CN109913627B - Modification method for simultaneously improving strength, plasticity and toughness of industrial pure iron - Google Patents
Modification method for simultaneously improving strength, plasticity and toughness of industrial pure iron Download PDFInfo
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Abstract
The invention discloses a modification method for simultaneously improving the strength, plasticity and toughness of industrial pure iron. The method takes common industrial pure iron as a blank, adopts a technical means of combining deep cooling large-load impact and uniform field heat treatment to refine the structure, greatly improves the strength, plasticity and impact toughness of the material, and has the advantages of simple preparation process, convenient operation, good economy, no micro-defects such as micro-pores, weak connection and the like.
Description
Technical Field
The invention relates to an industrial pure iron metal material, in particular to high-strength, high-plasticity and high-impact-toughness industrial pure iron and a preparation method thereof.
Background
The steel material is used as a traditional metal material and applied to the fields of bridge construction, automobiles, aerospace and the like, and the performance of the material is generally changed by processes such as cold and hot processing, alloy addition, heat treatment and the like according to different application scene requirements. The industrial pure iron is one of steel materials, the main chemical component is iron, the total content of impurities is less than 0.2%, the carbon content is 0.02% -0.04%, and the industrial pure iron has physical properties such as less impurity elements, excellent conductivity and the like, so the industrial pure iron is widely used in the fields of automobiles, electronic appliances, relays and the like. However, the strength of industrial pure iron is low, and the tensile strength of common coarse-grained iron is about 300MPa, so that the application of the industrial pure iron in certain industrial fields is limited.
The metal material strengthening mode mainly comprises fine grain strengthening, work hardening, dispersion strengthening and solid solution strengthening. The fine grain strengthening means includes strong plastic deformation, amorphous crystallization, electrodeposition, thermal spraying, etc., wherein the strong plastic deformation method has received much attention because it can prepare large-sized ultra-fine grain/nanocrystalline materials. The existing strong plastic deformation methods such as equal channel angular deformation, high-pressure torsion method, cyclic extrusion method and the like have corresponding application scenes and advantages, for example, the cyclic extrusion method is suitable for producing plate-shaped components such as ultra-fine grain hollow blade models, the equal channel angular deformation is suitable for producing block components such as ultra-fine grain bolts, and the high-pressure torsion method has higher grain refinement degree due to easy introduction of deformation twin crystals. Although the sample prepared by the method has no problems of microporosity and oxidation pollution, the method has the defects of complex and expensive equipment, low production efficiency and difficulty in producing large-size ultrafine crystal/nanocrystalline materials. And a large amount of dislocation is introduced in the plastic deformation process, so that the internal defects of the sample are increased, and the plasticity and the toughness are easily reduced. For example, foreign researchers have found that the yield strength, the maximum tensile strength and the microhardness of a sample are all remarkably improved after a A1100 pure aluminum plate is subjected to certain plastic deformation, but the elongation at break and the toughness are remarkably reduced. The studies of domestic scholars have found that after the 9Cr1Mo steel is plastically deformed, although the grains are refined to be ultra-fine grains, the elongation after fracture is obviously reduced. Therefore, when the strength of the material is improved, how to simultaneously enhance the plasticity and the toughness of the material is a core technical problem which needs to be solved urgently.
The application of the industrial pure iron in certain industrial fields is limited due to the lower strength of the industrial pure iron, and the industrial pure iron with high strength, high plasticity and high impact toughness has larger industrial application prospect and value due to the excellent mechanical property, physical property and chemical property. Through the structure refinement, the strength of the industrial pure iron can be greatly improved, and the plasticity and toughness of the industrial pure iron can be greatly improved, so that the industrial application of the industrial pure iron is greatly widened.
Disclosure of Invention
The invention aims to provide a modification method for simultaneously improving the strength, plasticity and toughness of industrial pure iron, and the plasticity and impact toughness of the industrial pure iron are improved while the high strength is maintained, so that the existing industrial application scene is further expanded, and higher requirements are met.
