The　aim　of　the　present　study　is　to　investigate　the　effects　of　rare　earth　and　aluminium　on　the　structural　variations　of　medium　carbon　Fe-B　cast　alloy　under　the　same　austenitising　temperature　and　different　austenitising　times.　It　is　observed　that　the　as　cast　microstructure　of　Fe-B　cast　alloy　consists　of　the　eutectic　boride,　pearlite,　martensite　and　ferrite.　Moreover,　the　as　cast　eutectic　boride　structures　are　greatly　refined,　and　a　blocky,　less　interconnected　boride　network　is　obtained　when　rare　earth　and　Al　are　added.　After　different　austenitising　times,　in　each　case,　the　phases　in　modified　Fe-B　cast　alloy　consist　of　the　boride　and　martensite.　The　addition　of　RE　in　Fe-B　cast　alloy　accelerates　the　diffusion　process　of　B　and　Fe　atoms　during　austenitising.　Based　on　this　favourable　condition,　the　numbers　of　the　fractured　boride　networks　and　isolated　granular　borides　increase　with　increase　in　austenitising　time.　The　boride　volume　fraction,　Vickers　hardness　of　martensite　matrix　and　boride,　and　Rockwell　hardness　of　Fe-B　cast　alloy　modified　by　rare　earth　and　aluminium　have　no　significant　change　at　different　austenitising　times.　However,　the　average　diameter　of　boride　decreases　and　the　impact　toughness　increases　with　increasing　austenitising　time.