粉末热锻制备9Cr-ODS钢的微观组织和力学性能研究

Study on microstructure and mechanical properties of 9Cr-ODS steel prepared by apowder hot forging process

ODS钢因其优异的高温力学性能和抗辐照能力被认为是新一代核反应堆最具潜力的结构材料之一。在机械合金化后,通过粉末热锻成型的方法制备了一种低活化9Cr-ODS钢。采用SEM、XRD、TEM及拉伸实验等研究了粉末形貌和粒度随球磨时间的变化规律,以及热处理后9Cr-ODS钢的微观组织及力学性能。实验结果表明,球磨至50 h后,粉末的粒度、晶粒尺寸和晶格畸变趋于稳态。热处理后的9Cr-ODS钢成功获得了具有高密度位错的回火马氏体组织,晶粒细小,析出相为M_(23)C_(6)碳化物及Y-Ti-O型氧化物。氧化物颗粒的平均直径为10.2 nm,数密度约为1.3×10^(22) m^(-3)。粉末热锻成型的9Cr-ODS钢的致密度达到了99.4%,并具有优良的强塑性,其室温抗拉强度和屈服强度分别为910 MPa和750 MPa,700℃时分别为200 MPa和160 MPa。

ODS steel is considered as one of the most promising candidate structural materials for advanced nuclear reactors due to its excellent high-temperature mechanical properties and radiation tolerance.A low activation 9 Cr-ODS steel was prepared by hot forging after powder mechanical alloying.The effects of mechanical milling on powder morphology and particle size were studied by scanning electron microscope(SEM)and X-ray diffraction(XRD)analysis.The microstructure of 9 Cr-ODS steel were observed by transmission electron microscope(TEM),and the mechanical properties were tested by tensile experiments.It is found that after ball milling for 50 h,the particle size,grain size and lattice distortion of the powders tended to be stable.The relative density of 9 Cr-ODS steel was 99.4%,indicating that the excellent compactness had successfully obtained by hot forging method.After heat treatment,9 Cr-ODS steel exhibited tempered martensite structure with high density of dislocations and fine grains.There were two types of precipitates in the matrix of 9 Cr-ODS steel,M_(23)C_(6) carbides with a size of 100-200 nm and Y-Ti-O nano-oxides with an average size of 10.2 nm.The number density of nano-oxides could reach about 1.3×10^(22) m^(-3).The tensile strength and yield strength of 9 Cr-ODS steel were 910 MPa and 750 MPa at room temperature,and 200 MPa and 160 MPa at 700℃,respectively.