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

Abstract

Disclosed are an iron-based alloy strengthened by an intermetallic compound (IMC) phase-coated nano-rare earth oxide phase and a preparation method thereof. The preparation method includes the following steps: step S1, preparation of a pre-alloyed powder; step S2, first mechanical alloying; step S3, mixing by ball milling; step S4, second mechanical alloying; step S5, thermomechanical densification; and step S6, solid solution heat treatment and aging heat treatment.

Claims

1. 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/m.sup.3; 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/m.sup.3 and maintains a high degree of coherency and a high thermal stability in the iron-based alloy matrix.

2. The method of claim 1, wherein the iron-based alloy is one selected from the group consisting of a Cr-containing full ferrite alloy and a Cr-containing ferrite/martensite alloy.

3. The method of claim 1, wherein the IMC phase comprises the IMC in step S2 alone; alternatively, the IMC phase comprises the IMC in step S2 and an alloying element in the iron-based alloy.

4. The method of claim 1, wherein the IMC in step S2 is one or more selected from the group consisting of NiAl series, TiAl series, FeAl series, TiSi series, NiSi series, NiTi series, NbAl series, RuAl series, MoSi series, and NbSi series.

5. The method of claim 1, wherein the REEO nano-phase exhibits a high thermal stability.

6. The method of claim 5, wherein the REEO nano-phase comprises one type of a complex oxide phase having three or more elements; alternatively, the REEO nano-phase comprises multiple types of complex oxide phases having three or more elements.

7. The method of claim 1, wherein the rare earth element-containing powder is one selected from the group consisting of a rare earth element oxide powder and a rare earth element hydride powder.

8. The method of claim 1, wherein the first mechanical alloying and the second mechanical alloying each are conducted using an omnidirectional planetary ball mill at a disk speed of 200 rpm to 400 rpm, a longitudinal speed of 10 rpm to 20 rpm, and a ball-to-material mass ratio of 5:1 to 10:1 for 5 h to 15 h; and the omnidirectional planetary ball mill is stopped for 5 min to 10 min and then changes a rotational direction every 15 min to 30 min of ball milling.

9. The method of claim 1, wherein in step S6, the solid solution heat treatment is conducted at a temperature of 800 C. to 1100 C. for 1 h to 3 h with a cooling process of water cooling, and the aging heat treatment is conducted at a temperature of 500 C. to 650 C. for 1 h to 3 h with a cooling process of water cooling.

10. An iron-based alloy strengthened by an IMC phase-coated REEO nano-phase prepared by the method of claim 1.

11. The iron-based alloy strengthened by an IMC phase-coated REEO nano-phase of claim 10, wherein the iron-based alloy is one selected from the group consisting of a Cr-containing full ferrite alloy and a Cr-containing ferrite/martensite alloy.

12. The iron-based alloy strengthened by an IMC phase-coated REEO nano-phase of claim 10, wherein the IMC phase comprises the IMC in step S2 alone; alternatively, the IMC phase comprises the IMC in step S2 and an alloying element in the iron-based alloy.

13. The iron-based alloy strengthened by an IMC phase-coated REEO nano-phase of claim 10, wherein the IMC in step S2 is one or more selected from the group consisting of NiAl series, TiAl series, FeAl series, TiSi series, NiSi series, NiTi series, NbAl series, RuAl series, MoSi series, and NbSi series.

14. The iron-based alloy strengthened by an IMC phase-coated REEO nano-phase of claim 10, wherein the REEO nano-phase exhibits a high thermal stability.

15. The iron-based alloy strengthened by an IMC phase-coated REEO nano-phase of claim 14, wherein the REEO nano-phase comprises one type of a complex oxide phase having three or more elements; alternatively, the REEO nano-phase comprises multiple types of complex oxide phases having three or more elements.

16. The iron-based alloy strengthened by an IMC phase-coated REEO nano-phase of claim 10, wherein the rare earth element-containing powder is one selected from the group consisting of a rare earth element oxide powder and a rare earth element hydride powder.

