Microstructures and properties of an equimolar AlCoCrFeNi high entropy alloy printed by selective laser melting

• Published in: Intermetallics Vol. 104; pp. 24 - 32
• Main Authors: Niu, P.D., Li, R.D., Yuan, T.C., Zhu, S.Y., Chen, C., Wang, M.B., Huang, L.
• Format: Journal Article
• Language: English
• Published: Barking Elsevier Ltd 01-01-2019; Elsevier BV
• Subjects: Crystallography; Deformation; Densification; Electron beam melting; Entropy; Epitaxial growth; Equiatomic AlCoCrFeNi; Flux density; Heat treatment; High entropy alloys; Intermetallic phases; Laser beam melting; Lasers; Microhardness; Microstructure; Preferred orientation; Selective laser melting; High entropy alloys; Selective laser melting; Equiatomic AlCoCrFeNi
• ISSN: 0966-9795; 1879-0216
• DOI: 10.1016/j.intermet.2018.10.018

The equimolar AlCoCrFeNi high entropy alloy (HEA) was printed by selective laser melting (SLM), with emphasis on its densification, phase identification, non-equilibrium microstructure and properties. The density of SLM samples increase gradually with the increase of volumetric energy density (VED) with the maximal relative density 98.4%. SLM samples are consisted of disordered body-center cubic phases (A2) and ordered body-center cubic phases (B2) which are different from the conventional cast or deformation with A2 and fcc phase; the content of B2 phase increases with the VED. Interestingly, the Fe-Cr precipitate, which has never been found in the cast one, is observed in the SLM one without heat treatment. The microstructure of SLM samples shows epitaxial growth of columnar A2 grain bundles perpendicular to the melt pool boundary with an average grain size of about 1.5 μm; the B2 phase is between the columnar A2 grains. At low VED, the SLM sample shows preferred orientation, and is gradually transformed to the crystallographic direction families at a higher VED. Besides, there exists the {100}A2∥{100}B2 orientation relationship in A2 and B2 phase. The maximal micro-hardness of 632.8Hv of SLM sample is higher than the cast one and the electron beam melting printed one.
•The equiatomic AlCoCrFeNi alloy was successfully printed by SLM.•The A2 and B2 phase were identified by EBSD.•The Fe-Cr precipitate was found in the SLM samples.•The micro-hardness of SLM samples reaches 632Hv.