Microstructural Refinement and Strain Hardening Behavior in Low-Density Ultrafine Pearlite Steel

Advanced low-density steels that meet energy shortages and high safety requirements have become a hot research topic in materials science. The addition of light elements with medium-Al content (5 wt%) to ultrahigh-strength pearlite cable steel alloy reduces the material density and causes a microstructural change from traditional θ-pearlite (ferrite + cementite) to θ-pearlite and κ-pearlite (ferrite + cementite + κ-carbide). The results show that the moderate addition of Al and Mn (5 wt%) promotes the formation of κ-carbide, which inhibits the diffusion of C and significantly delays the eutectoid transformation process of pearlite. Meanwhile, the transformation free energy of pearlite increases and obviously refines the lamellar spacing of the ultrafine pearlite by κ-carbide. Simultaneously, the interaction between κ-carbides and dislocations is initiated, which increases the strain hardening rate of ultrafine pearlitic steel.     

Particle Image Velocimetry Measurements within a Laboratory-Generated Swash Zone

A particle image velocimetry (PIV) technique is used to make vertically resolved two-dimensional measurements in swash zone flows, which are notoriously recalcitrant to quantitative measurement. The PIV implementation directs the light sheet into the measurement region from beneath the beach thus avoiding issues of free surface diffraction effects. Fluorescent particles and an optical filter are used to ensure that only particles, and not bubbles or free surface anomalies, are imaged. The spatially and temporally resolved velocity fields measured in a plunging and spilling wave-driven swash zone are used to investigate the boundary layer structure of the mean and turbulent quantities as well as the phase evolution of the bed shear stress, near-bed turbulent kinetic energy, and the dissipation. Results suggest that vertical structure in spilling and plunging wave forced swash zones are similar. The uprush phase is dominated by bore-generated and bore-advected turbulence, which evolves analogously to grid turbulence, while the downrush phase is ultimately dominated by boundary layer generated turbulence, which compares well near-bed with classic flat plate boundary layer theory.     

铜米电解工业化试验研究

以铜米为原料在铜电解系统进行工业化应用试验,主要对铜米电解的生产过程控制、能耗、产品质量的研究情况进行了阐述。工业试验结果表明,铜米电解工艺可以产出接近A级铜品质的阴极铜,目前技术条件下,铜米直接电解生产阴极铜工艺成本高,仍需进行改进。     

Microstructural Characteristics of a Stainless Steel/Copper Dissimilar Joint Made by Laser Welding

The microstructures and its formation mechanism of a stainless steel/copper dissimilar joint by laser welding were investigated. It was found that the two modes of joining, i.e., welding-brazing and fusion welding, depend on different processing parameters. In the welding-brazing mode, the interface between copper and the fusion zone has scraggy morphology because the molten pool is frozen by solid copper with high thermal conductivity. The interdiffusion of elements occurs in the neighborhood of the interface, which leads to the metallurgy bond of the mode. In the fusion welding mode, the liquid phase in the fusion zone undergoes not only primary but also secondary liquid separation due to the high cooling rate and high supercooling level of laser welding. Some microcracks generated in the fusion zone by thermal stress mismatch are healed by liquid copper filling.     

Microstructural Refinement of Bainite and Martensite for Enhanced Strength and Toughness in High-Carbon Low-Alloy Steel

This study attempts to determine the scope and extent of microstructural refinement through complete/partial recrystallization of prior cold deformed ferrite during austenitizing (1223 K (950 °C), 15 minutes) and/or austempering (543 K (270 °C), 30 minutes) followed by water quenching to obtain ultrafine bainitic sheaves along with thin martensitic plates in SAE 52100 steel. The volume fraction and sheaf/plate dimension (thickness/length) of bainitic ferrite and martensite were determined by optical and scanning/transmission electron microscopy studies coupled with compositional microanalysis. Marginal improvement in the tensile strength and significant improvement in the impact properties is obtained at an optimum level of prior cold deformation by tension in comparison to that recorded in austempered condition without prior deformation.     

