Common Causes and Cures
There are two types of cracks that can occur in aluminum welds:
stress cracks and hot cracks
occur when the weld is simply unable to withstand the forces applied to it. This can be due to a poor joint
design that is welded as designed, a weld that is just not strong enough for the application (not designed properly) or an
improper weld. Images 1A and 1B show fillet weld examples. Image 1A shows the profile of an acceptable weld. Image 1B
shows an excessively concave weld that failed through the effective throat (refer to Image 2). If the weld is inadequate for
any of the above mentioned reasons, it is very possible it will not withstand service conditions.
are a result of the chemistry. It can be the chemistry of the base alloy, the filler alloy or the combination
making the weld itself. The graph that follows shows the hot cracking sensitivity for some of the most common aluminum
alloy groups; Silicon (4XXX), Copper (2XXX), Magnesium (5XXX), and Magnesium-Silicide (6XXX).