شکل گیری فاز در استحکام جوش آلومینیوم 6060/4043

ABSTRACT Phase formation in 6060/4043 aluminum weld solidification

Al–Si–Mg extrusion alloys are widely used in fabricated structures because of their good corrosion resistance, moderate strength, and good weldability, provided that an appropriate filler alloy is used. When welded autogenously, these alloys have been found to be highly susceptible to solidification cracking [1,2]. However, when using an aluminum–silicon filler (e.g. alloy 4043), the weld pool is shifted to a composition with low cracking susceptibility [3,4]. The exact reason behind this improved cracking resistance remains
unclear.
To develop a better understanding of weldability requires knowledge of how welds solidify, including solidification path and phase formation. This is particularly important for modeling of weld defect formation (i.e. porosity and solidification cracking) [5,6], based upon the interdendritic pressure drop model of Rappaz et al.
[7]. A drop in liquid pressure arises from an inability to feed solidification and thermal shrinkage, which is affected by the solidification range and the nature of the phases present in the mushy zone.
Ternary phase equilibrium for the Al–Si–Mg alloy system is characterized by a quasi-binary occurring at a fixed magnesium–silicon ratio (Mg/Si = 1.73). Alloys that satisfy this ratio (i.e. fixed line on Al–Mg–Si ternary phase diagram) behave like a binary system consisting of -aluminum and Mg2Si. Using the quasi-binary as a line
of reference, alloys rich in silicon will form Si in addition to Mg2Si, ∗ Corresponding author. Tel.: +49 30 8104 1554; fax: +49 30 8104 1557. E-mail address: carl-edward.cross@bam.de (C.E. Cross). whereas alloys rich in magnesium will tend to form Mg5Al8.