Mechanism of microstructural refinement of deformed aluminum under synergistic effect of TiAl3 and TiB2 particles and impact on mechanical properties

To understand the synergistic effect of TiAl3 and TiB2 particles on grain refinement of α-Al, equal-channel angular pressing (ECAP) of Al-5Ti-1B (wt%) alloy was carried out. The ECAPed Al-5Ti-1B (wt%) alloy was characterized by X-ray Diffraction (XRD), electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). The results reveal that α-Al grains and TiAl3 phase of ECAPed Al-5Ti-1B (wt%) alloy were refined, while the average size of TiB2was marginally decreased. The tensile strength was increased from 128 MPa to 218 MPa, and the elongation was reduced from 26% to 20.6%. The transformation from dislocations to low-angle grain boundaries (LAGBs) and high-angle grain boundaries (HAGBs) resulted in continuous dynamic recrystallization (CDRX), which induced grain refinement during ECAP. From 3 to 6 passes of ECAP, CDRX occurred in the alloy, and as ECAP passes increased to 9, the rate of formation of LAGBs and the transformation rate from LAGBs to HAGBs reached a dynamic balance. The present study indicates that the second phase particles promote the formation of LAGBs but prolong complete-recrystallization time, such that complete-recrystallization leads to grain refinement. TiB2 particles are smaller than TiAl3 particles and this is caused by the composition of the alloy and its synthesis method, and compared with TiAl3, TiB2 with a smaller size had a more obvious influence on the formation of LAGBs and grain refinement.