17. The iron-based alloy strengthened by an IMC phase-coated REEO nano-phase of claim 10, wherein the first mechanical alloying and the second mechanical alloying each are conducted using an omnidirectional planetary ball mill at a disk speed of 200 rpm to 400 rpm, a longitudinal speed of 10 rpm to 20 rpm, and a ball-to-material mass ratio of 5:1 to 10:1 for 5 h to 15 h; and the omnidirectional planetary ball mill is stopped for 5 min to 10 min and then changes a rotational direction every 15 min to 30 min of ball milling.

18. The iron-based alloy strengthened by an IMC phase-coated REEO nano-phase of claim 10, wherein in step S6, the solid solution heat treatment is conducted at a temperature of 800 C. to 1100 C. for 1 h to 3 h with a cooling process of water cooling, and the aging heat treatment is conducted at a temperature of 500 C. to 650 C. for 1 h to 3 h with a cooling process of water cooling.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] To describe the technical solutions in the embodiments of the present disclosure more clearly, the following briefly introduces the accompanying drawings required for describing the embodiments. Apparently, the accompanying drawings in the following description show merely some embodiments of the present disclosure, and those of ordinary skill in the art may still derive other drawings from these accompanying drawings without creative efforts.

[0032] FIG. 1A shows a transmission electron microscopy (TEM) image of the nano-particles with a NiAl-coated YZrO core-shell structure in the novel heat-resistant iron-based alloy prepared according to Example 1 of the present disclosure.

[0033] FIG. 1B shows a three-dimensional atom probe tomography (APT) elemental analysis of the nano-particles with a NiAl-coated YZrO core-shell structure in the novel heat-resistant iron-based alloy prepared according to Example 1 of the present disclosure.

[0034] FIG. 1C shows a high-angle annular dark field-scanning transmission electron microscopy (HAADF-STEM) image of a typical nano-particle with a NiAl-coated YZrO core-shell structure in the novel heat-resistant iron-based alloy prepared according to Example 1 of the present disclosure.

[0035] FIG. 1D shows an energy dispersion spectroscopy (EDS) elemental surface scan image of the nano-particle in FIG. 1C.

[0036] FIG. 2A shows a HAADF-STEM image of a typical nano-particle with a NiAl-coated YAlO core-shell structure in the novel heat-resistant iron-based alloy prepared according to Example 1 of the present disclosure.

[0037] FIG. 2B shows an EDS elemental surface scan image of the nano-particle in FIG. 2A.

[0038] FIG. 2C shows a magnified HAADF-STEM image of the nano-particle in the frame of FIG. 2A.

[0039] FIG. 2D shows a fast Fourier transform (FFT) structural analysis of the nano-particle in the frame of FIG. 2C.

[0040] FIG. 3 shows room temperature and high temperature tensile curves of a novel heat-resistant iron-based alloy with nano-oxides YZrO and YAlO both being coated by NiAl prepared according to Example 1 of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0041] In order to enable those skilled in the art to better understand the technical solutions in the embodiments of the present disclosure and to make the above objects, features, and advantages of the present disclosure more obvious and understandable, specific embodiments of the present disclosure are further described below.

[0042] The endpoints and any values of ranges disclosed herein are not limited to the precise range or value, and these ranges or values should be understood to include values close to these ranges or values. In terms of numerical ranges, one or more new numerical ranges can be derived by combining the end values of each range, combining the end values of each range and the individual point values and combining the individual point values, and these numerical ranges should be considered as specifically disclosed herein.

[0043] The present disclosure provides a method for preparing an iron-based alloy strengthened by an IMC phase-coated REEO nano-phase, including the following steps: [0044] step S1, preparation of a pre-alloyed powder: preparing the pre-alloyed powder of the iron-based alloy by vacuum melting and gas atomization; [0045] 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; [0046] 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; [0047] 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; [0048] 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, where 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 [0049] 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, where during the solid solution heat treatment and 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/m.sup.3; 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, [0050] where, 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-particle with the core-shell structure has a total precipitation number density of 10.sup.22-10.sup.24 particles/m.sup.3 and maintains a high degree of coherency and a high thermal stability in the iron-based alloy matrix.

