Experimental and 3D MPFEM simulation study on the green density of Ti–6Al–4V powder compact during uniaxial high velocity compaction

Abstract

The preparation of qualified compacts with high green density during powder compaction is crucial to guarantee the final quality of the powder metallurgy products. In this paper, both experiments and 3D multi-particle finite element method (MPFEM) simulations were employed, in order to determine the relation between the final green density and the impact energy per unit mass Em for Ti–6Al–4V powder during uniaxial high velocity compaction. The compact’s springback during unloading was considered in the simulations. The influences of Em and coefficient of friction on the compaction behaviors were also investigated. The experimental relative green density of the cylindrical compact was improved from 0.842 to 0.955 when Em was increased from 73.5 J/g to 171.5 J/g. The critical Em to form a complete compact without obvious cracks was estimated 110 J/g. 3D MPFEM simulations can well predict the dynamic mechanical responses during compaction and depict the surface morphology at particulate scale. The percentage of springback was correlated with the reduction ratio of the elastic strain energy and closely related to the static friction force during unloading. Additionally, either increasing Em or coefficient of friction can reduce the percentage of springback. The influence of coefficient of friction on the maximum density was considerable but seemed weak on the final density. Eventually, the simulated relation between the final relative green density and Em showed remarkable agreement with the experimental results, by means of comprehensive investigations on the effects of both springback and coefficient of friction.