Alright... I cringe every time I hear titanium.
Although I agree that titanium is relatively strong and relatively light, I dont feel that it is the miracle material that everyone makes it out to be. Having machined and used the stuff, I still dont see the miracle in it at all.
Myth #1 - titanium is stronger than steel. While titanium (~140KPSI) is stronger than mild steels (~40KPSI ie, lawn chairs, exercise machines, paint cans, etc) it is actually weak when compared with higher grade steels such as 300M (~240KPSI - 300KPSI depending on application). 300M has twice the tensile strength as 6al4v (grade 5) titanium, but at much lower cost.
Myth #2 - titanium is harder than steel. While titanium is harder than some steels, tool steels easily go up to 60RC and cut titanium just fine. Even 300M (from previous example) can be easily hardened to 50-55RC and be used to cut titanium.
Titanium is difficult to weld. If you want to torch, arc, or MIG/TIG weld it... forget it. You will need to do it in a sealed chamber. The F14 uses a titanium box in the fuselage and Grumman (its maker) had to develop a new special electron beam welding process just to weld the thick sections required.
Like aluminum, titanium alloys are also notch sensitive. This means that even small scratches or nicks can lead to the part to failure after a number of stress cycles (ie, driving over bumps).
Titanium alloys are brittle. If you take a bar of 6al4v and you bend it too far, it will just snap into two pieces. If you crash a chassis made of the stuff, your car will explode like a ming vase. So much for crumple zones.
So why does everyone keep talking about titanium as if it were a miracle metal?
I have a feeling that its largely due to its extensive use in aircraft engines. One benefit of titanium is that it retains its strength relatively well when hot -- like in a flaming hot jet engine.
Titanium also is good in shear and has decent tensile so it makes good lightweight fasteners. The purer alloys (ie, weaker) used in fasteners also allow it to resist corrosion better.
On a slightly different note, the titanium corvette exhaust most likely uses pure titanium because it needs to be bent and rolled into the complex shapes. The stronger alloys that you would use for structural elements cannot be bent as such and probably need to be forged (expensive).
In conclusion, titanium is overly expensive to make and fabricate. Most of the time, you can get steel and aluminum to do the same job as titanium for a lot less money. The S2000 connecting rods for example are steel and hold up just fine despite being lightened extensively to run at 9000RPM.
So... I sincerely hope that honda uses titanium sparingly -- perhaps in the exhaust.
Personally, Im hoping they use a 4130 tube chassis paneled in with aluminum sheet with carbon fiber bodywork. A bonded and riveted aluminum tub chassis (like the elise) with CF bodywork would be nice too. I just hope they ditch the welded aluminum chassis design they are using now. Welded 5xxx and 6xxx series aluminum alloys just sucks.
Ugh... titanium.
