Optimization of numerical parameters and microstructure evolution on 2195 Al–Li alloy extrusion process

The present study designed a set of extrusion dies with unequal bearing lengths to investigate the extrusion deformation behavior of 2195 Al–Li alloy. With the standard deviation of the velocity field (SDV) and extrusion force as optimization objectives, the extrusion process parameters (billet temperature, die temperature and extrusion speed) were optimized using Taguchi method and orthogonal test. The results indicate that billet temperature is the most significant factor affecting SDV and extrusion force, with a range of 1.287 and 7.076, respectively. Furthermore, the optimal extrusion parameters were determined as billet temperature 420 °C, die temperature 410 °C and extrusion speed 0.2 mm/s, resulting in the SDV value of 0.3345 and the extrusion force of 17.059 MN. The grains on the extruded profile were flattened and elongated both in the extrusion direction and cross-section, showing obvious ∥TD and ∥TD preferred orientation, and discontinuous dynamic recrystallization (DDRX) and geometric dynamic recrystallization (GDRX) mostly occurred, but no significant differences in grain size were observed, thus verifying the accuracy of the numerical simulation. Additionally, the ultimate tensile strength, yield strength and elongation of the extruded profile reached 437.1 MPa, 345.9 MPa and 11.7%, respectively.