[0051] In some embodiments, the iron-based alloy is one selected from the group consisting of a Cr-containing full ferrite alloy and a Cr-containing ferrite/martensite alloy.

[0052] In some embodiments, the IMC phase includes the IMC in step S2 alone; alternatively, the IMC phase includes the IMC in step S2 and an alloying element in the iron-based alloy.

[0053] In some embodiments, the IMC in step S2 is one or more selected from the group consisting of NiAl series, TiAl series, FeAl series, TiSi series, NiSi series, NiTi series, NbAl series, RuAl series, MoSi series, and NbSi series.

[0054] In some embodiments, the REEO nano-phase exhibits a high thermal stability.

[0055] In some embodiments, the REEO nano-phase includes one type of a complex oxide phase having three or more elements; alternatively, the REEO nano-phase includes multiple types of complex oxide phases having three or more elements.

[0056] In some embodiments, the rare earth element-containing powder is one selected from the group consisting of a rare earth element oxide powder and a rare earth element hydride powder.

[0057] In some embodiments, the first mechanical alloying and the second mechanical alloying each are conducted using an omnidirectional planetary ball mill at a disk speed of 200 rpm to 400 rpm, a longitudinal speed of 10 rpm to 20 rpm, and a ball-to-material mass ratio of 5:1 to 10:1 for 5 h to 15 h; and the omnidirectional planetary ball mill is stopped for 5 min to 10 min and then changes a rotational direction every 15 min to 30 min of ball milling.

[0058] In some embodiments, in step S6, the solid solution heat treatment is conducted at a temperature of 800 C. to 1100 C. for 1 h to 3 h with a cooling process of water cooling, and the aging heat treatment is conducted at a temperature of 500 C. to 650 C. for 1 h to 3 h with a cooling process of water cooling.

[0059] The present disclosure further provides an iron-based alloy strengthened by an IMC phase-coated REEO nano-phase prepared by any one of the above methods.

Example 1

[0060] A method for preparing a heat-resistant iron-based alloy strengthened by NiAl-coated YZrO and YAlO nano-particles consisted of the following steps: [0061] step S1, a FeCrWZr pre-alloyed powder with a particle size of 5 m to 30 m was prepared by vacuum melting+argon gas atomization; where [0062] the FeCrWZr pre-alloyed powder consisted of the following components in percentage by weight: [0063] 15% of Cr, 2% of W, 0.7% of Zr, Fe as a balance, and inevitable impurities; [0064] step S2, first mechanical alloying: a raw material powder consisting of a Ni powder and a Al powder was subjected to high-energy ball milling according to a stoichiometric ratio of NiAl to obtain an IMC NiAl mechanically-alloyed powder; [0065] step S3, mixing by ball milling: the FeCrWZr pre-alloyed powder obtained in step S1, the IMC NiAl mechanically-alloyed powder, and a Y.sub.2O.sub.3 powder were mixed in a high-speed oscillating ball mill thoroughly under a first inert gas protection to obtain a mixed powder; where the mixed powder consisted of the following alloying components in percentage by weight: 15% of Cr, 2% of W, 0.7% of Zr, 5.5% of Ni, 2.5% of Al, Fe as a balance, and inevitable impurities; [0066] step S4, second mechanical alloying: the mixed powder was subjected to mechanical alloying ball milling fully under a second inert gas protection, such that [Ni] and [Al] in the IMC powder and [Y] and [O] in the Y.sub.2O.sub.3 powder were dissolved into an iron matrix in atomic form, to form a supersaturated solid solution mechanical alloying powder; [0067] step S5, thermomechanical densification: the supersaturated solid solution mechanical alloying powder was charged into a can, vacuumized, and subjected to thermomechanical densification by hot extrusion/hot isostatic pressing/spark plasma sintering to obtain an iron-based alloy bulk, where during the thermomechanical densification, the supersaturated [Ni], [Al], [Y], and [O] solute atoms in the iron matrix were precipitated, forming a large amount of dispersed YZrO and YAlO nano-oxide phases inside grains and at grain boundaries; the YZrO and YAlO nano-oxide phases had a particle size of 2 nm to 50 nm and a number density of about 110.sup.23 particles/m.sup.3; a NiAl phase was preferentially precipitated at the interfaces of the YZrO and YAlO nano-oxide phases to gradually coat the YZrO and YAlO nano-oxide phases, thus forming a core-shell nano-structure with a higher thermal stability; and a part of the NiAl phase was also precipitated separately; [0068] step S6, heat treatment: the iron-based alloy bulk was subjected to solid solution heat treatment and aging heat treatment, obtaining the heat-resistant iron-based alloy strengthened by NiAl coated YZrO and YAlO nano-particles; where the solid solution heat treatment and the aging heat treatment were conducted as follows: the solid solution heat treatment was conducted at 800 C. to 1,100 C. for 1 h to 3 h with a cooling process of water cooling, and the aging heat treatment was conducted at 500 C. to 650 C. for 1 h to 3 h with a cooling process of water cooling.

