Additive manufacturing of high-strength eutectic aluminium-nickel alloys – Processing and mechanical properties

Abstract The application of additively manufactured high strength aluminium base alloys is, among others limited due to either a lack in processability or economic feasibility with the alloys currently available. Within this work, the mechanical properties of additively manufactured eutectic Al-Ni alloys are investigated for the first time. With an average ultimate tensile strength of 545 MPa at an elongation at failure of 10.1 %, Al-7.5 wt. % Ni-2.0 wt. % Cu (AlNi7.5Cu2.0) is the first aluminium base alloy known to the authors that has been processed with Laser Powder Bed Fusion (LPBF) and surpasses an ultimate tensile strength of 500 MPa and an elongation at failure of 10 % while relying on economically feasible alloying strategies and elements (i.e. no addition of rare earth elements, such as Sc). The properties of the alloys investigated are assumed to be a consequence of the α-aluminium- and intermetallic Al3Ni-phase comprising the eutectic in combination with an ultrafine interlamellar spacing as a result of the cooling rates utilized in the LPBF process. The specific alloy compositions investigated in this work are Al-7.5 wt. % Ni (AlNi7.5), Al-7.5 wt. % Ni-0.5 wt. % Cu (AlNi7.5Cu0.5) and AlNi7.5Cu2.0. All alloys were manufactured crack free by LPBF with part densities >99.9 %. For the binary AlNi7.5 alloy, an average ultimate tensile strength of 484 MPa was determined at an elongation at failure of 5.4 % in the additively manufactured condition. The determined mechanical properties were continuously increased by addition of up to 2.0 wt. % copper.