Microstructural characterization of controlled forged HSLA-80 steel by transmission electron microscopy

In this study, transmission electron microscopy (TEM) was used to evaluate the effect of controlled forging followed by cooling at various rates on microstructure of an HSLA-80 steel. The observations demonstrate that water-quenched steel has finer multiphase constituents of lath martensite, bainite and twined martensite, whereas air-cooling has resulted in a mixture of bainitic ferrite, retained austenite or MA constituents along with some Widmanstatten ferrite. When the steel is cooled in sand, the maximum volume fraction of polygonal ferrite (PF) was produced which, in turn, increased volume fraction of MA constituents. Precipitation of fine -Cu, Nb and Ti carbides and carbonitrides was observed and identified using energy dispersive spectrometric analysis (EDS) and electron diffraction.     

Crystal growth and characterization of new nonlinear optical single crystals of l-alaninium fumarate

Amino acid based crystals exhibit excellent nonlinear and electro optical properties. A new nonlinear optical single crystal l-alaninium fumarate (LAF) belonging to the amino acid group was grown by slow evaporation solution growth technique. Single crystal X-ray diffraction study showed that LAF belongs to orthorhombic crystal system. The UV-Vis-NIR spectrum of LAF showed very good transparency in the region from 300 nm to 1100 nm. Fourier transform infrared is used to confirm the presence of various functional groups in the grown crystal. Thermal properties of the LAF crystal were carried out by thermogravimetric analysis (TGA) and differential thermal analysis (DTA) techniques, which indicate that the material does not decompose before melting. The melting point of grown crystal was observed as 267.5 °C by melting point apparatus. The existence of nonlinear optical (NLO) property of LAF was confirmed by second harmonic generation test using Nd:YAG laser fundamental wavelength of 1064 nm.     

Failure Analysis of an Air Turbine Starter

Air turbine starters (ATS) are used for the ground start of aircraft engines. This case history describes the failure of an ATS that occurred while starting a developmental gas turbine engine. Fractographic features indicated that few blades of the turbine rotor disc failed in a progressive mode while the remaining blades of the rotor disc indicated failure by overload. The rotor shaft also exhibited features of sudden overload. Analysis of the previous records revealed the observation of sparks developing while the starter was in operation. This indicated possibility of blade tip rubbing which resulted in fatigue crack initiation at the blade root leading to failure.     

Study of effect of quenching and deformation on KCl: Gd<Superscript>3+</Superscript> crystals by using conductivity measurements

The study of ionic conductivity vs reciprocal temperature of pure KCl and KCl crystal doped with 0.1, 0.3 and 0.5 mole % gadolinium has been carried out in as grown, quenched from elevated temperatures (100, 350 and 500°C) and annealed at various timings i.e. 2–3 h and deformed by different percentages. The plots exhibit three well-known regions, II, III and IV (extrinsic regions). The intrinsic region I was not observed in the plots as the conductivity measurements were taken up to 575°C. From the analysis of these plots, activation energies for the migration of cation vacancy and the association of gadolinium ion with cation vacancy in the lattice of KCl crystals are calculated. These values are compared with previously reported values. Further, an attempt is made to explain the existence of oxidation state of gadolinium ion in + 3 state rather than in + 2 state as reported earlier. The variation in conductivity with effect of concentration of impurity ion, quenching and annealing and deformation with various percentages are explained on the basis of formation of impurity vacancy dipoles, vacancy — vacancy pairs (which appear in the form of precipitation), storage of cation vacancies in the form of defects, introduction of fresh dislocations, etc.     

Plasma-melted nitrogen-bearing cast stainless steels—microstructure and tensile properties

Alloys of Fe-Cr-Ni and Fe-Cr-Mn were plasma arc-melted and chill cast in the form of ingots. Exposure of liquid melts to a nitrogen plasma for the purpose of adding nitrogen to the above alloys was used to dissolve varying amounts (up to 0.32 wt pct) of nitrogen. Carbon and sulfur were varied up to 0.5 and 0.056 wt pct, respectively. The alloys were evaluated for their monotonic behavior. It was observed that while strength and ductility parameters increased considerably with increasing nitrogen and carbon contents, both these parameters deteriorated with sulfur content. The analysis of the present results, along with the data from the literature, suggests that the strength parameters are predominantly chemistry dependent, particularly controlled by the nitrogen and carbon contents. The results also show that the alloys produced by this relatively new technique, plasma arc-melting, are comparable to those produced by other standard techniques. A.K. SINGH, formerly Postdoctoral Fellow, Department of Metallurgical Engineering, Institute of Technology, Banaras Hindu University.     

Large deflection analysis of clamped skew sandwich plates by parametric differentiation

The differential equations governing the large deflection behavior of skew sandwich plates are highly complex in nature and do not lend themselves for easy solution. In the study reported herein, this problem is solved by a numerical technique known as “parametric differentiation”. The non-linear differential equations in terms of displacements are transformed into a set of linear differential equations with variable coefficients. These are solved to give the gradients of the displacements in the load direction. The subsequent solution of a set of initial value problems yield the displacements proper. The results obtained by this method are compared with available results of other investigators and the agreement is found to be good. Load deflection characteristics have been presented for clamped skew sandwich plates.     

Equilibrium constants and thermodynamics of ionization of aqueous hydrogen sulfide

First (K₁) and second (₂) ionization constants for aqueous hydrogen sulfide reported by various investigators have been reviewed, along with results of related calorimetric measurements leading to corresponding enthalpies of ionization. Following critical analysis of the published results, we have selected what we regard as “best” values for the ionization constants and related thermodynamic quantities. We call particular attention to significant uncertainties in these quantities for the higher (above 25°C) temperatures that are generally most important in hydrometallurgy.     

In-vitro enzymic hydrolysis of the storage proteins of japanese barnyard millet (Echinochloa frumentacea)

To assess the nutritional quality of Japanese barnyard millet ( JBN , Echinochloa frumentacea Link), its protein content, quality and digestibility were studied. The proximate composition of the millet resembles that of other millets/cereals. The protein content had a mean value of 36.7 g kg^?1. Solubility fractionation showed glutelins to be the major storage protein (60.8%). Contents of phenolics and tannins were estimated and found to be low. The protein digestibility of JBN flours was high (84%). The digestibilities of the different protein fractions varied from 50.9% to 68.4% with pepsin and from 26.6 mg g^?1 to 55.8 mg g^?1 (α-amino N liberated) with trypsin. These differences have been discussed relative to differences in amino acid composition of the protein fractions as well as to the possible presence of antinutritional factors in the fractions.