Driving Force of Pressure-Assisted Sintering

The driving force of densification under an external pressure is determined by the pressure itself and also the contact area relative to the cross-sectional area of the particles. At the initial stage of HP of a compact with a simple cubic packing of spherical particles, the effective compressive pressure P at the contact area is expressed as  

A similar consideration of geometry can be used to estimate the effective pressure under HIP. Provided that a force equilibrium is maintained at the surface of particles, the effective pressure P at the initial stage can be expressed as  

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