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Abstract: Investigation of the microstructure of a compressed Ti66.1Cu8Ni4.8Sn7.2Nb13.9 nanostructure–dendrite composite reveals that the deformed bcc β-Ti dendrites form a stepped morphology at the interfaces between the individual dendrites and the nanostructured matrix of hcp α-Ti and bct Ti2Cu phases. Furthermore, there is a unique stained contrast during the propagation and the interaction of the shear bands in the dendrites indicating a local structural change near to the apex of the shear bands in the dendrite. In contrast, the shear bands pass through coherent grain boundaries between the hcp α-Ti and the bct Ti2Cu phases of the nanostructured matrix. [Copyright &y& Elsevier]

Abstract: Systematic investigations of the microstructural changes upon compression have been performed in order to elucidate the microscopic deformation mechanisms of the high-strength and ductile Ti66.1Nb13.9Ni4.8Cu8Sn7.2 nanostructure–dendrite composite. After 8% deformation, a rotation of β-Ti dendrites is observed during the interaction of slip and shear bands. This rotation leads to the formation of new slip bands in the dendrites. The β-Ti dendrites locally transform into ω phase during the interaction between the newly and the previously formed slip bands. The rotation of the dendrites causes local volume changes at the interfacial areas between the dendrites and the matrix, consisting of a mixture of hexagonal close-packed α-Ti and body-centered tetragonal Ti2Cu phases. This induces a rotational stress into the nanostructured matrix. After further deformation up to 25%, the shear bands penetrate the dendrite/matrix interfaces, producing extra interfaces. The nanostructured matrix exhibits a sandwiched microstructure in order to accommodate effectively the shear strains. These results suggest that structural coherency of the dendrite/matrix interfaces is important for controlling both the strength and the ductility of the nanostructure–dendrite composite. [Copyright &y& Elsevier]

The present study demonstrate the effect of stacking fault energy (SFE) on the evolution of crystallite size, dislocation density, twin density, stacking faults, and their mutual interactions during cryorolling in pure copper (SFE 78 mJ/m 2 ) and copper–zinc alloys with varying Zn content of 10 wt% (SFE 35 mJ/m 2 ), 20 wt% (SFE 19 mJ/m 2 ), and 30 wt% (SFE 14 mJ/m 2 ). The dislocation density, twin density and extrinsic fault probability increase whereas crystallite size decreases upon cryorolling and with the decrease of SFE. Accumulation of dislocations at the twin boundaries causes dynamic recrystallization, promotes grain refinement by forming subgrains inside the twin lamellae. Detail investigation on the activity of structural defects during cryorolling of Cu/Cu-Zn alloys has been done through resistivity measurements. Nanoindentation studies have performed to understand the deformation kinetics of the cryorolled Cu/Cu-Zn alloys with high concentration of structural defects in term of strain rate sensitivity and activation volume. A micromechanical model has been used to demonstrate the effect of SFE and the role of structural defects during nanostructuring at cryogenic temperature. [ABSTRACT FROM AUTHOR]

Nanotwinned α-brass (Cu–30 wt.% Zn) with varying lamellae thickness in the range of 28–170 nm, has been produced by cryorolling (CR). The effect of CR strain ( ɛ CR = 0.2–0.95) on the evolution of homogeneity and refinement in terms of twin lamellae thickness, twin spacing, and their distribution, have been studied using high-resolution transmission electron microscopy (HRTEM) and microhardness measurements. Analysis of X-ray peak broadening has shown that the crystallite size reduces down to 20 nm at ɛ CR = 0.95, which scales with the subgrain size in preexisting twin lamellae, as revealed under HRTEM. The effect of dislocation density and crystallite size on the strength of nanotwinned brass has been correlated using an analytical model. [ABSTRACT FROM AUTHOR]

Abstract: Nano-sized porous γ-aluminas have been successfully synthesized by control precipitation method using aluminium nitrate as precursor and different precipitating agents. The synthesized materials have been characterized by SEM, FTIR, XRD and N2 adsorption–desorption. Sample prepared by ammonium bicarbonate route possess spherical nano-sized particle with crystallite size in the range 4.7–5.7nm, surface area 190m2/g and pore volume ∼0.467cm3/g. It also exhibits excellent fluoride adsorption capacity. [Copyright &y& Elsevier]

The evolution of microstructure and the mechanical properties of a series of (Ni 0.912 Zr 0.088 ) 100- x Al x (0≤ x ≤4) eutectic composites, constitute of γ-Ni and Ni 5 Zr nanolamellar phases, have been presented. Al dissolves in γ-Ni phase preferentially, decreases its hardness and refines the microstructure. Strain rate jump test was performed in order to investigate the rate sensitivity. It has been found that activation volume increases from 39 b 3 to 46 b 3 upon Al addition. The strain rate sensitivity of the composites has been estimated to be ~0.008. The scanning and transmission electron microscopic studies have confirmed that dislocation meditated flow in nano-lamellar phases dominates the plastic deformation mechanism. Analysis based on Stroh's pile-up model suggests that the required shear stress for slip decreases and that for cleavage crack nucleation increases around a dislocation pile-up at the lamellae interface, upon Al addition. The nano-lamellar Ni 5 Zr strengthen the composite, whereas, dislocation slip endorses the global plasticity of high strength Ni-Zr-(Al) nanoeutectic composites. [ABSTRACT FROM AUTHOR]