Materials Behavior: Far from Equilibrium
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- Ranganathan, S. Metall and Mat Trans A (2008) 39: 1479. doi:10.1007/s11661-008-9532-3
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Metastable materials are ubiquitous. Cementite is the classical example, occurring in steels and cast irons in use from antiquity. In recent times, more spectacular examples have been discovered by sudden changes in composition; temperature; and pressure brought about by the deployment of novel processing routes such as rapid solidification, mechanical milling, and electron, ion, and laser irradiation. The materials thus produced have compositional, topological, and microstructural metastability with an extended range of properties and modified behavior. Over the past five decades, this area of research has attracted intense attention on both experimental and theoretical domains. Bhabha Atomic Research Centre (Mumbai, India) chose “Materials Behavior: Far from Equilibrium” as the theme of the meeting to celebrate its Golden Jubilee. The conference attracted a large number of participants from India and overseas. This issue of Metallurgical and Materials Transactions puts together 20 selected papers out of 48 invited talks.
The topics covered are solidification, metastable microstructures, irradiation-induced phase transformations, deformation, special materials, modeling and simulation, and nanomaterials and nanostructures. In the following, papers are highlighted by the paradigm of materials science processing, structure, properties, and performance with modeling cutting across this spectrum.
Siegfried Hecker’s paper, “Plutonium—an Element Never at Equilibrium” discusses this maverick metal, which is far from equilibrium. Keshaw Joshi and co-workers use both experiment and theory on d and f electron systems under pressure. Adam Pitchak et al. explore the effect of friction stir processing of investment-cast Ti-6Al-4V alloys. Michael Loretto and co-workers examine the factors influencing the return to equilibrium of quenched beta Ti alloys and massively transformed TiAl-based alloys. Raghavendra Tiwari and co-workers study niobium alloys, which are emerging as candidate materials for high-temperature applications, while Vikram Jayaram et al. consider titanium and zirconium boride ceramics. Rajarshi and co-workers investigate the phase stability in nanocomposite copper-niobium thin films and the effect of immiscibilty.
Several papers are concerned with the new capabilities in materials characterization by very sophisticated techniques. Parthasarathi Barat et al. use X-ray diffraction lines to map irradiated microstructures. High-resolution microscopy is employed by Satoshi Hata and his colleagues to follow long-period ordering in Al-rich TiAl alloys. Muraleedharan Kuttanellore et al. use three-dimensional atom probe in an effective fashion to follow tempering in an ultra-high-strength high-toughness steel.
Several papers address bulk metallic glasses produced by slow solidification. Rajarshi and co-workers study incipient plasticity and shear band formation. Upadrasta Ramamurty and his students report on the influence of cooling rate and enthalpy relaxation and fragility of a Pd-based bulk metallic glass. The effect of equichannel angular pressing of aluminum on its microstructure and properties is reported by G. Sastry and co-workers. Bathuls Viswanath et al. report on the synthesis, crystallization, and magnetic behavior of Fe-based metallic glasses. Indranil Manna and co-workers use an analytical model for deriving the effect of particle size on the thermal conductivity of nanofluid.
Modeling and simulation studies are equally prominent. Ulhas Kulkarni uses Monte Carlo simulation of ordering in Ni-Mo alloys. Yunzhi Wang et al. adopt phase-field modeling and analyze the effect of coupling among different extended defects. Kamanio Chattopadhyay et al. use the same route for simulation of events at the fusion interfaces during dissimilar welding. B.S. Murty and co-workers resort to thermodynamic and topological modeling for Cu-Zr-Ti-Ni bulk metallic glasses for determining the suitability of mechanical alloying. Ashok Arya et al. use the first-principles methodology to study the ordering behavior in Ni-Mo alloy as influenced by ternary additions.
With the theme as “far from equilibrium,” this collection of papers provides new insights at the cutting edge of research in a wide variety of materials. The contributions of Indian institutions make it evident that significant advances have occurred. It is pleasing to note that many contributions are by investigators drawn from different nations. This issue will attract and inspire many young investigators.