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How Do I Weld 2024 and 7075?
March 26, 2014Q - I come into contact with two aluminum alloys of which I have found difficulty in obtaining information about arc welding. These alloys are 2024 and 7075. Can you provide me with information on how to weld these alloys with either the GMAW or GTAW process?
A –The reason you are having difficulty finding information on welding 2024 and 7075 is that both of these materials belong to a small group of aluminum alloys that are generally considered as being unweldable by the arc welding process. These materials are often found on aircraft, sporting equipment and other types of high-performance, safety-critical equipment and are not usually arc welded on the original component. Probably, the two most commonly found aluminum alloys within this category are 2024, which is an aluminum, copper, magnesium alloy, and 7075, which is an aluminum, zinc, copper, magnesium alloy. Both of these materials can become susceptible to stress corrosion cracking after welding. This phenomenon is particularly dangerous because it is not detectable immediately after welding, and usually develops at a later date when the component is in service. The completed weld joint can appear to be of excellent quality immediately after welding. However, changes which occur within the base material adjacent to the weld during the welding process, can produce a metallurgical condition within these materials which can result in intergranular micro cracking, which may be susceptible to propagation and eventual failure of the welded component. The probability of failure can be high, and the time to failure is generally unpredictable and dependent on variables such as tensile stress applied to the joint, environmental conditions, and the period of time which the component is subjected to these variables.
It is strongly recommended that great care be taken when considering the repair of components made from these materials. It must be stressed that if there is any possibility of a weld failure becoming the cause of damage or injury to person or property, do not perform repair work by arc welding on these alloys and then return them to service.