Iron Influence on Copper Biosorption Using Anaerobic Sludge and Its Microstructural Characterization

With the purpose of determining the copper biosorption mechanism, iron influence on the bioremoval, and methane production in a batch system using an anaerobic sludge a systematic study was carried out. In addition, sludge was characterized before and after biosorption treatment by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS). According to results, Fe(III) has effect on copper biosorption. At neutral pH and concentrations from 50 to 300 mg/L, copper biosorption increases. However, at concentrations >300 mg/L a reduction in biosorption is observed. During biosorption, Fe(III) does not have an effect on both methane production and methanogenic activity; consequently, it is possible establishing that methanogenic bacteria are active under these conditions. Results of analysis by EDS reveal the copper presence into diatoms (2.66w%). In addition, biosorption of copper is by means diatoms-bacteria-polimeric matrix, and it is also bioaccumulated into diatoms.     

Microstructural Changes Produced by Fatigue in High-Purity Copper Severely Deformed by Cryogenic Rolling

High-purity Cu (99.995 pct pure) rods were cryogenically rolled through a 90 pct reduction in area and given a very brief low-temperature anneal. The resultant material was highly textured, had very low internal strains, and had a broad distribution of grain sizes with an average grain size of 150 to 300 nm. Samples were tested in stress-control tension-tension fatigue. Fatigue life was strongly improved over that of coarse-grain (CG) copper. The cycling caused significant softening and grain growth, especially at the lower stress amplitudes. Plastic strain was small but creep was evident. Clusters of long parallel protrusions that were quite uniformly spaced about 100 nm apart formed on the sample surfaces during fatiguing. Among the various microstructures seen in the fatigued specimens, transmission electron microscopy (TEM) pictures taken just inside the surface showed parallel dislocation lines many micrometers in length spaced about 100 nm from one another. It is possible that these dislocations are involved in the formation of the protrusions. The Institute of Metals Lecture, established in 1921, recognizes an outstanding scientific leader who is selected to present a lecture at the TMS Annual Meeting. The Robert Franklin Mehl Award was established in 1972. Julia Weertman received her BS, MS, and DSc in Physics at the Carnegie Institute of Technology (now CMU). She worked in ferromagnetic spin wave resonance at the United States Naval Research Laboratory for 6 years, took some time off to raise her family, and has since then been on the faculty of the Department of Materials Science and Engineering at Northwestern University, where she is now Walter P. Murphy Professor Emerita. Professor Weertman’s areas of research center on the mechanical behavior of metals and alloys and the underlying phenomena that give rise to the observed behavior. Her research currently is focused on determining the mechanical properties of a variety of nanostructured materials, their synthesis, the characterization of their structure, and the study of the deformation mechanisms in this small grain size regime. Professor Weertman is a member of the National Academy of Engineering and the American Academy of Arts and Sciences and is a Fellow of TMS, ASM International, and the Neutron Scattering Society of America. She received the Von Hippel Award from the Materials Research Society and the Achievement Award from the Society of Women Engineers. She served on the MRS Board of Directors, is on the Editorial Board of the MRS Bulletin, and currently is chair of the Awards Committee of the MRS.     

Microstructural characterization of a

A detailed investigation concerning the microstructural characteristics of a rapidly solidified Al-Mg-Mn powder alloy has been carried out. A range of microstructures was observed in the atomized powder: dendritic, cellular, and featureless morphologies. Variations in structure have been related to cooling rate, nucleation undercooling, and recalescence during solidification. A metastable Al-Mn phase was created during atomization and was present in two distinct morphologies. Decomposition behavior during thermal and thermomechanical processing has been studied. An interesting feature was the retention of the metastable phase through the initial consolidation stages.     

