The recrystallization behavior of Al-6Mg-0.4Mn-0.15Zr-xSc (x = 0.04–0.10 wt%) alloys

Highlights: • Recrystallization starting temperature increases 25–75 °C by addition of Sc and Zr. • Recrystallization finishing temperature increases ≥250 °C by addition of Sc and Zr. • A large span between recrystallization starting and finishing temperatures • Spherical Al₃(Sc,Zr) particles exhibit the stripe distribution. • Recrystallized grain nucleate at phase poor region, but was pinned at rich region -- Abstract: The recrystallization behavior of Al-6Mg-0.4Mn-0.15Zr-xSc (x = 0.04, 0.07, 0.10 wt%) alloys was studied using micro-hardness test, optical microscopy and transmission electron microscopy (TEM). The optical micrographs of the alloys with different Sc contents after being annealed at 100–550 °C for 1 h showed that the recrystallized nucleus formed between 275 and 325 °C at the original grain boundaries, and grew quite slowly until 550 °C and above, indicating a 250 °C large span of recrystallization starting and finishing temperatures in the alloys. The TEM observation showed the stripe distributed spherical Al₃(Sc,Zr) particles with phase rich region and phase poor region. The recrystallized subgrains with partial HAGBs was found at the phase poor region, but was pinned at the boundary of the phase rich region. The recrystallization driving and pinning pressures of the phase rich regions of the alloys with 0.04 and 0.1Sc wt% were estimated according to Zener drag mode. The results indicated an effective pinning effect of Al₃(Sc,Zr) particles on the recrystallized grain at lower than 475 °C. The large span between recrystallization starting and finishing temperatures could be attributed to the stripe distribution of the Al₃(Sc,Zr) particles.