Showing papers by "Defence Metallurgical Research Laboratory published in 2022"

Compression and creep behaviour of Ti-46.5Al-xNb-yCr-zMo-0.3B (x=3.5, 5; y, z=0,1,2) alloys

Abstract: The microstructure, compression and creep behaviour of γ-TiAl based alloys containing 46.5 at.% Al with varying amounts of beta stabilizing elements Nb, Cr and Mo have been investigated in the present work. Compression tests were carried out at room temperature as well as high temperature (800 °C), and creep tests were carried out at 800 °C and at a stress of 300 MPa. Compression and creep studies were conducted in a standard microstructural condition after a solutionizing and ageing treatment and fracture surfaces and deformation microstructures were analysed after creep. The effect of beta stabilizing elements on compression and creep were assessed in terms of beta phase formation, different phase constituents and solid solution strengthening mechanisms. Creep studies were also carried out at 750, 800 and 850 °C and stresses of 250, 300 and 350 MPa to evaluate the creep deformation mechanisms in these alloys and are presented in the current work.

Metamodels to describe the high temperature deformation behaviour of Al 2014+2wt%TiB₂ composite

Abstract: Isothermal hot compression tests were conducted on Al 2014 + 2 wt% TiB2 composite at different temperatures (300–450°C) and strain rates (0.001–1 s−1). Using the compression test data, an attempt was made to establish the constitutive relationship for the material by employing three different metamodels such as response surface methodology (RSM), genetic algorithm (GA), and artificial neural network (ANN). The capability of these metamodels towards establishing the non-linear constitutive relation between the process parameters such as temperature, strain rate and strain and flow stress has been ascertained using standard statistical parameters, namely, correlation coefficient (R) and average absolute relative error (AARE). A cubic regression equation was suggested by RSM, while 3–15-1 neural network architecture provided a better correlation. The results obtained are presented and discussed here.

Advanced Characterization and Calphad in Design and Development of Advanced High Strength Steels

Abstract: Microstructure plays an important role in achieving the desired set of mechanical properties. Any design and development of new grades of steels or improvement in properties of the existing steels necessitates the understanding of the structure–property correlations through extensive microstructural characterization. Once the microstructure at different length scales has been understood, microstructural engineering through modification of the phases and phase fractions, size and distribution of the second phase via modification of the composition and processing windows may be applied to achieve the desired properties. This article describes our efforts in advanced characterization of ultra-high strength (UHS) steels using electron microscopy and 3D atom probe supported by thermodynamic calculations in the Calphad framework. TEM and APT characterization of UHS steel developed earlier at DMRL revealed the presence of atomic scale clusters of both carbon rich and carbon lean clusters. It is believed that these clusters can significantly influence both strength and toughness along with other strengthening mechanisms. These carbon lean clusters have been used as the base to tailor the microstructure for enhanced mechanical properties. ThermoCalc has been employed extensively to design a new set of compositions for experimental validation and optimization of the processing windows. Experimental results on the designed alloys reveal significant fraction of undissolved precipitates and more than 50 percent austenite when the steel containing 5wt. % Cr and Mo austenitized at 1150 °C. Atom probe results further suggest the formation of clusters and their composition approaches toward M2C with increase in tempering temperature. The volume fraction and Cr/Mo ratio of the M2C type clusters broadly correlates well with the ThermoCalc predictions.

