Just for grins and giggles, I pulled out my olde book of materials and the following fell out (all units in micrometers per mK):
Ti, 8.6
Al, 23.1
Mg, 24.8
Iron, 12
Carbon Steel, 10.8
Looks like Blue72s hit the nail on the head. I will have to hit my local bolt supplier on monday...
Catca:
As for your problem have you considered a wasted stud? We had a stud pull on a part and the local ex-F16 mechanic suggested this option (dont ask). Basicly its a stud that is say M10 on one end and M8 for the rest. Just drill the buggered hole oversize and tap. Since the only oversize part goes in the hole, you would never know the stud is 'goofy'.
Edit:
Found the pdf for rosan slimserts. Cool stuff. You can even get them silver plated. Those would be perfect for exhaust studs. I may have to call and see if they will give a few samples for 'testing' purposes. I've gotten some kick ass stuff by just asking...
Edit 2X:
Here is the link to alcoa for the rosan info...
http://www.unirexinc.com/alcoa.htm
tadd