Hypereutectic Al-Ce-X (X=Mn, = Mn, Cr, V, Mo, W) alloys fabricated by laser powder-bed fusion

We characterize the microstructures and high-temperature mechanical properties of Al-2Ce and ternary Al-2Ce-1X (at.%) alloys fabricated by laser powder-bed fusion (LPBF), where X = Mn, Cr, V, Mo, and W are slow-diffusing transition metals. All ternary alloys show a hypereutectic microstructure in the as-LPBF state, containing an interconnected network of eutectic Al11Ce3 phases (similar to 10 vol.%) and an additional population of submicron, equiaxed Al20CeX2 primary precipitates (similar to 10 vol.%) which are isomorphous among these five alloys. Similar microstructures are present in arc-melted rods and atomized powders but are coarser due to the slower cooling rates in these processes. The hardness of the as-LPBF ternary Al-Ce-X alloys (1300-1400 MPa) is higher than that of the binary Al-Ce alloy (similar to 1100 MPa) due to the higher volume fraction of strengthening phases. Furthermore, during exposure at 400 degrees C for up to three months, greater hardness retention is achieved in the ternary Al-Ce-X alloys (65-75%) than in the binary Al-Ce alloy (similar to 55%), which is attributed to the extreme coarsening resistance of the Al20CeX2 precipitates imparted by the very slow-diffusing ternary solute. These coarsening-resistant Al20CeX2 precipitates also substantially improve alloy creep resistance, increasing the threshold stress for dislocation creep at 300 degrees C from similar to 32 MPa for the binary Al-Ce alloy to similar to 77-100 MPa for the ternary Al-Ce-X alloys, and at 400 degrees C from 40 MPa for the ternary Al-Ce-V alloy.