[0069] The result analysis is as follows. FIGS. 1A-1D show a heat-resistant iron-based alloy strengthened by the NiAl-coated YZrO core-shell structure: FIG. 1A shows TEM observation results; FIG. 1B shows characterization analysis of three-dimensional APT; and FIG. 1C shows a HAADF-STEM image and FIG. 1D shows an EDS elemental surface scan image. In FIG. 1A, a large number of dispersed nano-strengthening particles are shown, with a total number density of about 110.sup.23 particles/m.sup.3. The elemental analysis of FIGS. 1B-1D confirms that the nano-strengthening particles have a core-shell structure of NiAl shell and YZrO core, in which the arrows mark a part of the individually precipitated NiAl phase.

[0070] FIGS. 2A-2D show a heat-resistant iron-based alloy strengthened by NiAl-coated YAlO core-shell structure, where FIGS. 2A-2B show a HAADF-STEM image and an EDS elemental surface scan image of a typical nanoparticle with a core-shell structure, respectively; and FIGS. 2C-2D show a magnified HAADF-STEM image of the nano-particle in the frame of FIG. 2A and an FFT analysis of the nano-particle in the frame of FIG. 2C, respectively, indicating that the core is a Y.sub.4Al.sub.2O.sub.9 nano-oxide phase that shows a high degree of coherency with the NiAl shell and the ferrite matrix.

[0071] FIG. 3 is obtained from the data in Table 1, and shows room temperature and high temperature tensile curves of a novel heat-resistant iron-based alloy strengthened by NiAl-coated nano-oxides YZrO and YAlO prepared according to Example 1 of the present disclosure.

TABLE-US-00001 TABLE 1 Room temperature and high temperature mechanical properties of the novel alloy (in annealed state) Temperature ( C.) YS (MPa) UTS (MPa) EL (%) 25 1095 72 1280 20 14.2 0.1 600 497 43 541.5 35 27.9 2.5

