Effect Of Manganese On As-cast And Heat Treatment Microstructure And Properties Of High Boron Iron-based Alloy

High boron iron-based alloy with wear-resistant phases of boride,has excellent casting properties because of containing a large amount of eutectic structure formed by Fe₂B and austenite.The alloy with boron as alloying element is a new kind of wear-resistant material,which has low cost and excellent liquid molding performance.Due to the high brittleness of Fe₂B,the toughness of the material is poor.However,retained austenite in steel can improve toughness,while Mn is beneficial to its existence in steel.Therefore,the effect of Mn on the microstructure and properties of as-cast and heat-treated alloys is studied in this paper.The as-cast microstructure of the high boron iron-based alloy consists of dendritic and eutectic microstructure.With the increase of manganese content,the volume fraction of dendrite decreases from 20.51%to 17.24%.The eutectic microstructure mainly exists in the fishbone,strip and plate shape.When the manganese content reaches 8%,a chrysanthemum-like microstructure is formed around the dendritic microstructure in addition to the eutectic microstructure.Manganese is enriched in boride.The iron-based solid solution in the eutectic is martensite and retained austenite,and its manganese content is lower than that of boride,which is equivalent to the edge of dendritic microstructure.The center of the dendrite is ferrite,and the edges are martensite and retained austenite.As the manganese content increases from 2%to 10%,the amount of retained austenite in the alloy increases from 0.33%to 47.10%.With the increase of quenching temperature,the trend of network boride disconnection is obvious,and the effect of network disconnection is the best at 1050?.Tempering has little effect on the morphology of boride.As the tempering temperature increases,the hardness of the alloy decreases,and the toughness of the alloy generally increases first and then decreases.The research on the heat treatment process shows that the impact toughness of sample containing 8%Mn after quenching at 1000°C and tempering at 500°C reaches 4.54 J/cm²,which is larger than that of 1.86 J/cm² in the as-cast alloy,and the relative wear resistance is 2.4 times that of as-cast alloy.