Department of Metallurgical and Materials Engineering

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Preprints

On the tensile creep deformation behaviour of wrought single-phase $\gamma$-TiAl

In the present study, using ICME approach, the development of Co-Cr-Fe-Ni-V based single-phase FCC high entropy alloy (HEA) has been explored. The simulation guided composition was arc melted and verified using microstructure characterization. The as-cast sample was subjected to deformation at a strain rate of 0.1 s−1in the temperature range of 1073–1373 K. The flow stress behavior in this temperature range could be correlated with the evolution of microstructure using EBSD. Based on these results, the deformation behavior of the alloy at elevated temperature is rationalized. The current study realizes the ICME approach to develop novel single-phase FCC HEA. © 2021 Elsevier B.V.

World University root node

Journal of Alloys and Compounds

Design and deformation characteristics of single-phase Co-Cr-Fe-Ni-V high entropy alloy

There is considerable research interest in developing medium Mn steels as part of the 3rd generation of advanced high strength steels, mainly due to the possibility to achieve high tensile strength-high ductility combination at an affordable cost. In the present work, we have designed a steel chemistry and its thermomechanical processing route based on a computational approach based on CALPHAD with an objective to achieve tensile strength and uniform elongation in excess of 1000 MPa and 20%, respectively. The influence of alloying elements on factors such as weldability, coatability and formability are also taken into account while designing the steel chemistries. The alloy chemistry was optimised to achieve at least 50% of retained austenite and a stacking fault energy in the range 12–20 mJ m−2 to activate transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP) effects. The designed steel was cast and thermomechanically processed to produce ultrafine-grained ferrite and austenite microstructure with ~50% of retained austenite. Analysis of local composition by atom probe tomography revealed preferential partitioning of Mn and C to austenite during intercritical annealing, thereby enhancing its stability. The optimised microstructure resulted in tensile strength and uniform elongation in excess of 1300 MPa and 26%, respectively. The stress-strain curves revealed serrations and a staircase type of strain hardening. A detailed study of the strain hardening behaviour showed that this can be attributed to the occurrence of discontinuous TRIP effect and deformation twinning in the austenite. This was further corroborated by transmission electron microscopy of the deformed samples which showed the presence of nano-twins in the austenite phase while the XRD and EBSD of the deformed samples showed a significant drop in the austenite fraction post deformation. © 2021 Elsevier B.V.

Materials Science and Engineering A

High strength-high ductility medium Mn steel obtained through CALPHAD based alloy design and thermomechanical processing

Halbach EMATs can efficiently generate shear horizontal (SH) guided wave modes. Using the Halbach magnet structure, the EMATs can enhance the magnetic flux density within a material forming ultrasonic waves with relatively large amplitude. The paper first presents a comparison analysis of double-row Halbach EMATs with double-row PPM EMATs using Finite Element based simulation models for SH0 ultrasonic wave generation. The study then analyses the wave interference effects created by the staggered double-row Halbach EMAT configurations. This is also performed using numerical Finite Element Models (FEM) and experimentally validated in an Aluminum plate specimen. It is observed that the steering of the ultrasonic guided waves can be associated and predicted for different double-row staggered PPM EMAT configurations. © 2021 Elsevier Ltd

Department of Mechanical Engineering

NDT and E International

Characterising the beam formation of SH waves using double-row Staggered Halbach EMAT configurations

An extensive analysis of radiative flux biases in the Climate Forecast System Model Version 2 (CFSv2) is done. Annual mean and seasonal variations of biases at the surface and top of the atmosphere (TOA) are reported in the global domain. Large regional biases in shortwave (SW) and longwave (LW) radiation are observed over convectively active zones in the tropics. The relative contribution of various processes responsible for the reported biases is quantified. The poor simulation of clouds and inadequate representation of surface properties seem to be major contributors. Over certain regions, errors due to different processes add up, whereas, over other regions, errors tend to nullify each other. Surface and atmospheric variables taken as input parameters in the radiative transfer modules are compared with satellite-based observations. The maximum biases in SW and LW radiation are observed over the regions of persistent low clouds. The magnitude of the SW and LW biases at the TOA is in phase with the biases in cloud fraction by and large. However, the error in the radiative fluxes due to errors in surface radiative properties is of equal importance. The cold bias in near-surface air temperature reported in other studies may partly be attributed to an underestimation in the net SW radiation at the surface. In the present study, a plausible prescription is also provided to correct the source of the biases. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.