The technical solution for realizing the purpose of the invention is as follows:
a modification method for simultaneously improving the strength, plasticity and toughness of industrial pure iron comprises the following steps:
1) cryogenic treatment of industrial pure iron: completely immersing cylindrical industrial pure iron into liquid nitrogen and keeping the temperature at-196 ℃ for more than 30 min;
2) and (3) impact treatment under a large load: immediately putting the cooled industrial pure iron into a normal-temperature carbon steel sheath, and performing unidirectional high-speed impact on the industrial pure iron by a 4000kg air hammer, wherein the impact speed of the unidirectional high-speed impact is 7.35m/s, and the impact frequency is once to obtain the industrial pure iron with the deformation amount of 0.45-0.50;
3) heat treatment in a uniform temperature field: placing the impact treatment material into a uniform temperature field heat treatment furnace for heat treatment, wherein the temperature range is 580-620 ℃, the heat preservation time is 1h, and cooling the impact treatment material to room temperature along with the furnace after heat treatment;
4) removing the sheath: after the carbon steel sheath is removed by heat treatment of the material, the cylindrical industrial pure iron with high strength, high plasticity and high impact toughness can be obtained.
Preferably, the carbon steel sheath is in a hollow cylindrical shape, the height of the carbon steel sheath is the same as that of the cylindrical industrial pure iron in the step 1), and the industrial pure iron is just completely embedded into the sheath core.
The invention has the beneficial effects that: 1. the carbon steel sheath at normal temperature has good plasticity, has a binding effect on the material, and can keep the integrity of the material after impact; 2. through large load impact and heat treatment, the structure is refined, and the lath-shaped cementite is converted into a spherical cementite, so that the strength, the plasticity and the impact toughness of the industrial pure iron are greatly improved; 3. the industrial pure iron with large size, high strength, high plasticity and high impact toughness can be prepared, and conditions are provided for wider industrial application; 4. the in-situ modification method has no defects of weak connection, pollution, microporosity and the like; 5. the modification process has the advantages of simple process, convenient operation, high production efficiency and good economy.
Detailed Description
The technical solution of the present invention will be further specifically described below by way of specific examples.
The invention discloses a modification method for simultaneously improving strength, plasticity and toughness of industrial pure iron, which comprises the following steps:
1) cryogenic treatment of industrial pure iron (-196 ℃): completely immersing large-size cylindrical industrial pure iron into liquid nitrogen and keeping for 30 min;
2) and (3) impact treatment under a large load: and (3) immediately putting the cooled industrial pure iron into a normal-temperature carbon steel sheath, wherein the sheath is in a hollow cylindrical shape, the height of the sheath is consistent with that of the cylindrical industrial pure iron in the step (1), and the industrial pure iron is just completely embedded into the core part of the sheath. Simultaneously carrying out unidirectional single-pass high-speed impact on the iron and the steel by a 4000kg air hammer, wherein the impact speed is 7.35m/s, and finally obtaining high-distortion industrial pure iron with the strain capacity of 0.45-0.50;
3) heat treatment in a uniform temperature field: placing the material subjected to the impact treatment into a uniform temperature field heat treatment furnace for heat treatment, wherein the annealing temperature range is 580-620 ℃, the heat preservation time is 1h, and cooling the material to room temperature along with the furnace after the heat treatment;
4) removing the sheath: after the carbon steel sheath is removed by heat treatment of the material, the cylindrical industrial pure iron with high strength, high plasticity and high impact toughness can be obtained.
