E-IJPM: Vol. 44/4 - MPIF

CONSOLIDATION OF ALUMINUM POWDER DURING EXTRUSION
Figure 5. Extrusion pressure vs. ram displacement curves as a function of ram
displacement. Aluminum powder grade AM 625
30
resulting curves are shown in Figures 3–5 for the
three powder grades.
Porosity and Hardness
For porosity and hardness measurements
mounted samples were cut longitudinally (Figure
6) and polished.
Porosity was measured by means of an image
analyzer using LECO software with a Hitachi
camera. Area measurements were an average of
1,640 µm × 1,300 µm per measurement. Porosity
measurements were carried out on the precompacted
billets and the partially extruded billets
(12%, 23%, and 33% ram displacement) for the
Figure 6. Mounted samples for porosity and hardness distribution measurements
three grades of powder. This was done to determine
the level of densification of the billets within
the extrusion container prior to extrusion (12%
and 23% ram displacement) and after extrusion
(33% ram displacement). Porosity measurements
were also carried out on the extrudates (99% ram
displacement) for the three powder grades.
Because of the symmetry of the billets, porosity
measurements were performed on one half of the
longitudinal cross section. In the case of the
extrudate samples, measurements were carried
out on the entire sample. Porosity distributions
for the precompacted powder billets and the partially
extruded billets are shown in Figures 7–9,
(a)
(b)
Figure 7. Porosity profiles of precompacted billet as a function of ram displacement:
(a) 2D and (b) 3D. Aluminum powder grade AM 603
Volume 44, Issue 4, 2008
International Journal of Powder Metallurgy