The　microstructures　and　mechanical　properties　of　a　Fe-Cr-B　alloy　containing　1.4　wt.-%　B　and　5.0　wt.-%　Cr　were　researched　after　different　heat　treatment　processes.　The　results　indicate　that　the　as-cast　microstructure　of　the　Fe-5Cr-1.4B　alloy　consists　of　M2B　(M　=　Fe,　Cr),　M-7(C,　B)　3,　alpha-Fe　and　gamma-Fe.　The　netlike　eutectic　M2B　phase　is　distributed　in　the　matrix.　After　water　quenching,　the　netlike　eutectic　M2B　phase　begins　to　fracture,　the　metallic　matrix　transforms　into　martensite　and　secondary　M-23(C,　B)(6)　borocarbides　are　precipitated.　When　the　quenching　temperature　exceeds　1050　degrees　C,　the　number　of　precipitated　secondary　borocarbides　is　reduced.　After　quenching,　the　macro-and　microhardness　of　the　samples　increase　with　the　increase　of　temperature,　and　the　hardness　reaches　a　maximum　value　at　1050　degrees　C.　When　the　temperature　exceeds　1050　degrees　C,　the　hardness　value　will　slightly　decrease.　After　tempering　treatment,　the　matrix　precipitates　as　miniature　secondary　borocarbides,　and　the　martensite　begins　to　soften,　and　the　hardness　is　lower　compared　to　that　quenched　by　heat　treatment.　The　decreasing　hardness　tendency　becomes　more　pronounced　with　the　increase　of　the　tempering　temperature.　Moreover,　the　impact　toughness　reaches　its　maximum　value　(7.35　J　x　cm(-2))　when　the　tempering　temperature　ranges　at　500　degrees　C.