Variations in stir zone and thermomechanically affected zone of dissimilar friction stir weld of AA5083 and AA6082 alloys

Variations in composition, microhardness (in the thermomechanically affected zone) and texture in the tool domain of the dissimilar friction stir weld of AA5083-O and AA6082-T6 alloys were investigated. The contents of the major alloying elements in the weld zones were determined using inductively coupled plasma?atomic emission spectroscopy. It was observed that a slight drop in the content of the alloying elements results from the friction stir welding process with the Mg content being the most affected amongst the major alloying elements in the two alloys. By relating the mass fractions of the major alloying elements in the parent metals of both alloys to those of the stir zone, the relative proportions of the two alloys in the stir zone were estimated with the results showing that at least 60% of the materials in the stir zone are from the retreating side of the weld. It was also revealed that the changes in the hardness profile in the thermomechanically affected zone of the retreating side are predominantly influenced by changes in grain size in that domain. Finally, the investigation further revealed that the texture component in the tool shoulder domain is different from the texture component in the tool pin domain.     

Application of electrochemical techniques to organic coatings (AETOC 2013)

Abstract

AETOC 2011 took place in Emmetten, Switzerland on the 24–27, April 2013. This was the latest in a sequence of biannual meetings which have taken place since 1999. The meeting falls under the auspices of the European Federation of Corrosion Coatings Working Party and was the ninth international workshop in the series. Previous meetings have been held in Genoa, Italy in 1984; Schliffkopf in the Black Forest, Germany in 1999; Jurata, near Gdansk in Poland, in 2001; at Sintra near Lisbon, Portugal in 2003; at Villard de Lans near Grenoble, France in 2005; at Baiona in Northern Spain in 2007; at Grado, Northern Italy in 2009 and at Mons, Belgium in 2011.     

DISTRIBUTION OF SULFUR IN HIGH TEMPERATURE PHASES OF CAST IRON

The distribution of subversive element sulfur in high temperature phases during solidificationof cast iron was investigated by means of liquid quenching method and autoradiography.Theresults show that in grey cast iron,sulfur is concentrated in the liquid,flake graphite and in theperipherial area of D-type supercooled graphite eutectic cells,but less sulfur is in austenite.Besides,the content of sulfur in A-type graphite is higher than that in D-type graphite,andsulfur content in eutectic austenite is a little higher than that in primary austenite.While,innodular graphite cast iron less sulfur is in liquid and austenite,but more in nodular graphite.The blackness of the spots on the emulsion film corresponds to the atomic percentage ofradioactive substances located on the surface of the specimen.     

FORMATION LAW OF PHASES IN ULTRAFINE POWDERS OF Al-Cu ALLOY PREPARED BY GAS EVAPORATION PROCESS

１ＩＮＴＲＯＤＵＣＴＩＯＮＵｌｔｒａｆｉｎｅｐｏｗｄｅｒｓｗｉｔｈａｐａｒｔｉｃｌｅｓｉｚｅｌｅｓｔｈａｎ１００ｎｍｈａｖｅｅｘｃｅｌｅｎｔｐｒｏｐｅｒｔｉｅｓｉｎｃｏｎｔｒａｓｔｔｏｃｏａｒｓｅｇｒａｉｎｍａｔｅｒｉａｌｓ［１,２］ａｎｄｈａｖｅｗ...     

Reduction in Microsegregation in Al-Cu Alloy by Alternating Magnetic Field

The microsegregation behavior of the Al-4.5 wt%Cu alloy solidified at different cooling rates under the alternating magnetic field(AMF) was investigated.The experimental results showed that the amount of non-equilibrium eutectics in the interdendritic region decreased upon applying the AMF at the same cooling rate.The change in microsegregation could be explained quantificationally by the modifications of dendritic coarsening,solid-state back diffusion and convection in the AMF.The enhanced diffusivity in the solid owing to the AMF was beneficial for the improvement in microsegregation compared to the cases without an AMF.In contrast,the enhanced dendritic coarsening and forced convection in the AMF were found to aggravate the microsegregation level.Considering the contributions of the changes in above factors,an increase in solid diffusivity was found to be primarily responsible for the reduced microsegregation in the AMF.In addition,the microsegregation in the AMF was modeled using the analytical model developed by Voller.The calculated and experimental results were in reasonable agreement.     

