Thermomechanical deformation of powder-based porous aluminium: Part I. Evolution of pore structure

Abstract

Thermomechanical deformation of powder-based porous aluminium from the partially to the fully consolidated states requires specific attention to accurate description of the evolution of pore structure and the stress—strain behavior at elevated temperature. Part I of this study aims at developing the understanding of pore morphology changes with deformation. The effects of initial porosity and the evolution of global porosity and pore morphology with applied thermomechanical deformation are examined. Only densification is tested experimentally. Rapidly solidified aluminium powders are compacted into preforms with relative porosities varying from 0 to 20%. The preforms are then subjected to a uniaxial stress compression test at elevated temperature with a controlled true strain rate varying from 0.01 to 10 per second. At various stages of deformation, the pore structures are evaluated at room temperature. The changes of mean pore size, pore shape, pore size distribution and orientation of pores with respect to principal strain are quantified using optical image analysis and SEM. The mechanism of compaction of porous aluminium is also discussed. The experimental results will be used in Part II of this study, in which a constitutive model is evaluated and the evolutions of porosity and pore structure simulated.