Fusion weldability studies in aerospace AA7075-T651 using high-power continuous wave laser beam techniques

• AA7075-T651 is highly susceptible to macroporosity and intergranular cracking in the heat-affected zone.
• Cold wire laser welding reduces macroporosity.
• Heat-affected zone cracking is minimized by controlling preweld temperature.
• Strength recovery by post-weld natural aging improves heat-affected zone strength.

The weldability of AA7075-T651 during keyhole laser and laser–arc hybrid welding was studied using microstructural and X-ray radiography techniques. The results showed that the application of cold wire laser welding reduced macroporosity, while the problem of heat-affected zone (HAZ) cracking was appreciably minimized by modifying the amount of heat in the HAZ. It was also found that the welding condition that minimized macroporosity was found unfavorable for resistance to HAZ cracking and vice versa. A compromise between these competing weld discontinuities was realized by a combination of localized modification of the strength of the HAZ and the application of cold wire laser welding. Also, differences were observed in the extent of porosity for Ar-shielded and He-shielded laser welds, where Ar shielding appeared to be more effective in minimizing porosity. In addition, the ability of AA7075-T651 to recover mechanical strength by post-weld natural aging will be useful when post-weld heat treatment is not practicable.

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