Direct laser deposited CoCrFeNiMn high-entropy alloys: relationship between pores-microstructure- tensile properties

Abstract

The equiatomic CoCrFeNiMn high entropy alloys (HEAs) has been successfully manufactured using direct laser deposition (DLD) technique. The size and number of porosities, the microstructures along the height of samples and the tensile properties of DLDed HEAs prepared under room (293 K) and cryogenic temperatures (77 K and 200 K) were investigated. The results show that DLDed HEAs exhibit directional solidification, forming dendritic columnar grains with long pores at the grain boundary in bottom regions and transiting to equiaxed grains close to top regions. And in the top regions, the pores are round and the numbers are greatly reduced. Compared with tensile properties of DLDed HEAs, the 77 K tensile samples cut from the top region have better performance, but the elongation of 293 K tensile samples in the middle region and 200 K tensile samples in the bottom region are similar, owing to the difference of porosity and microstructure in the two regions.

Keywords

• direct laser deposition technology
• cocrfenimn
• pore
• microstructure
• tensile property