Climate Dynamics

An assessment of radiative flux biases in the climate forecast system model CFSv2

In the present work, quinaldic acid and chloroacetic acid are used to synthesize Quinolinium 2-Carboxylate 2-Chloroacetic acid (compound 1). Conventionally, the crystal structure of the sample is determined by the single crystal X-ray diffraction method. 1H NMR, 13C NMR, FT-IR, and UV-–visible spectral studies are also carried out to confirm the crystal structure of compound 1. In this respect, compound 1 exhibits inhibitory activity against 1HNY, as evidenced by the molecular docking study. The in silico biological activities are studied, and the results are correlated with the reference drug. Since the molecular structures are optimized, DFT calculations are implemented to find the significant regions for enzymatic activities. The binding affinity values are found for compound 1, which formed an interaction with 1HNY. As evident from the MEP maps, the negative regions are localized over the carboxyl group and are suitable for antidiabetic activity. © 2021

Journal of Molecular Structure

Studies of synthesis, crystal structure and antidiabetic activity of quinolinium 2-carboxylate 2-chloroacetic acid

The hybrid network of Si3N4 whiskers and conducting carbon fiber has great potential for microwave absoprtion applications. The high electrical conductivity of the carbon fiber helps to transform the microwave transparent Si3N4 into microwave absorbing materials. Herein, the microwave absorption performance of 5–20 vol % of carbon fiber reinforced reaction bonded Si3N4 (Cf-RBSN) composites have been discussed in detail. The Cf reinforcement tuned the X-band dielectric properties of the RBSN composites. The 5 vol % Cf-RBSN composite exhibit a minimum reflection loss (RLmin) of −36.16 dB (99.998% microwave absorption) at 11.89 GHz and a high specific reflection loss of 920 dB. g−1 for 5.9 mm thickness, while 20 vol % Cf-RBSN composites resulted in RLmin of −22.86 dB at 11.56 GHz with a low thickness of 1.5 mm. Thus, the superior microwave absorption performance of the prepared lightweight composites results from the multiple interfacial polarization, dipole polarization, and conduction loss due to the 3D network of interconnected Si3N4 whiskers and Cf. © 2021 Elsevier Ltd and Techna Group S.r.l.

Ceramics International

Tunable microwave absorption performance of carbon fiber-reinforced reaction bonded silicon nitride composites

Short aggregation prone sequence motifs can trigger aggregation in peptide and protein sequences. Most algorithms developed so far to identify potential aggregation prone regions (APRs) use amino acid residue composition and/or sequence pattern features. In this work, we have investigated the importance of atomic-level characteristics rather than residue level to understand the initiation of aggregation in proteins and peptides. Using atomic-level features an ensemble-classifier, ANuPP has been developed to predict the aggregation-nucleating regions in peptides and proteins. In a dataset of 1279 hexapeptides, ANuPP achieved an area under the curve (AUC) of 0.831 with 77% accuracy on 10-fold cross-validation and an AUC of 0.883 with 83% accuracy in a blind test dataset of 142 hexapeptides. Further, it showed an average SOV of 48.7% on identifying APR regions in 37 proteins. The performance of ANuPP is better than other methods reported in the literature on both amyloidogenic hexapeptide prediction and APR identification. We have developed a web server for ANuPP and it is available at https://web.iitm.ac.in/bioinfo2/ANuPP/. Insights gained from this work demonstrate the importance of atomic and functional group characteristics towards diversity of atomic level origins as well as mechanisms of protein aggregation. © 2020 Elsevier Ltd

Department Of Biotechnology

Fulltext

Journal of Molecular Biology

ANuPP: A Versatile Tool to Predict Aggregation Nucleating Regions in Peptides and Proteins

Industrial servo presses have been used to successfully demonstrate improved formability when deforming sheet metals. While the time dependent viscoplastic behavior of material is attributed to the observed formability improvement, much less effort has been devoted to understand and quantify the underlying mechanisms. In this context, the hole expansion test (HET) of a dual phase steel was interrupted at pre-defined punch travel heights to understand the time-dependent effects on stretch-flangeability. The effect of pre-strain, hold time and edge quality on hole expansion ratio (HER) improvement was studied. The present study shows that the HER improves significantly in interrupted HET. This improved HER is due to the combined effects of stress relaxation and friction on deformation behavior. The ductility improvement estimated from uniaxial stress relaxation tests was used to estimate the contribution of stress relaxation and friction, respectively, in HET. This study shows that friction plays a significant role in improving HER at high pre-strain. It was also demonstrated that frictional effects are largely influenced by edge quality. © 2020 CIRP

CIRP Journal of Manufacturing Science and Technology

On the interplay of friction and stress relaxation to improve stretch-flangeability of dual phase (DP600) steel

Cold spray deposition involves a unique combination of high strain rate and moderate to high strain deformation of powder particles that contrasts it from conventional severe plastic deformation techniques. In the present work, a systematic study of the microstructure and micromechanical properties of cold sprayed Cu and Cu–Al alloys, which are known for significant variation in stacking fault energy with small alloying addition, is presented. The deposition process results in significant grain refinement (<50 nm) and profuse deformation twinning with very fine twins (<20 nm) in the Cu–Al alloys. The theoretical predictions of the extent of grain refinement using a dislocation-based model agree well with the experimental observations for the alloys, even in the presence of significant twinning. The inherent discrete nature of the cold spray coating deposition results in significant heterogeneity and hence extensive hardness mapping has been performed to establish structure-property correlations at the micrometer length scale. Furthermore, the various factors influencing the hardness of the coatings are analytically determined and it was found that the strengthening contribution from the boundary (grain/twin) is much lower than that determined from Hall-Petch type relationship in case of the alloys that showed significant twinning. A twin mediated deformation mechanism in the presence of fine twins, which subsequently de-twin, is found to explain the lower boundary strengthening. © 2021 Elsevier B.V.