Modelling of compaction of titanium composite powders
The quality of finished products is determined at the stage of compaction. High-pressure cold compaction sometimes fails to provide the coalescence of VT-22 high-strength titanium alloy powder particles. Particle coalescence is governed by mechanical characteristics, the spherical particle shape and hard oxide on the particles of the VT-22 powder. This results in the low strength workpieces. To ensure the strength of a compact, powder additives with more plastic properties are used. Simulation is applied to find an optimum additional powder and its volume. The process of compaction is simulated with the use of a representative volume element for a composite made of the VT-22 and PTM-1 powders. The forming and coalescence of particles are represented in uniform triaxial and uniaxial compression. It is shown that the increase in the percentage of VT-22 to more than 50 % in the mixture prevents the uniform spreading of the more ductile component PTM-1. The parameters of the modified Drucker-Prager Cap model are identified for 50/50 and 75/25 VT-22 and PTM-1 powder composites. Compaction in a closed container is simulated. Problems are solved with the application of program packages developed for Abaqus. Experiments on compacting and breaking workpieces made of the pure powders and their two mixtures are made to validate the adequacy of the solution results.