Weldability Studies of Different Aluminum Alloys 6061 and 7075
Aluminum 6061 and 7075 have high strength of weight ratio and good corrosion resistance but they are poor in weldability, 7075 especially. The major problems are distortion, porosity, hot cracking and HAZ strength reduction. This research was to explore the weldability of 6061 and 7075 precipitated hardening aluminum alloys under Gas Metal Arc (GMA) welding process, and filler metals ER4043 and ER5356 were used. A series of experiments including pulsed welding current, post weld heat treatment, micro hardness testing, tensile testing, bending test, optical microscope, SEM and EPMA were used to investigate the relationship between mechanical properties and microstructure. The experimental results showed that hot cracking canbe reduced in 7075 aluminum alloy welds made with suitable preheat. The proper post weld heat treatment can effectively increae the strength in fusion zone and HAZ. Precipitation in grain boundary and grain interior can cause hot cracking in 7075 aluminum alloy weld. The porosity content of the pulsed-current weld is in general found to be comparatively lower than that of the continuous current weld. The increase in zinc pickup in fusion zone can enhances the ultimate tensile strnegth of the weldment.
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