5 ms·

I wonder if there are likely to be any metallurgical differences (e.g., strength, flexibility, likelihood to crack, etc.) between cast and stamped parts? My sen

I wonder if there are likely to be any metallurgical differences (e.g., strength, flexibility, likelihood to crack, etc.) between cast and stamped parts? My sense is that it's generally understood that 3D printing methods for metal produce weaker parts than casting, but I'm not sure how different non-3D printing methods compare.

avernon 6y ago
Tesla is using a proprietary alloy to make this part be strong enough and cost effective to do.
- apendleton 6y ago
  Neat. Do you have a link with more info about this? I guess I'm curious if they needed to switch alloys when they switched from stamping to casting, and if so, how the properties of the new material differ from the properties of the old one.
  - avernon 6y ago
    https://electrek.co/2020/02/07/tesla-aluminum-alloys-die-casting-in-electric-car-parts/ https://electrek.co/2020/02/07/tesla-aluminum-alloys-die-cas...
  - mcot2 6y ago
    https://electrek.co/2020/02/07/tesla-aluminum-alloys-die-casting-in-electric-car-parts/ https://electrek.co/2020/02/07/tesla-aluminum-alloys-die-cas... Tesla and SpaceX share a few employees in this space actually.
- gamblor956 6y ago
  Apple’s alloy expert Charles Kuehmann So the guy who led the materials research that resulted in the infamous bending iPhone is Tesla's chief scientist on this project? Not promising, though on the other hand cars are supposed to bend and flex in the event of an accident...
hwillis 6y ago
It depends very heavily on the type of metal. Metal strength is primarily determined by the shape of the microscopic grains making up its structure. Pressing, stretching, and squeezing those grains is one way to shape them. Chemical processes are another. Production method matters a ton in steel, where a LOT of strength comes from the way the metal was formed, and is only fully lost when the steel is near melting temperature. Alloy steels don't care so much how they were formed, but they're usually too expensive. Aluminum is different, and cast parts can be very strong if they're heat treated properly. The most common aluminum alloys (pure aluminum is nearly useless) are made with copper. Copper causes smaller grains to form as aluminum solidifies, and then over time it precipitates out from the bulk material and ends up in the borders between grains of purer aluminum. When stress attempts to pull grains past each other, the copper atoms act like wedges and keep everything from moving. Because the copper creates the grain shape itself, you don't need to work aluminum alloys to make them strong. Aluminum is semi-noteworthy (but far from unique) in that it loses strength very quickly when worked. You need to change a bunch of alloying elements to control for shrinkage (or at least delay until the part can be ejected from the mould), viscosity, temperature, oxygen tolerance etc. but I don't know much about all that. I know cast alloys are weaker than the strongest extruded alloys, but not by that much. There aren't problems with brittleness etc like you can get with steel. Also note that "cast iron" is a metal in its own right, and is NOT just steel/iron that has been cast. Cast iron is the highest-carbon (1-3%) alloy of steel, and that is what makes it weak and brittle- not the fact that it's cast. That much carbon causes a bunch of ceramic and graphitic phases to form all kinds of weird (but extremely cool, metallurgically) garbage.

avernon 6y ago

Tesla is using a proprietary alloy to make this part be strong enough and cost effective to do.

apendleton 6y ago
Neat. Do you have a link with more info about this? I guess I'm curious if they needed to switch alloys when they switched from stamping to casting, and if so, how the properties of the new material differ from the properties of the old one.
- avernon 6y ago
  https://electrek.co/2020/02/07/tesla-aluminum-alloys-die-casting-in-electric-car-parts/ https://electrek.co/2020/02/07/tesla-aluminum-alloys-die-cas...
- mcot2 6y ago
  https://electrek.co/2020/02/07/tesla-aluminum-alloys-die-casting-in-electric-car-parts/ https://electrek.co/2020/02/07/tesla-aluminum-alloys-die-cas... Tesla and SpaceX share a few employees in this space actually.
gamblor956 6y ago
Apple’s alloy expert Charles Kuehmann So the guy who led the materials research that resulted in the infamous bending iPhone is Tesla's chief scientist on this project? Not promising, though on the other hand cars are supposed to bend and flex in the event of an accident...

hwillis 6y ago

It depends very heavily on the type of metal. Metal strength is primarily determined by the shape of the microscopic grains making up its structure. Pressing, stretching, and squeezing those grains is one way to shape them. Chemical processes are another. Production method matters a ton in steel, where a LOT of strength comes from the way the metal was formed, and is only fully lost when the steel is near melting temperature. Alloy steels don't care so much how they were formed, but they're usually too expensive. Aluminum is different, and cast parts can be very strong if they're heat treated properly. The most common aluminum alloys (pure aluminum is nearly useless) are made with copper. Copper causes smaller grains to form as aluminum solidifies, and then over time it precipitates out from the bulk material and ends up in the borders between grains of purer aluminum. When stress attempts to pull grains past each other, the copper atoms act like wedges and keep everything from moving. Because the copper creates the grain shape itself, you don't need to work aluminum alloys to make them strong. Aluminum is semi-noteworthy (but far from unique) in that it loses strength very quickly when worked. You need to change a bunch of alloying elements to control for shrinkage (or at least delay until the part can be ejected from the mould), viscosity, temperature, oxygen tolerance etc. but I don't know much about all that. I know cast alloys are weaker than the strongest extruded alloys, but not by that much. There aren't problems with brittleness etc like you can get with steel. Also note that "cast iron" is a metal in its own right, and is NOT just steel/iron that has been cast. Cast iron is the highest-carbon (1-3%) alloy of steel, and that is what makes it weak and brittle- not the fact that it's cast. That much carbon causes a bunch of ceramic and graphitic phases to form all kinds of weird (but extremely cool, metallurgically) garbage.