The evolution of quasicrystal during additive manufacturing and aging treatment of a Si-modified Al–Mn-Sc alloy

By adding Si to Al–Mn-Sc alloy, an aging strengthened aluminum alloy with stable quasicrystal (QC) phase for additive manufacturing (AM) was developed, in which the QC-Al81Mn19 in as-printed sample transforms to QC-Al74Mn20Si6 by the long-range reaction-diffusion of Si atoms (Al81Mn19+Si → Al74Mn20Si6+Al6Mn) during aging strengthening (holding at 325°C for 4 h), rather than crystallizing into intermetallic compounds. In AM process, the Mn-rich clusters (QC-embryo) nucleate from melt, subsequently, the matrix transforms to QC-phase as follows: matrix → clusters (nuclei) → GP-zones → long-period stacking order → QC-phase during subsequent solid-state phase transformation of AM thermal cycling.