Enhanced strengthening effect of aging heat treatment found in additively-formed CoCrFeNiTi-based multiprincipal element alloy

The strengthening effect caused by the fine precipitation in microcellular structures during aging heat treatment (AHT) in CoCrFeNiTi-based multiprincipal element alloys fabricated using laser-powder bed fusion (L-PBF) was investigated. L-PBF fabricated products after AHT at 923–1173 K demonstrated hardness of 692 HV, and ultimate tensile strength of 1824 MPa, whereas solution heat-treated products exhibited a hardness of 530 HV and ultimate tensile strength of 1562 MPa. X-ray diffraction, scanning electron microscopy, and scanning transmission electron microscopy demonstrated the presence of intermetallic compounds in the microcellular structures formed during L-PBF solidification. Microcellular structures in as-built specimens accompany dislocation networks and elemental segregation around microcellular walls. The hierarchical structure increases the strengthening effect of AHT by forming a large number of fine multiple intermetallic compounds. AHT after solution heat treatment causes the growth of strengthening nanoscale precipitates in equiaxed grains with a lower amount of grain boundary precipitates. The different responses to AHT in specimens with and without solution heat treatment are important issues for controlling the properties of additively manufactured products. [Display omitted] •Aging heat treatment of CoCrFeNiTi-based multiprincipal element alloy was explored.•L-PBF products with 692-HV hardness and 1824-MPa tensile strength were obtained.•Fine multiple intermetallic compounds precipitated in aging heat treatment products.•Microcells in L-PBF products altered precipitate distributions to strengthen them.