Effect of plain strain deformation on grain strengthening mechanism of Fe-Al2O3 metal matrix nanocomposites

The present paper reports the effect of plain strain deformation on grain strengthening mechanism of iron (Fe) - alumina (Al2O3) Metal Matrix Nanocomposites (MMNCs) fabricated through powder metallurgical (P/M) processing. Specimens for the present study were weighed in required amount, ball milled, compacted at a load of 5, 6 and 7 tons followed by sintering in an atmospheric controlled furnace at 1100 °C for 1 hour. Plain strain deformation of samples was carried out at a load of 5 tons under different interfacial condition i.e. dry, solid lubricant and liquid lubricant. XRD studies reveal the formation of iron, alumina and nano iron-aluminate (FeAl2O4) phases respectively. Maximum average sintered density investigated for the specimen is found to be 4.6179 gm/cc compacted under 7 tons of load and minimum sintered density is found to be 4.4572 gm/cc for specimen compacted under 5 tons of load. Overall, fabricated Fe-Al2O3 metal matrix nanocomposites with powder metallurgy route when characterized for plain strain deformation shows strengthening between grain and grain boundary which can be a good candidate material for application in railways especially while designing railway structures and tracks.

Signatures of slip in dewetting polymer films

Thin polymer films on hydrophobic substrates are susceptible to rupture and hole formation. This, in turn, initiates a complex dewetting process, which ultimately leads to characteristic droplet patterns. Experimental and theoretical studies suggest that the type of droplet pattern depends on the specific interfacial condition between the polymer and the substrate. Predicting the morphological evolution over long timescales and on the different length scales involved is a major computational challenge. In this study, a highly adaptive numerical scheme is presented, which allows for following the dewetting process deep into the nonlinear regime of the model equations and captures the complex dynamics, including the shedding of droplets. In addition, our numerical results predict the previously unknown shedding of satellite droplets during the destabilization of liquid ridges that form during the late stages of the dewetting process. While the formation of satellite droplets is well known in the context of elongating fluid filaments and jets, we show here that, for dewetting liquid ridges, this property can be dramatically altered by the interfacial condition between polymer and substrate, namely slip. This work shows how dissipative processes can be used to systematically tune the formation of patterns.

Unexpected thermal annealing effects on the viscosity of polymer nanocomposites

Viscosity of polymer nanocomposites evolves unexpectedly slowly. The resulting variations in the viscosity ratio depend on the particle–polymer interfacial condition.

Homogenization of composite electrets

We study the two-scale homogenization of the diffraction interfacial condition for the diffusion equation relevant to a composite medium which has a periodic structure. The results are applied to the electric field potential within a dielectric composite body when there is a difference in dielectric permittivity between the composite components in the presence of interfacial static charges. The principal result is that the interfacial charge distribution is equivalent to an apparent bulk charge which can be calculated starting from the composite geometry. We perform the corrector analysis and establish that the corrector terms strongly depend on the interfacial charge.