Microstructure refinement and strengthening of Al–Cu alloys manipulated by nanocrystalline phases formed by in situ crystallization of Ni–Nb–Ti metallic glasses in melt

In this study, the thermal stability of Ni–Nb–Ti metallic glasses was investigated under isothermal and non-isothermal conditions. The effectiveness of NiTi phases, one of the nanosized crystallized phases, as grain refiners for Al–Cu alloys was also investigated from a crystallographic point of view using the edge-to-edge matching (E2EM) model. Thermal analysis showed that NiTi phases promote solidification of α-Al, and these nanocrystalline phases also promote an Al–Cu eutectic reaction and inhibit the growth of eutectic phases. A significant refining effect of α-Al grains from 402.7 μm to 69.1 μm was achieved with 0.05 wt.% nanocrystalline phases. Simultaneously, values for yield strength, ultimate tensile strength and fracture strain of inoculated Al–Cu alloys were increased by 18%, 13% and 78% to 363.2 MPa, 534.3 MPa and 11.92%, respectively, when compared with those of uninoculated Al–Cu alloys. Strengthening mechanisms of Al–Cu alloys manipulated by the nanocrystalline phases are grain boundary strengthening and precipitation strengthening.