TWI Industrial Member Report Summary 496/1994
M B D Ellis, M F Gittos and I Hadley
For many years, 6xxx aluminium alloys for structural applications have been welded up to approximately 25mm in thickness. However, there is a lack of data and experience for thicker section (50-100mm) products now coming into use. Susceptibility to HAZ cracking in these materials has been observed, and previous work at TWI indicates cracking to be most likely when the parent/filler combination is such that the bulk solidus of the parent is above that of the resultant weld metal. Since such alloys are now being used for safety critical applications (e.g. offshore structures), it is desirable to generate a better understanding of the causes of microcracking, its significance to structural integrity and methods for detection, repair and avoidance of the defects.
A project has been initiated at TWI to examine the welding behaviour of thick section aluminium alloys. This report considers the properties of MIG welded, 80mm thick 6082-T651 plate. Multipass welds were produced using Al-Si and Al-Mg filler wires. Metallographic examination and mechanical tests (tensile and R-Curve) were carried out on the welds in order to obtain data on heat-affected zone (HAZ) toughness.