Compact and Broadband Printed Antennas

Abstract: In recent years device industries has shown substantial interest in low-profile and conformal circuits to meet the requirements of evolving wireless technologies and standards. There is an increasing interest towards development of integrated/on chip antennas especially for wireless devices. Achieving broad impedance and radiation bandwidth from a compact antenna has been a challenging task. There are several research groups who pioneered in development of the compact broadband antennas for wireless devices. This chapter discusses techniques used to design compact and broadband antennas. The design techniques discussed in this chapter includes design of broadband printed microstrip and slot antennas, Metamaterial inspired antennas, Antennas integrated with periodic structures, and composition of resonators for compact antenna design. Some of the examples presented in this chapter also pertains to the millimeter wave antennas where metamaterial inspired configurations are used. Here, the term broadband antenna is associated with those antennas which provides consistent impedance bandwidth i.e., the return loss <10 dB (Voltage standing wave ratio-VSWR <2) and consistent radiation bandwidth i.e., characteristics such as gain, efficiency and radiation pattern are consistent for a given impedance bandwidth. Most of the antennas discussed here are printed antenna i.e., they are printed on a low-loss dielectric substrate with specific permittivity. As the value of substrate’s permittivity contributes towards antenna design, its selection for the antenna design is done based on end use/application of the antenna.

On Structure-Equipment-Piping Interactions Under Earthquake Excitation

Abstract: Generally, seismic risk is discussed with respect to the structures that include lifelines. Less discussed with regard to the equipment and piping that also contribute to the total seismic risk in terms of life and economy. In view of this, in the present paper, the detailed procedure to estimate the design seismic forces in equipment and piping systems is discussed. Focus is given on structure-equipment interaction and equipment-piping interaction. Detailed explanation is made on generation inputs for the design of floor-mounted equipment and piping systems. Also, procedure for evaluating the response of piping system supported at multi locations of structure is explained.

Experimental and correlation study of destructive and non-destructive testing on blended concrete with metakaolin and bagasse ash

Abstract: The utilization of industrial wastes has been the hub of squander minimization research for environmental, economic and technical reasons. Bagasse is an off-shoot from sugar industries, which is ignited to develop the power needed for numerous activities in the factory. Its high pozzolanic property and the presence of alumina and silica content can enrich the properties of concrete. Metakaolin is a primitive output accomplished by calcinating kaolin clay inside a temperature sort of 650 to 800°C utilized to produce materials with lower porosity, greater strength, denser microstructure, greater resistance to ions improved durability. An experimental investigation has been done on blended concrete with a combined effect of Bagasse ash (B), and Metakaolin (M) with percentages 10%+2.5%, 20%+5%, 30%+7.5%, and 40%+10%, which are designated as B1M1, B2M2, B3M3, and B4M4 respectively were incorporated in Ordinary Portland Cement (OPC). The fresh (workability) and hardened properties (Splitting tensile and compressive strength) of concrete were compared to Control Concrete (CC) and also checked the contrast of non-destructive strength values over destructive testing.

Structure, processing, property correlation of metastable β titanium Ti-5Al-5Mo-5V-3Cr alloy

Abstract: This work reports the evolution of “Structure, Processing, Property Correlation of Metastable β Titanium Ti-5Al-5Mo-5V-3Cr alloy” as a function of different aging temperatures (625,725 and 775 °C) for 4 h subsequent to solution heat treatment. The hot-rolled sheet was heat treated in β phase field and then water quenched. The solution heat treated in β phase field and then water quenched samples were aged at 625, 725 and 775 °C for 4 h. The hot-rolled sample shows the presence of α and β phases. The β-solution heat treated in β phase field and then water quenched sample of the alloy exhibits single β phase. The intensities of X-ray peaks are varying and β (211) peak shows the maximum intensity. The maximum intensity can be ascribed to β (211) texture. The solution heat treated in β phase field and then water quenched sample aged at 625 °C for 4 h shows the very fine hexagonal α phase precipitates as compared to the samples aged at 725 and 775 °C for 4 h. The samples aged at 725 and 775 °C for 4 h has resulted in precipitate-free zones as a result of the rejection of Mo, V, and Cr (β stabilizing elements) during nucleation and growth of α precipitates along the β grain boundaries. The Vickers hardness values of the alloy increase from solution heat treated in β phase field and then water quenched to all aging temperatures. The sample aged at 625 °C for 4 h shows the maximum hardness which is due to the presence of fine α phase precipitates. This can be ascribed to typical precipitation hardening.