Effect of Grain Size on Superplastic Deformation of Metallic Materials

The superplastic deformation exhibited by metals with different grain sizes and their corresponding deformation mechanism influences the industrial metal-forming processes. The coarse-grained materials, which contain grain size greater than 20 μm, exhibited superplastic deformation at high homologous temperature and low strain rate of the order of 10−4 s−1. Fine grain materials (1–20 μm) are generally considered as favorable for superplastic deformation. They possess high-strain-rate sensitivity “m” value, approximately, equal to 0.5 at the temperature of 0.5 times the melting point and at a strain rate of 10−3 to 10−4 s−1. Ultrafine grains (100 nm to less than 1 μm) exhibit superplasticity at high strain rate as well as at low temperature when compared to fine grain materials. It is attributed to the fact that both temperature and strain rates are inversely proportional to the grain size in Arrhenius-type superplastic constitute equation. The superplastic phenomenon with nano-sized grains (10 nm to less than 100 nm) is quite different from their higher-scale counterparts. It exhibits high ductility with high strength. Materials with mixed grain size distribution (bimodal or layered) are found to exhibit superior superplasticity when compared to the homogeneous grain-sized material. The deformation mechanisms governing these superplastic deformations with different scale grain size microstructures are discussed in this chapter

Effect of Post-Annealing Treatment on Mechanical Properties of ZnO Thin Films

The present work was focused to study nanomechanical properties of ZnO thin films deposited on different substrates (Corning Glass and Fused Quartz) using DC-sputtering. The crystallinity and microstructure are correlated with process conditions and post annealing treatment in NH3 environment, which in turn affects the mechanical performance. The structural growth accompanied a change in crystalline nature and microstructure as the substrate is altered from corning glass substrate to fused quartz at similar synthesis conditions. The post deposition annealed ZnO thin films demonstrated agglomerated particles with no clear grain boundaries having nano-cracks present in the morphology, which is attributed as NH3 effect on microstructure. The mechanical properties such as hardness (6.89-7.76 GPa), Young’s modulus (94.9-124.6 GPa), and coefficient of friction ̴ (1.0-3.0) of ZnO thin films were measured using three sided pyramidal Berkovich nanoindentation. Load-unload segment of indentation curve of thin films which is measured at continuous loading revealed no event of discontinuity (≥ 2 nm) during loading/unloading, indicating no fracture or delamination during indentation. The critical load of ZnO thin films failure was analysed using scratch testing ramp loading and the value of critical load was found around ̴535.6 µN to ̴668.4 µN

Experimental investigation and Monte Carlo Simulation of glass transition in polymer nanocomposites

Journal of Metastable and Nanocrystalline Materials23339-34

Thermodynamics of surface compositional segregation in Ni-Co nanoparticles

10.1016/S0921-5107(02)00221-0Materials Science and Engineering B: Solid-State Materials for Advanced Technology952116-123MSBT

Monte Carlo simulation of surface segregation in nanoparticles

Journal of Metastable and Nanocrystalline Materials23203-20

Thermodynamic modeling of surface segregation in Au-Ti nanoparticles

Journal of Metastable and Nanocrystalline Materials23259-26

XFEM Simulation of Tensile and Fracture Behavior of Ultrafine-Grained Al 6061 Alloy

In the present work, the tensile and fracture behavior of ultra-fine grained (UFG) Al 6061 alloy was simulated using extended finite element method (XFEM). UFG Al 6061 alloy processed by cryorolling (CR) and accumulative roll bonding (ARB) was investigated in this work. Numerical simulations of two-dimensional and three-dimensional models were performed in “Abaqus 6.14” software using an elastic-plastic approach, and the results obtained were validated with the experimental results. The specimens corresponding to the three-point bend test, compact tension test with center crack, and double edge cracks were analyzed using XFEM (eXtended Finite Element Method) approach. In XFEM, the partition of unity (PU) was used to model a crack in the standard finite element mesh. The tensile and fracture properties obtained from the simulation were in tandem with the experimental data. UFG Al alloy showed higher tensile strength and fracture toughness compared to their bulk solution treated counterparts. Fracture toughness was measured in terms of stress intensity factor and J integral. In CR Al alloys, with increasing thickness reduction, an increase in stress intensity factor and a decrease in the J integral was observed. This behavior is attributed to the increase in strength and decrease in ductility of CR samples with increasing thickness reduction. In ARB Al alloys, the strength and ductility have increased with an increase in number of cycles. It also revealed an increase in both the stress intensity factor and J integral in ARB processed Al alloys with increase in number of cycles, as evident from XFEM simulation results

Activities of Al in the Al-Ga-In-Sb system in the temperature range of 1073-1273 K

The multicomponent alloy systems containing group III and V elements are particularly important for their electrical and optoelectronic applications. An accurate knowledge of their thermodynamic properties provides the essential tool in the determination of the phase equilibria which will be useful in processing the semiconducting materials. It may be mentioned that Zbitnew et al. [1] studied the quaternary system using x-ray Debye Scherrer powder photographic technique and x-ray fluorescence for the lattice parameter measurements and the chemical analysis respectively. They have shown that there is complete miscibility between Al-Sb, Ga-Sb, and InSb compounds which results in the formation of isomorphous pseudoternary solid solutions. Thermodynamic modelling of the quaternary system has been carried out by Sharma et al. [2] using a quasi sub-sub regular solution model based on the available information of the constituent binary and ternary properties. In the absence of any activity data, the present investigation measures the activities of Al in the liquid Al-Ga-In-Sb system using a concentration cell of the type

Thermodynamics and phase equilibria in the Al-In-Sb system

As part of a program for determination of the thermodynamic properties of the group III and V alloys and assessment of the phase equilibria, the activities of aluminum in the liquid Al-In-Sb system have been measured using a concentration cell of the type Al (1)/NaCl+KCl+3 mole pct $AlCl_3Al-In-Sb$ (1) The measurements are carried out along the constant compositional paths of $x_{Sb}=0.1$ and 0.2 over a temperature range of 1073 to 1273 K. The measured activity data in the system exhibit positive deviations from ideality. The deviations increase progressively with the In content of the alloys for a constant compositional path of Sb. The magnitude of the aAl as a function of In is found to decrease significantly with the increase in the Sb content of the alloys. The behavior is consistent with the existence of the liquid-liquid immiscibility in the syste