mohsenzaeem's blog

In this work, superelastic and shape memory properties of single crystalline and polycrystalline yttria stabilized tetragonal zirconia (YSTZ) nanoparticles are studied by atomistic simulations. N. Zhang and M. Asle Zaeem. Superelasticity and shape memory effect in zirconia nanoparticles. Extreme Mechanics Letters 46 (2021) 101301 (8 pages).

A modified phase-field model for fracture is presented which includes the material strength and cleavage planes to quantitatively predict the crack propagation path and the mechanical response in polycrystalline brittle materials. Computational Materials Science 197 (2021) 110642 (11 pages).

Mechanical performance of silicon nanopillars with homogeneous and gradient nanotwinned structures are investigated through a series of molecular dynamics simulations. The most observed Σ3 twin boundary (TB) with two preferable (lowest surface energy) planes of {111} and {001} are used to generate homogeneous and gradient nanotwinned structures. Simulations of compression and tension of nanotwinned pillars reveal an extra strengthening behavior due to the addition of Σ3 TBs when compared to the single crystalline nanopillar without any TBs.

Dear iMechanica colleagues, I am pleased to share with you our newest paper on qauntitative prediction of rapid solidification. S. Kavousi, B. Novak, D. Moldovan, and M. Asle Zaeem. Quantitative prediction of rapid solidification by integrated atomistic and phase-field modeling.

The effects of applied load on the formation and reorientation of deltahydrides in alpha-zirconium matrix are studied by a multiphase field model.

(open access) C. Cissé and M. Asle Zaeem. An asymmetric elasto-plastic phase-field model for shape memory effect, pseudoelasticity and thermomechanical training in polycrystalline shape memory alloys. Acta Materialia 201 (2020) 580-595.

A phase-field model based on a modified form of the regularized formulation of Griffith’s fracture theory is presented to investigate intergranular and transgranular crack propagations in polycrystalline brittle materials. Grains and grain boundaries are incorporated in the crack initiation and propagation model based on a phase-field model for grain growth, in which the elastic anisotropy varies based on the grain orientation angle, and the grain boundary energy is related to the misorientation angle of the adjacent grains.

Open Access
A. Emdadi, J. Watts, W.G. Fahrenholtz, G.E. Hilmas, and M. Asle Zaeem. Predicting effective fracture toughness of ZrB2 based ultra-high temperature ceramics by phase-field modeling.  Materials & Design 192 (2020) 108713 (11 pages).

Thomas, M.S. Manju, K.M. Ajith, S.U. Lee and M. Asle Zaeem. Strain-induced work function in h-BN and BCN monolayers.  Physica E: Low-dimensional Systems andNanostructures 123 (2020) 114180 (9 pages).  

Abstract

C. Cissé and M. Asle Zaeem. A phase-field model for non-isothermal phase transformation and plasticity in polycrystalline yttria-stabilized tetragonal zirconia.  Acta Materialia 191 (2020) 111-123. 

S. Thomas, A. Kulangara Madam, and M. Asle Zaeem. Stone-Wales defect induced performance improvement of BC3 monolayer for high capacity lithium-ion rechargeable battery anode applications. The Journal of Physical Chemistry C (2020) (10 pages). 

N. Zhang and M. Asle Zaeem. Nanoscale flaw tolerance behaviour of polycrystalline tetragonal zirconia nanopillars. International Journal of Mechanical Sciences 173 (2020) 105405 (7 pages). 

A. Mahata, M. Asle Zaeem. Size effect in molecular dynamics simulation of nucleation process during solidification of pure metals: investigating modified embedded atom method interatomic potentials.

Directional solidification of Al-11 at % Cu is investigated by molecular dynamics (MD) simulations utilizing second nearest neighbor modified embedded atom method (2NN-MEAM) interatomic potential. The condition for directional solidification is produced by imposing dissimilar temperatures at the model boundaries along the [1 0 0] solidification direction to create a temperature gradient. During solidification, the solid-liquid front travels through the Al-Cu liquid along the [1 0 0] direction towards the high temperature end.

Shape memory ceramics, such as yttria-stabilized tetragonal zirconia (YSTZ), offer unique properties including ultra-high operating temperatures and high resistance to oxidation. However, they are susceptible to formation of defects during manufacturing and/or by mechanical deformation. To completely take advantage of their shape memory properties, it is necessary to fully understand the nano-structural evolution of defects under external stimuli. In this study, defect evolution behaviors in YSTZ nanopillars are investigated by atomistic simulations.

We studied the oxidation behavior of face-centered cubic Al0.3CoCrCuFeNi high entropy alloy through first-principles calculations. Three surface orientations were chosen for oxidation, and all the possible combinations of atomic positions at these surfaces were considered. The adsorption energy of oxygen adhesion to the studied surfaces was the lowest for the sites with more neighboring Cr atoms, and the second most favorite site for oxygen adsorption had more neighboring Al atoms.

Formation of solidification defects and their evolution in uniaxial tensile deformation of solidified polycrystalline aluminum (Al) were investigated by molecular dynamics (MD) simulations. First, solidification process was simulated both isothermally and with different quench rates. At the initial stages of nucleation, coherent twin boundaries and/or fivefold twins formed depending on the quench rate or the undercooling temperature.

A PostDoc/Research Assistant Professor Position is available immediately on DFT/Phase Field Modeling at the Colorado School of Mines. The applicants should have a PhD degree in Mechanical Engineering, Materials Science or in a relevant field, with a strong background in DFT calculations and phase-field modeling. The project involves simulating structures/phases, kinetics and nano/microstructural evolution in advanced manufacturing. Please send your CV with 2-3 of your recent and reverent publications to zaeem@mines.edu (Prof. Asle Zaeem).

Shape memory ceramics are a unique family of shape memory materials with a wide variety of applications, such as ultra-high energy dissipation and high-temperature actuation. Along with significant progress in the experimental study of zirconia-based shape memory ceramics in recent years, computational simulations have exhibited powerful capabilities in revealing nano/microstructure-dependent deformation and failure mechanisms in these materials.