MICRODISTRIBUTION OF NODULIZER IN VARIOUS PHASES OF CAST IRON

应用有机电解液低温电解及放射性测量方法,测定了普通铸铁及高纯Fe-C-Si合金中的合金化Ce量及石墨中的Ce量,石墨中的Ce量大都略高于或相近于基体中的Ce量,在Ce含量相同的情况下,铸铁中的合金化Ce量比钢中多。 涂层法自射线照相结果表明:Ce在片状石墨中呈均匀分布,而在球状石墨中的分布却是多样的。开花状石墨中的Ce多于片状石墨及球状石墨中的Ce.球状石墨周围的铁素体及珠光体是贫Ce.远离球状石墨的珠光体及莱氏体是富Ce.初生奥氏体枝晶转变形成的珠光体和蜂窝状莱氏体都含有较少的Ce,而板状渗碳体型莱氏体含Ce较多.Ce明显富集于共晶时最后凝固的区域。球状石墨的形成主要取决于原铁水中的反球化剂(硫)含量,它的影响比球化剂的残留量或合金化量的作用更大。     

Synthesis and characterization of electrodeposited Ni-Pd alloy electrodes for methanol oxidation

A wide compositional range of Ni-Pd alloy catalysts were prepared by electrodeposition for use as anode materials for methanol oxidative fuel cells in alkaline conditions. Structural characterization of the electrocatalysts in their as-plated condition revealed that the Ni-Pd catalysts synthesized were nanocrystalline, single phase, face centered cubic materials, indicating the formation of complete solid solution in the alloy. Compositional analysis of the alloys indicated that the palladium composition of the alloy increased with decrease in current density. This change in the composition of the alloy resulted in a shift in the X-ray diffraction peaks. The percentage shift in the d-spacing calculated from X-ray diffraction is in good agreement with percentage of palladium in the alloy. The electrocatalysts prepared are active for methanol oxidation in alkaline medium.     

Formation of Mesoferrite and Granular Bainite in Low-Carbon Low-Alloy Steel

Special features in the formation of mesoferrite and granular bainite in low-carbon low-alloy steels are considered. A diagram of isothermal decomposition of austenite in steel 20Kh2NAch is plotted and the range of existence of mesoferrite is determined. Morphological differences between the granular intermediate structure formed in the isothermal decomposition of supercooled austenite in the intermediate temperature range and the granular bainite formed in the decomposition of austenite in continuous cooling are determined. The role of mesoferrite in the formation of these structures is considered.     

Two decades of change in graduate education in metallurgy/materials—A perspective

It is now almost a decade since the introduction of massive federal support to universities for graduate education and research in the materials field. Accordingly, it is appropriate to examine the changes in the nature and activity of the field which have occurred during this period, both in the universities themselves, and in professional practice in industry and government, and also the implications of such changes for graduate education in metallurgy and materials science in the future.The present paper examines the growth of relevant university activities in the field over the past 10 years in comparison with that during the preceding decade and with the growth of engineering, science and advanced education in general in the United States, i.e., the question of the supply of new personnel with advanced training in the materials field. While it is appreciated that the nature and quality of education must be of prime importance, this paper deals principally with the numerical aspects of graduate education in materials, rather than with the philosophy, as a necessary first step in the broader study which is advocated.     

Laser-aided manufacturing in Ukraine

Started in the early 1960s, R&D development in laser technology in Ukraine is still in progress in spite of some decline in 1990–1993 caused by drastic political and economic changes in the country. There are, indeed, some interesting and original results in all known industrial applications. Some of them are presented in this report. The international ties with colleagues and joint projects with copartners from different countries are becoming common practice. The significant intellectual potential and gained research and industrial experience serve as a basis for more than 40 years of academic activity in laser technology in the country. Graduates of the Laser Technology and Materials Science Department of the Kiev Polytechnic Institute (engineers, masters, PhD holders) are quite successful in their career both in Ukraine and in different countries of the world. Collaboration within the framework of the European Union as well as with different institutions in North America and Asian countries is increasing quite rapidly. The text was submitted by the author in English.     

Dependence of viscosity of Cu9In4 intermetallics melt on thermal history

The temperature dependence of the dynamic viscosity of Cu9In4 intermetallics melt has been investigated in five kinds of different heating and cooling processes with a torsional oscillation viscometer, It has been found that the viscosity of all Cu9In4 intermetallics decreases with increasing temperature in five kinds of different thermal processes. Thermal history has considerable effect on the viscosity. The viscosity in the cooling process with high superheating is greater than that in the cooling process with low superheating. The viscosity in the heating process is greater than that in the cooling process. No anomalous change in viscosity is measured in three kinds of cooling processes with low superheating. The anomalous change occurs at about 1050℃ in cooling with high superheating and at 800℃ in heating. Furthermore, the structural variation in different thermal processes has also been discussed on the basis of the change in viscosity and DSC analysis.     

