Abstract
In this paper, the discrete element method framework is employed to determine and analyze the stresses induced during and after the powder metallurgy process of particle-reinforced composite. Applied mechanical loading and the differences in the thermal expansion coefficients of metal/intermetallic matrix and ceramic reinforcing particles during cooling produce the complex state of stresses in and between the particles, leading to the occurrence of material defects, such as cracks, and in consequence the composite degradation. Therefore, the viscoelastic model of pressure-assisted sintering of a two-phase powder mixture is applied in order to study the stress field of particle assembly of intermetallic-ceramic composite NiAl/AlO. The stress evaluation is performed at two levels: macroscopic and microscopic. Macroscopic averaged stress is determined using the homogenization method using the representative volume element. Microscopic stresses are calculated both in the body of particles and in the contact interface (necks) between particles. Obtained results are in line with the cooling mechanism of the two-phase materials.
Highlights
Composite materials are an important class of advanced materials made from two or more components
The discrete element model considers the microstructure of the particle-reinforced composite and the phenomena associated with sintering, such as the influence of material densification on residual and thermal stresses during and after the powder metallurgy process
C =1 in which summation is over all Nc contacts in the representative volume element; Fc is the total contact force for each contact; VRVE is the volume of representative volume elements (RVE); and Lc is the so-called branch vector connecting the centroids of two particles, i and j, defined as follows, (i)
Summary
Composite materials are an important class of advanced materials made from two or more components. There are more sophisticated analytical methods such as the self-consistent method established by Eshelby [15] or Mori–Tanaka’s average stress theory [16] These two classical methods enriched with interface debonding mechanisms have been used as theoretical bases of a mesoscopic constitutive model of particle-reinforced titanium matrix composites at high temperatures [17]. The main objective of the present paper consists in numerical modeling of the stress response of a mixture of intermetallic and ceramic powder subjected to the uniaxial hot pressing process by taking into account phenomena occurring at microscopic and macroscopic scales. The discrete element model considers the microstructure of the particle-reinforced composite and the phenomena associated with sintering, such as the influence of material densification on residual and thermal stresses during and after the powder metallurgy process
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