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.

Correlating Ultrasonic Attenuation and Microtexture in a Near-Alpha Titanium Alloy

Abstract: Near-α titanium alloys are an integral part of aeroengines; however, since the 1970s, it has been recognized that laboratory and field components fail in a reduced number of cycles when a dwell at the peak stress is imposed. Research over the last few decades has shown that one of the primary reasons for the debit in fatigue life is related to the presence of microtexture in these alloys. Many aeroengine components were forged before the concept of microtexture, and its deleterious effects, had been realized. Thus, because of the increased potential for early failure of these components, a need exists for a nondestructive method to assess the degree of microtexture present in legacy hardware in order to separate those which are prone to dwell fatigue failure from those that are not. Hardware with a high degree of microtexture can be scheduled for more frequent inspections to reduce the risk of in-flight failure. The present work describes a methodology by which this can be achieved using ultrasonic attenuation measurements of the component in pulse-echo imaging mode. The results indicate nearly linear dependence of ultrasonic attenuation on microtextured region size in the d/λ = 0.1 to 1.0 range, where d and λ are the effective microtexture region size in the direction of wave propagation and the ultrasonic wavelength, respectively.

Tensile anisotropy associated microstructural and microtextural evolution in a metastable beta titanium alloy

Abstract: Tensile anisotropy behaviour of metastable beta titanium alloy β-21s (Ti–15Mo–2.7Nb–3Al–0.2Si) sheet in solution treated condition is evaluated at room temperature along three different orientation (rolling direction, 45° to rolling direction and transverse direction). In addition to fractographic studies, the microstructural and microtextural evolution is investigated in the post-tensile deformed condition through optical metallography, scanning electron microscopy (SEM) and Electron Backscattered Diffraction (EBSD). Quantification of mechanical anisotropy by evaluating the % In-Plane Anisotropy (%IPA), Anisotropic Index (δ), yield loci and plastic strain ratio indicated considerable anisotropy in strengths and ductility. Irrespective of testing orientation, the deformed microstructure is characterized by fine to coarse planar slip bands, however the slip bands observed along 45° is relatively widely spaced. The evolution of dislocation density obtained from kernel average misorientation (KAM) maps is unaffected by the tensile testing direction. Although EBSD derived Taylor factor maps revealed slip mediated deformation behaviour dominated by {110} slip systems along all testing directions, the Taylor factor distribution divulged complex dependence on test orientation. Despite weak to moderate microtextural changes are noticed in α-fiber and β-fiber texture components, the textural evolution is strongly influenced by the testing orientation.

Effect of particle shape on the erosion of Cu and its alloys

Abstract: The main objective of the present work is to evaluate the effect of stacking fault energy (SFE) on the erosion rate of Cu and Cu-base alloys using angular particles as erodents and to compare the above behaviour with the obtained in an earlier study using spherical particles as erodents. Towards the above purpose the erosions rates of Cu, Cu-5.3 Al and Cu-20Zn were determined at two different impact angles (90° and 30°), at two different impact velocities and using angular SiC and SiO 2 particles as erodents. The results indicate that the erosion rate of Cu and its alloys decreases with increased SFE and further increases with decreasing impact angle indicative of a ductile response. This is in contrast to the erosion behaviour of Cu and its alloys, with spherical steel shots as erodents, wherein the erosion rate increased with an increase in SFE and also exhibited a maximum at normal impact angle. This contrasting erosion behaviour has been attributed to the higher strain rate and hence reduced dynamic recovery with angular particles when compared with spherical particles.