旋转磁场调控优化Cu-Cr-Zr-Si合金组织和性能

凝固过程是金属材料制备的核心环节，该过程决定了金属的铸态组织及性能。本文以Cu-Cr-Zr-Si合金为研究对象，对其施加旋转磁场，研究了真空下不同磁场电流对Cu-Cr-Zr-Si合金的凝固组织和性能的影响。组织结果表明，随磁场电流增大，晶粒尺寸减小。当磁场电流从40 A增加至120 A，基体的晶粒尺寸从270 μm细化至58 μm。此外，还观察到晶粒形貌逐渐从柱状晶转变为等轴晶，随磁场电流增大，等轴晶区域占比逐渐增加。性能分析表明：相比于未加磁场的合金，在磁场电流 I=40，80 和 120 A 条件下，合金抗拉强度分别提高了 6.1%，7.3%和19.2%；屈服强度提高了6.1%，10.%和19.4%；伸长率则分别提高17.4%，26.1%和60.9%。强度和塑性的提高主要归因于晶粒细化和等轴晶粒占比的提高。合金电导率在很大程度上不受旋转磁场的影响。在凝固过程中施加旋转磁场被认为是调控微观组织实现性能提高并可规模化生产的关键技术。     

金属材料组织性能改变方式

金属材料及其性能在机械加工中有着非常重要的作用,通过对金属材料内部组织结构的改变,就能够影响到其工艺性能以及使用性能。本文主要通过对金属材料组织性能的方式进行研究,从不同方面加强对金属材料性能的改变。     

测试方法对测定金属材料屈服强度的影响探析

金属材料作为工业生产中重要的生产原料,其性能与使用效用一直受到格外关注。屈服强度是金属材料性能在力学领域上的表现形式,而对于屈服强度的测定,要先进行屈服点的选定。测定金属材料的屈服点在一定程度上影响着金属材料屈服强度的测试结果,而拉伸对于金属材料性能的测定来说是最好的方法之一,能够在一定程度上、一定领域内对于金属材料的性能进行科学有效的判定。     

不同磁场作用对AZ31镁合金的凝固组织的影响

镁合金是具有优越性能的金属材料,镁合金的加工是目前国内外正在深入进行研究的新课题.实验发现在镁合金的凝固过程中施加低频或静态磁场都能细化晶粒,但静磁场得到的细化效果要优于低频交流磁场,同时随磁感应强度的增加,静磁场细化晶粒的效果明显提高;在静磁场条件下晶界共晶体组织的厚度明显减小,同时在晶内出现了大量细小块状化合物,这有利于改善镁合金的综合性能.     

电磁场对改善钢材质量的作用

研究了电磁制动技术对结晶器内钢液流动及夹杂物迁移行为的作用,以及电磁搅拌和电磁超声波对钢材料凝固组织的影响。研究结果表明,在恒稳电磁场作用下,钢液内形成的与钢液流动相反的电磁力可有效地控制钢液流动、稳定液面波动,有利于夹杂物的去除;在电磁搅拌和电磁超声波的作用下,金属的凝固组织得到细化,等轴晶比率明显提高。计算了磁场对奥氏体／铁素体及铁素体／奥氏体平衡边界的影响,磁场对相图的奥氏体／铁素体界限产生很大影响,使其向高成分或高温度区域移动;随成分不同,磁场每增加1T,钢的Ae3温度升高2～3℃。研究了电场奥氏体化对中碳合金钢40MnMoV性能的影响,与常规工艺处理样品相比,电场奥氏体化可使其硬度值升高,且冲击性能和拉伸性能的指标都有所提高。     

电场时效对2014铝合金的微观组织和力学性能的影响

通过拉伸试验、硬度测试、X射线衍射(XRD)分析、扫描电子显微镜(SEM)及透射电子显微镜(TEM)分析技术,研究了170℃×10 h电场时效工艺条件对2014铝合金板的微观组织和力学性能的影响.实验结果表明,电场时效有助于提高2014铝合金板的屈服强度和硬度,而且2014铝合金板的屈服强度和硬度随电场强度的升高而增加.电场时效使2014铝合金板的主织构由非电场时效的{001}<110>织构转变为{001}<210>织构,且{001}<210>织构的强度呈现出随电场强度升高而增强的趋势.电场时效2014铝合金板的屈服强度和硬度的提高主要归因于其微观组织和织构的转变.     

