Strengthening CoCrFeNi high entropy alloys via additive manufacturing with laser shock modulation of melt pool

Abstract

A novel synchronous laser shock modulation of melt pool (LSMMP) method was proposed to enhance melt pool convections and inhibit columnar crystal growth mainly found in additive manufacturing high entropy alloys (HEAs) via an additional second pulsed laser. The effect of laser shock on the microstructure of HEAs under the same additive manufacturing parameters was discussed assisted by finite element method (FEM). Results of electron backscattered diffraction (EBSD) show that grain refinement occurs in LSMMPed HEAs under optimal parameters. The strengthened plane texture is observed in the LSMMPed HEAs from three crystallographic orientations of [100], [110], and [111]. The Vickers hardness of HEAs is enhanced by grain refinement and there is no elemental segregation in the LSMMP process. The validation of LSMMP by tensile tests also indicates that the LSMMPed HEAs have better ductility. The present results demonstrate the fast real-time interference capability of LSMMP in metal additive manufacturing.