fusion welding aluminium 7075

[PTwizz]

I would like to know what would be the effect of using a 'fusion welding' process on aluminium 7075-T6 with respect to the materials mechanical properties. The process involves heating to 380°C for the time taken to carry out the 'welding'(probably of the order of 5 minutes).
I have plenty of figures for the effects of thermal ageing over many hours, but nothing that approaches 380°C.

Pete.

 

[unclesyd]

The problem will be in the weld and HAZ.
What is the planned use of the component?
How thick is the weldment?

Preheat temperatures up to 800̊F are given for preheat in the ALCOA handbooks it leaves every thing open on the need for heat treating. The one thing it mentions several times is welding as fast as practical.

 

[PTwizz]

The component is part of a hydraulic damper. The weld is to add material to a small area (6 x 4mm) which has become thin-walled due to a manufacturing error. Part of the component (approx 10mm from the weld area) comes under high stress (up to 300MPa at up to 150°C peak).

The 'fusion welding' process is similar to soldering and can be accomplished very quickly with some practise.

Cheers for the help,

Pete.

 

[kenvlach]

‘Fusion welding' ~255^oC below the melting point of Al 7075?

In any event, consider that the fusion welding will result in the loss of the T6 properties.
If the welding process gives ~homogeneous alloy, proper post-weld heat treatment can restore the properties: Solutionize+quench, then artificially age to the T6 temper. Download MIL-H-6088G, Heat Treatment of Aluminum Alloys, at

http://assist1.daps.dla.mil/quicksearch/

for additional information.


If this welding process gives a non-homogeneous alloy composition (one which cannot solutionize the welded alloy to a single phase solid in a reasonable time), scrap the part and manufacture anew.

 

[PTwizz]

Thanks kenvlach,

I had no intention of using the repaired part for anything other than testing, largely to satisfy my own curiosity concerning the merits of the process. I have now used the process to repair a sample which was used for tensile testing. I will re-test the part today.

Pete.

 

[TVP]

7075-T6 is generally considered to be unweldable, due to poor ductility and toughness of the weld. There is no filler wire that can result in a product that can be fully solutioned and re-aged to the minimum mechanical property requirements of 7075-T6.

 

[PTwizz]

The process I am using is closer to soldering than welding. The 'filler rod' amalgamates effectively with the parent material. A tensile test of the my first attempt with this process showed:

1) I need more practice to achieve a good join. I had successfully joined about 20% of the desired area.

2) That the area where the amalgum had formed, failed in shear at a stress of around 200Mpa.

Not very impressive if you call it a weld, but pretty good for a soldered joint.

Pete.