اتصال آلیاژهای آلومینیوم 5083 و 6061 به روش جوشکاری اصطکاکی تلاطمی

Joining of 5083 and 6061 aluminum alloys by friction stir welding

اتصال آلیاژهای آلومینیوم 5083 و 6061 به روش جوشکاری اصطکاکی تلاطمی

ABSTRACT

Friction stir welding (FSW) has emerged as a new solid state joining technique [1], especially for aluminum alloys [2–6]. In this process, a rotating tool travels down the length of contacting metal plates, and produces a highly plastically deformed zone through the associated stirring action. The localized heating zone is produced by friction between the tool shoulder and the plate top surface, as well as plastic deformation of the material in contact with the tool [1].

At the present time, FSW is used mainly for joining similar materials. For dissimilar welding, there have been few systematic studies aimed at clarifying the effect of material combination and welding conditions on weld properties [7, 8].

 

اثر فشار اکسیژن بر خواص فیلم های ZnO دوپ شده با Nb

Influence of oxygen pressure on the structural, electrical and optical

properties of Nb-doped ZnO thin films prepared

by pulsed laser deposition

اثر فشار اکسیژن بر خواص ساختاری، الکتریکی و نوری فیلم های ZnO

دوپ شده با Nb آماده شده توسط لایه نشانی لیزری پالسی

ABSTRACT

Nb-doped zinc oxide (NZO) transparent conductive thin films with highly (0 0 2)-preferred orientation were deposited on glass substrates by pulsed laser deposition method in oxygen ambience under different oxygen pressures. The as-deposited films were characterized by X-ray diffraction (XRD), Field emission-scanning electron microscopy (FE-SEM), electrical and optical characterization techniques. It was found that a desirable amount of oxygen can reduce the related defect scattering and enhance the carrier mobility. The resistivity and average optical transmittance of the NZO thin films are of 10−4 Ω cm and over 88%, respectively. The lowest electrical resistivity of the film is found to be about 4.37 × 10−4 Ω cm. In addition, the influence of oxygen pressure on optical properties in NZO thin films was systematically studied as well.

 

مقدمه ای بر دایکست با فشار بالا و عیوب رایج در دایکست

Introduction Of High Pressure Die-Casting

And Common Defects In Die-Casting

مقدمه ای بر دایکست با فشار بالا و عیوب رایج در دایکست 

ABSTRACT

Die casting is a manufacturing process that can produce geometrically complex metal parts through the use of reusable molds, called dies. The die casting process involves the use of a furnace, metal, die casting machine, and die. The metal, typically a non-ferrous alloy such as aluminum or zinc, is melted in the furnace and then injected into the dies in the die casting machine. There are two main types of die casting machines - hot chamber machines (used for alloys with low melting temperatures, such as zinc) and cold chamber machines (used for alloys with high melting temperatures, such as aluminum). The differences between these machines will be detailed in the sections on equipment and tooling. However, in both machines, after the molten metal is injected into the dies, it rapidly cools and solidifies into the final part, called the casting. 

 

بررسی مواد کامپوزیتی زمینه آلومینیم تقویت شده با نانولوله های کربنی

Investigation of carbon nanotube reinforced

aluminum matrix composite materials

بررسی مواد کامپوزیتی زمینه آلومینیم تقویت شده با نانولوله های کربنی

ABSTRACT

We have increased the tensile strength without compromising the elongation of aluminum (Al)–carbon nanotube (CNT) composite by a combination of spark plasma sintering followed by hot-extrusion processes. From the microstructural viewpoint, the average thickness of the boundary layer with relatively low CNT incorporation has been observed by optical, field-emission scanning electron, and high-resolution transmission electron microscopies. Significantly, the Al–CNT composite showed no decrease in elongation despite highly enhanced tensile strength compared to that of pure Al. We believe that the presence of CNTs in the boundary layer affects the mechanical properties, which leads to well-aligned CNTs in the extrusion direction as well as effective stress transfer between the Al matrix and the CNTs due to the generation of aluminum carbide.

