Preparation of in situ Al3Nb-NbB2-NbC/Al inoculant and its effect on microstructures and properties of weldable Al-Cu-Mn alloy

The in-situ Al3Nb-NbB2-NbC/Al inoculant (Al-5Nb-0.75B4C) ingots and ribbons were prepared with Al-Nb and B4C powers to refine the Al-Cu-Mn alloy. The Al3Nb-NbB2-NbC/Al inoculant ribbons showed excellent inoculant effect, which modified the dendrite crystals to equiaxed crystals and refined the grains from ~100 µm to ~30 µm. The transmission electron microscopy (TEM) images of the Al-Cu-Mn alloys reveal that the θ′ phases were refined from ~83 nm to ~40 nm and their number densities were also increased significantly. The selected area electron diffraction (SAED) patterns indicate that there are orientation relationships (ORs) between α-Al and Al3Nb, NbB2 and NbC, which suggest that these particles possess nucleation potency to α-Al. After inoculated by 1% Al3Nb-NbB2-NbC/Al ribbons, the ultimate tensile strength and elongation of the Al-Cu-Mn alloy were improved from 435 MPa and 8.4% to 514 MPa and 11.5%, respectively. The welding microstructure and property of the Al-Cu-Mn alloy inoculated by 1% Al3Nb-NbB2-NbC/Al inoculant were also improved significantly.