Defence Metallurgical Research Laboratory

About: Defence Metallurgical Research Laboratory is a facility organization based out in Hyderabad, India. It is known for research contribution in the topics: Microstructure & Alloy. The organization has 1208 authors who have published 2662 publications receiving 51663 citations.

Synthesis and study of structural, magnetic and microwave absorption properties in multiferroic BiFeO 3 electroceramic

Abstract: Phase pure nano-sized BiFeO3 (BFO) has been successfully prepared by citrate based sol–gel method. X-ray diffraction study revealed the formation of pure and well-crystallized BiFeO3 nano-crystallites in a rhombohedral perovskite phase for the samples sintered at 600 °C. The examination of microstructure showed uniform hexagonal shaped grains. From magnetisation measurement, it was observed that an increase in sintering temperature from 600 to 700 °C decreased the remanent magnetization from 0.025 to 0.003 emu/g suggesting a weak ferromagnetic nature at room temperature. Moreover, better microwave absorption properties with minimum reflection loss were also observed. Impedance measurements were performed by vector network analyser in frequency range 8.2–12.4 GHz for the sample annealed at 700 °C. From the dielectric permittivity (e = e′ − je″) and magnetic permeability (µ = µ′ − jµ″) measurements, it was found that the observed dielectric and magnetic losses were higher in the case of BFO sintered at 700 °C.

Effect of friction stir and activated-GTA welding processes on the 9Cr–1Mo steel to 316LN stainless steel dissimilar weld joints

Abstract: The consequence of friction stir welding (FSW) and activated-gas tungsten arc welding (A-GTAW) processes on the evolution of microstructure and mechanical properties of 9Cr–1Mo (P9) steel to 316LN ...

Normal and Oblique Impacts of Hard Projectile on Single and Layered Plates-An Experimental Study

Abstract: The phenomenon of ordnance velocity impact of projectile on single and layered plates is of interest for many applications. In this paper. an experimental study of normal and oblique impacts or an ogive shaped, hard steel projectile on single and layered plates of mild steel and aluminium is presented. The projectiles were fired at an impact velocity of about 820 ms-1. The plate thickness was varied in the range 10 mm to 40 mm and the ratio of plate thickness to the diameter of the projectile varied in the range 1.5 to 13.0. Observations on target damage and measurements of incident and residual velocities for different angles of impact are presented. Plate thickness t*, for which the incident velocity is the ballistic limit, is determined. Computer simulations were carried out using a hydrodynamic code to simulate the normal impact of a projectile and compared these with the experimental results. Experiments were performed to evaluate the response of these plates of intermediate thickness when layered. and the results were compared to the results of single plate of same total thickness.

Ferromagnetism in the multiferroic alloy systems BiFeO3-BaTiO3 and BiFeO3-SrTiO3: Intrinsic or extrinsic?

Abstract: Among the different bulk alloys of the room temperature multiferroic compound BiFeO3, alloying with ATiO3 (A = Ba, Sr, Pb) is interesting as they have been reported to induce ferromagnetism under certain conditions. While this makes them interesting as potential multiferroic magnetoelectric materials, there is a lack of clarity on the origin of ferromagnetism in these systems. We have performed a detailed magneto-structural analysis on two alloys, namely, BiFeO3-BaTiO3 and BiFeO3-SrTiO3, and found the systems' propensity for the formation of ferrimagnetic hexaferrite (BaFe12O19 and SrFe12O19) phases. Though insignificantly small to the extent of being undetectable by x-ray powder diffraction, we prove that the ferromagnetic character of the specimen is entirely due to spontaneous precipitation of the hexaferrite grains. While our results suggest that care should be exercised before attributing ferromagnetism in such alloy systems as intrinsic to the perovskite phase, the propensity for the spontaneous precipitation of the hexaferrite phase in these multiferroic alloy systems is encouraging as it provides an opportunity for designing self-grown ferroelectric-ferromagnetic composites with good magnetoelectric coupling.