I was curious about the state of welding a month or so back and it seemed like aluminium robot welding is pretty much state of the art. It can produce a exceptionally good frame but only some of the largest manufacturers can do it. It's still much easier to robot weld steel frames at high volumes. When I looked at some of the smaller manufacturers they would often weld steel frames themselves but buy in their aluminium frames from one of the key large manufacturers like fuji-ta. Welding aluminium frames manually is a high skill level process where as steel can be welded well manually with a far shallower learning curve. It seems like once a basic steel welding level has been obtained they start welding children's bikes and then once they reach a slightly higher standard of welding go onto adult bikes. I'm not saying this is the standard procedure everywhere just one example company I read about. A lot of aluminium frames are still welded manually as far as I can tell by many manufacturers. Some surprisingly good aluminium frames come out of Vietnamese and Cambodian factories that are owned by Taiwanese firms. Often their main failing is inferior painting that is more likely to chip. I think they used these countries because of restrictions on Chinese bikes into Europe plus of course the much lower wage rate than China.

I think someone may have pointed this out already but if the tube itself fails that is poor design and/or material quality but if the weld itself fails that is more likely a manufacturing quality issue.