S.V.Nagender Naidu

The high-temperature thermal expansion of Ni3Al measured by X-ray diffraction and dilation methods

The lattice parameters of Ni3Al have been determined accurately for the temperature range 25 to 594 degrees C by a high-temperature X-ray powder diffraction method. These data are used to evaluate the coefficients of thermal expansion at various temperatures. The thermal expansion of Ni3Al has also been measured from 25 to 1000 degrees C by a dilation method. The thermal expansion values obtained by the dilation method are in good agreement with those determined by the X-ray diffraction method at around room temperature, but the agreement deteriorates with increase in temperature.

Calculated phase diagrams of CuW, AgW and AuW binary systems

Abstract Phase diagrams for Cuue5f8W, Auue5f8W systems have been calculated based on available thermodynamic data. It was assumed that there is no mutual solid solubility in all the cases. Liquid phase equilibria were calculated on the basis of sub-regular solution model using Miedenas interaction parameters. Vapour phase boundaries have also been determined.

The Cr−W (Chromium−Tungsten) system

Diagramme dequilibre, liquidus solidus et solvus. Structure cristalline et parametres cristallins dalliages Cr-W. Parametres dinteraction thermodynamiques pour le systeme Cr-W

Calculated phase diagrams of Cu-W, Ag-W and Au-W binary systems

Abstract Phase diagrams for Cu-W, Au-W systems have been calculated based on available thermodynamic data. It was assumed that there is no mutual solid solubility in all the cases. Liquid phase equilibria were calculated on the basis of sub-regular solution model using Miedemas interaction parameters. Vapour phase boundaries have also been determined.

High temperature thermal expansion characteristics of Ni3Al alloys

The thermal expansion of Ni3Al alloys with and without ternary additions have been investigated with the aid of a dilatometer. The Ni3Al alloys were studied over the temperature range 25–1000 °C. The coefficient of thermal expansion α of all the aluminides studied in this investigation varies linearly with the temperature. The coefficient of thermal expansion of Ni3Al is found to show an increase with the decrease in Al content from stoichiometric composition. B and Zr additions decrease the value α of Ni3Al alloys at room temperature while Hf and Ti additions do not alter it significantly.

Thermal expansion characteristics of Ti3Al and the effect of additives

Abstract A perusal of the literature indicates that there exist significant differences in the data on the coefficients of thermal expansion α of Ti3Al. While X-ray studies indicate an increase in the values of a with temperature, the dilatometric data had shown an anomalous variation in the intermediate temperature ranges. In view of the discrepancy existing between these data and also to study the influence of the alloying element on physical and mechanical properties of Ti3Al, determination of the thermal expansion coefficients of stoichiometric Ti3Al, Ti3Al-5at.%Nb and Ti3Al-7.5at.%Nb and microhardness measurements of these alloys have been undertaken. The effect of heat treatment on the thermal expansion coefficients of Ti3Al-5at.%Nb and Ti3Al-7.5at.%Nb is studied in the present investigation. The variation in the thermal expansion coefficient with the radius ratio of titanium to that of the additive element is examined.

X-ray determination of microstructural parameters of eroded Cu-Al alloys

Abstract Copper and Cu-Al alloy samples of dimensions 30 mm × 30 mm × 6 mm (in the α phase), containing 5.47, 8.19 and 13.03 at.% Al, were prepared. All the samples were suitably annealed and one of the surfaces of each sample was deformed by erosion. X-ray diffraction profiles were measured for both the annealed and the eroded surfaces of each sample. X-ray diffraction analysis of eroded materials is being reported for the first-time in this paper. The microstructural parameters were evaluated from peak shift, peak asymmetry and also peak broadening analysis of powder pattern peaks studied by the Fourier analysis of line shapes. The microstructural parameters obtained in this study using X-ray techniques, with erosion, are compared with those obtained with other deformation methods, namely wear and filing. The results are discussed and some broad conclusions are reached.

Effect of third elements on the microhardness of Ni3Al

Abstract The room-temperature microhardness of Ni 3 Al with and without third elements has been studied using the Vickers indentation technique. In pure Ni 3 Al phase alloys, the hardness value increased with decreasing Al concentration from stoichiometric composition. This increase is attributed to the defects present at off-stoichiometric compositions. The addition of third elements Hf, Zr, Ti and Si increased the hardness value of Ni 3 Al suggesting the solid-solution strengthening effect. The presence of 0.20 at% boron in Hf- and Zr-containing alloys shows a softening effect at small concentrations of Hf and Zr.

X-ray characterisation of eroded 316 stainless steel

Abstract Deformation produced during the erosion of 316 stainless steel specimens by the impact of SiC particles is studied by X-ray diffraction. Erosion studies are made, at different impact angles, on samples simultaneously heated to different high temperatures. For the samples eroded at room temperature the deformation stacking fault probability values are found to be 5 × 10 −3 and 3 × 10 −3 for impact angles of 90° and 30° respectively. Variation of deformation stacking fault probability is correlated with the changes in the hardness value.

Debye characteristic temperatures and associated parameters of Cu-Al alloys

Determination a partir des intensites integrees des rayons X des reflexions de Bragg a partir de Cu et des alliages Cu-5 a 13% at Al des parametres cristallins, des facteurs de Debye-Waller, des temperatures de Debye et de la racine carree moyenne des amplitudes de vibration atomique. Influence de la concentration daluminium. Effet du facteur de desordre dynamique sur lamplitude de vibration