Search

Discrete dislocation dynamics (DDD) codes enable researchers and scientists to explore the mechanical behavior of a material as impacted by its composition and microstructure. Understanding the strengthening mechanisms is very important for the development of new materials with improved and desired mechanical properties. One of the material strengthening/hardening mechanisms is solution hardening, and this method can be fundamentally understood from particle misfit models and the theory/implementation of dislocation dynamics. The overlapping of the eigenstrain fields of the misfit particles or solutes and the dislocations impedes the motion of dislocations and results in material hardening. This article incorporates the misfit particle model in a 3D DDD code in an attempt to capture this phenomenon and find the strength of solid solutions (for a binary Cu–Ni system) from the simulated stress–strain diagram. This study/research finds a good agreement between the simulation results and experimental data. The authors also correlate the strength differentials as a function of solute concentrations and compare them with relations in the literature. [ABSTRACT FROM AUTHOR]

The influence of carbon nanotube dispersion techniques (surfactant-assisted dispersion, ultrasonication and magnetic stirring) and surface functionalization of carbon nanotubes on mechanical properties of nanocomposites fabricated via powder metallurgy techniques is characterized. Functionalized multiwalled carbon nanotubes dispersed using a combination of techniques results in Al/functionalized multiwalled carbon nanotube composites with excellent microstructure and enhanced mechanical properties. Nonfunctionalized carbon nanotubes dispersed using zwitterionic surfactants show good dispersion patterns on Al powder surfaces and results in composites with good strength and relative densities are also obtained. Carbon nanotubes dispersed solely via shear mixing techniques resulted in highly embrittled composites with poor microstructure. Also discussed in this study is the usefulness of scanning electron microscopy in conjunction with image analysis techniques in characterizing porosity in Al/carbon nanotube composites. [ABSTRACT FROM AUTHOR]

Abstract: In the current investigation the microstructural and mechanical properties of zinc compacted pallets were investigated. The pallets were compacted to different normalized densities (81–93%) under different pressures of 150, 200 and 450MPa, respectively. The effect of sintering the samples under inert environment at 378°C was also studied. Instrumented nanoindentation tests were utilized to deduce the mechanical properties of the compacted pallets. Nanoscratch tests were employed to qualitatively measure the sample resistance to plastic deformation. It was observed that there are two mechanisms driving the improvement of the mechanical properties. One mechanism is due to recrystallization driven by the increasing dislocation density and the other mechanism is due to consolidation of the particles into a continuous network due to diffusion and grain growth under high temperature sintering. The results also reveal that the mechanical properties and densities of the tablets are not linearly proportional to the compaction pressure. Higher compaction pressures resulted in denser tablets with higher elastic modulus and hardness. Upon sintering the compacts soften but also form a solid network due to the neighboring particles diffusion. Therefore, the hardness value drops but the reduced modulus increases. Furthermore, the nanoscratch tests revealed that higher compaction pressure produce not only a more compacted tablet, but also a more homogeneous one. [Copyright &y& Elsevier]