗晶低碳钢，发现该材料中有纳米结构的γ-Fe生成。讨论了纳米结构的生成机制。脉冲电流作用时间短，加热速度快，改变相变势垒的效应和快速冷却的条件是生成纳米结构的原因，电流降低热力学形核势垒是一个不容忽视的因素。     

Cementite Decomposition in Spherical Graphite Iron by Electropulsing

The influence of electropulsing on cementite decomposition in the spherical graphite iron has been studied.The results indicated that the cementite was decomposed in a short time by high current density electropulsing.With increasing electropulsing time, the in situ nucleation of graphite in cementite was accompanied with the quick decomposition of cementite. The dislocation accumulation adjacent to the cementite and the quick diffusion of carbon atom by electropulsing were main reasons for the quick decomposition of cementite. The in situ nucleation of graphite in the cementite resulted from the dislocation climbing crossing the cementite lamellae.     

高速钢高温变形再结晶规律研究

本文研究了W9Mo~3Cr~4V钢的热变形奥氏体动态再结晶规律。结果表明:由于形变诱发析出碳化物的影响,W9Mo~3Cr~4V钢热变形奥氏体动态再结晶方式与低碳低合金钢的晶界弓出机构和晶界生核机构不同,是通过亚晶合并形成再结晶晶粒的,即亚晶合并机构。当形变速率较低时,可由亚晶粒直接形成再结晶晶粒。形变温度和形变速率对W9Mo~3Cr~4V钢热变形奥氏体动态再结晶影响比较复杂,不能简单地用Z参数来统一描述。     

Electropulsing strengthened 2GPa boron steel with good ductility

For the purpose of further enhancing the mechanical properties of a boron steel used in the automotive industry, the electropulsing is applied to strengthen the steel. The results show that the steel exhibits unexpected high strength and ductility. The engineering ultimate-tensile-strength and fracture strain are about 2022 MPa and 0.246, respectively. The microstructure examinations indicate that the martensitic was refined greatly during the electropulsing strengthening process. The fine martensitic with high-density dislocation makes the steel with good mechanical properties. The amazing results can be attributed to the thermal and athermal effects of the electropulsing. Due to the effect of rapid heating during electropulsing, a large overheating could be obtained, which could result in the high nucleation rate of austenite. Moreover, the pulse current itself can increase the austenite nucleation rate by decreasing the thermodynamic barrier. Finally, the fine lath-martensitic with high-density dislocation formed during the subsequent quenching process.     

Effect of Electropulsing on Recrystallization and Mechanical Properties of Silicon Steel Strips

Electropulsing-induced recrystallization and its effect on mechanical properties of oriented silicon steel strips (Fe-3.0%Si) were studied by optical microscopy, scanning electron microscopy and electron back-scatter diffraction. The results indicated that electropulsing accelerated recrystallization, and decreased the temperature of recrystallization. Electropulsing favors refinement of the grain structure of the alloy. Effects of electropulsing on strength and elongation of the alloy were discussed from the point view of dislocation dynamics, microstructural changes, and electropulsing kinetics.     

Microstructure and formability of AZ31B magnesium alloy sheet under continuous pulse current

Utilising electropulsing treatment (EPT) to improve the formability of metals is of paramount importance for engineering applications. The effects of EPT on the microstructure and formability of AZ31B magnesium alloy sheet were investigated. The results indicated that the microstructure and mechanical properties were slightly improved with the increase of current density, while the formability was promoted distinctly. Besides, the formability of the specimen after EPT was better than that of the specimen annealed at the same temperature, which indicated that pulse current can effectively increase the formability of the sheet. Further studies confirmed that the athermal effect caused by the pulse current made great contribution to the dislocation mobility and improved the formability of the sheet.