Influence Of Secondary Phases Research Articles

Influence of secondary phase on residual stress of plasma sprayed glass coatings

The behaviour of glass coatings during thermal spray deposition is fundamentally different from that of metal and ceramic coatings because quench stresses can berelaxed during spraying. However, the expansion coefficient mismatch between the coating and the steel substrate remains an important source of residual stress and this paper investigates the effect of incorporating an alumina second phase into the glass to reduce the mismatch. Real time measurements on the deflection of coated specimens during spraying show that the residual stress can be reduced to zero by controlling the second phase content. The results also show that substantial temperature variations may be developed across large substrates during spraying as a consequence of the scanning action. These variations can affect the residual stress owing to the thermally activated nature of the stress relief and the marked sensitivity of glass properties to temperature. This research indicates that the pattern of residual stress developed in glass coatings is complex and will depend upon the substrate dimensions and the process operating conditions.

Sintering of TCP–TiO 2 biocomposites: influence of secondary phases

TCP–TiO 2 ceramic biocomposites with various α-to- β TCP ratios can be prepared by quenching the α phase. The presence of dopants (Ca, P, or Na) leads to the precipitation of secondary phases, which decreases the densification of titania. In the system TCP–TiO 2, there is a eutectic with a composition of 63 wt% TCP–37 wt% TiO 2 at a temperature of 1380°C.

Hydriding properties of the Zr(Cr 0.5Ni 0.5) α (1.75≤ α≤3.5) alloy system

We studied a series of Zr(Cr 0.5Ni 0.5) α alloys (1.75≤ α≤3.5) in order to investigate the effect of the stoichiometry and the influence of secondary phases on the electrochemical capacity. The main phase in the alloys is the hexagonal C14 Laves phase for α≤2 and the cubic C15 Laves phase for α>2. The secondary phases Zr 2Ni 7 and Zr 2NiH x (for α=1.75), as well as Zr 7Ni 10 and precipitated Cr (for α≥2) were found together with the Laves phases. The highest capacity was found for α=2 (383 mAh g −1, H/M=1.0, discharge current 4 mA g −1) and the amount of the secondary phase Zr 7Ni 10 is 11%. Normalization of the capacity with regard to the relative amount of Laves phase in the alloy gives the highest value for α=2.25 where only 7.5% Zr 7Ni 10 was found. The absolute capacity measured at a low discharge current depends mainly on the cell volume of the Laves phase whereas the kinetics are determined by the binary Zr–Ni phases. More important than the exact amount is the type of binary Zr–Ni phase.

A model for description of structure forming processes during reheating steels for thermal treatment

Modern production technologies, applied for parts or billets of steels for heat treatment, demand a possibility to predict the resulting and important structure parameters. The description of the austenite structure before transformation is also interesting for technologies with austenite transformation. A concept is presented to model austenitizing, including austenite nucleation, austenite nuclei growth and austenite grain growth. Monte‐Carlo‐Simulation is the mathematical method for modelling. The influence of secondary phases, especially the dissolution, is taken into account by using an additional part of the model. The mathematical method therefore is finite‐differences. Based on this concept, a model is developed for description of austenization during reheating. The variables for input are estimated at metallografical plane. Tests were carried out with case hardening steels and tempering steels. Austenite nuclide density and grain growth behaviour were estimated, both according to the initial state.

Investigation by electron diffraction microscopy of (RE)Ba2Cu3O6+xSy polycrystalline ceramic compounds: Interpretation of unexpected superstructures and influence of secondary phases

An original synthesis route has been followed to prepare ceramic YBa2Cu3O6+xSy materials. The samples have been studied by X-ray, high resolution optically polarized microscopy, transmission electron microscopy and X-ray microanalysis. A granular layer of a sulphur containing phase is observed at the crust of the pellet and leads to a set of broken rings on electron diffraction micrographs; the pellet itself is covered by hexagonal CuS micrograins. Although it is not clear how much sulphur is exactly entering the 1-2-3 phase, its presence does influence the behaviour of the oxygen deficient material. Instead of the Ortho II superstructure, a week Ortho IV superstructure is observed. Moreover most of the grains are untwinned. Thermodynamic data show an instability region for sulphur reactivity in the oxygen range 6.55 to 6.75.

Influence of calcination, sintering and composition upon microwave properties of the Ba6−xSm8+2x/3Ti18O54-type oxide

Dielectric ceramic compositions for microwave applications belonging to the (BaO) (Sm2O3) (TiO2) ternary phase diagram were studied. Calcination, sintering, microwave properties and influence of secondary phases were investigated. By varying composition and/or sintering process, a high dielectric constant with low dielectric losses and modulable negative or positive temperature coefficient of the resonant frequency can be reach.

Influence of Secondary Phases on the Localized Corrosion of Thermally Aged AISI 316L Stainless Steel Weld Metal

Abstract The pitting resistance of AISI 316L stainless steel (SS) weld metal in as-deposited and aged conditions was evaluated by determining the critical pitting potential in an acid chloride solu...