A thermodynamic description of the Al–Fe–Si system over the whole composition and temperature ranges via a hybrid approach of CALPHAD and key experiments

A comparison of composite metal foam's properties and other comparable metal foams

Mg3Sb2-based Zintl compounds have recently attracted attention as a potential candidate for thermoelectric applications due to their low thermal conductivity and promising thermoelectric performance (i.e. ZT = 0.6 at 773 K in Mg3Sb2−xBix). We have reported previously that isoelectronic Bi3− substitution of Sb3− leads to a moderate increase in the electrical conductivity, enhanced Seebeck coefficient and reduced thermal conductivity. Herein, we report a large enhancement of the electrical conductivity while maintaining the Seebeck coefficient by substituting Pb4− on Sb3− sites in Mg3Sb2−xPbx (0 ≤ x ≤ 0.3) alloys. Transport measurements reveal that optimum doping of 10 at% Pb4− on Sb3− enhances the ZT to 0.84 at 773 K which is comparable to bismuth telluride and selenide industrial materials which are toxic and expensive. The enhancement in ZT is attributed to a decrease in lattice thermal conductivity and simultaneously an increase in the power factor resulting from the significant increase in the electrical conductivity. We observe that Pb4− substitutions on Sb3− sites in Mg3Sb2−xPbx (0 ≤ x ≤ 0.3) increase the hole carrier concentration. Electronic transport data of Mg3Sb2−xPbx (0 ≤ x ≤ 0.3) alloys have been analyzed using a single parabolic band model and have been compared to Mg3Sb2. The relatively high figure of merit and affordable material ingredients coupled with one step synthesis process makes these materials a promising cost effective solution as thermoelectric materials.

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Enhancing thermoelectric properties of a p-type Mg3Sb2- based Zintl phase compound by Pb substitution in the anionic framework

Galvanised steel to aluminium joining by laser and GTAW processes

Bimetallic automotive components consisting of an Al–Si light alloy reinforced with a cast iron insert have been manufactured by gravity die moulding. Special precautions have been taken to ensure a uniform wetting of the insert by the liquid light alloy. Under these conditions, three intermetallic compounds are formed at the insert/alloy interface: η (Al 5 Fe 2 ), τ5 (Al 7.4 Fe 2 Si) and τ6 (Al 4.5 FeSi). Upon subsequent heat-treatment, τ2 (Al 5 Fe 2 Si 2 ) and τ10 (Al 12 Fe 5 Si 3 ) also appear. Growth of these compounds is discussed in terms of thermodynamics, kinetics and reaction mechanism in the Al–Fe and Al–Fe–Si systems. The effect of these chemical changes on the mechanical properties of the insert/alloy joint will be examined.

Interface chemistry in aluminium alloy castings reinforced with iron base inserts

Different experimental techniques were combined to acquire better insight into the solid-liquid phase equilibria that tend to be established in the Al-Fe-Si ternary system at 727 °C under a pressure of 1 atm (101,350 Pa). Isothermal diffusion experiments followed by oil quenching were first carried out. The crystal nature, lattice parameters, morphology, and chemical composition of the different solid phases in equilibrium with the liquid were determined by x-ray diffraction, optical microscopy, scanning electron microscopy, and electron probe microanalysis. Points on the liquidus boundary were then positioned both directly by chemical analysis of liquid samples taken from solid-liquid mixtures equilibrated at 727 °C and indirectly by thermal analysis of Al-Si mixtures with controlled iron additions. On the one hand, it has been confirmed in agreement with currently accepted data that the compounds ϑAl13Fe4, αAl7.4Fe2Si (τ5), and δAl3FeSi2 (τ4) are in equilibrium at 727 °C with Al-Fe-Si liquids, the compositions of which have been refined. On the other hand, the authors have shown that the ternary compound γAl3FeSi is in equilibrium at 727 °C with a ternary Al-Fe-Si liquid containing 10.5 to 16.5 at.% Si and 3.2 to 3.5 at. % Fe.

Solid-liquid phase equilibria in the Al-Fe-Si system at 727 °C

Characterization of Magnesium Antimonide Mg3Sb2 at the Surface of an Sb-refined AS7G0.3 Aluminium Alloy

Reaction Layer Sequences at the Interface Between Iron and Al-Si Alloys

le present travail s'inscrit dans le cadre d'un programme visant a realiser des assemblages titane/alliage d'aluminium. A cette fin, une etude generale des interactions chimiques dans le systeme Al-Si-Ti a ete entreprise. En premier lieu, l'aspect thermodynamique de ces interactions a ete precise par la determination experimentale des equilibres liquide-solide s'etablissant a 1000 K dans le systeme ternaire Al-Si-Ti. Dans une deuxieme etape, les zones de reaction interfaciales formees a differents stades de l'interaction entre le titane et un alliage liquide Al-Si ont ete caracterisees par microscopie (optique et electronique) et microsonde electronique. A partir des resultats obtenus, un mecanisme reactionnel est propose pour decrire la cinetique de croissance de ces zones.

F. Barbeau

Papers

Interface chemistry in aluminium alloy castings reinforced with iron base inserts

Solid-liquid phase equilibria in the Al-Fe-Si system at 727 °C

Characterization of Magnesium Antimonide Mg3Sb2 at the Surface of an Sb-refined AS7G0.3 Aluminium Alloy

Reaction Layer Sequences at the Interface Between Iron and Al-Si Alloys

Comportement chimique du titane dans un alliage liquide aluminium-silicium