Effects of rotational speed on the mechanical properties and performance of AA6061-T6 aluminium alloy in similar rotary friction welding

Similar rotary friction welding with AA6061-T6 rod material was carried out at four variations of rotational speed in order to study the effect of rotational speed on the joint properties. The increase in rotational speed produces higher hardness value in DRZ area, i.e. the lowest microhardness value in the DRZ area was 129 VHN at 380 rpm and increased to 192 VHN at 1700 rpm due to a grain refinement process that increased the hardness as the Hall�Petch equation. Otherwise, in the HAZ and TMAZ area, the microhardness profile has a decreasing trend due to the welding rotation increases. All welded joints have a lower strength than the base metal, about 68% for tensile and 83% for fatigue. The observations on the fracture surface of tensile and fatigue test showed that the fracture's area occurs in the same region where the lowest microhardness and roughness grain sizes occur.