Example 2

[0072] A method for preparing a heat-resistant iron-based alloy strengthened by NiAl-coated YTiZrO and YZrO nano-particles consisted of the following steps: [0073] step S1, a FeCrWZr-Ti pre-alloyed powder with a particle size of 5 m to 30 m was prepared by vacuum melting+argon gas atomization; where [0074] the FeCrWZr-Ti pre-alloyed powder consisted of the following components in percentage by weight: [0075] 15% of Cr, 2% of W, 0.5% of Zr, 0.5% of Ti, Fe as a balance, and inevitable impurities; [0076] step S2, first mechanical alloying: a raw material powder consisting of a Ni powder and a Al powder was subjected to high-energy ball milling according to a stoichiometric ratio of NiAl to obtain an IMC NiAl mechanically-alloyed powder; [0077] step S3, mixing by ball milling: the FeCrWZrTi pre-alloyed powder obtained in step S1, the IMC NiAl mechanically-alloyed powder, and a Y.sub.2O.sub.3 powder were mixed in a high-speed oscillating ball mill thoroughly under a first inert gas protection to obtain a mixed powder; where the mixed powder consisted of the following components in percentage by weight: 15% of Cr, 2% of W, 0.5% of Zr, 0.5% of Ti, 5.5% of Ni, 2.5% of Al, Fe as a balance, and inevitable impurities; [0078] step S4, second mechanical alloying: the mixed powder was subjected to mechanical alloying ball milling fully under a second inert gas protection, such that [Ni] and [Al] in the IMC powder and [Y] and [O] in the Y.sub.2O.sub.3 powder were dissolved into an iron matrix in atomic form, to form a supersaturated solid solution mechanical alloying powder; [0079] step S5, thermomechanical densification: the supersaturated solid solution mechanical alloying powder was charged into a can, vacuumized, and subjected to thermomechanical densification by hot extrusion/hot isostatic pressing/spark plasma sintering to obtain an iron-based alloy bulk, where the supersaturated [Ni], [Al], [Y], and [O] solute atoms in the iron matrix were precipitated during the thermomechanical densification, forming a large amount of dispersed YTiZrO and YZrO nano-oxide phases inside grains and at grain boundaries; the YTiZrO and YZrO nano-oxide phases had a particle size of 2 nm to 40 nm and a number density of about 21023 particles/m.sup.3; a NiAl phase was preferentially precipitated at the interfaces of the YTiZrO and YZrO nano-oxide phases to gradually coat the YTiZrO and YZrO nano-oxide phases, thus forming a core-shell nano-structure with a higher thermal stability; and a part of the NiAl phase was also precipitated separately; [0080] step S6, heat treatment: the iron-based alloy bulk was subjected to solid solution heat treatment and aging heat treatment, obtaining the heat-resistant iron-based alloy strengthened by NiAl-coated YTiZrO and YZrO nano-particles, where the solid solution heat treatment and the aging heat treatment were conducted as follows: the solid solution heat treatment was conducted at 800 C. to 1,100 C. for 1 h to 3 h with a cooling process of water cooling, and the aging heat treatment was conducted at 500 C. to 650 C. for 1 h to 3 h with a cooling process of water cooling.

Example 3

[0081] A method for preparing a heat-resistant iron-based alloy strengthened by Ti (Al, W)-coated YSiZrO and YZrO nano-particles consisted of the following steps: [0082] step S1, a FeCrWZrSi pre-alloyed powder with a particle size of 5 m to 30 m was prepared by vacuum melting+argon gas atomization; where [0083] the FeCrWZrSi pre-alloyed powder consisted of the following components in percentage by weight: [0084] 15% of Cr, 2% of W, 0.5% of Zr, 0.2% of Si, Fe as a balance, and inevitable impurities; [0085] step S2, first mechanical alloying: a raw material powder consisting of a Ti powder and a Al powder was subjected to high-energy ball milling according to a stoichiometric ratio of TiAl to obtain an IMC TiAl mechanically-alloyed powder; [0086] step S3, mixing by ball milling: the FeCrWZrSi pre-alloyed powder obtained in step S1, the IMC NiAl mechanically alloyed powder, and a Y.sub.2O.sub.3 powder were mixed in a high-speed oscillating ball mill thoroughly under a first inert gas protection to obtain a mixed powder; where the FeCrWZrSi pre-alloyed powder consisted of following components in percentage by weight: 15% of Cr, 2% of W, 0.5% of Zr, 0.2% of Si, 3.0% of Ti, 2.5% of Al, Fe as a balance, and inevitable impurities; [0087] step S4, second mechanical alloying: the mixed powder was subjected to mechanical alloying ball milling fully under a second inert gas protection, such that [Ni] and [Al] in the IMC powder and [Y] and [O] in the Y.sub.2O.sub.3 powder were dissolved into an iron matrix in atomic form, to form a supersaturated solid solution mechanical alloying powder; [0088] step S5, thermomechanical densification: the supersaturated solid solution mechanical alloying powder was charged into a can, vacuumized, and subjected to thermomechanical densification by hot extrusion/hot isostatic pressing/spark plasma sintering to obtain an iron-based alloy bulk; where during the thermomechanical densification, the supersaturated [Ni], [Al], [Y], and [O] solute atoms in the iron matrix were precipitated, forming a large amount of dispersed YSiZrO and YZrO nano-oxide phases inside grains and at grain boundaries; the YTiZrO and YZrO nano-oxide phases had a particle size of 2 nm to 40 nm and a number density of about 210.sup.23 particles/m.sup.3; a Ti (Al, W) phase was preferentially precipitated at the interfaces of the YSiZrO and YZrO nano-oxide phases to gradually coat the YSiZrO and YZrO nano-oxide phases, thus forming a core-shell nano-structure with a higher thermal stability; and a part of the Ti (Al, W) phase was also precipitated separately; [0089] step S6, heat treatment: the iron-based alloy bulk was subjected to solid solution heat treatment and aging heat treatment, obtaining the heat-resistant iron-based alloy strengthened by Ti (Al, W)-coated YSiZrO and YZrO nano-particles, where the solid solution heat treatment and the aging heat treatment were conducted as follows: the solid solution heat treatment was conducted at 800 C. to 1,100 C. for 1 h to 3 h with a cooling process of water cooling, and the aging heat treatment was conducted at 500 C. to 650 C. for 1 h to 3 h with a cooling process of water cooling.

