Search results for "Metallurgy"
showing 10 items of 1419 documents
Numerical Procedure For Residual Stresses Prediction In Friction Stir Welding
2011
The prediction of residual stresses is a relevant and, under many points of view, still open issue for a proper welding process design. In the present paper a 3D FE model, with general validity for different joint configurations, was used to simulate the Friction Stir Welding (FSW) process of butt joints through a single block approach. The model is able to predict the residual stresses by considering thermal actions only, thanks to a new time efficient approach. A good agreement between calculated and experimentally measured data was found; the effectiveness of the presented numerical procedure was evaluated by comparing the calculation times of the proposed method with the ones of already…
Corrosion of stainless steel in food and pharmaceutical industry
2021
Abstract Stainless steels are widely used in the food and pharmaceutical industry because of their high corrosion resistance and superior mechanical properties. These features are crucial because produced foodstuffs and drugs must comply with high purity and quality standards. Just a proper selection of stainless steel grade can prevent corrosion phenomena that can be detrimental to the whole manufacturing process. Food/drugs production process phases will be here analyzed and discussed with a particular emphasis on the possible corrosion mechanism of stainless steels in those particular operating conditions. Recent advances on the methods to assess corrosion of stainless steels in food and…
Scanning electron microscopy study of twins in ZnSe single crystals grown by solid-phase recrystallization
2001
ZnSe single crystals were grown from n-type microcrystalline boules by a solid phase recrystallization (SPR) method. During SPR, twinned regions appear with different electronic recombination properties. The recrystallizations were performed under different atmospheres, Ar or Se, and pressures to investigate the influence of growth conditions on these structural features. Recombination properties were studied by means of cathodoluminescence (CL) and remote-electron beam induced current (REBIC). Wavelength dispersive X-ray (WDX) mappings were also performed to analyze possible differences in stoichiometry related to the presence of extended defects.
An Investigation of the Thermal Effects in Orthogonal Cutting Associated with Multilayer Coatings
2001
Abstract This paper deals with an experimental and analytical investigation into the tool-chip interface behaviour, influencing the temperature and heat transfer at the multilayered coated-tool rake face during orthogonal cutting of carbon and stainless steels. New methodology for assessing the amount of thermal energy generated when machining with a coated tool insert with natural and restricted contact coupled with a metallic chip, using thermophysical properties of the sliding materials is developed in this study. It was proven, based on the heat flux analysis, that the use of advanced coatings with an intermediate Al 2 O 3 layer can substantially improve the heat flow into the chip at d…
Material flow in fsw of aa7075-t6 butt joints: continuous dynamic recrystallization phenomena
2006
In the paper the continuous dynamic recrystallization (CDRX) phenomena occurring in the FSW of AA7075-T6 butt joints is investigated at the varying of the most relevant technological and geometrical parameters. In particular, both experiments and numerical simulations obtained utilizing a 3D Lagrangian implicit, coupled, rigid-viscoplastic model have been developed on FSW butt joints. The resulting microstructure at the core of the weldings is correlated to the material flow occurring during the FSW process.
Influence of geometrical ratios in forgeability of complex shapes during hot forging of Ti-6Al-4V titanium alloy
2014
Abstract Titanium alloys are considered desirable materials when both mechanical properties and weight reduction are requested at the same time. This class of materials is widely used in application fields, like aeronautical, in which common steels and light-weight materials, like aluminum alloys, are not able to satisfy all operative service conditions. Most of manufacturing processes of titanium alloy components are based on machining operations, which allow obtaining very accurate final shapes but, at the same time, are affected by several disadvantage like material waste and general production costs. During the last decade, the forging processes for titanium alloys have attracted greate…
Friction Stir Welding as an Effective Alternative Technique for Light Structural Alloys Mixed Joints
2014
Abstract The increasing use of structural light alloys in the aeronautical, automotive and transportation industry is pushing researchers to find new solutions for the production of innovative components. Mixed joints made out dissimilar alloys represent a challenge for engineers to the difficulties arising in welding materials characterized by significantly different mechanical, thermal and chemical properties. In the paper, an overview of the most used process to produce dissimilar joints of aluminum, magnesium and titanium is given. Both fusion based and solid state welding processes can be used. Although the joining of these materials is possible, particular attention must be taken to t…
A new fixture for FSW processes of titanium alloys
2010
FSW of titanium alloys is nowadays one of the most challenging welding operations, even with a solid state process, due to the thermo-mechanical and thermo-chemical characteristics of such materials. Due to the relevant application of titanium alloys in the aeronautic and aerospace industries, in the recent years few attempts were carried out to develop FSW processes aimed to maximize the mechanical performances of the welded parts. In the paper a new fixture is presented allowing obtaining effective FSW joints of titanium blanks, which were investigated through mechanical and metallurgical tests highlighting the peculiarities of FSW of titanium alloys.
<title>Hardening and long-range stress effects in LiF caused by high-fluence irradiation with fast Bi, Ni, Kr, and S ions</title>
2005
The limits of the hardening, and the effects of ion-induced internal and long-range stresses in LiF crystals irradiated with Bi, Ni, Kr, and S ions, having a specific energy of the order of 10 MeV/u and the fluence up to 1013cm-2, are studied. A considerable hardness increase, bending of the crystals, formation of dislocations in distant nonirradiated parts of the crystals, and initiation of fracturing under the high-fluence irradiation are observed. It is shown that the irradiation with heavy ions (Bi) gives rise to dislocations and work hardening mainly in the region adjacent to the irradiated one. In the case of lighter ions (Ni and S), the work hardening takes place also inside the irra…