Changes in the potential and vibrational energies upon the formation of vacancies in the oxygen-alloyed cores of crystallite-conjugation regions of polycrystalline Cr, Cu, and Ir

The changes in the potential and vibrational energies upon the formation of vacancies in the oxygen-alloyed (OA) cores of crystallite-conjugation regions (CCRs) in polycrystals of d transition metals Cr, Cu, and Ir have been determined. The potential energy increases upon the formation of vacancies (upon the formation of complexes of vacancies with oxygen atoms) in the OA cores of CCRs in the polycrystalline Cr, Cu, and Ir. However, the vibrational energy decreases upon the formation of vacancies in the OA cores of CCRs in these polycrystals, as in the OA cores of CCRs in polycrystals of the 4d and 5d transition bcc metals Mo, Ta, and W. The volume of the OA cores of CCRs in polycrystals of Cr, Cu, and Ir decreases upon the formation of vacancies. The changes in the interatomic interactions and dynamic properties in the regions of vacancy localization in the OA cores of CCRs coincide with analogous changes introduced into the lattices of metals by split interstitials.     

海水环境中微生物附着对钝性金属开路电位的影响

采用电化学技术和荧光显微技术研究了微生物附着对钝性金属在海水中开路电位的影响．研究中发现，在自然海水中。钝性金属的开路电位逐渐正移达300mV．显微镜原位观察表明，浸入海水后，微生物在金属表面逐渐寄居附着。形成微生物膜．微生物的数量与开路电位按相同方式增加．但在灭菌海水中以及铜电极情况下，开路电位保持不变，微生物也很少附着在表面上．此外，钝性金属界面双层电容在自然海水中逐渐减少。但在灭菌海水中，由于没有微生物膜存在。电容值保持不变．这些结果证实，微生物在表面的附着和寄居生长是导致钝性金属开路电位正移的主要原因．     

NbFe合金的生产现状和发展

评述了中国及世界主要的NbFe合金生产厂家的生产能力、现状及世界钢铁工业对NbFe合金的需求状况,展望了中国NbFe合金的未来发展趋势.巴西CBMM公司是世界上最大的NbFe合金生产企业,最近几年NbFe合金生产能力已有相当大的提高,NbFe合金产量占世界总产量的70%以上,其中出口约14 800t.中国钢铁中铌的平均含量仅为美国和欧洲的15%,因此来自中国铌的需求量至少有6倍的增长空间.宁夏东方有色集团金联公司是中国最大的NbFe合金生产厂家,其NbFe合金生产量快速增长,2005年上半年达580t,占中国NbFe合金产量的75%以上.     

热处理对SiCp/Al复合材料强度和塑性的影响

采用粉末冶金法制备了d300 mm的15%SiCp/Al(体积分数)复合材料坯锭,研究了挤压态和T4态复合材料的力学性能和断裂特点,揭示了基体强度和颗粒开裂对复合材料强度与塑性的影响规律。结果表明:复合材料T4态拉伸强度保持在560 MPa的水平下,延伸率仍高达7%以上;与挤压态相比,T4态复合材料拉伸强度和屈服强度分别提高了68.5%和105%,但塑性保持在同一水平。断口观察表明:挤压态复合材料以基体断裂为主,而T4态复合材料除了基体断裂外,还存在SiC颗粒开裂现象;基体强度严重影响复合材料的断裂形式,颗粒开裂有利于提高复合材料的塑性。     

Changes in the vibrational energies and interatomic spacings upon the formation of vacancies in the volumes and in the cores of crystallite-conjugation regions of polycrystalline transition metals with cubic lattices