Example 4

[0090] A method for preparing a heat-resistant iron-based alloy strengthened by NiTi-coated YTiO nano-particles consisted of the following steps: [0091] step S1, a FeCrWTi pre-alloyed powder with a particle size of 5 m to 30 m was prepared by vacuum melting+argon gas atomization; where [0092] the FeCrWTi pre-alloyed powder consisted of the following components in percentage by weight: [0093] 15% of Cr, 2% of W, 0.5% of Ti, Fe as a balance, and inevitable impurities; [0094] step S2, first mechanical alloying: a raw material powder consisting of a Ni powder and a Ti powder was subjected to high-energy ball milling according to a stoichiometric ratio of NiTi to obtain an IMC NiTi mechanically-alloyed powder; [0095] step S3, mixing by ball milling: the FeCrWTi pre-alloyed powder obtained in step S1, the IMC NiTi mechanically-alloyed powder, and a Y.sub.2O.sub.3 powder were mixed in a high-speed oscillating ball mill thoroughly under a first inert gas protection to obtain a mixed powder; where the mixed powder consisted of the following components in percentage by weight: 15% of Cr, 2% of W, 3.0% of Ti, 4.5% of Ni, Fe as a balance, and inevitable impurities; [0096] step S4, second mechanical alloying: the mixed powder was subjected to mechanical alloying ball milling fully under a second inert gas protection, such that [Ni] and [Ti] in the IMC powder and [Y] and [O] in the Y.sub.2O.sub.3 powder were dissolved into an iron matrix in atomic form, to form a supersaturated solid solution mechanical alloying powder; [0097] step S5, thermomechanical densification: the supersaturated solid solution mechanical alloying powder was charged into a can, vacuumized, and subjected to thermomechanical densification by hot extrusion/hot isostatic pressing/spark plasma sintering to obtain an iron-based alloy bulk, where during the thermomechanical densification, the supersaturated [Ni], [Ti], [Y], and [O] solute atoms in the iron matrix were precipitated, forming a large amount of dispersed YTiO nano-oxide phases inside grains and at grain boundaries; the YTiO nano-oxide phase had a particle size of 2 nm to 40 nm and a number density of-21023 particles/m.sup.3; a NiTi phase was preferentially precipitated at interfaces of the YSiZrO and YZr-O nano-oxide phases to gradually coat the YTiO nano-oxide phase, thus forming a core-shell nano-structure with a higher thermal stability; and a part of the NiTi phase was also precipitated separately; [0098] step S6, heat treatment: the iron-based alloy bulk was subjected to solid solution heat treatment and aging heat treatment, obtaining the heat-resistant iron-based alloy strengthened by NiTi-coated YTiO nano-particles, where the solid solution heat treatment and the aging heat treatment were conducted as follows: the solid solution heat treatment was conducted at 800 C. to 1,100 C. for 1 h to 3 h with a cooling process of water cooling, and the aging heat treatment was conducted at 500 C. to 650 C. for 1 h to 3 h with a cooling process of water cooling.