Comparative example 1
1) The industrial pure iron (original crystal grains are equiaxial and have the size of 25 mu m) is a solid cylindrical sample with the diameter of 99.5mm and the height of 100mm, the sheath material is a hollow cylindrical shape of Q235B carbon structural steel, the inner diameter is 100mm, the outer diameter is 120mm, the height is 100mm, and the industrial pure iron is completely immersed in liquid nitrogen and kept for 30 min;
2) after cooling the industrial pure iron, immediately taking out the industrial pure iron and placing the industrial pure iron into a Q235B carbon structural steel sheath placed on a workbench, simultaneously carrying out unidirectional single-pass high-speed impact on the industrial pure iron and the Q235B carbon structural steel sheath by a 4000kg air hammer, wherein the impact speed is 7.35m/s, and finally obtaining the high-distortion industrial pure iron with the strain capacity of 0.50;
3) after removing the sheath of the impact treatment material, processing the impact treatment material into a tensile sample and a Charpy V-notch standard impact sample according to the national standard;
4) the mechanical property experiment is carried out, and the tensile strength is 755MPa, the elongation after fracture is 9.5 percent, and the impact toughness is 28.5J/cm2Compared with the raw material (tensile strength 430MPa, elongation after fracture 25.75%, impact toughness 47.5J/cm)2) The tensile strength is significantly improved, while the elongation after fracture and impact toughness are reduced.
Comparative example 2
1) The industrial pure iron (original crystal grains are equiaxial and have the size of 25 mu m) is a solid cylindrical sample with the diameter of 99.5mm and the height of 100mm, the sheath material is a hollow cylindrical shape of Q235B carbon structural steel, the inner diameter is 100mm, the outer diameter is 120mm, the height is 100mm, and the industrial pure iron is completely immersed in liquid nitrogen and kept for 30 min;
2) after cooling the industrial pure iron, immediately taking out the industrial pure iron and placing the industrial pure iron into a Q235B carbon structural steel sheath placed on a workbench, simultaneously carrying out unidirectional single-pass high-speed impact on the industrial pure iron and the Q235B carbon structural steel sheath by a 4000kg air hammer, wherein the impact speed is 7.35m/s, and finally obtaining the high-distortion industrial pure iron with the strain capacity of 0.50;
3) removing the sheath of the impact treatment material, processing the impact treatment material into a tensile sample and a Charpy V-notch standard impact sample according to the national standard, putting the tensile sample and the Charpy V-notch standard impact sample into a uniform temperature field heat treatment furnace for heat treatment, wherein the annealing temperature is 420 ℃, the heat preservation time is 1h, and cooling the impact treatment material to room temperature along with the furnace after the heat treatment;
4) the mechanical property experiment is carried out, and the tensile strength is 700MPa, the elongation after fracture is 9.75 percent, and the impact toughness is 40J/cm2Compared with the raw material (tensile strength 430MPa, elongation after fracture 25.75%, impact toughness 47.5J/cm)2) The tensile strength is high, and the elongation after fracture and the impact toughness are low.
Comparative example 3
1) The industrial pure iron (original crystal grains are equiaxial and have the size of 25 mu m) is a solid cylindrical sample with the diameter of 99.5mm and the height of 100mm, the sheath material is a hollow cylindrical shape of Q235B carbon structural steel, the inner diameter is 100mm, the outer diameter is 120mm, the height is 100mm, and the industrial pure iron is completely immersed in liquid nitrogen and kept for 30 min;
2) after cooling, the industrial pure iron is immediately taken out and placed into a Q235B carbon structural steel sheath which is placed on a workbench, and unidirectional single-pass high-speed impact is simultaneously carried out on the industrial pure iron and the Q235B carbon structural steel sheath by a 4000kg air hammer, wherein the impact speed is 7.35m/s, and finally the high-distortion industrial pure iron with the strain capacity of 0.45 is obtained;
3) removing the sheath of the impact treatment material, processing the impact treatment material into a tensile sample and a Charpy V-notch standard impact sample according to the national standard, putting the tensile sample and the Charpy V-notch standard impact sample into a uniform temperature field heat treatment furnace for heat treatment, wherein the annealing temperature is 660 ℃, the heat preservation time is 1h, and cooling the impact treatment material to room temperature along with the furnace after the heat treatment;
4) the mechanical property experiment is carried out, and the tensile strength is 380MPa, the elongation after fracture is 38 percent, and the impact toughness is 155J/cm2Compared with the raw material (tensile strength 430MPa, elongation after fracture 25.75%, impact toughness 47.5J/cm)2) The elongation after fracture and impact toughness are higher, and the tensile strength is lower.
