Pre-strain effect on the abnormal grain growth for aircraft 2219 aluminium alloy under indirect hot forming condition

The indirect hot stamping of the aluminum alloy process is a robust, high-precision technology to manufacture complex-shaped, thin-wall aircraft aluminum components. However, one of the key issues is the abnormal grain growth (AGG) during this process, leading to apparent surface defects. This study comprehensively investigates the AGG behavior of 2219 aluminum alloys under the indirect hot stamping conditions, which ware simulated by a room temperature tension, representing pre-forming, and a subsequent solution heat treatment (SHT) simulating the subsequent thermal history of the hot stamping. Electron backscatter diffraction (EBSD) tests were performed to identify grain structures of 2219 aluminum alloys. Grain morphology, geometrically necessary dislocation (GND), and texture were systematically examined through user-defined MTEX codes. A processing window based on the quantitative microstructure analysis and material strength was established. The result demonstrates that AGG occurs during the SHT stage. The critical room temperature pre-strain level for the occurrence of AGG during the SHT stage (i.e., 535°C × 30 min) is 4% for both O-temper and W-temper 2219 aluminum alloy. Critical thresholds for AGG initiation were identified at average grain size > 64 μm and GNDs < 5×10 12 m -2 . The established process window enables simultaneous prevention of coarse-grained defects and preservation of mechanical performance in the simulated indirect hot stamping process. These findings provide critical insights for designing pre-forming conditions in aerospace aluminum component manufacturing. • Critical pre-strain thresholds for AGG is 4% for both O-temper and W-temper alloy. • Initial large grains and the texture induce the occurrence of AGG • Island grain emerges through competitive boundary migration and recrystallization. • Process window balancing grain structure and strength is established.