Publications de Alireza Ghafarollahi

Strengthening mechanisms in dilute and random solid solution high-entropy BCC alloys

Tuning the mechanical properties of metals, including strength, through adjusting the type and/or concentration of added solute elements, has been recognized as an effective way to design and produce materials with desired or optimized mechanical propertie ...

EPFL2022

Screw-controlled strength of BCC non-dilute and high-entropy alloys

William Curtin, Alireza Ghafarollahi

The impressive mechanical properties of single phase BCC High Entropy Alloys (HEAs) has renewed interest in understanding the mechanisms controlling strength in BCC alloys. Theory and simulation of strengthening of screw dislocations in HEAs shows that scr ...

PERGAMON-ELSEVIER SCIENCE LTD2022

High energy barriers for edge dislocation motion in body-centered cubic high entropy alloys

William Curtin, Francesco Maresca, Alireza Ghafarollahi, Recep Ekin Kubilay

Recent theory proposes that edge dislocations in random body-centered cubic (BCC) high entropy alloys have high barriers for motion, conveying high strengths up to high temperatures. Here, the energy barriers for edge motion are computed for two model allo ...

NATURE RESEARCH2021

Theory of kink migration in dilute BCC alloys

William Curtin, Alireza Ghafarollahi

Plastic deformation in elemental BCC metals and dilute alloys is controlled by the slower of the kink pair nucleation and kink migration processes along screw dislocations. In alloys nucleation is facilitated and migration inhibited, leading to a concentra ...

2021

Theory of double-kink nucleation in dilute BCC alloys

William Curtin, Alireza Ghafarollahi

Yielding in pure BCC metals and dilute substitutional alloys occurs by double-kink nucleation and propagation along screw dislocations. At low temperatures, the yield stress is controlled by double-kink nucleation. Here, an analytical statistical model is ...

PERGAMON-ELSEVIER SCIENCE LTD2020

Solute/screw dislocation interaction energy parameter for strengthening in bcc dilute to high entropy alloys

William Curtin, Francesco Maresca, Alireza Ghafarollahi

Strengthening, i.e. increased stress required to move a dislocation, in dilute or complex alloys arises from the totality of the interaction energies between the solutes and an individual dislocation. Prevailing theories for strengthening in bcc alloys con ...

IOP PUBLISHING LTD2019

Scattering of transverse surface waves by a piezoelectric fiber in a piezoelectric half-space with exponentially varying electromechanical properties

Alireza Ghafarollahi

In the present work, an analytical solution is presented for the scattering of transverse surface waves by a homogeneous piezoelectric fiber contained in a functionally graded piezoelectric half-space with exponential variation. The boundary value problem ...

2019

An embedded couple stress micro-/nano-obstacle with micro-inertia incident upon by SH-waves

Alireza Ghafarollahi

2018

Scattering of SH-waves by an elliptic cavity/crack beneath the interface between functionally graded and homogeneous half-spaces via multipole expansion method

Alireza Ghafarollahi

In this study, based on multipole expansion method an analytical treatment is presented for the anti-plane scattering of SH-waves by an arbitrarily oriented elliptic cavity/crack which is embedded near the interface between exponentially graded and homogen ...

2018