Effect Of Spark Plasma Sintering Temperature On Microstructure And Mechanical Properties Of 14Cr-ODS Ferritic Steel

Nano-structured ODS steels are the leading candidate structural materials for first wall application in future fusion reactors because of their excellent radiation tolerance, helium embrittlement resistance and improved high-temperature properties. The excellent properties of nano-structure ODS steels come from the characteristic microstructure, depending strongly on the composition and manufracture technology. In this paper, the effect of spark plasma sintering temperature on the microstructure and mechanical properties of 14Cr-ODS steel was studied. The supersaturated alloy powders with nominal composition Fe-14Cr-2W-0.3Ti-0.3Y2O3 (wt%) were prepared by mechanical alloying (MA), and then consolidated by spark plasma sintering (SPS) at 950?,975?,1000? and 1025?, respectively. The following results were obtained:(1) The relative density of 14Cr-ODS ferritic steels prepared by SPS at 950?,975 ?,1000? and 1025? are all above 97%.(2) The average grain sizes increases with the increase of sintering temperature. The average grain sizes of 14Cr-ODS steels sintered at 950?,975?,1000? and 1025? are 0.17 ?m,0.21 ?m,0.51 ?m, respectively.(3) Two kind of precipiatates, Y-Ti-O-enriched precipitates and TiCr2O4 complex precipitates, are both formed in 14Cr-ODS ferritic steels consolidated by SPS at 950?, 975?,1000? and 1025?. The average sizes of two kinds of precipitates increase and the number densities decrease as the sintering temperature increased. The density of TiCr2O4 in 950? SPS sample is 1.14×1020/m3 with average size of 56.1 nm, and the density of Y-Ti-O precipitates is 6.67×10/m3 with average size of 5.7 nm. The density of TiCr2O4 in 975? SPS sample is 1.12×1020/m3 with average size of 70.6 nm, the density of Y-Ti-O precipitates is 7.75×1022/m3 with average size of 6.6 nm. The density of TiCr2O4 in 1000? SPS sample is 7.91×1020/m3 with average size of 130.3 nm, the density of Y-Ti-O precipitates is 5.44×1022/m with average size of 9.6 nm. The density of TiCr2O4 in 1025? SPS sample is 6.69×1020/m3 with average size of 167.5 nm, the density of Y-Ti-O precipitates is 4.74×1022/m3 with average size of 30.3 nm.(4) The hardness of the 14Cr-ODS ferritic steels decrease with the increase of sintering temperature. The hardness of ODS steels sintered at 950?,975?,1000? and 1025? are 858 HV,759 HV,586 HV and 554 HV, respectively.(5) The 14Cr-ODS ferritic steels show a good strength and plasticity at room and high temperature. The tensile strength decreases and the toughness increases with the increasing sintering temperature.