Alloys
What is the major source of carbon emissions for most primary aluminium alloys?
the energy used in the electrolysis process
coal: around 20 kg CO2 per kg Al
water: down to 4 kg CO2 per kg Al
Which rule defines how phase diagrams are built?
The Gibbs Phase Rule
What is the correlation between the silicon content and the amount of available alpha phase?
The higher the silicon content the lower the available alpha phase.
The cut of is at an AlSi8Cu3
When did Prof. Fleming discover semi-solid casting in his lab at the MIT?
In the early 1970s
Where is the challenge in business development with Rheocasting
New properties and alloys needs to be implemented in the drawing from people you most likely don't know.
What is the difference between a T6 and a T5 heat treatment?
T6: solutionizing - quenching - ageing
T5: ageing
What is the latent heat?
The energy that is needed or set free from a phase change
How can you spot the difference between a HPDC and a Rheocasting microstructure?
Globular microstructure in Rheocasting with 2 alpha phases
How many Rheocasting-Processes are not temperature-controlled?
1 - The Comptech Rheometal Process
Which widely used HPDC alloy can be used in Rheocasting with only an adaptation to the internal specification to solve common casting issues?
A380 - 226 - 46000 - AlSi8Cu3
or A356
or AlSi7MnMg
Why is post-consumer scrap so desirable, and where is the challenge with it?
The carbon footprint is counted as zero.
Impurities in the scrap are included in the later alloy. Selection of scrap sources is essential.
Why doesn't the temperature change when the solidification hits the eutectic line?
There are three phases in the equation, so there is no additional degree of freedom
What is the difference between an ideal HPDC and Rheocasting in the filling process?
HPDC: turbulent
Rheocasting: Laminar
What is the difference between Rheocasting and Thixomolding?
Rheocasting: liquid -> semi-solid
Thixomolding: solid -> semi-solid
Why is Giga-/Megacasting an excellent application for Rheocasting?
Long flow length and good mechanical properties are required
Machines and tools are expensive. Massive cost savings.
Why does adding high-conductivity metals like copper or silver reduce the conductivity of aluminium?
When and why do dendrites form?
They form in alloys as soon as the heat flow inverts into the remaining melt during solidification
What is the reason for the good flow behaviour of a Rheocasting slurry in the casting process?
The applied shear forces
How does the GISS process work?
Introducing Argon bubbles into the melt using a graphite diffuser before pouring.
Why does Rheocasting offer an advantage for sustainable castings with high post-consumer scrap content?
The silicon content can be reduced to allow for higher impurity levels
The stirring and shear forces break down brittle AlSiFe intermetallic needles.
Why do smaller grains increase the strength and ductility?
The pressure field of dislocations is too weak to introduce new dislocations in the neighboring grain. New glide systems in the same grain are activated first. This increases the resistance against deformation and the material gets more ductile
Which one of the two types of nucleation needs less undercooling and why?
The heterogenious because it uses existing surfaces as nucleation point
Where does the outstanding flow length come from in Rheocasting?
How does the Rheometal process work?
Cast EEM and cool it down
Cut of ingate
Stirr EEM into shotweight.
EEM melts off - Slurry forms
Why is casting Heat Sinks in Rheocasting a great Idea?
2 Reasons!
You can use high conductivity alloys, like the Rheocool
High solid fractions fill ribs and base at the same time