铜闪速吹炼过程颗粒行为仿真研究

通过UDF函数在FLUNET中增加冰铜颗粒的燃烧模块建立闪速吹炼仿真模型,进行了闪速吹炼炉冶金过程多场仿真研究。通过对给定工艺条件下的颗粒的温度、氧化程度、颗粒运动速度、存活时间和沉淀池分布情况的模拟研究发现:颗粒在反应塔内不断地偏离反应塔中央,在反应塔内,平均偏移距离约0.6 m;闪速吹炼炉内颗粒温度上升速度受颗粒直径的影响,颗粒越小,温度上升越快,对于20μm的颗粒在距离反应塔顶1~1.5 m处其温度即可达到最高点。     

高强度铜闪速熔炼过程颗粒行为仿真研究

通过在Fluent中增加铜精矿颗粒燃烧模块,建立闪速熔炼仿真模型,对闪速熔炼炉冶金过程颗粒行为进行仿真研究。通过在给定工艺条件下对颗粒的运动速度及轨迹、存活时间、颗粒温度变化、氧化程度及颗粒在沉淀池分布状况进行模拟。研究表明,精矿颗粒在进入反应塔内平均存留时间较短,并不断偏离反应塔中央,闪速熔炼炉内颗粒温度受颗粒直径的影响,粒度越小,温度上升越快,20μm的颗粒受漩涡的影响程度比较大且易随烟气排出。     

Microstructural and Mechanical Characteristics of Porous Irons Produced with Small Particle Size Corn Starch

Powder Metallurgy and Metal Ceramics - The space holder technique was widely used in manufacturing high melting-point porous metals. Corn powders with a smaller size (11.4 μm on average) than...     

电解铜箔粒子类缺陷的成因分析与管控措施

铜箔作为电子电路行业中一种重要的功能性基础材料,在印制电路板、覆铜箔层压板及锂离子电池等领域被广泛应用。粒子类缺陷是电解铜箔典型的质量问题,本文对电解铜箔的生产工艺过程逐一梳理,阐释粒子类缺陷的表面形貌特征与危害。结合铜箔生产实践,重点对生箔铜瘤、表处镀铜、切屑铜粉、异物等几类典型粒子缺陷的成因进行逐一分析,总结归纳出一套涵盖监控过滤器的效果与寿命、处理生箔机台的绝缘与密封、添加剂配方的优化、处理机导电辊工况的管控、切刀的调整与更换、生产环境的洁净保障等全过程粒子类缺陷管控的有效措施。     

铜尾矿库尾矿全粒径规模化低碳消纳研究

某大型矿冶集团针对该集团铜尾矿库尾矿大量堆存,安全环境风险突出,新建尾矿库选址困难、尾矿消纳途径有限等问题,通过长期摸索研究和对铜尾矿库尾矿粒径分布、成分、化学属性、浸出毒性和放射性等因素进行分析,探索出通过胶凝改造技术充填、制备公路工程无机结合料和铜尾矿资源脱硫分级综合利用的低碳材料消纳模式,尾矿库尾砂能够全粒径规模化消纳利用。单位产品分别消纳尾矿0.075t/t、0.1275 t/t和1t/t,降碳1.564t/t、0.054t/t和0.5195t/t,并分别具有40.0971元/t、12.1235元/t和14.4653元/t的环境正效益,同时协同处置了大量其他固体废物,真正实现了铜尾矿全粒径规模化增值消纳,在全国范围内有很好的借鉴意义。     

铜冶炼企业重金属污染物粒径分布特征研究

对某铜冶炼企业铜冶炼有组织源和无组织源进行监测研究,并利用AERMOD空气质量模型对企业重金属污染物扩散情况进行模拟,通过对铜冶炼企业环境空气质量浓度预测值与监测值的拟合结果来验证铜冶炼企业废气中重金属污染物粒径分级的合理性。结果表明,污染源粒径分级参数的选择对铜冶炼企业重金属污染物的空气质量浓度计算结果有显著影响;当采用"双闪"工艺的铜冶炼企业重金属污染物铅、铜、砷、锌粒径参数质量百分比为25%、质量中位径为8μm时,AERMOD空气质量模型能较好地模拟该企业重金属污染物的扩散。