Feor tig welding and Tig aluminum welding, can we use carbon dioxide as an inert gas ? or do we need Argon only....how about argon/c02 mix?

Use only pure argon for tig welding or you will cuss....a lot!!. When you get some seat time and gt really proficient you may find a mix of 50/50 argon/helium to be useful for welding aluminum 1/8" and thicker. I know I use it all the time and it really makes a big difference when tig welding thicker aluminum. Dont even try using Argon/CO2 or Nitrogen, or Straight CO2.