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.

Cold rolling texture in AISI 304 stainless steel

Abstract: Evolution of texture during cold rolling of austenitic AISI 304 stainless steel is presented here. The annealed steel plate has been unidirectionally cold rolled up to 90% reductions under two different rolling conditions. Effect of rolling conditions on transformation of austenite to strain-induced α′ martensite phase and evolution of texture in both the phases have been studied as a function of rolling reduction. The X-ray diffraction (XRD) technique has been employed to quantify the volume fractions of austenite and martensite phases and to study the textural development in the steel in rolled conditions. Optical and transmission electron microscopy studies have been carried out to see the microstructural changes due to cold rolling. Texture in the α′ martensite is found to be governed by the initial texture of the parent austenite phase according to the Kurdjumov–Sachs relationship, even up to maximum deformation levels.

Aging behaviour of Al–Cu–Mg alloy–SiC composites

Abstract: The age-hardening kinetics of powder metallurgy processed Al–Cu–Mg alloy and composites with 5, 15 or 25 vol% SiC reinforcements, subjected to solution treatment at 495 °C for 05 h or at 504 °C for 4 h followed by aging at 191 °C, have been studied The Al–SiC interfaces in composites show undissolved, coarse intermetallic precipitates rich in Cu, Fe, and Mg, with its extent varying with processing conditions Examination of aging kinetics indicates that the peak-age hardness values are higher, and the time taken for peak aging is an hour longer on solutionizing at 504 °C for 4 h, due to greater solute dissolution Contrary to the accepted view, the composites have taken longer time to peak-age than the alloy, probably due to lower vacancy concentration, large-scale interfacial segregation of alloying elements, and inadequate density of dislocations in matrix The composite with 5 vol% SiC with the lowest inter-particle spacing has shown the highest hardness

Hardness and tensile properties of tungsten based heavy alloys prepared by liquid phase sintering technique

Abstract: Several tungsten heavy alloys based on W–Ni–Cu and W–Ni–Fe were made recently at DMRL by liquid phase sintering route. These alloys were heat treated and characterized in terms of density, hardness and tensile properties. Although the densities of W–Ni–Cu based heavy alloys were found to be relatively higher than those of W–Ni–Fe based heavy alloys, the former exhibited inferior tensile properties and hardness values than the latter alloys. In both these heavy alloys, un-melted solid tungsten particles were bonded together by the respective low melting matrix alloy. The strength of the matrix or the bonding strength of the interface (between tungsten particles and matrix) was found to control the nature of final fracture. Poorer matrix strength or interfacial strength was found to initiate the fracture by separation of tungsten particles either by matrix failure or by interface failure. On the other hand, tensile fracture takes place predominantly by cleavage fracture of tungsten particles, if both the matrix and interface are stronger than the tungsten particles. The tensile fractured surfaces were examined under scanning electron microscope (SEM). Failure stress is observed to be lower in case of separation of tungsten particles (due to matrix and interface failure) than that in case of cleavage fracture (transgranular fracture) of tungsten particles. SEM image of fractured surfaces clearly indicated that failure in case of W–Ni–Cu based heavy alloys was due to matrix and/or interface (between tungsten grain and matrix) failure, where as, W–Ni–Fe based heavy alloys were failed predominantly by cleavage fracture of tungsten particles. This was evidenced by poorer tensile properties obtained for W–Ni–Cu based heavy alloys as compared to those of W–Ni–Fe based heavy alloys. The present sets of results indicate that heavy alloys based on W–Ni–Fe and W–Ni–Cu can be strengthened by minor additions of Co, Mo and Fe selectively. Higher strength (>850 MPa) of the heavy alloys are associated with the finer tungsten grain size and cleavage fracture of tungsten particles. Where as, the lower strength is associated with the larger tungsten grain size and interface and/or matrix failure. It is found in this study that as the tungsten grain size decreases, the tensile fracture mode changes gradually from interface failure to matrix failure to tungsten grain cleavage failure.