Thixoforming : Semi-solid Metal Processing

Load (kN)
strain to rupture, leading to a progressive (from a statistical point of view) deagglomeration
of the solid network. As the active solid fraction decreases down to 0.4, we
observe a strong decrease in the strain rate within the two solid phases, indicating
that, at this moment, it is the liquid s turn to carry most of the strain. Since the liquid
viscosity is much lower than the solid viscosity, this leads to a load drop. At this stage,
since the solid bonds are no longer (or very slightly) deforming, the spatial
distribution of the liquid and solid does not change any further. The semi-solid
Equivalent strain rate (s -1 )
4
3,5
3
2,5
2
1,5
1
0,5
80
70
60
50
40
30
20
10
0
0
f s = 0.8
f s = 0.6
f s = 0.7
0
0
10
20
30
Displacement (mm)
Figure 7.7 Simulated load–displacement curves of isothermal
compression tests for different solid fractions.
Active solid fraction Overall strain rate
Strain rate within the
solid bonds
10
Strain rate within
the solid particules
Displacement (mm)
Figure 7.8 Simulated strain rate evolutions within the overall
material, the solid bonds and the solid particles and active solid
fraction as a function of displacement during a compression test.
20
30
7.4 Results and Discussionj233
40
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
40
Active solid fraction