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Sintering phenomena and mechanical strength of nickel based materials in direct metal laser sintering process—a molecular dynamics study

Published online by Cambridge University Press:  24 June 2016

Yi Zhang
Affiliation:
Department of Mechanical Engineering, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana, USA
Jing Zhang*
Affiliation:
Department of Mechanical Engineering, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana, USA
*
a) Address all correspondence to this author. e-mail: [email protected]
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Abstract

This paper presents an atomistic scale model on sintering of nickel particles in direct metal laser sintering process. Both sintering phenomena and mechanical strength of sintered particles are simulated using molecular dynamics method. A two-particle atomistic model is developed to investigate the diffusion of atoms during nickel sintering. The diffusion of particle surface is higher than the particle core, with calculated activation energy of nickel particle diffusion 6.10 kJ/mol in the particle core, and 6.24 kJ/mol on the particle surface, which are reasonably in agreement with the experimental data of 7.89 kJ/mol. The sintered model shows a 5-fold twinning structure at 1200 K, and two parallel twin boundaries at 1300 K. The mechanical properties of nickel nanoparticles sintered at various heating rates are investigated using uniaxial tensile test simulations. The results show that higher heating rate during sintering increases the mechanical strength of the sintered material. Deformation mechanism of sintered structures is illustrated from the correlation between stress and dislocation evolution.

Type
Articles
Copyright
Copyright © Materials Research Society 2016 

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