I'm not at all familiar with welding this metal. I was told it's a no go to try welding 6061 to 7075 but have no idea if this is correct. All I know is 7075 is "stronger" (?) than 6061. I'm assuming the 7075 is denser/stronger/machines better?????????
welding aluminum
- Thread starter Mobuck
- Start date
NikA
Hunter
The primary hardening mechanism for aluminum alloys is the precipitation of secondary phase particles in the matrix. This contrasts most steels where hardening is primarily achieved through solute addition to the matrix and precipitation of secondary phases at grain boundaries.
The hardening process in aluminum alloys therefore requires a more extensive heat treatment process, and makes them more prone to thermal shock. In weldability terms, this means that some aluminum alloys, when welded, are extremely likely to crack on cooling. This can also be the result of different rates of thermal expansion between the aluminum matrix and the secondary phase. To the best of my knowledge, 7075 is on the list of aluminum alloys that are not considered weldable, along with most cast Al alloys.
Can 6061 be welded to 7075? Probably, with enough patience, something will stick. It's highly inadvisable to make any sort of structural weld with these two alloys due to the risk of cracking.
What equipment do you have at your disposal? Al welding also requires a way to deal with the almost instantaneous formation of oxides on the Al surface: typically, a TIG setup with AC, or occasionally, special sticks with a reducing flux (I have a box of these but have never used them and understand they have probably been discontinued for some time due to the difficulty of use).
You might have better success brazing two aluminum pieces together; while the filler rod is typically much more expensive, the likelihood of making a viable joint is much higher given appropriately selected filler.
The hardening process in aluminum alloys therefore requires a more extensive heat treatment process, and makes them more prone to thermal shock. In weldability terms, this means that some aluminum alloys, when welded, are extremely likely to crack on cooling. This can also be the result of different rates of thermal expansion between the aluminum matrix and the secondary phase. To the best of my knowledge, 7075 is on the list of aluminum alloys that are not considered weldable, along with most cast Al alloys.
Can 6061 be welded to 7075? Probably, with enough patience, something will stick. It's highly inadvisable to make any sort of structural weld with these two alloys due to the risk of cracking.
What equipment do you have at your disposal? Al welding also requires a way to deal with the almost instantaneous formation of oxides on the Al surface: typically, a TIG setup with AC, or occasionally, special sticks with a reducing flux (I have a box of these but have never used them and understand they have probably been discontinued for some time due to the difficulty of use).
You might have better success brazing two aluminum pieces together; while the filler rod is typically much more expensive, the likelihood of making a viable joint is much higher given appropriately selected filler.
NikA
Hunter
As far as strength differences, you'll need info on the heat treatment/temper (usually denoted by the alloy designation followed by the temper spec, e.g., AL6061-T6) to determine exactly what sort of mechanical properties you're dealing with. 7075 alloys are typically stronger due to the addition of extra alloying elements, but not necessarily for different tempers. The higher strength probably does not make the alloy more machinable in most cases (is rarely does without the addition of specific elements to promote chip formation); the difference in density is usually fairly small in the case of alloys that have approximately the same base element (both 6061 and 7075 are 90+% aluminum).
SAJohn
Hunter
Rivets are your friends when joining aluminum parts.
I am very familiar with 7075 as it used to be popular with aircraft manufacturers because of its' high strength. In my aircraft survivabilty days, we discovered that wet wings in A-4's which used 7075-T6 would fail badly due to the brittleness of this alloy when subjected to gunfire.
The Navy lost more A-4's in that war than any other type of Navy aircraft.
I am very familiar with 7075 as it used to be popular with aircraft manufacturers because of its' high strength. In my aircraft survivabilty days, we discovered that wet wings in A-4's which used 7075-T6 would fail badly due to the brittleness of this alloy when subjected to gunfire.
The Navy lost more A-4's in that war than any other type of Navy aircraft.
OP
That's what I was afraid I'd hear. Sounds like we'll stick to JB weld and a snug fit.
NikA said:
yeah, that's exactly what I was going to say....
radicalrod
Hunter
Try that magic Aluminum rod I see on FB all the time....just need a torch....
Looks easy peasy to me.....RR
Looks easy peasy to me.....RR
Jimbo357mag
Hawkeye
You can braze aluminum and many Youtube videos make it look easy.
Durafix Aluminum Welding Rods
https://www.youtube.com/watch?v=n1njyuPBIH0
Durafix Aluminum Welding Rods
https://www.youtube.com/watch?v=n1njyuPBIH0
A question I know something about....
There is not a good way to weld 7075, yes you can weld it, but if subjected to the loads
that required 7075 in the first place it will fail !!!
If it was a strictly decorative application then yes you can stick the two parts together.
You might look at some of the products that West Systems makes to bond aluminum
if it's something important.
Dave
Edit.... I'll machine 7075 all day long over 6061......
There is not a good way to weld 7075, yes you can weld it, but if subjected to the loads
that required 7075 in the first place it will fail !!!
If it was a strictly decorative application then yes you can stick the two parts together.
You might look at some of the products that West Systems makes to bond aluminum
if it's something important.
Dave
Edit.... I'll machine 7075 all day long over 6061......
exavid
Hunter
I've had good luck brazing with those rods you see at fairs. On one of my home built aircraft a radiator got punctured by a stone thrown up by the propeller. The braze repair was still in good condition on the airplane several years later. I've also brazed aluminum to aluminum several times for various things and found the fluxed rods worked very well. I used a MAPP gas torch for the jobs. It was easier than hauling my oxy/acetylene rig around. The oxy/acetylene rig is best if you're working outdoors with shifting breezes and shadows. Indoors the MAPP rig which is cheap works well unless you're working on big parts. I've brazed some test pieces and tried to break them apart in my big bench vice but usually the parts don't break on the braze line.
https://duckduckgo.com/?q=aluminum+brazing+rods&t=ffab&ia=shopping
https://duckduckgo.com/?q=aluminum+brazing+rods&t=ffab&ia=shopping
OP
I did more searching last night and watched a couple of videos on the use of those "wonder rods" for brazing aluminum. I think those will work fine for what I need and have ordered a few to test. What is surprising is that they're using a common propane torch for heat as those are about the "dirtiest" heat source available. Maybe it's just too easy to overheat with an oxy/acetylene torch?
I used to be a pretty good hand at brazing broken cast and thin sheet metal--this was WAY before MIG/TIG became available to anyone with a few hundred bucks.
I used to be a pretty good hand at brazing broken cast and thin sheet metal--this was WAY before MIG/TIG became available to anyone with a few hundred bucks.
daveg.inkc
Hunter
Main thing is to clean aluminum. It melts 1200 degrees. Oxidized much higher. Prep area brass brush, 240 grit, to get shiny. And preheat it. Aluminum is easy with correct procedure. I welded with TIG many years. SMAW, “stick” works, too. Clean and preheat!
don't know if this will be of any help but saw it and thought of this post ,
https://www.hilifebox.com/products/hilifebox%E2%84%A2-solution-welding-flux-cored-rods?variant=29580627017830
https://www.hilifebox.com/products/hilifebox%E2%84%A2-solution-welding-flux-cored-rods?variant=29580627017830
OP
I received my little package of "wonder rod" yesterday but it's going to be a while before the weather allows any testing. If this stuff works as advertised, it will hold my project together.
