Laser powder-bed fusion of a high entropy alloy with outstanding intrinsic mechanical properties

Abstract

In the past few years, laser powder-bed fusion (LPBF) of high entropy alloys (HEAs) has gained significant interest. We investigated a HEA (PdPtRhIrCuNi) elaborated by LPBF, and studied its microstructure and mechanical properties. This alloy has potential applications in luxury industries, as well as in medical technologies. The microstructure consists of two coherent FCC phases behaving as a single-phase structure, with strong segregation of different elements in the dendritic and inter-dendritic regions. It is much finer than that inherited from arc-melting, as reported in the literature, because of the much higher cooling rate of the LPBF process. Two cracking mechanisms were identified: solidification and liquation, and in both of them, the cracks propagate through grain boundaries and inter-dendritic regions. Despite the presence of micro-cracking, the mechanical properties in compression, bending, and wear resistance are outstanding. A new hybrid technique, called 3D laser shock peening (3D LSP), was effective in reducing crack density.