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.

On the dynamic embrittlement of copper-chromium alloys by sulphur

Abstract: The high temperature ductility of copper-chromium alloys has been examined in the temperature range of 25–700°C. Copper-chromium alloys exhibit severe intermediate temperature loss in ductility. The loss in ductility is associated with the ingress of sulphur along the grain boundaries under the influence of tensile stress, followed by decohesion of grain boundaries. Integranular facets of the fracture surface exhibit striations, indicative of quasi-static, step-wise crack growth process.

Strengthening of Al/20 v/o TiC composites by isothermal heat treatment

Abstract: A chemical potential gradient exists across the reinforcement/matrix interface of metal-matrix composites which serves as the basis for either diffusion or chemical reaction between the two components at high temperatures. While poor control of this reaction may degrade mechanical properties, it may also be employed to improve them. Such improvements as an increase in elastic modulus in the case of Al-Mg/SiC(p) are attributable to improved load transfer, due either to an interactive diffusion process at the interface or the 'keying' effect of interfacial Al4C3. A systematic study is presently undertaken of the effects of 600 C exposure on the microstructure and mechanical properties of Al/20 vol pct TiC; a reduction in tensile ductility is associated with an increase in strength and elastic modulus. 5 refs.

Effect of Postweld Aging Treatment on Fatigue Behavior of Pulsed Current Welded AA7075 Aluminum Alloy Joints

Abstract: This article reports the effect of postweld aging treatment on fatigue behavior of pulsed current welded AA 7075 aluminum alloy joints. AA7075 aluminum alloy (Al-Zn-Mg-Cu alloy) has gathered wide acceptance in the fabrication of light weight structures requiring high strength-to weight ratio, such as transportable bridge girders, military vehicles, road tankers, and railway transport systems. The preferred welding processes of AA7075 aluminum alloy are frequently gas tungsten arc welding (GTAW) process and gas metal arc welding (GMAW) process due to their comparatively easier applicability and better economy. Weld fusion zones typically exhibit coarse columnar grains because of the prevailing thermal conditions during weld metal solidification. This often results inferior weld mechanical properties and poor resistance to hot cracking. In this investigation, an attempt has been made to refine the fusion zone grains by applying pulsed current welding technique. Rolled plates of 10 mm thickness have been used as the base material for preparing multipass welded joints. Single V butt joint configuration has been prepared for joining the plates. The filler metal used for joining the plates is AA 5356 (Al-5Mg (wt.%)) grade aluminum alloy. Four different welding techniques have been used to fabricate the joints and they are: (i) continuous current GTAW (CCGTAW), (ii) pulsed current GTAW (PCGTAW), (iii) continuous current GMAW (CCGMAW), and (iv) pulsed current GMAW (PCGMAW) processes. Argon (99.99% pure) has been used as the shielding gas. Rotary bending fatigue testing machine has been used to evaluate fatigue behavior of the welded joints. Current pulsing leads to relatively finer and more equi-axed grain structure in GTA and GMA welds. Grain refinement is accompanied by an increase in fatigue life and endurance limit. Simple postweld aging treatment applied to the joints is found to be beneficial to enhance the fatigue performance of the welded joints.

An in vitro analysis of H1N1 viral inhibition using polymer coated superparamagnetic Fe3O4 nanoparticles

Abstract: Monodispersed Fe3O4 nanoparticles were prepared by a polyol assisted solvothermal method and their activity against H1N1 influenza A virus was studied. The present study also elucidates the influence of size, shape and surface properties of the pristine, as well as polymer coated, magnetite nanoparticles. X-ray diffraction and Fourier transform infrared spectroscopic observations confirm the high crystallinity and the polymer attachment with the magnetite nanoparticles. Transmission electron microscopy (TEM) images confirm the monodispersed nanoprisms and flower like morphologies of the magnetite nanoparticles. The superparamagnetic behavior and other magnetic properties were also studied by measuring the hysteresis loop using a vibrating sample magnetometer. The cell viability studies of the magnetite nanoparticles using a standard MTT assay confirm the non-toxic nature of the samples. Reverse transcription polymerase chain reaction (RT-PCR) analysis confirms the Fe3O4 nanoparticles inhibit influenza viral RNA synthesis in MDCK cells.