Hot deformation behavior and three-dimensional processing maps of in situ (ZrB2+Al2O3) np/AA6111 composite

The optimum processing window at elevated temperatures is of great importance for the secondary forming of metallic materials. So, the purpose of the present study is to obtain the true stress-strain curves, establish the constitutive equations and draw the 3D hot working diagrams through hot compression tests, as well as combine the relevant microstructures to determine the optimum processing window of in situ (ZrB2+Al2O3) np/AA6111 composite. The findings showed that the optimal processing domain was identified within the temperature range of 400-450 degrees C and a strain rate of 0.001-0.007 s-1, which corresponded to a fully dynamic recrystallization structure. Furthermore, in comparison to ZrB2 nanoparticles, the ZrB2+Al2O3 nanoparticles exhibited a significant enhancement effect on dynamic recrystallization and dynamic recovery, resulting in an elevated flow stress, activation energy (Q), and a broader optimum processing window of in situ (ZrB2+Al2O3) np/AA6111 composite. This phenomenon can be attributed to the advantageous properties of the ZrB2+Al2O3 nanoparticles, including their finer size (a hexagonal or quadrangular shape of ZrB2 with sizes between 20 and 100 nm and a spherical shape of Al2O3 with sizes between 10 and 50 nm), more uniform distribution (a network structure), and superior interface structure (the interfaces of ZrB2 and Al2O3 were semi-coherent and coherent; an adhesion interface between ZrB2 and Al2O3 nanoparticles). The relevant mechanisms were discussed in detail.