试验速率对金属材料力学性能的影响

试验速率对金属材料力学性能影响很大,本文通过对比分析不同试验速率对钢材、铝合金、镁合金、钛合金等金属材料力性性能的影响,结果表明:试验速率对钢材屈服点影响较大,对铝合金和镁合金材料的塑性影响较大,对钛合金屈服强度影响较大。对于不同金属材料,合理控制试验速率,有利于提高对金属材料力学性能测试的准确性。     

《金属学》若干基本概念问题

“《金属学》若干基本概念问题”作为一篇供大家讨论的文章把它发表出来,旨在收取提高教学质量的效果。本文从六个方面对《金属学》教材中的一些基本概念提出问题,并发表了作者的意见:一、金属材料的结构及其对性能的影响;二、组织和组织组成物;三、决定金属材料性能的基本因素;四、影响金属材料显微组织的因素;五、相平衡自由度;六、相图若干概念。     

CeO2对2024铝合金显微组织和拉伸性能的影响

利用金相组织观察、扫描电镜分析、X射线衍射分析和拉伸性能检测等方法,研究了不同CeO2含量对2024铝合金显微组织及力学性能的影响.结果表明,CeO2能够细化2024铝合金的铸态组织和退火态组织.CeO2与金属Al反应生成的Ce,与基体中的Al和Cu形成新相Al3Ce、CeCu2.添加CeO2能够提高2024铝合金的抗拉强度和屈服强度,而且添加0.25%(质量分数,下同)时能够获得最佳性能,铸态下的抗拉强度和屈服强度分别提高了55%和50%,退火态下的抗拉强度和屈服强度分别提高了30%和17%.但是CeO2的加入量过高,反而使合金的性能降低.当未添加CeO2时,2024铝合金断口表面呈准解理和韧窝状态,表现为脆性与韧性结合的混合断裂特征,而添加一定量的CeO2时,合金呈现出塑性断裂特征.     

电场时效对铝锂合金性能和断裂特征的影响

研究了电场时效处理对 14 2 0合金板材性能的影响 ,探讨了其作用机理。研究发现 ,电场时效可在一定程度上提高合金的延伸率 ,且试样作负极时效果更明显 ;但电场对合金的强度几乎没有影响 ;电场时效还改变了合金的断裂方式 ,减小了沿晶分层断裂比例 ,增加了穿晶断裂比例和微区塑性变形。电场是通过对空位的作用来影响合金的析出相变、PFZ的形成和合金元素的晶界偏析 ,从而改善合金的性能     

辊套材料对铸轧区磁感应强度影响的实验研究

电磁场快速铸轧技术要求辊套材料不仅具有高导热系数、高承载能力和高抗疲劳能力，而且要具有磁场控制能力，保证铸轧区足够的磁感应强度，达到细化晶粒、改善板坯组织性能的目的．本文主要从介质对电磁场的集肤效应、涡流效应、磁场衰减以及屏蔽效应的角度，研究辊套对铸轧区电磁场的影响．     

脉冲电流作用下金属熔体内电磁场分布的数值模拟

 将脉冲电流作用于铁素体不锈钢,发现经过脉冲电流处理后等轴晶比例大幅增加,晶粒明显缩小。建立了考虑集肤效应的三维电磁场瞬态有限元模型,利用ANSYS软件对电极及熔体内的电场、磁场、电磁力分布进行了计算,结果表明,由于集肤效应使得电磁场主要集中在电极周围和熔体上部,且在脉宽的后期电磁场的方向由于涡流的存在而发生变化;电极间距对熔体电磁场均匀性具有较大影响;随着脉冲电流的脉宽减小,熔体上部的电磁场增强,但集肤深度也越小,同时作用时间缩短。     

在电场中奥氏体化对低碳钢显微组织及淬透性的影响

研究了低碳钢在直流静电场中进行奥氏体化后淬火的显微组织。结果表明：与无电场处理的试样相比,加电场奥氏体化后的试样在随后的淬火过程中获得了较多的马氏体,淬透性提高,并且电场强度为2kV／cm时硬度最大。这是因为电场增加奥氏体的稳定性,抑制随后冷却过程中由扩散控制的奥氏体向珠光体的转变,使CCT曲线右移。     

