Search results for "Metallurgy"

Inverse growth transport in thermal chromia scales on Fe–15Cr steels in oxygen and in water vapour and its effect on scale adhesion

2007

Chromia scales of near equivalent thickness were thermally grown on Fe–15Cr steels in 16O2 followed by 18O2 and in H216O followed by H218O. SIMS oxygen isotope profiles showed that oxidation in oxygen proceeded by outward chromium transport, whereas oxidation in H2O involved inward transport of hydroxide species. Adhesion measurements using room temperature tensile testing could quantify adhesion energy: 20 J m−2 for O2-grown scales and 80 J m−2 for scales formed in H2O, a result of this mass transport inversion.

Sintered (Nd, Tb)–(Fe, Ti)–B+C permanent magnets

2001

Abstract This paper undertakes a study of the effect of carbon addition on the magnetic properties, the microstructure and corrosion resistance of Nd14.60Tb0.20Fe77.56Ti1.24B6.40+C sintered permanent magnets. It is shown that a 0.12 wt.% C addition increase the remanence and the maximum energy product and reduces (slightly) the intrinsic coercivity. The corrosion resistance in atmospheric environment is also significantly improved by this element.

A Grain-Scale Model of Inter-Granular Stress Corrosion Cracking in Polycrystals

2017

In this contribution, we propose a cohesive grain-boundary model for hydrogen-assisted inter-granular stress corrosion cracking at the grain-scale in 3D polycrystalline aggregates. The inter-granular strength is degraded by the presence of hydrogen and this is accounted for by employing traction-separation laws directly depending on hydrogen concentration, whose diffusion is represented at this stage through simplified phenomenological relationships. The main feature of the model is that all the relevant mechanical fields are represented in terms of grain-boundary variables only, which couples particularly well with the employment of traction-separation laws.

Physico-chemical characterization of perlite of various origins

1985

Abstract Pearlstones (perlite) from Sardinia (Italy). Milos (Greece) and Siberia (USSR) have been evaluated in terms of chemical composition, phase analysis, iron distribution, morphology and thermal properties, for application as raw material in zeolite synthesis.

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

1997

Beta-forging of Ti6Al4V titanium alloy powders consolidated by HIP: Plastic flow and strain-rate relation

2014

Ti6Al4V is probably the best known and studied titanium alloy, not only for aerospace applications. Nevertheless the deformation behavior still represents a challenge if any modification in the deformation process is required or introduced. This work deals with deformation behavior description of Ti6Al4V HIPped powders during high temperature deformation tests carried on in the Beta-region. Laboratory compression and tensile tests have been coupled with relaxation tests in order to achieve robust data about strain rate sensibility m-coefficient and activation energy Q. These results have been fitted for the assessment of a more general exponential deformation law. The final result is a “Dor…

Can metals be a liquid glass?

2009

The melting of transition metals on compression is a challenging topic. Computer simulations suggest that hot-compressed tantalum becomes a one-dimensional, liquid-like glass, with important implications for understanding planetary interiors.

Validation of frictional studies by double-cup extrusion tests in cold-forming

1996

Abstract Studies on frictional conditions in cold-forming have shown that, for a given lubricant, friction factor values are strongly affected by the test method. In the present paper, different cold-forging processes of an aluminium alloy, are modelled by a FEM numerical code using the m values obtained by both the double cup extrusion and ring compression tests. It appears that the m values given by the ring tests can be effectively used in the simulation of upsetting processes, while the m values derived by the double cup extrusion tests are more appropriate for predictions in extrusion and closed-die forging operations.

Evaluation of Residual Stresses During Fatigue Test in an FSW Joint

2008

At present, friction stir welding (FSW) represents one of the most interesting techniques in the field of welding. The process is has been implemented in industrial practice for joining aluminium alloys, while the welding of the titanium alloy and the steels is still primarily in a developmental stage.

Formability of Friction Stir Welded AZ31 Magnesium Alloy Sheets

2010

The formability of friction stir welded AZ31 magnesium alloy sheets was investigated by means of uniaxial tensile and hemispherical punch tests performed under different process conditions. The results of the tensile tests were analysed in terms of flow stress and ductility at different temperature and strain rate; the hemispherical punch tests, carried out at different temperatures, provided the limiting dome height. The formability of FSW-ed blanks was compared to the one exhibited by the base material in order to evaluate the quality of the welded joints.