Search results for "Metallurgy"

Enhanced thermoelectric performance in the p-type half-Heusler (Ti/Zr/Hf)CoSb0.8Sn0.2 system via phase separation

2014

A novel approach for optimization of the thermoelectric properties of p-type Heusler compounds with a C1b structure was investigated. A successful recipe for achieving intrinsic phase separation in the n-type material based on the TiNiSn system is isoelectronic partial substitution of Ti with its heavier homologues Zr and Hf. We applied this concept to the p-type system MCoSb0.8Sn0.2 by a systematic investigation of samples with different compositions at the Ti position (M = Ti, Zr, Hf, Ti0.5Zr0.5, Zr0.5Hf0.5, and Ti0.5Hf0.5). We thus achieved an approximately 40% reduction of the thermal conductivity and a maximum figure of merit ZT of 0.9 at 700 °C. This is a 80% improvement in peak ZT fr…

Design Of Experiments for the optimization the process parameters of thixotropic aluminum alloy

2006

The success of the thixoforming process depends on the possibility to confer to material, when it is found in the semisolid state, a microstructure characterized by globular particles of solid phase surrounded by a continuous film of liquid phase; such microstructure is obtainable through particular thermo-mechanical treatments. In the present research, in order to optimize the influence of process parameters in the step in which the thixotropic properties are conferred to the AA7075 aluminum alloy, the statistic technique of the Design Of Experiments (DOE) has been used. The advantages in the application of such technique are expressible in terms of reduction the times of development of pr…

Cell Parameters of Fine-Grain BaTiO<sub>3</sub> Powders

1993

Producing and working with iron

2019

Combining archaeological studies and archaeometric analyses, this synthesis presents the importance of the iron economy in the eastern part of the Paris Basin from the First Iron Age to the early Middle Ages. The first contributions of this research project concern technological changes in the production system of iron objects. The attention paid to the share of recycling in production somewhat modifies the previous discourse in attempts to quantify the types of forged objects (tools, weapons, ornaments, etc). Additionally, the link between the status of the excavated sites (agricultural holding, rural hamlet, fortified site, large settlements) and the type of forging activity that was carr…

Tool Wear and Damage

2008

This chapter provides comprehensive knowledge regarding tool wear mechanisms and characterizes their physical fundamentals. Adhesion, abrasion, diffusion and oxidation are selected as predominant mechanisms controlling tool wear, depending on the mechanical and thermal conditions at the rake and flank faces. The analytical models describing the wear rate and volumetric material loss for different wear mechanisms are provided. The tool wear indicators related to crater, flank and notch wear specified in ISO 3685 are presented for both flat-faced and grooved tools. Tool life is defined and corresponding models, including the influence of cutting speed, feed and the depth of cut, are derived. …

Influence of mechanical properties of the sheet material on formability in single point incremental forming

2004

Abstract New trends in sheet metal forming are rapidly developing and several new forming processes have been proposed to accomplish the goals of flexibility and cost reduction. Among them single point incremental forming operations, in which the final shape of the component is obtained by the relative movement of a simple and small punch with respect to the blank, appear quite promising. In the paper, material formability issues in incremental forming were studied. Some relevant correlations among material formability and other mechanical properties of the material were analysed. The FLD 0 value, i.e. the major strain at fracture in plane strain conditions, was determined for different mat…

Thermal and Hydrodynamic Analysis of the Melting Process in the Cold Crucible Using 3D Modeling

2008

Friction Stir Welding Of AA6082-T6 Sheets: Numerical Analysis And Experimental Tests

2004

3D numerical simulation of the Friction Stir Welding process is developed with the aim to highlight the process mechanics in terms of metal flux and temperature, strain and strain rate distributions. The numerical results have been validated though a set of experimental tests.

Mechanism of brittle fracture in a ductile 316 alloy during stress corrosion

1990

Abstract The ductile f.c.c. 316 alloy is shown to exhibit brittle transgranular (and intergranular) stress corrosion cracking in a 153°C MgCl2 solution at free corrosion potential. Tests on smooth and pre-cracked specimens are performed to identify the mechanisms of fracture. Transgranular cracking is related to both a discontinuous microcleavage mainly on {100} planes and a microshearing on {111} planes. A new physical modelization is proposed to explain the brittle transgranular cracking. It is based on the influence of the localized anodic dissolution on the enhancement of the plasticity at the crack tip. The formation of dislocation pile-ups and the conditions of restricted slip induce …

Bonding prediction in friction stir consolidation of aluminum alloys: A preliminary study

2018

Friction Stir Consolidation (FSC) is a solid-state process that results in consolidation of metal powders or chips producing solid billet through severe plastic deformation and the solid-state bonding phenomena. This process can be used both for primary production and for metal scrap recycling. During the FSC process, a rotating die is plunged into a hollow chamber containing the finely divided, unconsolidated material to be processed. In this paper, a FEM numerical model for the prediction of the quality of the consolidated billet is presented. In particular, a dedicated bonding criterion that takes into account the peculiar process mechanics of this innovative technology is proposed.