Controlling　the　columnar　to　equiaxed　grains　transformation　is　the　main　method　for　improving　the　mechanical　properties　of　Ti　alloys　by　additive　manufacturing.　The　effects　of　different　Fe　contents　on　the　grain　morphology,　microstructure,　and　mechanical　properties　(including　hardness　and　strength)　of　Ti-6Al-4V　produced　by　laser　wire　deposition　were　studied.　Columnar　β　grains　in　the　deposit　were　transformed　into　equiaxed　grains　by　the　addition　of　Fe.　Iron　caused　the　formation　of　the　ω　and　TiFe　phases,　which　promoted　the　formation　of　a　uniform　ultrafine　microstructure.　The　dispersed　TiFe　acted　as　a　nucleation　site　for　the　α　phase　and　promoted　the　formation　of　the　nanometer-scale　α　phase.　Iron　played　the　role　of　solid　solution　strengthening,　fine　grain　strengthening,　and　dispersion　strengthening　in　the　deposit.　Additionally,　it　significantly　improved　the　mechanical　properties　of　the　deposit.　The　average　hardness　of　the　deposit　gradually　increased,　and　the　hardness　distribution　gradually　homogenized　as　the　Fe　content　increased.　The　compressive　strength　of　the　deposit　was　as　high　as　2830　MPa,　and　the　compressive　plastic　deformation　reached　43%　by　adding　3.3　wt%　Fe.　©　2021　Elsevier　B.V.