Firearms use either 7075 or 6061. 6061 aluminum alloy is better known as aircraft aluminum. The M-16's receiver is made with 7075 aluminum, as is the frame of the Beretta Model 92, one of the longest serving models in American history.
By Frank Armao February 12, 2020
Article on welding 6061aluminum
We fabricate and weld 6061-T6 aluminum in various product forms. We understand that the ultimate tensile strength (UTS) of welded 6061-T6 is significantly lower than the starting strength. However, a few people have told me recently that we can restore the strength of welded components after welding to T6 levels by performing a low-temperature aging treatment after welding. Is this true?
I wish that were true because it would make life a lot simpler. Unfortunately, it is not.
The required minimum UTS for almost all 6061-T6 product forms is 40 KSI. However, all fabrication codes (AWS D1.2, ASME Boiler and Pressure Vessel Code, etc.) only require a minimum of 24 KSI UTS after welding. This is the value you need to meet when tensile testing is part of qualifying a welding procedure. It typically isn't very difficult to do. Usually you obtain 25 or 26 KSI on testing the tensile samples.
So what happens if you follow recommendations and age the welded sample before testing? The heat-affected zones (HAZs) do age up a bit, but you will find that when you test the tensile samples, they are only 1 to 2 KSI stronger than unaged samples—in the range of 25 to 27 KSI, which isn't anywhere close to T6 properties.
The only way to completely restore T6 properties is to perform a complete reheat treatment of the component. This consists of a solution heat treatment at around 1,000 degrees F followed by a rapid cold-water quench, followed by the low-temperature (400 F) aging treatment. This process is complex and difficult, but certainly possible if you have the experience and skill.
From Blackstone Advance Technologies on welding 7075
It is technically possible to weld 7075 aluminum. If a welder applies heat, they can join two pieces together. But the result isn't what a layperson might think.
When a welder applies high heat to 7075 aluminum, it creates microcracks as it cools. These are too small to be seen by the naked eye, so a casual observer would think the 7075 aluminum welded just fine.
Unfortunately, these microcracks have a serious impact on the tensile strength of the metal, and makes the weld very brittle. It doesn't take a lot of pressure for the weld to snap.
It's true that it's still possible to weld 7075 aluminum for some industrial applications, such as repairing molds for injection or blow molding plastics. However, these are extremely limited, non-structural applications -- and structural applications are exactly where this strong, lightweight material excels.
Some researchers are developing methods for safely welding 7075 aluminum and other alloys. It's possible that down the line these techniques will see industrial application, but they take highly specialized materials and processes. Right now, it's impossible for the average welder to safely work with 7075 aluminum.
Just because a welder can do something doesn't mean they should. It is technically possible to weld 7075 aluminum and comparable alloys, but never for any structural applications. The result simply isn't safe.
ME
As I mentioned earlier there is now a high tech filler metal that improves the weld ability of 7075
MetaLi LLC, has started to sell the nanotechnology enhanced aluminum 7075 welding wires
(
https://www.metaliusa.com/)
Get out your wallet and be prepare to pay more than your frame is worth for some filler metal then heat treat it afterwards to get a frame that will still not be 100%
PS, 2 of my brothers and I weld and fit. All three of us have been certified pipe welders. One brother got his certs as a ASME certified welding inspector. Even if we don't know how to weld something we know how to find out.
Like I said. It should not be a problem for a piece of grip frame. But a slide, a slide stop hole, a rail, under the barrel shank on a revolver. No, if you want any high percentage of original strength out of it.
I do have a digitally controlled HT over that can ramp and hold and could possibly HT a weld. BUT, doing it and maintaining tolerances while heating a piece of light 100% finished aluminum up to 1000f and then water quenching it and following that by a long soak at 400f may well be another story. Plus you would need to remove any steel from the frame like hammer, trigger, rebound and cylinder lock studs, firing pin bushing etc before proceeding. Steel does not expand or contract at the same rate as aluminum
Once again a new gun would be cheaper unless you had the equipment, knowledge and time to burn on a big maybe.
