Microstructure evolution of AZ31B sheet deformed by electric hot temperature-controlled single point incremental forming

Electric hot incremental forming (EHIF) is a flexible sheet forming process based on the Joule heating effect and the accumulation of local plastic deformation to achieve the final shape. This study carried out the EHIF for AZ31B sheet, using an indirectly method of controlling the temperature of the sheet by controlling the temperature of the tool. The truncated pyramid shell with a depth of 25 mm was finally obtained. The microstructure characteristics at different forming zones of the component were analyzed by optical microscope (OM) and electron back scatter diffraction (EBSD) technique. The main reason for the improvement of the formability was attributed to the dynamic recrystallization (DRX) which was affected by the cumulative effect of heat during the tool feeding process. In the early forming zone, due to the weak heat accumulation, the development of DRX was restricted, and twinning and slip played a prominent part in the sheet deformation. Non-basal slip induced the texture transition from {0001} <11–20> to {0001} <10-10> and created conditions for twinning. The twins grew up to coordinate the deformation due to the subsequent deformation and contributed to further unidirectional deflection of the basal texture orientation. The DRX took a leading role in the final forming zone, making the basal texture characteristics inherited but showing a weakening trend.