Search results for "engineering.material"

Sheet metal forming of titanium blanks using flexible media

1998

Abstract Sheet metal forming processes using flexible media are increasingly utilized in the industrial practice due to the relatively low tooling cost. In the present investigation, a rubber forming process is applied to the manufacturing cycle of a titanium alloy component for acoustic tweeters. The proposed process allows a reduction in manufacturing costs and production time since it permits the elimination of some joining operations. The FEM analysis has permitted the definition of the optimal process parameters and tooling geometry. Accordingly, several components have been produced; the achieved quality level is comparable with the one obtained utilizing the conventional technology a…

Improving friction stir welding of blanks of different thicknesses

2007

Friction stir welding (FSW) appears to be a promising process even in the welding of blanks of different thicknesses. Actually, such particular tailor welded blanks (TWBs) are usually characterized by a reduction in ductility due to the utilized fusion welding process. In this paper the authors, starting from a preliminary feasibility study, investigate the possibility to improve the mechanical performances of friction stir welded blanks of aluminum alloy with different thicknesses. Both experiments and a FE analyses are developed for a few case studies with different thickness ratios between the blanks. The numerical investigations are performed with the aim to highlight the material tempe…

Friction Stir Welding of Tailored Blanks: Investigation on Process Feasibility

2006

Tailor welded blanks (TWBs) are conventionally produced by laser or traditional welding processes. In either case, the joints are created by solid-liquid-solid phase transformations that result in undesirable microstructures and tensile residual stresses detrimental to joint performance. This study investigates feasibility of an alternate joining process, friction stir welding (FSW). The joining of AA7075-T6 blanks of different thickness is investigated through FE analyses and controlled experiments. It is found that for a successful joint, the welding parameters have to be carefully designed so that the resulting metal flow and the temperature history during FSW are consistent for the two …

Corrosion protection of Nd–Fe–B type permanent magnets by zinc phosphate surface conversion coatings

2001

Abstract The use of protective zinc phosphate top coatings to protect Nd–Fe–B type permanent magnets against corrosion is discussed. The progress of the phosphatisation process has been tested by simultaneous measurement of pH near surface, corrosion potential, substrate mass loss and phosphate coating mass gain. The corrosion behaviour of the magnet in phosphate solution was analyzed by the anodic polarization technique and the general resistance of the magnet to corrosion was evaluated by the Akimov drop test. It is shown that immersion of the magnet in the acidified (pH=2) phosphating solution containing Zn(II), nitrate and fluoride ions resulted in the formation of well adhered, thin an…

Evolution of microstructures and mechanical properties during dissimilar electron beam welding of titanium alloy to stainless steel via copper interl…

2013

Abstract The influence of operational parameters on the local phase composition and mechanical stability of the electron beam welds between titanium alloy and AISI 316L austenitic stainless steel with a copper foil as an intermediate layer has been studied. It was shown that two types of weld morphologies could be obtained depending on beam offset from the center line. Beam shift toward the titanium alloy side results in formation of a large amount of the brittle TiFe2 phase, which is located at the steel/melted zone interface and leads to reducing the mechanical resistance of the weld. Beam shift toward the steel side inhibits the melting of titanium alloy and, so, the formation of brittle…

Oxidation behavior of γ-TiAl coated with zirconia thermal barriers

2002

Abstract The applicability of the thermal barrier coating concept, which is an established concept for Ni-base alloys, was investigated for the first time for γ-TiAl. As potential bond coats, the following surface treatments were applied: Al-diffusion coating, Al-diffusion coating combined with short term pre-oxidation in air, short term pre-oxidation in oxygen of a rough surface finish γ-TiAl sample without aluminide coating. For the purpose of lowering the temperature of the γ-TiAl substrate surface, and thus, to prolong the life time, a zirconia thermal barrier coating (TBC) was applied on top of the above-mentioned modified TiAl surfaces. Oxidation resistance of the modified γ-TiAl allo…

New Ceramics for the Information Storage: Nanoparticles of Titanium Ferrites. Influence of Oxidation and Reduction Reactions upon the Coercivity

1997

Mechanical properties and corrosion behaviour of low carbon martensitic stainless steel after machining

2014

The influence of different combinations of cutting conditions on the mechanical behaviour (microhardness), the microstructure and the corrosion behaviour in NaCl solution (using the electrochemical microcell technique and pulse potentiodynamic testing) of a low carbon martensitic stainless steel (grade X4CrNiMo16.5.1 stainless steel) after tempering treatment was studied. Microhardness was increased on the machined surface. In addition, the electrochemical experiments have shown that the machined materials have a heterogeneous electrochemical behaviour. Significant effect of machining on pitting corrosion was noticed. The pitting potential was found to decrease as the microhardness increase…

Early-stage detection of surface stress corrosion cracking at the subgranular level

2014

The strain field at the interface between an alloy and its oxide layer has been mapped using nanopatterned gauges resistant to the environment of the primary nuclear medium. It was found that oxidation has decreased the alloy ductility, thereby enabling some grain boundary opening to be detectable from 1.8 % strain. It is shown that statistics of extreme rare events of hotspots quantify the occurrence of the local opening of intergranular cracks, and thereby the ageing process.

Mode I failure modeling of friction stir welding joints

2008

This paper analyzes mechanical response by finite element method up to the decohesion failure in fracture mode I for joints of friction stir welding (FSW) of an aluminum alloy. It first describes experimental investigations on specimens with FSW embedded, subjected to uniform traction and local punch tests used to characterize local elastic and plastic material parameters. The heterogeneity of the mechanical properties induced by the FSW process is taken into account for the elastic-plastic finite element simulation. The growing damage and the opening failure of the welding zone are described by the adoption of a cohesive interface model with specific mechanical properties.