Characterization of Al–Cr and Al–Cr–Ni Alloys Produced via Cr- and Ni-Bearing Oxides

Abstract Al–Cr and Al–Cr–Ni alloys were synthesized via in-situ aluminothermic reduction of CrO 3 and NiO in molten aluminum at 1000 °C using cryolite as a flux. XRD and SEM/EDX analyses confirmed the formation of Al–Cr intermetallics (Al 7 Cr, Al 4 Cr, Al 8 Cr 5 ) in the binary alloys, while the ternary alloys additionally contained (Al 3 Ni) and complex Al–Cr–Ni phases (AlCrNi 2 , Al 0.983 Cr 0.017 , and Cr 7 Ni 3 ). Differential thermal analysis (DTA) revealed sequential events corresponding to CrO 3 decomposition, aluminum melting, and rapid aluminothermic reduction accompanied by intermetallic formation. Chromium recovery increased steadily with CrO 3 content in the absence of NiO but was markedly reduced in its presence due to competitive reduction. Nickel recovery in the Al–Cr–Ni alloys was relatively consistent, ranging from 0.83 to 0.99 wt pct Ni, corresponding to 30 to 33 pct of the added NiO. Although NiO reduction is thermodynamically more favorable than Cr 2 O 3 reduction, actual recoveries were influenced by kinetic factors including mixing efficiency, temperature, fluxing, and slag entrapment. Cryolite fluxing and mechanical stirring were identified as critical parameters governing both the rate and extent of metal recovery. Graphical Abstract