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

The density of Al2O3–CaO–MgO–SiO2 system is calculated using a model for molar volume. The model is similar to the one used for enthalpy of a multicomponent solution in the CALPHAD approach. The expression for molar volume consists of two terms: one representing the volume contribution from pure components and the other the volume of mixing. The molar volume of mixing takes into account of the binary and the ternary interactions. A total of 565 experimental density data for the constituent unary, binary and ternary systems were collected from the literature. These were used as input to simultaneously optimise the model parameters describing the molar volume, after ensuring that the data belong to a fully molten state. During the optimisation 48 data points that showed significant deviation from the average trend were excluded. The optimised model parameters for the unary, binary and ternary subsystems were used to calculate the density of the quaternary system. The calculated results were compared with experimental data. Finally, it is shown that the volume of mixing of binary systems correlates well with the corresponding enthalpy of mixing. © 2020 Elsevier Ltd

World University root node

Calphad: Computer Coupling of Phase Diagrams and Thermochemistry

Modelling the density of Al2O3–CaO–MgO–SiO2 system using the CALPHAD approach

Shape memory alloys are used in diverse fields. It is Ni–Ti alloys that are predominantly used for applications capitalizing on the functional properties of shape memory and superelastic effect. These properties are influenced by factors, such as alloy composition, alloying addition, thermal and mechanical treatment, etc. In any application, the transformation temperatures of the alloy/device are very critical. Moreover, the stability of transformation temperatures and a smaller hysteresis are preferred. Ni–Ti alloys have their own limitations, such as low transformation temperatures and lack of ductility. In order to overcome these limitations, researchers have used ternary additions, such as Zr, Hf, Cu, Pd and Au. The use of copper is practicable because of its lower cost as compared to Ti and Ni. Substitution of Cu for Ni up to   25% in an equiatomic NiTi alloy causes it to exhibit SME. The transformation temperatures of NiTiCu exhibit less sensitivity to composition and a smaller thermal hysteresis. In this work, therefore, the effect of methods of quenching on transformation temperatures and microstructure of an Ni–Ti–4Cu (at.%) alloy has been explored. The material was cast using vacuum induction melting. It was solutionized at 950 °C for 2 h and cooled using different methods/quenchants: liquid nitrogen, water at room temperature, air, annealing (furnace cooling). The samples quenched by different techniques were characterized by XRD, DSC, OM, SEM and hardness test. The results indicated that the martensite plate size varied in samples quenched using different quenchants even though the morphology was the same in all specimens. In addition, the transformation temperatures and hardness values of the alloy specimens varied as the intensity of quenching varied. The results are presented and discussed in detail in the paper. © 2020, The Indian Institute of Metals - IIM.

Transactions of the Indian Institute of Metals

The Effect of Quenching Methods on Transformation Characteristics and Microstructure of an NiTiCu Shape Memory Alloy

It is generally accepted that severe plastic deformation (SPD) has the ability to produce ultrafinegrained (UFG) and nanocrystalline materials in bulk. Recent developments in high pressure torsion (HPT) processes have led to the production of bimetallic composites using copper, aluminum or magnesium alloys. This article outlines a new approach to fabricate multilayered Ni-Ti nanocomposites by a patented SPD technique, namely, high speed high pressure torsion (HSHPT). The multilayered composite discs consist of Ni-Ti alloys of different composition: a shape memory alloy (SMA) Ti-rich, whose Mf > RT, and an SMA Ni-rich, whose Af < RT. The composites were designed to have 2 to 32 layers of both alloys. The layers were arranged in different sequences to improve the shape recovery on both heating and cooling of nickel-titanium alloys. The manufacturing process of Ni-Ti multilayers is explained in this work. The evolution of the microstructure was traced using optical, scanning electron and transmission electron microscopes. The effectiveness of the bonding of the multilayered composites was investigated. The shape memory characteristics and the martensitic transition of the nickel-titanium nanocomposites were studied by differential scanning calorimetry (DSC). This method opens up new possibilities for designing various layered metal-matrix composites achieving the best combination of shape memory, deformability and tensile strength. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.

