Skip to main content

Table 3 Common problems encountered in fusion welding of aluminium alloys, metallurgical aspects and prevention strategies (based on (Kou 2003))

From: Investigation of weld defects in friction-stir welding and fusion welding of aluminium alloys

Difficulties encountered Type of alloy Metallurgical aspects promoting the defect Microstructure Solutions
Solidification cracking Higher strength alloys (e.g. 2014, 6061, 7075) ◦ Solidification temperature range
◦ Grain structure
◦ Primary solidification phase
◦ Quantity of eutectic liquid at the end stage of solidification
◦ Coarse columnar dendritic structure—higher susceptibility
◦ Fine equiaxed dendritic structure with abundant eutectic liquid—lower susceptibility
♦ Appropriate dilution ratio
♦ Appropriate control of minor alloying elements
♦ Grain refinement—using agents
♦ Magnetic arc oscillations
♦ Reduce strains—preheating
♦ Improve weld bead shape
Loss of strength in HAZ Work hardened materials and heat-treatable alloys ◦ Increase in heat input/unit length—increases the size of HAZ and retention time above effective recrystallisation temperature ◦ Deformed grains (due to work hardening) that tend to recrystallise (forming strain free, soft grains)—softens the HAZ ♦ Reduce heat input—weld process like EBW or GTAW
Liquation cracking Higher-strength alloys ◦ Wide PMZ—high thermal conductivity and wide freezing temp range
◦ Large solidification shrinkage
◦ Large thermal contraction
◦ Grain boundary (GB) liquid—weakens the PMZ ♦ Appropriate filler material
♦ Reducing heat input—multipass welding, etc.
♦ Decrease in degree of restraint
♦ Oscillating arc method