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+--- Thread: 5XXX: Aluminum Magnesium Filler Alloys (/Thread-5XXX-%09Aluminum-Magnesium-Filler-Alloys)
5XXX: Aluminum Magnesium Filler Alloys - Keganhirl - 07-10-2019
he 5XXX fillers, of which 5356 is the most common, often are simple AlMg binary alloys. With these, the higher the Mg content, the stronger the welds. Some higher-strength 5XXX fillers, such as 5556 and 5183, also have manganese added to further increase the strength.
The weld appearance is not as smooth because 5XXX fillers are not as fluid and because of the presence of Mg, which sometimes leaves behind a black weld residue, especially during GMAW.
However, the mechanical properties of the 5XXX fillers are much better than those of the 4XXX fillers. The ductility of 4043 filler is between 6 and 10 percent, while that of 5356 is about 25 percent. The shear strength of 5356 is approximately 50 percent higher than that of 4043.
While the tensile strength of 5356 is also greater than that of 4043, this advantage is usually negated by the fact that in most cases the heat-affected zone (HAZ) of a groove weld is the weak point, not the weld itself.
The 5XXX alloys are used for three main types of applications. First, they are used to join 5XXX base materials to each other. In this application, the general rule is to use a filler alloy with slightly more Mg than the base alloy.
- 5554 or 5754 is used to weld alloys with low Mg content like 5052, 5154, and 5454.
- 5356 is used to weld intermediate-strength alloys such as 5086 and 5083. Sometimes 5183 is selected for increased mechanical properties.
- 5183, 5556, and 5087 are used to weld the highest-strength 5XXX alloys.
Finally, 5XXX fillers, again primarily 5356, should be used to weld 5XXX and 6XXX alloys when the weldment will be anodized after welding. As mentioned previously, if a 4XXX filler is used in this application, the welds will anodize to an unattractive black color.
5XXX fillers should not be used to weld 3XX casting alloys, such as A356 and A319, because these materials contain a lot of Si and excessive magnesium silicide will be formed.
When it comes to selecting the proper filler alloy, operators must understand their application and its objectives and also know their base material and its properties. This knowledge will affect which filler metal to use. Careful consideration of all factors involved will pave the way for making the right filler metal choice with confidence and with a successful end result.