29-03-2012, 12:01 PM
Semi-Solid Processing
[attachment=19163]
Introduction
• Semi-solid processing originated from work by
researchers at MIT in 1971 experimenting on
the rheological behaviour of Sn-15Pb alloy
• The semisolid slurry with a spheroidal
microstructure of 0.4-0.6 weight fraction solid
suspended in liquid had a very low value of
flow resistance and that it would be possible to
use this in developing new forming processes.
SSM=Near-net shaping process
• Near net shaping process is a process that fabricate
products close to the final shape resulting in reduction
of subsequent machining process.
Near net shaping process such as
– Fine casting
– Spray forming
– Injection molding
– Superplastic forming (Sheet metals)
– Semisolid forming ect.
Why semi-solid?
• SSM process combines advantages of casting
(Liquid) and forming (solid) processes
• The microstructure of the semi-solid alloy is
non-dendritic consisting of spheroidal solid
phase suspended in the liquid phase before and
during forming
SIMA
• In the SIMA process, the billet is hot worked above
the recrystallisation temperature (for a given
percentage transformation e.g. 50 percent), and then
lightly or moderately cold worked to induce grain
boundary migration. Subsequent partial melting at
high angle boundaries causes fragmentation and
transformation into the spheroidal structure.
Liquid state method (Rheo-route)
• The MHD (MagnetoHydroDynamically
stirred)
(MHD technology is based on a fundamental law of
electromagnetism: When a magnetic field and an
electric current intersect in a liquid, their repulsive
intersection propels the liquid in a direction
perpendicular to both the field and the current )
Advantages
In comparison to solid-state operations (forging,
rolling, extrusion etc.),
1. semisolid slurries fill the die more evenly
under pressure
2. Complicated shapes can be made more easily
using lower loads
3. The operation requires lower energy,
resulting in lower overall production costs
Disadvantages
1. Relatively higher feedstock material cost
2. Precise control of operating condition is
required.
3. Liquid segregation may occur as a result of
non-uniform heating
[attachment=19163]
Introduction
• Semi-solid processing originated from work by
researchers at MIT in 1971 experimenting on
the rheological behaviour of Sn-15Pb alloy
• The semisolid slurry with a spheroidal
microstructure of 0.4-0.6 weight fraction solid
suspended in liquid had a very low value of
flow resistance and that it would be possible to
use this in developing new forming processes.
SSM=Near-net shaping process
• Near net shaping process is a process that fabricate
products close to the final shape resulting in reduction
of subsequent machining process.
Near net shaping process such as
– Fine casting
– Spray forming
– Injection molding
– Superplastic forming (Sheet metals)
– Semisolid forming ect.
Why semi-solid?
• SSM process combines advantages of casting
(Liquid) and forming (solid) processes
• The microstructure of the semi-solid alloy is
non-dendritic consisting of spheroidal solid
phase suspended in the liquid phase before and
during forming
SIMA
• In the SIMA process, the billet is hot worked above
the recrystallisation temperature (for a given
percentage transformation e.g. 50 percent), and then
lightly or moderately cold worked to induce grain
boundary migration. Subsequent partial melting at
high angle boundaries causes fragmentation and
transformation into the spheroidal structure.
Liquid state method (Rheo-route)
• The MHD (MagnetoHydroDynamically
stirred)
(MHD technology is based on a fundamental law of
electromagnetism: When a magnetic field and an
electric current intersect in a liquid, their repulsive
intersection propels the liquid in a direction
perpendicular to both the field and the current )
Advantages
In comparison to solid-state operations (forging,
rolling, extrusion etc.),
1. semisolid slurries fill the die more evenly
under pressure
2. Complicated shapes can be made more easily
using lower loads
3. The operation requires lower energy,
resulting in lower overall production costs
Disadvantages
1. Relatively higher feedstock material cost
2. Precise control of operating condition is
required.
3. Liquid segregation may occur as a result of
non-uniform heating