The changes in the vibrational energies and the signs of changes in the interatomic spacings upon the formation of vacancies in the bulk of metal and in the cores of the crystallite-conjugation regions (CCR) in polycrystalline transition metals with bcc and fcc lattices have been determined. The vibrational energy increases upon the formation of a vacancy in the bulk of metal because of a positive “relaxation” contribution to the change in the force constant of the atoms surrounding a vacancy. Positive “relaxation” contributions to the changes in the force constants and, correspondingly, an increase in the vibrational energy of the atoms surrounding a vacancy arise also upon the formation of “split” vacancies (S vacancies) in the cores of CCRs of polycrystalline transition metals with a face-centered cubic lattice. The positive “relaxation” contributions to the changes of the force constant of atoms in the region of localization of S vacancies are caused by a decrease in the interatomic spacings upon their formation, just as upon the formation of conventional vacancies in the bulk of metals. The vibrational energy of the nearest environment of the vacancies that are formed in the CCR cores in the polycrystalline d transition metals with a bcc lattice decreases because of a negative “relaxation” contribution to the change in the force constants. The cores of the high-angle CCRs in polycrystalline d transition metals with a bcc lattice are characterized by a negative internal pressure. Therefore, vacancies with positive relaxation volumes ν_BCC > 0 are formed in them, causing an increase in the interatomic distances in the nearest environment of such vacancies.     

Indentation-induced localized deformation and elastic strain partitioning in composites at submicron length scale

Three-dimensional spatially resolved strains were mapped in a model NiAl/Mo composite after nanoindentation. The depth-dependent strain distributed in the two phases and partitioned across the composite interfaces is directly measured at submicron length scale using X-ray microdiffraction and compared with a detailed micromechanical stress analysis. It is shown that indentation-induced deformation in the composite material is distinct from deformation expected in a single-phase material. This difference arises in part from residual thermal strains in both phases of the composite in the as-grown state. Interplay between residual thermal strains and external mechanical strain results in a complex distribution of dilatational strain in the Mo fibers and NiAl matrix and is distinct in different locations within the indented area. Reversal of the strain sign (e.g., alternating tensile/compressive/tensile strain distribution) is observed in the NiAl matrix. Bending of the Mo fibers during indentation creates relatively large ～1.5° misorientations between the different fibers and NiAl matrix. Compressive strain along the 〈0 0 1〉 direction reached ?0.017 in the Mo fibers and ?0.007 in the NiAl matrix.     

Grain boundary segregation of phosphorus in iron-vanadium alloys

Grain boundary segregation of phosphorus has been studied in Fe---V---P and Fe---V---P---C alloys through fracture experiments in a scanning Auger microprobe with the objective of examining the effects of vanadium on the interaction processes operative under circumstances when the structure in the interior of the grain (in the present case carbide formation) and grain boundary segregation occur simultaneously. It is understood that to predict and analyse the behaviour of an alloy, it is pertinent to consider the atomic interactions both at the grain boundaries and in the grain interior and that between the constituents and the grain boundaries. The study suggests that the determining factor for suppression or decrease in the migration of phosphorus to the grain boundaries is whether vanadium is present in the combined form (say, carbide) or is available in solid solution form. When vanadium is present in solid solution form, grain boundary segregation of phosphorus is low because of the chemical interaction of vanadium and phosphorus. However, as carbon is increasingly introduced in the alloy, vanadium now preferentially interacts with carbon in view of a higher interaction for carbon as compared to that of phosphorus. A consequence of this is an increase in the grain boundary concentration of phosphorus. In such a situation, the presence of excess carbon in addition to what is stoichiometrically required to precipitate the entire vanadium as vanadium carbides serves as a palliative with regard to the reduction in the intergranular concentration of phosphorus. This palliative behaviour is explained in terms of the site-competition model. An effort is also made to examine the behaviour of segregating elements in terms of a whole range of probable interactions (both at the grain boundaries and in the grain interior) and chemical interaction energies.     

铝合金双面搅拌摩擦焊初步研究

提出了双面搅拌摩擦焊这种新的焊接方法，对比研究了6K32-T4铝合金搅拌摩擦焊与双面搅拌摩擦焊接头的组织和硬度，并对双面搅拌摩擦焊焊缝进行了XRD分析。研究发现：铝合金双面搅拌摩擦焊与搅拌摩擦焊焊缝组织分区相同；双面搅拌摩擦焊焊缝的硬度略低于搅拌摩擦焊，且焊缝硬度下降区域范围更大；双面搅拌摩擦焊后焊缝依然保持为原有相组成；双面搅拌摩擦焊比搅拌摩擦焊焊接线能量更大，采用双面搅拌摩擦焊代替搅拌摩擦焊有利于提高焊接效率并消除焊缝隧道型缺陷、改善焊缝的性能。