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Al-Mg-Si alloys are known to be highly susceptible to solidification cracking except when using an appropriate filler metal (e.g., 4343 or 5356), although the amount of dilution required to avoid cracking has never been a well-defined quantity. The aim of the present study is to determine a relationship between filler metal dilution, local strain rate conditions, and cracking susceptibility. Making use of the controlled tensile weldability (CTW) test and local strain extensometer measurements, a boundary has been established between crack and non-crack conditions for different local strain rates and dilution amounts, holding all other welding parameters constant. This boundary, presented in the form of critical strain rate-dilution map, defines the critical amount of 4043 filler metal required to avoid solidification cracking when arc welding 6060 aluminium, depending upon local strain rate.
Aluminium alloy 6060 is typical of a family of Al-Mg-Si extrusion alloys, which are considered weldable only
when using an appropriate filler alloy such as 4043 (Al-5Si) or 5356 (Al-5Mg). This study concerns the
thermal analysis and solidification path determination of aluminium alloy 6060 diluted with variable amounts
of 4043. Casting of controlled mixtures of alloys 6060 and 4043 was used to simulate different weld dilutions
in order to facilitate thermal analysis. Thermal analysis and metallography were applied in order to reveal
solidification reactions and phases, and allow calculation of solid fraction versus temperature curves.
Although the liquidus temperature was little affected, different phases formed with increased 4043 dilution,
with a trend toward lower temperature reactions and a larger fraction interdendritic constituent.