Vasily I Lutsyk; Vera P Vorob’eva; Anna E Zelenaya
Abstract
The T-x-y-z diagrams of quaternary Na2MoO4-Na2CrO4-Na2WO4-Na2SO4, Fe-Ni-Co-Cu, Pb-Cd-Bi-Sn systems and their four-dimension (4D) computer models are considered. Geometric constructions of these diagrams are described by special di-, uni- and invariant states schemes. Assumed liquidus of the Fe-Ni-CoFeS-NiS-CoS ...
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The T-x-y-z diagrams of quaternary Na2MoO4-Na2CrO4-Na2WO4-Na2SO4, Fe-Ni-Co-Cu, Pb-Cd-Bi-Sn systems and their four-dimension (4D) computer models are considered. Geometric constructions of these diagrams are described by special di-, uni- and invariant states schemes. Assumed liquidus of the Fe-Ni-CoFeS-NiS-CoS subsystem T-x-y-z diagram on the basis of the data about the structure of the border systems is predicted and the 4D computer model is designed. The possibilities of calculating of three- (3D) and two-dimensional (2D) iso- and polythermal sections are shown.
Christina Kr
Abstract
Recently, a new approach was developed and published which focuses on the preparation of inorganic foams and their application in foam concrete production. Through the incorporation of nanostructured pozzolans in the foam structure, so-called three-phase-foams show a higher stability than foams only ...
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Recently, a new approach was developed and published which focuses on the preparation of inorganic foams and their application in foam concrete production. Through the incorporation of nanostructured pozzolans in the foam structure, so-called three-phase-foams show a higher stability than foams only based on surfactants. Due to pozzolanic hardening, shrinkage cracks were healed and reaction products can be observed. By implementation of nanotubes in the foam structure as nanoreinforcement, a further stabilization was reached. After incorporation of wet three-phase-foams in cement paste, foam concretes with improved mechanical properties were achieved. It was also shown that the pore size distribution was similar to the introduced three-phase-foams and also smaller pore sizes can be observed compared to foam concretes based on surfactant foams. Additionally, a specific shell-like pore structure was obtained and a theoretical model developed. This could be confirmed by investigations of the influence of the surfactant used on the formation and carbonation of calcium hydroxide. To further enhance the mechanical properties of foam concretes based on three-phase-foams, an UHPC (Ultra-high Performance Concrete) formulation has been applied. Resultant UHPC foam concretes showed dense packed borders, improved homogeneity related to the pore size distribution and enhanced mechanical properties. Furthermore, the UHPC approach was combined with nanoreinforcement.
Adnan I. O. Zaid; Ahmad O. Mostafa
Abstract
ZAMAK 5 alloy is known to solidify in a large grain dendritic structure, which negatively affects its mechanical properties and surface quality. It is therefore of prime importance to reduce its grain size in order to overcome these drawbacks. In this paper, the effect of addition of hafnium (Hf) on ...
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ZAMAK 5 alloy is known to solidify in a large grain dendritic structure, which negatively affects its mechanical properties and surface quality. It is therefore of prime importance to reduce its grain size in order to overcome these drawbacks. In this paper, the effect of addition of hafnium (Hf) on the microstructural and mechanical characteristics of ZAMAK 5 alloy has been investigated. An amount of 0.10 wt.% Hf was introduced to the starting alloy using the well-established microalloying technique. The microstructural examination revealed that addition of Hf transformed the large grained dendrites into fine grains, which turned to increase its hardness number by 2.5% and slightly enhance its both yield and fracture stresses. The wear resistance was determined using a pin-on-disc test at different loads, speeds and time periods and the mass loss results of both alloys, before and after Hf addition, were compared with each other. The results indicated that ZAMAK 5 possesses better performance against wear at minimum speed, load and time (23.4m/min., 5N and 15min). Whereas, the Hf-containing alloy showed 42% improved performance against wear at severe experimental conditions of 153.5 m/min., 20N and 60min. The cumulative mass loss results were presented by three dimensional graphs in terms of speed, time and load, which indicated that the mass loss is a function of the three parameters. However, the graphs did not specify the most influential factor on the wear behaviour of both alloys. Full factorial design of experiments was used to identify the effect of parametric interaction on the cumulative mass loss of tested specimens and accordingly the speed was considered to be the main factor. The grain refined alloy is recommended to work under reduced speed and load conditions for prolonged service life.
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