Hot workability and densification behavior of sintered powder metallurgy Al-B4C preforms during upsetting

The workability and the densification behavior of a porous Al-B4C preforms have been carried out in the present investigation. Hot upsetting tests have been carried out on Al-B4C powder metallurgy (P/M) preforms having an initial preform density of 0.9 and having different B4C compositions of 2%, 4% and 6%. The samples were compressed between two flat dies in a hydraulic press of 50 ton capacity under varying deformation temperatures such as 200 °C, 300 °C, 400 °C and 500 °C under the tri-axial stress state condition. The workability and densification behavior of Al-B4C preforms were analyzed till the initiation of cracks on the outer surface of the preform. The experimental results were analyzed for the various deformation parameters such as axial strain, relative density, formability stress index and different stress ratio parameter under the tri-axial stress state condition. The formability and densification behavior were discussed with the axial strain (εz) during the hot upsetting process. The relationships between the various stress ratio parameters (σq/σeff, σm/σeff) and formability stress index (βσ) as a function of the relative density under the tri-axial stress state condition were established.