arXiv subjects

Iyad Alabd Alhafez

Publications and source records attributed to Iyad Alabd Alhafez.

3 recordsLinked to original sources

arXiv2026

Thermal History-Dependent Coalescence Mechanisms and Sintering Dynamics in Al-6.8%Cu Nanopowders

Aluminum-Copper (Al-Cu) alloys are essential materials for weight reduction critical structures in the aerospace and automotive industries, yet achieving their maximum ultrahigh-strength potential remains limited by nanoscale defect control during powder metallurgy processing. We employ large-scale molecular dynamics simulations on Al-6.8%Cu nanoparticles to explore atomic-scale mechanisms governing the full thermal sintering cycle. We demonstrate that while the sintering temperature primarily initiates neck formation, the subsequent cooling rate is the dominant kinetic parameter dictating the final microstructure. Fast cooling rates trap a significantly higher density of stacking faults and can unexpectedly lead to the formation of an amorphous phase at the interparticle interfaces, a feature critically dependent on the rate of thermal dissipation. We confirm a clear shift in the coalescence mechanism from plastic deformation (dislocation slip) at low temperatures (300 K and 450 K) to mass transport via atomic diffusion at high temperatures (600 K). These findings provide essential, atomic-scale guidelines for controlling thermal processing, particularly cooling rates, to design defect-stabilized, high-performance Al-Cu components.

cond-mat.mtrl-sci↗

arXiv2019

Nanoscratching of metallic glasses -- An atomistic study

Tribological properties of materials play an important role in engineering applications. Up to now, a number of experimental studies have identified correlations between tribological parameters and the mechanical response. Using molecular dynamics simulations, we study abrasive wear behavior via nanoscratching of a Cu$_{64.5}$Zr$_{35.5}$ metallic glass. The evolution of the normal and transverse forces and hardness values follows the behavior well known for crystalline substrates. In particular, the generation of the frontal pileup weakens the response of the material to the scratching tip and leads to a decrease of the transverse hardness as compared to the normal hardness. However, metallic glasses soften with increasing temperature, particularly above the glass transition temperature thus showing a higher tendency to structurally relax an applied stress. This plastic response is analyzed focusing on local regions of atoms which underwent strong von-Mises strains, since these are the basis of shear-transformation zones and shear bands. The volume occupied by these atoms increases with temperature, but large increases are only observed above the glass transition temperature. We quantify the generation of plasticity by the concept of plastic efficiency, which relates the generation of plastic volume inside the sample with the formation of external damage, viz. the scratch groove. In comparison to nanoindentation, the generation rate of the plastic volume during nanoscratching is significantly temperature dependent making the glass inside more damage-tolerant at lower temperature but more damage-susceptible at elevated temperatures.

physics.comp-ph↗

arXiv2017

Nanoscratching of iron: a novel approach to characterize dislocation microstructures

A new approach for characterizing the dislocation microstructure obtained from atomistic simulations is introduced, which relies on converting properties of discrete lines to continuous data. This data is represented by a number of density and density-like field variables containing detailed information about properties of the dislocation microstructure. Applying this methodology to atomistic simulations of nanoscratching in iron reveals a pronounced "length scale effect": With increasing scratching length the number of dislocations increases but the density of geometrically necessary dislocations remains constant resulting in decreasing shear stress. During scratching dislocations are mostly generated at the scratch front. The nucleation rate versus scratching length has an approximately antisymmetric shape with respect to the scratch front leading to an almost constant curvature.

cond-mat.mtrl-sci↗