Progress in Research on Solidification in a Strong Static Magnetic Field

Strong magnetic fields available from superconducting magnets are opening a way to new phenomena that could lead to new methods in materials processing including solidification. The principal research involving solidification in strong static magnetic fields is emphasizing four aspects: control of crystal orientation, convection damping, thermoelectric magnetohydrodynamics (TEMHD) and change in thermodynamics. Under high magnetic intensity, aligned structural textures are induced in both magnetic and non‐magnetic materials. Since in strong magnetic field the melt flow is suppressed by convection damping, the microstructure being formed during solidification is affected heavily; this phenomenon applies to eutectic, monotectic and peritectic alloys as well as to dendritic morphologies typical of directional solidification. If strength and orientation of a magnetic field are controlled appropriately, this strong damping effect will generate more homogeneous crystals as a result of achieving diffusion‐controlled solute transport conditions. TEMHD more easily occurs in strong magnetic fields, resulting in equiaxed crystals even under directional solidification. It is evidenced experimentally and theoretically that the thermodynamics of phase transformation and nucleation are changed by strong magnetic fields.     

Effects of a High Magnetic Field on the Microstructure of Ni-Based Single-Crystal Superalloys During Directional Solidification

High magnetic fields are widely used to improve the microstructure and properties of materials during the solidification process. During the preparation of single-crystal turbine blades, the microstructure of the superalloy is the main factor that determines its mechanical properties. In this work, the effects of a high magnetic field on the microstructure of Ni-based single-crystal superalloys PWA1483 and CMSX-4 during directional solidification were investigated experimentally. The results showed that the magnetic field modified the primary dendrite arm spacing, γ′ phase size, and microsegregation of the superalloys. In addition, the size and volume fractions of γ/γ′ eutectic and the microporosity were decreased in a high magnetic field. Analysis of variance (ANOVA) results showed that the effect of a high magnetic field on the microstructure during directional solidification was significant (p < 0.05). Based on both experimental results and theoretical analysis, the modification of microstructure was attributed to thermoelectric magnetic convection occurring in the interdendritic regions under a high magnetic field. The present work provides a new method to optimize the microstructure of Ni-based single-crystal superalloy blades by applying a high magnetic field.     

凝固过程中的脉冲磁场和脉冲磁力研究

用数值模拟方法研究了凝固样品中的脉冲磁感应强度和电磁力的分布特性。模拟结果表明，脉冲磁场凝固条件下，脉冲磁感就强度和电磁力分布具有轴向、径向分布的不对称性和不均匀性。这种分布特性有助于了解脉冲磁场对金属凝固组织的细化作用。     

由运动带电体看电场与磁场关系

通过研究一些带电体的电场和磁场在两个不同惯性系之间的相对变换 ,得到某些反映运动物体电场磁场公式 ,并阐明电场和磁场的相对性和统一性     

Electromagnetic Environmental Impact of 500-kV Double-Circuit Transmission Lines

The strength of the power frequency electric intensity and magnetic field of the 500-kV double circuit transmission lines was calculated by using the equivalent charge method and the Ampere's Law,and the environmental impact factors of the fields were evaluated. By optimizing the phase sequence,the frequency electric intensity and magnetic field strength can be reduced. Within a distance of 25 m from the center of the transmission line,the power frequency electric intensity and magnetic field strength fall off sharply with the distance increase.Finally,the best phase sequence and the minimum ground clearance of the transmission lines were obtained to meet the requirements of the least impact on envionment.     

Influence of Electric Field on Mechanical Properties of Al-Li Alloy Containing Cerium and Electronic Mechanism

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Effect of Rare Earths on Microstructure and Properties of TiC-based Cermet／Cu Alloy Composite Wear Resistant Materials

The effect of rare earth (RE) oxide on the microstructure and properties of TiC-based cermet/Cu alloy composite hardfacing materials was investigated by using scanning electron microscope (SEM), transmission electron microscope(TEM), impact test and wear test. The mechanism of RE oxide for improving the phase structure and the impact toughness was also discussed. The experimental results indicate that the microstructure of the matrix can be refined, and the micro- porous defects can be eliminated by adding RE oxide into the composite materials. The polycrystalline and amorphous phase structure is formed at the interface of cermet and matrix metal. The formed structure enhances the conjoint strength of interface. The frictional wear resistance can be improved obviously, although the microhardncss of the matrix metal can not be effectively increased by adding RE oxide.