Study On SPS Preparation Process And Mechanical Properties Of Oxide Dispersion Strengthened Ferrite Alloy

Oxide Dispersion Strengthened(ODS)steels are developed on the basis of ferrite steel.Nanoscale oxides is formed in ferrite alloy by adding Y₂O₃,Which can pin dislocations and grain boundaries in matrix.The ODS steels have good high temperature mechanical properties and excellent resistant on irradiation damage because nanoscale oxides with high density distributed in the alloy.In this paper,powders were prepared by mechanical alloying(MA)and followed by spark plasma sintering(SPS)for solidification.In the experiment,Fe-(9-14)Cr and Fe-(9-14)Cr-0.25Y₂O₃ alloy powders were sintered at 950? by SPS.The relative density and hardness of the alloy were measured.8CrY and 13 CrY alloys were irradiated by Fe2+ under 2.5 Me V at 500?.Fe-9Cr-0.25Y₂O₃-2W ?Fe-9Cr-0.25Y₂O₃-0.2Ti ? Fe-9Cr-0.25Y₂O₃-2W-0.2Ti ? Fe-13Cr-0.25Y₂O₃-2W ?Fe-13Cr-0.25Y₂O₃-0.2Ti and Fe-13Cr-0.25Y₂O₃-2W-0.2Ti alloys were consolidated by SPS at selected different temperatures of 950??1000?? 1050? and 1150?.The relative density,hardness and tensile properties of the alloy samples were measured by the balance,Vickers hardness tester and universal electronic testing machine.The microstructure of the alloy sintered at 1050? were characterized by transmission electron microscopy(TEM).The effect of Cr content on the hardness and relative density of the alloys were systematically analyzed.The surface morphology of the irradiated samples were observed by scanning electron microscopy(SEM).The conclusions are following:(1)The relative densities of Fe-(9-14)Cr and Fe-(9-14)Cr-0.25Y₂O₃ alloys sintered at 950? are all about 96%,and the hardness of the alloys increases with the increase of Cr content.(2)For six ODS alloys prepared at different sintering temperatures,the relative density of the alloys sintered at 950? is under 90%,and the relative density of the alloys sintered above 1000? is generally above 98%.The grain size of Fe-(9/13)Cr-0.25Y₂O₃-2W and Fe-(9/13)Cr-0.25Y₂O₃-2W-0.2Ti alloys increases gradually with the increase of temperature.All six alloys sintered at 1000? have the highest tensile strength.(3)The highest hardness of 13 CrYW alloy sintered at 1050? is 745.47 HV,and the highest tensile strength of 13 CrYW alloy sintered at 1000? is 1175.36 MPa.The 9CrYW alloy sintered at 1000? has the highest hardness of 572.42 HV and the highest tensile strength of 935.22 MPa.At the same SPS temperature,13 CrYW alloys have high hardness and tensile strength and small grain size.(4)The highest hardness of 13 CrYTi alloy sintered at 1150? is 563.46 HV,and the highest tensile strength of 13 CrYTi alloy sintered at 1000? is 1127.12 MPa.The highest hardness of 9CrYTi alloy sintered at 1050? is 482.23 HV,and the highest tensile strength of 9CrYTi alloy sintered at 1000? is 1054.71 MPa.At the same SPS temperature,13 CrYTi alloys have high hardness and tensile strength.(5)The 13 CrYWTi alloy sintered at 1000? has the highest hardness of 693.75 HV and the highest tensile strength of 1516.82 MPa.The 9CrYWTi alloy sintered at 1000? has the highest hardness of 586.54 HV and the highest tensile strength of 1457.07 MPa.At the same SPS temperature,13 CrYWTi alloys have small grain size,high hardness and tensile strength.(6)Statistics of precipitated phases of(12-14)CrY alloy sintered at 950?.The average size of precipitates is 16.80 nm and the number density is 8.14×1020/m³ in 12 CrY alloy;the average size of precipitates is 10.94 nm and the number density is 8.69×1020/m³ in 13 CrY alloy;the average size of precipitates is 10.83 nm and the number density is 9.53×1020/m³ in 14 CrY alloy.Statistics of precipitated phases of alloys sintered at 1050?.The average size of precipitates is 19.45 nm and the number density is 1.21×1021/m³ in 13 CrYW alloy;the average size of precipitates alloy is 26.12 nm and the number density is 6.22×1020/m³ in 9CrYW alloy.The average size of precipitates is 18.53 nm and the number density is 1.31×1022/m³ in 13 CrYTi alloy;the average size of precipitates is 22.75 nm and the number density is 1.12×1022/m³ in 9CrYTi alloy.The average size of precipitates is 15.70 nm and the number density is 1.12×1022/m³ in 13 CrYWTi alloy;the average size of precipitates is 16.44 nm and the number density is 1.14×1022/m³ in 9CrYWTi alloy.