| Iron-based alloys have the advantages of good comprehensive performance,corrosion resistance and low price,and have good application prospects in the nuclear industry,transportation and other fields.The introducing of B2 phase precipitation can greatly improve the strength of iron-based alloys,but at the same time,it also significantly reduces the room temperature ductility,which limits the wide application of B2 phase-strengthened iron-based alloys.In this paper,aiming at improving the strong plasticity of B2 phase-strengthened iron-based alloys,by changing the hot rolling and aging processes,the effects of different hot-rolling and aging temperatures on the microstructure,properties and aging behavior of B2-phase-strengthened ironbased alloys were studied.The design and research of phase-strengthened iron-based alloys provide scientific guidance and have important engineering application background.In this paper,field emission scanning electron microscopy,transmission electron microscopy,electron backscatter diffraction analysis and other characterization methods are used to observe and analyze the microstructure,precipitation and phase transformation process of the samples in different heat treatment states in detail.The results show that the hot rolling and aging temperature have a great influence on the alloy structure and precipitation behavior,which can refine the grains and promote the precipitation of B2 phase in the matrix.Therefore,the volume fraction of B2 phase in the hot rolled alloy samples is significantly higher than that in the untreated alloy.Rolled alloy.With the increase of hot rolling temperature,the volume fraction of B2 phase in the matrix decreases,and the shape of B2 phase precipitation is nearly spherical in the ferrite matrix,but not in the austenite matrix due to the difference in the structure of the matrix phase.It is a regular strip,and the EDS results show that its B2 phase precipitation is mainly enriched in Ni,Co and Al elements.With the progress of aging,austenite gradually transforms to ferrite,and the aging temperature increases,and the transformation speed is accelerated.The effects of different hot rolling processes on the hardness,strength and ductility of the alloy were studied through micro-Vickers hardness test and tensile property test analysis.The results show that hot rolling can make the alloy have better strength and toughness.When aged at 550℃,the elongation of the unrolled alloy decreased from21% at 12 h to 5% at 300 h,and the strength-plastic product decreased from 17 GPa·%to 9 GPa·%.After hot rolling,the strength and ductility of the alloys are significantly improved.The 600℃ hot-rolled alloy has the highest strength,but the ductility is relatively poor;the 1000℃ hot-rolled alloy has relatively low strength,but the overall plasticity is the best.The hot-rolled alloy at 1000℃ has the best strength and toughness when aged at 550℃ for 240 h,and the maximum elongation and maximum strengthplastic product are 40% and 56 GPa·%,respectively.When aged at 700°C,the strength of the unrolled alloy is improved,but the aged samples are all brittle fractures.However,the strength and plasticity of the 800℃ hot-rolled alloy are significantly improved,and the strength and toughness performance are the best at 12 h,and the elongation and strength-plastic product are 16% and 24 GPa·%,respectively.It can be seen that under the same aging conditions,increasing the hot rolling temperature can improve the comprehensive strength and toughness of the material;while under the same hot rolling temperature,the increase of the aging temperature will make the comprehensive strength and toughness of the material worse. |
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