EFFECT OF DIFFERENT APPLICATION PRESSURES ON ROTARY-FRICTION-WELDED AA2024-T6 JOINTS

An AA2024-T6 aluminium alloy was welded with a rotary-friction-welding technique using different forging pressures under constant friction pressure. It was found out that the increasing forging pressure has an adverse effect on the tensile strength of the welded joint. The maximum tensile strength was 366.22 MPa for a forging pressure of 80 MPa. However, the failure energies and elongations were decreased as the forging pressure increased. The minimum elongation was 15.45 %, while the minimum failure energy was 4.35 J with a forging pressure of 120 MPa. This situation is attributed to the loss of ductility up to a degree in high forging pressures and temperatures induced in the HAZ. In microstructural examinations the existence of the S phase has dominant role in determining the local hardness. The S phase is affected by the welding heat in the heat-affected zone, the thermomechanically affected zone and the dynamically recrystallized zone. The hardness is increased up to the middle of the TMAZ. In this zone the heat input caused an aging effect and increased the dispersed S phase in the intergranular zones. The aging mainly governed by the heat input increased the hardness up to beginning of the recrystallization zone.