V0.5Nb0.5ZrTi refractory high-entropy alloy fabricated by laser addictive manufacturing using elemental powders

In this work, a V0.5Nb0.5ZrTi refractory high-entropy alloy is successfully fabricated by the selective laser melting (SLM) method using elemental powders as precursors. A crack-free SLM-prepared (SLMed) sample with a nearly single BCC structure is acquired with a volume energy density (VED) of 333 J/mm3. However, when the VED is lower or higher than 333 J/mm3, microcracks are generated in the SLMed samples. The finite element method simulation reveals that there are two mechanisms for generation of cracks. When VED < 333 J/mm3, Zr particles are not completely melted. Cracks are formed around the Zr particles due to the crystalline structure and co-efficient of thermal expansion mismatches between the unmelted Zr particles and the alloyed BCC matrix. When VED > 333 J/mm3, cracks are formed due to thermal stress induced by the large temperature gradient during the SLM process. In addition, the SLMed crack-free sample exhibits much better mechanical properties than the as-cast counterpart. The current study provides a reference for the application of SLM technology to prepare re-fractory high-entropy alloys with excellent mechanical properties using elemental powders as the precursor.