Optimization of new alloy compositions based on the Al–Cu–Mg–Y(Er)–Cr system for additive manufacturing

Evolution of the microstructure of new Al–Cu–Mg–Y(Er)–Cr alloys is studied during casting, surface laser melting, simulating selective laser melting, and subsequent homogenization annealing. A structure of surface laser melting tracks without defects of crystallization origin, in particular, hot cracks, is obtained. At the same time the track zone does not have a shrinkage cavity and porosity. The grain structure of tracks is represented by a narrow zone of columnar crystals and a zone of equiaxed crystals about 5 μm in size. During homogenization of the AlCuYMgCr–L alloy particles grow in size to approximately 500 nm, while in AlCuErMgCr–L alloy they grow to a significantly larger size of 2 μm. A common feature for both alloys is presence within aluminum solid solution of a large number of particles less than 100 nm in size. According to studies and thermodynamic calculations conducted previously, during alloy homogenization of these alloys, heterogenization should occur with nucleation of L1₂–Al₃(Zr,Y)/L1₂–Al₃(Zr,Er) and Al₄₅Cr₇ phases dispersoids.