Starter – What do you think this might
be? Write your thoughts down on your
mini white boards
Starter – Get out your metal
foam/powder metallurgy fact sheet.
Collect a piece of A4 paper. Take a look
at each others and write down any new
information that is not on our fact sheet.
To be able to design an information
leaflet which communicates how
powder metallurgy and metal foams are
produced.
To be able to identify the key features
of powder metallurgy and metal foams.
This is a modern way of producing metal
part to exact sizes by blending elements or
metal powders together.
The powders are then compacted
(squashed) in a die (like a mould) and
heated in a sintering furnace to bond the
particles.
The process of powder metallurgy includes
blending, mixing, pressing and sintering.
There are many advantages:
• It can be used to make parts that are
very difficult to machine like gears very
accurately
• The surface finish after Powder
Metallurgy is complete is very smooth
and shiny and so doesn’t need work to
file or smooth the parts
• It requires relatively low processing
temperatures.
• It produces a uniform microstructure.
• There is no waste, so materials are used
efficiently.
http://www.youtube.com/watch?v=O7U4HWjYcqo
Metal foams – most are made from aluminium,
although steel can also be used. There are many
benefits of metal foams, including a very good
strength-to-weight ratio.
Metal foams are cellular structures made with metal
rather than polymers.
They are often used as soundproofing in vehicles, or
as crash protection.
In electronics they can be used as heat sinks.
http://www.azom.com/article.aspx?ArticleID=8097
How metal foams are made
Production Method
Metallic melts can be foamed by creating gas bubbles in the liquid.
These gas bubbles in the metallic melt tend to rise to the surface due
to the high buoyancy forces in the high-density liquid. In order to
prevent this from happening, the viscosity of the molten metal has
to be increased. This can be done by adding fine ceramic powders or
alloying elements to form stabilizing particles in the melt.
Three ways of foaming metallic melts are listed below:
•Injecting gas into the liquid metal from an external source
•Causing the precipitation of gas that had just been dissolved in the
liquid
•Causing an in-situ gas formation in the liquid by admixing gasreleasing blowing agents to the melt
The properties of metal foams
Metals that Can Be Used
The metal that is commonly used to make metal foams is
aluminium. However, other varieties of metals can be used to make
the foam, such as titanium and tantalum.
Properties of Metal Foam
The key properties of metal foam are as follows:
• Ultralight material (75–95% of the volume consists of void spaces)
• Very high porosity
• High compression strengths combined with good energy
absorption characteristics
• Thermal conductivity is low
• High strength
The engineering applications of metal foams
Applications
The main applications of metal foams and porous metals are listed below:
• The closed variety is used for structural applications requiring loadbearing features, and for weight-saving and impact-absorbing structures in
vehicles
• The open variety is ideal for vibration and sound absorption, filtration
and catalysis at high temperatures, for heat exchange and in medical
devices.
• The open variety is also useful in functional applications such as filtration
and damping.
• Foam metal is being used as an experimental prosthetic in animals.
• Metal foams with high strengths can act as high-capacity impact-energy
absorbers.
• Automotive industry - the foams reduce the number of parts in the car
frame, facilitate assembly, thereby reducing costs and improving
performance.
The advantages of metal foams compared to other
materials
Currently, body Armor plate inserts are made
of ceramic composites. However, they are
bulky, heavy, and vulnerable to accidental
fracture. A plate insert made of the new
composite metal foam, on the other hand,
could be significantly thinner and lighter.