Gearhead Jim

It's eating the donuts that will overstress your frame, aluminum or steel.

TNTC4VETTE

JPN7075U

I was only curious because I may purchase a Z06 while still keeping my Z51. On airplanes, the harder aluminum alloys crack worse than the softer ones. Airplanes like to flex. If they don't flex then stuff breaks. I also have a friend with the big Yamaha cruiser, maybe dreamliner? that had a hairline crack develop in his cast aluminum frame. I'm sort of curious why chevy would spend tons extra for that frame to lose 140 lbs? Don't get me wrong, I love the looks of the Z06 frame in aluminum.

JoesC5

GM also uses low production vehicles as testbeds. Limits their exposure, if things don't work out as expected.

Knowing that gas mileage standards are going to continue to go up, they are looking for ways to save gas, not just in the corvette but accross the lineup. The only way for them to get some real world long life testing of an aluminum frame is to build some cars and put them out there for testing. That doesn't mean that they shortchanged anyone on their engineering, as they have a pretty good idea as to the results before putting something new into production. Dana builds the aluminum frame for GM and they also wanted to gain real world experience in building aluminum frames.

I have a Z06, and I'm not a bit concerned about the aluminum frame failing.

HOXXOH

Choosing the correct alloy, temper, and process for the application sometimes has cost as a consideration. Aircraft use trumps cost due to the simple fact that failure is almost always catastrophic and involves human life. While most aircraft components are extremely weight conscious, materials such as lead and depleted uranium are also used.

6063 alloy, especially in T5 temper, is most commonly used for extrusions where the stresses are lower priority than cost or finish. I'm not saying you can't hydroform 6063-T5 or that it isn't what's being used, but it certainly wouldn't be high on my list of choices.

The 7075 and 6061 alloys are easily formed in the 0 condition and then heat treated (aged) to T4 or T6. Not only are these hard when aged, but are flexible and easy to machine.

Cracks can occur in cast aluminum and are more common just like in cast iron, but the alloys are different.

Without knowing the specific criteria for the development of the Z06, I could speculate that GM wanted to continue their racing program and the standard C6 was not quite enough to dominate GT2. Then meeting the minimum volume requirements also allowed a streetable version to be sold to the general public for a premium. The minimum requirements for NHRA legal cars is 50 production units, but they were usually all sold to hand-picked buyers who never licensed them. It just depends on the rules of the game you want to play.