where should an NHT aluminum weld fail during tensile test

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Many aluminum welding books say that the weakest point of aluminum butt joint is the HAZ which is next to the weld itself. Assuming the weld is defect-free (all discontinuities are within the required limit), where would the joint break during the tensile test? I guess it should be HAZ. Then why so many of them break at the weld itself? Thanks a lot.
Reply:Aluminum reacts opposite from steel when heated and cooled slowly, it actually gets harder. So I would say it depends on type of filler and cool down time or procedure could or would make it go either way.I hate being bi-polar it's awsomeMy Heroes Have Always Been Cowboys
Reply:First and last time I ever try to help you man! Bye Bye I hate being bi-polar it's awsomeMy Heroes Have Always Been Cowboys
Reply:Originally Posted by weldermikeAluminum reacts opposite from steel when heated and cooled slowly, it actually gets harder. So I would say it depends on type of filler and cool down time or procedure could or would make it go either way.
Reply:Are you talking from experience. I am!I hate being bi-polar it's awsomeMy Heroes Have Always Been Cowboys
Reply:Please give me an example of either of the two situations you mentioned then.Have we all gone mad?
Reply:Originally Posted by weldermikeFirst and last time I ever try to help you man! Bye Bye
Reply:Originally Posted by hotrodderEh?Sorry but you're still wrong...
Reply:Originally Posted by likefotoMany aluminum welding books say that the weakest point of aluminum butt joint is the HAZ which is next to the weld itself. Assuming the weld is defect-free (all discontinuities are within the required limit), where would the joint break during the tensile test? I guess it should be HAZ. Then why so many of them break at the weld itself? Thanks a lot.
Reply:Originally Posted by sn0border88Hey!  Who are you to argue with experience!
Reply:i am with sn0 need to know base metal and filler used and tx before weldMiller Xmt 350Lincoln Ln-25Ahp 200xSmith Gas Mixer AR/HTig is my Kung FuThrowing down dimes and weaving aboutInstagram http://instagram.com/[email protected]
Reply:Originally Posted by sn0border88Please give me an example of either of the two situations you mentioned then.
Reply:Originally Posted by weldermikeAluminum reacts opposite from steel when heated and cooled slowly, it actually gets harder...
Reply:Originally Posted by WeldingWookiei am with sn0 need to know base metal and filler used and tx before weld
Reply:thanks everyone for answering my question. (and also sorry for my bad English  - I'm not a native English speaker).According to what I'm taught, HAZ of non-heat treatable alloys (5052, 5083 etc) is annealed during welding; while the HAZ of heat treatable alloys (6061, 6063 etc) go through complicated microstructure evolving process such as partial annealing, aging and/or over-aging. Either of them has the weakest point at HAZ. Let's take 6061 as an example. For 6061 (Al-Mg-Si heat treatable alloy), either 4043 or 5356 could be used as filler wire. If this HAZ theory being ture (the HAZ decides the joint strength), then it does not matter which filler wire your use. That sounds quite unbelievable to me.Last edited by likefoto; 04-17-2012 at 09:42 AM.
Reply:Originally Posted by KelvinFrom heating and slow cooling? As I understand it, that is how "normalizing" is done, and it pretty much always softens steel, regardless of carbon content (assuming the steel wasn't already normalized). Quenching (fast cooling) is what hardens steel (assuming it's hardenable)...
Reply:Originally Posted by sn0border88Ah, some how I read that and in my mind thought fast cooling.  You're correct, assuming the material goes above the transformation temperature, slow cooling should result in a range of softer microstructures.
Reply:Alright finally home from work and don't have to use that crappy phone. Like I said earlier this is by no means any way to check tensile strength, but just used for comparison. I did this quick in between jobs so aluminum was somewhat dirty, too small tungsten, too small filler, and didnt have time to play around with different types of filler which could change all the variables all day long(used 4043 on both, it was laying right in front of me). But anyway I promised some pics. The first piece was welded, let sit for 2minutes then cooled in water. One wimpy smack with a small hammer and it was on the floor, so soft I could have wiggled it off by hand. The second piece I welded, and let it cool for about 10 minutes on its own. Tough as nails, beat the crap out of it, and had to tighten the vice twice. That one broke in the weld as well but like I said, I promised some pics just to prove my side the story, and with proper size tungsten, filler rod, and different tensile filler I could have played with this all day long and probably came up with any outcome that could be argued. In my first post I said harder, I should have said normalize, but like I said i'm not much of a journalist.  Attached ImagesI hate being bi-polar it's awsomeMy Heroes Have Always Been Cowboys
Reply:Its an interesting question, one that I am reasonably sure cannot be done full justice on this forum.  Try posting it here instead, but please make sure to include all pertinent information upfront. http://www.aws.org/cgi-bin/mwf/board_show.pl?bid=8Have we all gone mad?
Reply:Originally Posted by weldermikeAlright finally home from work and don't have to use that crappy phone. Like I said earlier this is by no means any way to check tensile strength, but just used for comparison. I did this quick in between jobs so aluminum was somewhat dirty, too small tungsten, too small filler, and didnt have time to play around with different types of filler which could change all the variables all day long(used 4043 on both, it was laying right in front of me). But anyway I promised some pics. The first piece was welded, let sit for 2minutes then cooled in water. One wimpy smack with a small hammer and it was on the floor, so soft I could have wiggled it off by hand. The second piece I welded, and let it cool for about 10 minutes on its own. Tough as nails, beat the crap out of it, and had to tighten the vice twice. That one broke in the weld as well but like I said, I promised some pics just to prove my side the story, and with proper size tungsten, filler rod, and different tensile filler I could have played with this all day long and probably came up with any outcome that could be argued. In my first post I said harder, I should have said normalize, but like I said i'm not much of a journalist.
Reply:Correct, different fillers would change the game completeley, I just did this quick to show how cooling process with aluminum will change hardness, or normalize.I hate being bi-polar it's awsomeMy Heroes Have Always Been Cowboys
Reply:Originally Posted by sn0border88Its an interesting question, one that I am reasonably sure cannot be done full justice on this forum.  Try posting it here instead, but please make sure to include all pertinent information upfront. http://www.aws.org/cgi-bin/mwf/board_show.pl?bid=8