Positions available in my lab beginning July 2009:

Following are some prospective research topics for the incoming PhD students.

Some of these research areas can become possible thesis topics for incoming ME students as well. It has been our experience that often  ME students get bitten by the research bug, sometimes as early as in their first semester at IISc. So, if you are an ME student considering converting to PhD and working on one of the following topics, please contact me.

I am also looking for a motivated project assistant with a background in mechanical properties and microstructure.

For details, feel free to contact me via email (karthik_at_materials.iisc.ernet.in).

Prospective research areas:

1. A first principles study of alloying additions in magnesium. Two technological issues plague the usage of Mg alloys for structural applications despite their light weight. These problems are related to limited room temperature ductility and poor galvanic corrosion resistance. We aim to address some of these issues computationally. First principles (ab initio) based electronic structure calculations employing the Density Functional Theory (DFT) are an extremely robust and successful approach for describing the ground state properties of atoms, molecules and condensed phases including metals, intermetallics, semiconductors, and insulators. This is because crystal structure and properties of materials are almost entirely determined by the details of inter-atomic bonding and electronic structure. First principles techniques are thus capable of providing significant insights, complementing experiments and thus assisting in alloy design of Mg alloys. To understand the role of alloying on strength and ductility, we will conduct a systematic first principles study of the effect of several different alloying additions on mechanical properties of Mg alloys (starting with pure Mg and AZ31 as baseline alloys). While strength and ductility cannot be simulated directly, clues about these properties can be ascertained indirectly. One could study the effect of solutes on lattice parameters, c/a ratios, elastic constants, stacking fault energies on different planes, extent of bond directionality, cohesive energies, lattice strains, segregation, etc; these may be used as inputs in models for predicting strength and ductility. These parameters will also help in understanding the behavior of these alloys during processing and plastic deformation. To address the poor corrosion resistance, the effect of deleterious additions like Fe, Ni, Co and Cu on electronic structure and the potential positive effects of Al, Mn and Zr can will be studied. These computational studies will be complemented with critical validatory experiments.

2. A project involving atomistic simulations of sliding interactions between ductile metals. The changes occurring at the sliding interface due to interactions between ductile metals is characterized by numerous phenomena. These include plastic deformation, nanocrystallization and amorphization, frictional heating, mechanical mixing, wear and material transfer, among others. To gain insights into these very complex and dynamic phenomena, experimental techniques are often inadequate. Hence atomistic simulations. The idea is to explore microstructural evolution during sliding and how its related to friction. There is scope for expanding this project also to a full PhD. In such a case, it will involve both tribological experiments and characterization alongside computation

3. A study of the effect of Zr and Sc additions on the mechanical properties of Al-Mg alloys. The aim of this work will be to understand the nature of the Al₃(Sc_xZr_1-x) precipitate and how precipitates affect strain ageing behavior and texture evolution. Of particular interest is to find out how Zr affects the structural stability of the Al₃Sc precipitate. In light of this, we will do HRTEM studies of precipitate morphology and interactions with dislocations. We will also employ with first principles calculations of parameters relevant to mechanical properties of the precipitate. In particular, we will be studying the effect of Zr additions on structural stability of the precipitate, the misfit strains and energy associated with the matrix-precipitate interface and the APB energy.

4. High strain rate behavior of Metal-Intermetallic Laminates (MILs). MILs consist of alternating ductile metallic and brittle intermetallic layers. The specific mechanical properties of the MILs make them attractive materials for ballistic applications such as in armors which require a combination of high strength, hardness and light weight. Deformation of the ductile phase allows for energy dissipation and this makes MILs suitable for impact loading. In this study thin alternating foils of two reactive metals will be subjected to diffusion bonding during which interdiffusion and subsequent reaction between the two metals (eg., Al and Cu, or Al and Ti) leads to the formation of a hard intermetallic phase at the interface.  The high strain rate deformation of these materials will be studied with a special emphasis on understanding the effect of phase fraction and thickness of individual layers. Microstructural characterization of the interface and its interactions with dislocation and cracks will be areas of focus.

5. Interaction between dislocations and precipitates determines strength in many engineering alloys including nickel based superalloys. Such interactions between individual dislocations and precipitates is well-established for simple geometries and analytical models exist. However, in reality, an ensemble of dislocations interacts with an ensemble of precipitates. The type and density of dislocations as well as the size, volume fractions and spatial distribution, and nature of the precipitates, all play important roles. Consequently several competing mechanisms by which dislocations escape precipitates, may coexist. Discrete dislocation dynamics (DD) is a power  computational technique that allows one to deal with such complex systems. In this work, we will be using DD for studying such interactions in nickel based superalloys.

Summer Internships: These internships/projects are open for B.Tech and dual degree students broadly in the area of Materials Science and Engineering. You are encouraged to apply to the department via the following official channels programs: JNCASR  Summer Research Fellowships Program, IISc Young Engineering Fellowships, The Indian Academy of Sciences Fellowship or Kishore Vaigyanik Protsahan Yojana. Interns cannot be entertained outside these programs owing to lack of adequate housing for interns and and other campus policies.