Microstructural study of Zn-11% Al and Zn-27% Al alloys

in Proceedings of the 25th Annual Conference of Metallurgists (1986)

Zinc-aluminium alloys with small amounts of copper and magneisum (ZA alloys) are used in a number of casting processes. They offer the foundry industry a family of zinc alloys with a wide range of ... [more ▼]

Zinc-aluminium alloys with small amounts of copper and magneisum (ZA alloys) are used in a number of casting processes. They offer the foundry industry a family of zinc alloys with a wide range of mechanical properties able to meet a large spectrum of performance criteria. However promising the characteristics of these alloys, microstructural studies of them are incomplete. It has been shown that copper additions to ZA alloys modify the number of the phase existing in the binary zinc-aluminium system as well as their transformation kinetics. Microstructural studies have shown not only the heterogeneity of the microstructure but also the presence of a zinc-rich metastable phase and the evolution of the composition of the ternary phase Zn-Al-Cu (T) during ageing. This situation is not surprising as several studies have shown the existence of metastable phases in the binary system Al-Zn with high aluminium content. the complexity of the microstructure leads us to search further for a better understanding of the binary Zn-Al alloys, with Al contents corresponding to ZA 12 and ZA 27 wihout any Cu and Mg, in order to precise about the complex evolution to stable phases observed in these alloys. [less ▲]

Microporosity formation in nickel-base superalloys in relation to their solidification sequence

in Proceedings of the International Conference of High Temperature Alloys for Gas Turbine and Other Applications (1986)

This work is aimed at showing how the proneness of superalloys to microporosity formation can be estimated by the tsP* pararneter which makes use of various solidification features. The latter can be ... [more ▼]

This work is aimed at showing how the proneness of superalloys to microporosity formation can be estimated by the tsP* pararneter which makes use of various solidification features. The latter can be derived from quantitative differential thermal analysis (DTA) resuits through the original method described in the text. The technique was applied to two IN 100 master meUs of distinct grades (virgin or revert) which had been showrt to behave very differently in the foundry. It led to ascribe the poorer performance of the revert meit to its particular solidification sequence leading higher dendrite tortuosity and lesser residual liquid fluidity. [less ▲]

The investment casting and processing of cobalt-base and cobalt-bearing superalloys

in Second Congress Cobalt Metallurgy and Uses (1985)

To cope with the demands of engine manufacturers and other users, superalloys have been brought to work in service at temperatures which represent a very substantial fraction of their melting point. In ... [more ▼]

To cope with the demands of engine manufacturers and other users, superalloys have been brought to work in service at temperatures which represent a very substantial fraction of their melting point. In addition to high temperature capability, they must exhibit mechanical strength, not only under static, but also under cyclic stressing conditions, and offer appropriate oxidation and corrosion resistance. This can only be achieved by tailoring their chemistry and processing conditions to the particular needs of the application under consideration. The evolution of component design and alloy chemistry, and some compositional effects and processing improvements in cast Ni-base superalloys are discussed. [less ▲]

Le nickel, Addendum au Chapitre VI du cours de "Connaissance des Matériaux métalliques" consacré à l'étude des non-ferreux

Learning material (1985)

Review of hot shortness problems in copper-containing steel

in ATB Metallurgie (1983), 23(3), 7-1-724

The problem of hot shortness is first briefly discussed in terms of the recycling of scraps and the occurrence of various residual elements in steel. The phenomenon is then defined and described as a ... [more ▼]

The problem of hot shortness is first briefly discussed in terms of the recycling of scraps and the occurrence of various residual elements in steel. The phenomenon is then defined and described as a function of the factors influencing its different stages : copper solubility in austenite, copper phase melting point, wettability of the liquid copper rich phase, oxidation, furnace atmosphere, occlusion and diffusion. The effect on these phenomena of other residual or alloying elements is discussed. The paper concludes with the different ways to minimize the hot shortness problems and with hints on the more efficient use of copper containing scraps. [less ▲]

Modelling micropore formation during directional solidification

in metallurgical report CRM (1982), 59

In this work we have developed two criteria which can characterize the susceptibility to microporosities formation of alloys. These defects are influential in determining mechanical properties of ... [more ▼]

In this work we have developed two criteria which can characterize the susceptibility to microporosities formation of alloys. These defects are influential in determining mechanical properties of materials. The first criterion is used when the fraction eutectic is important : then the porosity formation is essentially caused by dissolved gases of formed during chemical reactions. The second is employed when the alloy possesses low fraction eutectic. In that case, because of the pressure drop, the liquid is unable to feed through interdendritic spaces to accomodate solidification shrinkage. The pressure drop is composed of two terms which influence in contrary direction : the first is due to solidification shrinkage and the second to gravity. This term is the most important except for low fraction eutectic. The fraction liquid (or the fraction eutectic) is an important factor. It depends on the alloy composition and on solidification conditions. In fact, we have showed that, depending on initial alloy concentration, the solidification conditions have opposite effects on the fraction liquid : if Co>KCe, the fraction liquid decreases if the ratio G/R decreases and if Co<KCe it increases if the ratio G/R decreases. [less ▲]

Application de la diffraction des rayons X en métallurgie, Notes des Travaux Pratiques de Métallurgie Physique

Learning material (1982)

Etude de la formation des microporosités dans l'alliage Ni-TiC en solidification dirigée

Report (1981)

Perspectives et développement des matériaux composites à matrice aluminium

Learning material (1980)

Les matériaux composites à matrice aluminium, Chapitre X du cours "Connaissance des matériaux aérospatiaux"

Learning material (1979)