Iron-Based Alloy Strengthened by Intermetallic Compound Phase-Coated Nano-Oxide Phase and Preparation Method Thereof

A method for preparing an iron-based alloy strengthened by an intermetallic compound (IMC) phase-coated rare earth element oxide (REEO) nano-phase, comprising:

• step S1, preparation of a pre-alloyed powder:
• preparing the pre-alloyed powder of the iron-based alloy by vacuum melting and gas atomization;
• step S2, first mechanical alloying:
• subjecting a raw material powder for forming an IMC to high-energy ball milling according to a stoichiometric ratio of the IMC to obtain an IMC mechanically-alloyed powder;
• step S3, mixing by ball milling:
• mixing the pre-alloyed powder of the iron-based alloy obtained in step S1, the IMC mechanically-alloyed powder obtained in step S2, and a rare earth element-containing powder in a high-speed oscillating ball mill thoroughly under a first inert gas protection to obtain a mixed powder;
• step S4, second mechanical alloying:
• subjecting the mixed powder obtained in step S3 to mechanical alloying ball milling under a second inert gas protection to obtain a supersaturated solid solution mechanical alloying powder;
• step S5, thermomechanical densification:
• charging the supersaturated solid solution mechanical alloying powder obtained in step S4 into a can, vacuumizing, and conducting thermomechanical densification by hot extrusion/hot isostatic pressing/spark plasma sintering to obtain an iron-based alloy bulk, wherein a large amount of dispersed REEO nano-phase precipitates inside grains and at grain boundaries of an iron-based alloy matrix during the thermomechanical densification;
• and
• step S6, solid solution heat treatment and aging heat treatment:
• subjecting the iron-based alloy bulk to a solid solution heat treatment and an aging heat treatment to obtain the iron-based alloy strengthened by the IMC phase-coated REEO nano-phase, wherein during the solid solution heat treatment and the aging heat treatment, the REEO nano-phase further precipitates, and the REEO nano-phase has a particle size of 2 nm to 30 nm and a number density of 1022-1024 particles/m3;
• an IMC phase preferentially precipitates with a phase interface of the REEO nano-phase as a heterogeneous nucleation site, and then almost all of the REEO nano-phase is gradually wrapped, thereby forming a nano-particle with a core-shell structure with a REEO nano-phase having three or more elements as a core and the IMC phase as a shell;
• and a small amount of single-phase nano-particles of the IMC phase are also separately precipitated;
• wherein, the obtained iron-based alloy strengthened by the IMC phase-coated REEO nano-phase features heat resistance;
• since almost all of the REEO nano-phase is wrapped, the nano-particles with the core-shell structure have a total precipitation number density of 1022-1024 particles/m3 and maintains a high degree of coherency and a high thermal stability in the iron-based alloy matrix.