Fulltext

Metals

Structural characteristics of multilayered ni-ti nanocomposite fabricated by high speed high pressure torsion (Hshpt)

In this study, a hybrid dual drug-loaded hydroxyapatite-oxidized dextran methacrylate core-shell nanocarrier was formulated and explored for combinatorial delivery of doxorubicin (DOX) and methotrexate (MTX) to bone cancer. The synthesized nanocarrier was well characterized by different techniques. In vitro drug release studies in both acidic (pH 5) and alkaline (pH 7.4) conditions showed sequential release of MTX followed by DOX in a sustained manner for 10 days. Biocompatibility and cytotoxicity studies performed using drug-loaded nanoparticles (NPs) on fibroblast L929 cells and osteosarcoma MG63 cells (OMG63) showed that the NPs were highly biocompatible and showed concentration-dependent toxicity. Gene expression studies in OMG-63 cells exhibited the upregulation of caspase-3 and BAX which confirmed the apoptosis induced by dual drug-loaded NPs. The nanocarrier is expected to be a potential bone void filling material, as well as a platform for sequential delivery of DOX and MTX for the treatment of bone cancer. Copyright © Materials Research Society 2020.

Journal of Materials Research

Hydroxyapatite-dextran methacrylate core/shell hybrid nanocarriers for combinatorial drug therapy

Laser beam directed energy deposition (DED-LB) differs from other metal additive manufacturing (AM) methods as it allows high building rates and manufacturing of multi-material components via in-situ alloying. This is especially compelling in combination with high-manganese steel (HMnS), as the mechanical properties can be influenced significantly by tailoring the chemistry-dependent stacking-fault energy (SFE). In DED, this can be used to design parts based on local deformation behavior. However, the increased affinity of HMnS to oxygen causes high amounts of oxide formation in the manufactured parts, ultimately deteriorating the mechanical properties due to premature cracking. To investigate the responsible mechanisms, two sets of processing parameters resulting in varying melt pool sizes were applied to produce X30Mn23 steel with up to 1 wt% in-situ alloyed Al. The melt pool was first modeled using a finite element method (FEM) approach and correlated with microstructure evolution (OM, SEM, EDS, EBSD, APT) and mechanical properties (tensile test). Interaction of the melt pool with the atmosphere and therefore oxide formation was successfully prevented by reducing the melt pool size, making the application of HMnS in DED feasible. The crack formation by oxides and its prevention are discussed in detail. Finally, the feasibility to manufacture HMnS with an in-situ alloying approach is critically evaluated. © 2019 Elsevier B.V.

Materials Science and Engineering A

Defect formation and prevention in directed energy deposition of high-manganese steels and the effect on mechanical properties

In this study, the effect of Fe in precipitation strengthened Al-Co-Cr-Fe-Ni-Ti complex concentrated alloys (CCAs) is investigated. The amount of Fe significantly affected the γ′ morphology, microstructural stability, lattice misfit, solvus temperature and mechanical behaviour. The decrease in the Fe content from 11.5 (Al7.8Co20.6Cr12.2Fe11.5Ni40.7Ti7.2) to 0 (Al7.8Co20.6Cr12.2Ni52.2Ti7.2) at% changed the precipitate morphology from spherical to cuboidal upon 50h ageing at 900°C. Also, the lattice misfit and solvus temperature of the alloy increased from 0.097 to 0.41% and 1109 to 1199°C, respectively, with the complete removal of Fe from the alloy system. Coarsening studies at 900°C (up to 550h) revealed that the γ′ coarsening was driven by evaporation and condensation (EC) mechanism in Al7.8Co20.6Cr12.2FexNi52.2-xTi7.2 (x=11.5, 5 and 0, in at%) alloys. The coarsening rate constants (Kr) were calculated for the three alloys; among them, the alloy without Fe showed the least value (2.83 × 10−27 m3 s−1). The obtained results on the effect of Fe in L12 strengthened CCAs offer a new platform for the development of advanced high-temperature alloys. © 2020 Acta Materialia Inc.

