Heat distribution in welds of a 6061-T6 aluminum alloy obtained by modified indirect electric arc

Thermal cycles and isothermal sections were determined analytically by using the Rosenthal thin plate model, as well as by means of finite element method. The simulation model provides an acceptable approximation to thermal cycles measured during the welding process. A discrepancy for the analytical model with respect to the experimental results was found. Due to the thermal effect a hardness decrement of 43% (60 HV_0.1) with respect to the base material (107 HV_0.1) at a distance of 18 mm from the center of the welding bead was observed. The weld thermal cycle measured experimentally at this distance traverses the C-curve for the β′ precipitation phase at a peak temperature of 380 °C, with a dwell-time of approximately 10 s. The presence of rod-shape β′ precipitates was observed on a transmission electron microscopy image. A correlation between isothermal sections and the hardness distribution for different zones of the welded joint was identified.