 

انواع خوردگی Corrosion

Corrosion

خوردگی 

ABSTRACT

Corrosion is often associated with welded structures, since the microstructure, properties, and composition of the weld metal and HAZ may be quite different than those of the base metal. Corrosion takes a number of forms, as described in the  following section, and may result in general (uniform), localized, or microstructurespecific attack.

Often, the corrosion rate associated with welds is much higher than the base metal. The reason for this is usually a combination of the effect of microstructure and residual stress. Highly stressed regions surrounding welds may result in accelerated corrosion relative to the base metal. For example, the spot welds in automotive steels are normally the first place where corrosion attack takes place in car bodies.

 

پیشرفت‌ها در فناوری پالایش فولاد و چشم‌انداز آینده

Advances in Steel Refining Technology and Future Prospects

پیشرفت‌ها در فناوری پالایش فولاد و چشم‌انداز آینده

ABSTRACT

By the 1980s, Nippon Steel Corporation established a separated refining process based on hot-metal pretreatment,2) whereby the contents of silicon, sulfur, and phosphorus in hot metal were decreased before the decarburization in converters, using torpedo ladle cars, hot-metal ladles, or converters as the reaction vessels. Thereafter, technical developments such as the following were achieved:
separation of desulfurization from the other hot-metal pretreatment; separate processing of hot-metal dephosphorization from decarburization; development of hot-metal dephosphorization using converters as the reaction vessels and not requiring fluorine; improvement in reaction efficiency of these processes; recycled use of slag; adjustment of silicon content in hot metal in case of excessively high Si; and increase in converter capacity for hot-metal dephosphorization in converters.

 

فرایند انجماد و ساختار ریختگی در ریخته گری شمش

Solidification and Processes and Cast Structures

فرایند انجماد و ساختار ریختگی

ABSTRACT

This swction deals with three tranitional solidificationprocesses: ingot casting, continous casting, and welding. however, the last to processe hold a key importance in todays technology. almost entire molten metal is cast into solid state by either the traditional ingot casting or reatively modern continuous casting. the development of the ingot and continuously cast structure as well as fusion welding structure and weld cracking are briefly described.

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رفتار زینترینگ و مقاومت هیدروژنی دولومیت واکنشی

Sintering, consolidation, reaction and crystal growth by

the spark plasma system (SPS)

رفتار زینترینگ و مقاومت هیدروژنی دولومیت واکنشی

ABSTRACT

Sintering of raw dolomite and hydroxides derived from dolomite was carried out in the temperature range 1350–1650 °C. The hydroxide derived from dolomite was developed through pre-calcination of dolomite followed by its hydration. For hydroxide development, after precalcination one sample was air-quenched and the other powder was furnace cooled before hydration. The air quenched samples showed better densification than that of the furnace cooling process at the same temperature. Fe2O3 addition enhances sintering by liquid formation at higher temperature. The grain size of doloma with Fe2O3 addition is bigger than that without additive. Hydration resistance was related to densification and grain size of sintered dolomite.

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فرایند زینترینگ انفعالی و خواص ترموالکتریک کاربیدهای غنی از بور

Reactive sintering process and thermoelectric properties of

boron rich boron carbides

فرایند زینترینگ انفعالی و خواص ترموالکتریک کاربیدهای غنی از بور

ABSTRACT

Dense boron rich boron carbides were reactive sintered by hot pressing at 2050 °C using elementary boronsingle bondcarbon compositions with carbon contents of 9.1, 11.1, 13.3 and 18.8 at.%. The following material characteristics are presented: relative density, SEM images, EDX, X-ray diffraction and corresponding lattice parameters, Seebeck coefficient, electrical conductivity and thermoelectric power factor. Significant grain growth has been obtained with increasing boron content. A deeper understanding of the boron and carbon reaction and the overall sintering process is gained by thermal and chemical analysis in combination with X-ray diffraction. Additionally a thermal experiment with boron and carbon layers illustrates the solid state diffusion behaviour. The found results of boron carbide properties of this paper correspond with results by other authors. The aim is to correlate technological aspects of sintering procedure with material properties. This should help to improve the thermoelectric efficiency of boron carbide based materials.

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