Materialia

On the effect of Fe in L12 strengthened Al–Co–Cr–Fe–Ni–Ti complex concentrated alloy

Renewable harvesting of clean energy using the benefits of multi-metallic catalytic materials of high entropy alloy (HEA, equimolar Cu–Ag–Au–Pt–Pd) from formic acid with minimum energy input has been achieved in the present investigation. The synergistic effect of pristine elements in the multi-metallic HEA drives the electro-oxidation reaction towards non-carbonaceous pathway. The atomistic based simulations based on DFT rationalize the distinct lowering of the d-band center for the individual atoms in the HEA as compared to the pristine counterparts. Further this catalytic activity of the HEA has also been extended to methanol electro-oxidation to show the unique capability of the novel catalyst. The nanostructured HEA, prepared using a combination of casting and cryomilling techniques can further be utilized as the fuel cell anode in the direct formic acid/methanol fuel cells (DFFE). © 2020 Elsevier Ltd

Materials Today Energy

Formic acid and methanol electro-oxidation and counter hydrogen production using nano high entropy catalyst

The reaction of magnesium diboride with water results in an intermediate borohydride product which leads to the simultaneous reduction of graphitic oxide (GO) and the formation of magnesium hydroxide. In this work, the thermo-optical properties of magnesium diboride modified reduced graphene oxide–based nanofluids have been explored. The study primarily focuses on the reaction mechanism of magnesium diboride and GO by using liquid exfoliation technique. Suspension after liquid exfoliation mainly consisted of a turbid supernatant and precipitate which was composed of boron-based nanosheets (CBNs) and a composite of magnesium hydroxide and reduced graphene oxide (CBNs-rGO), respectively. Nanofluids were subsequently formulated from the obtained products of the reaction. CBNs form a stable suspension in water and ethylene glycol because of its attached borohydrides and hydroxyl hydrophilic sites. CBNs nanofluids show good thermal conductivity with poor light absorption properties in the visible wavelength range. Whereas, CBNs-rGO nanofluids show  95% attenuation in the radiation with a significant enhancement of  30% and 20% in thermal conductivity as compared with Deionized water– and ethylene glycol–based fluids, respectively. © 2020 Elsevier Ltd

Department Of Physics

Materials Today Chemistry

In situ reduction of graphitic oxide by amorphization of magnesium diboride for the superior thermo-optical property based nanofluid applications

Various blends containing glycerol, castor oil (NCO) and cashew nut shell liquid (CNSL) were made following soft computational techniques and the blend consisting 60% glycerol and 40% NCO was proposed, which exhibited 37% less coefficient of friction (CoF) than NCO and CNSL and 50% less CoF and comparable extreme pressure properties to non-biodegradable commercial mineral oil (CMO). Accelerated wear was indicated by particle quantifier index for CMO, NCO and CNSL samples while normal wear was observed in glycerol and the proposed blend. SEM and 3-D profilometer images exhibited more damaged surfaces in NCO and CNSL than other lubricants. Raman spectra indicated the presence of FeOOH, OH, HOH and fatty acids on the wear tracks of the proposed blend. © The Author(s) 2020.

Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology

Artificial neural network and multi-criterion decision making approach of designing a blend of biodegradable lubricants and investigating its tribological properties

Grain boundary structure-property relationship was studied in a Ni-base 602CA coarse-grained alloy using a novel correlative tracer diffusion-analytical microscopy approach. Co-existence of several short-circuit contributions to tracer diffusion was distinguished at higher temperatures. These contributions were related to different families of high-angle grain boundaries with distinct coverages by precipitates and segregation levels as revealed by HAADF-STEM combined with EDX measurements and a detailed atom probe tomography analysis. Annealing at such conditions resulted in Cr23C6-type carbides co-existing with an α-Cr-Mn-enriched phase in addition to sequential segregation layers of Al, Ni, and Fe around them. Curved and hackly grain boundaries showed a high density of plate-like carbides. In contrast, straight grain boundaries were composed of globular carbides with similar chemical composition variations and additionally with alternating layers of Cr and Ni in-between the carbides, similar to spinodal microstructures. At lower temperatures, hackly interfaces with Cr and Cr-carbide enrichment dominated and the alloy annealed at 403 K contained plate-like Cr23C6-type carbides surrounded by a Ni-rich layer around them. The Ni grain boundary diffusion rates at these relatively low temperatures showed an anomalous character being almost temperature independent. This specific diffusion behaviour corresponds to a metastable grain boundary transition which is explained by a concomitant relaxation of transformation-induced elastic strains occurring on a longer time scale in comparison to those for grain boundary diffusion. Thermodynamic insights into the probable mechanism of decomposition at grain boundaries are provided. The paper provides solid evidences towards the existence of grain boundary phase transitions in the Ni-base multi-component alloy. It underlines the capabilities of the correlated kinetic-structure measurements as a tool to probe such changes. © 2020 Acta Materialia Inc.