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Particle size has a significant effect on mechanical properties of particle reinforced metal matrix composites (PRMMCs). Here, the effect of particle size on mechanical properties of SiCp/Fe composite has been studied using a finite element (FE) model incorporated with the Taylor-based nonlocal theory (TNT) of plasticity, where the tested particle size is 5, 10, 16, 21, 28 and 40μm, respectively. The results indicate that the TNT-FE model overcomes the shortage of the traditional FE model, which cannot deal with the intrinsic size effect. With the particles of 20 vol.%, the simulated flow stress of the iron matrix composite reinforced by 16μm SiC particles is the highest and then follows the order of 28 > 5 > 10 > 21 > 40μm particle reinforced ones, close to the tendency of experimental results. A large area of compressive stress zone is observed in the matrix near the particles in the composites reinforced by 16 and 28μm particles, which implies that the matrix can be well protected during loading, so that the load-bearing capability is better. The purpose is to optimize mechanical property of SiCp/Fe composite by adjusting particle size and eventually to design PRMMCs from microstructural control.

Onset plasticity of metallic nano-lines or nano-beams is of considerable scientific and technological interest in micro-/nano- mechanics and interconnects of patterned lines in electronic devices, where capability of resistance to deformation is important. In this study, a multiscale quasicontinuum (QC) method was used to explore such an issue in a nano-scale copper (Cu) line protruding from a relatively large single crystal Cu substrate during compression. The results show that the yield stress of a rectangular beam on the substrate can be greatly reduced compared with that of a flat surface of the same area. For the rectangular line, the aspect ratio (width/height) affects dislocation morphology at the onset plasticity without much change of yield stress. However, for the trapezoidal line, the yield stress decreases with the base angle (α), especially when the α is over 54.7°. As the sidewall orientation changes from 〈100〉 at α = 0°, then to 〈111〉 at α = 54.7° and finally to 〈110〉 at α = 90°, a higher surface energy could enable easier dislocation formation and lower yield stress. Meanwhile, it is found that the interaction between the line and the support substrate also shows a great effect on yield stress. Moreover, although it is possible to open two extra dislocation slip planes inside from the two bottom corners of the Cu line with the α over 54.7°, dislocation nucleation derived from them is only observed at α = 90°.