Optimizing Ni-rich intermetallic and mechanical properties at room and elevated temperatures for Al-Cu-Ni alloys by coupling travelling magnetic fields with sequential solidification

Nickel can enhance the elevated temperature property of Al alloys, but blocky and aggregated Ni-rich intermetallic induced by high Ni content can seriously reduce the properties at room and elevated temperatures. Accordingly, finding ways to optimize Ni-rich intermetallic and performance at room and elevated temperatures is of great significance. In this regard, we couple travelling magnetic fields (TMF) with sequential solidification to alter the content, morphology, distribution and growth of Ni-rich intermetallic in Al-Cu-based alloys with high Ni content, further to increase the related performance. Moreover, simulations are combined with experiments to comprehensively reveal the mechanisms on these optimizations during each stage of solidification process. Current findings indicate that Ni-rich intermetallic and matrix phase α-Al are effectively refined, modified and diffusely distributed, and growing in random directions by TMF process. Hence, the performance at both room and elevated temperatures are greatly improve. Specifically, Down-TMF increases the UTS, YS, elongation and hardness at 298 K from 147.8 MPa, 90.8 MPa, 6.0 % and 75.6 kg·mm⁻² without TMF to 186.7 MPa, 102.7 MPa, 10.4 % and 85.2 kg·mm⁻². While, Up-TMF raises them to 179.2 MPa, 95.1 MPa, 8.5 % and 83.2 kg·mm⁻². Additionally, Dwon-TMF improves the UTS, YS and elongation at 473 K from 99.0 MPa, 77.6 MPa and 17.3 % without TMF to 153.7 MPa, 86.1 MPa and 18.2 %, and from 74.7 MPa, 65.6 MPa and 18.5 % at 573 K to 84.4 MPa, 75.8 MPa and 25.7 %. While, Up-TMF promotes their elevated performance to 162.9 MPa, 88.9 MPa and 17.6 % at 473 K, and to 87.2 MPa, 77.0 MPa and 22.5 % at 573 K, respectively. Noteworthily, Down-TMF generates more overall positive effects than Up-TMF.