Comparative example 4
1) The industrial pure iron (original crystal grains are equiaxial and have the size of 25 mu m) is a solid cylindrical sample with the diameter of 99.5mm and the height of 100mm, the sheath material is a hollow cylindrical shape of Q235B carbon structural steel, the inner diameter is 100mm, the outer diameter is 120mm, the height is 100mm, and the industrial pure iron is completely immersed in liquid nitrogen and kept for 30 min;
2) after cooling, the industrial pure iron is immediately taken out and placed into a Q235B carbon structural steel sheath placed on a workbench, and unidirectional single-pass high-speed impact is simultaneously carried out on the industrial pure iron and the Q235B carbon structural steel sheath through a 4500kg air hammer, wherein the impact speed is 7.60m/s, and finally the high-distortion industrial pure iron with the strain capacity of 0.54 is obtained;
3) removing the sheath of the impact treatment material, processing the impact treatment material into a tensile sample and a Charpy V-notch standard impact sample according to the national standard, putting the tensile sample and the Charpy V-notch standard impact sample into a uniform temperature field heat treatment furnace for heat treatment, wherein the annealing temperature is 570 ℃, the heat preservation time is 1h, and cooling the impact treatment material to room temperature along with the furnace after the heat treatment;
4) the mechanical property experiment is carried out, and the tensile strength is 560MPa, the elongation after fracture is 20.3 percent, and the impact toughness is 56J/cm2Compared with the raw material (tensile strength 430MPa, elongation after fracture 25.75%, impact toughness 47.5J/cm)2) The tensile strength and impact toughness are high, and the elongation after fracture is low.
Comparative example 5
1) The industrial pure iron (original crystal grains are equiaxial and have the size of 25 mu m) is a solid cylindrical sample with the diameter of 99.5mm and the height of 100mm, the sheath material is a hollow cylindrical shape of Q235B carbon structural steel, the inner diameter is 100mm, the outer diameter is 120mm, the height is 100mm, and the industrial pure iron is completely immersed in liquid nitrogen and kept for 30 min;
2) after cooling, the industrial pure iron is immediately taken out and placed into a Q235B carbon structural steel sheath which is placed on a workbench, and unidirectional single-pass high-speed impact is simultaneously carried out on the industrial pure iron and the Q235B carbon structural steel sheath by a 3000kg air hammer, wherein the impact speed is 6.50m/s, and finally the high-distortion industrial pure iron with the strain capacity of 0.43 is obtained;
3) removing the sheath of the impact treatment material, processing the impact treatment material into a tensile sample and a Charpy V-notch standard impact sample according to the national standard, putting the tensile sample and the Charpy V-notch standard impact sample into a uniform temperature field heat treatment furnace for heat treatment, wherein the annealing temperature is 630 ℃, the heat preservation time is 1h, and cooling the impact treatment material to room temperature along with the furnace after the heat treatment;
4) the mechanical property experiment is carried out, and the tensile strength is 490MPa, the elongation after fracture is 23.3 percent, and the impact toughness is 45J/cm2Compared with the raw material (tensile strength 430MPa, elongation after fracture 25.75%, impact toughness 47.5J/cm)2) The tensile strength is high, and the elongation after fracture and the impact toughness are low.
Example 1
1) The industrial pure iron (original crystal grains are equiaxial and have the size of 25 mu m) is a solid cylindrical sample with the diameter of 99.5mm and the height of 100mm, the sheath material is a hollow cylindrical shape of Q235B carbon structural steel, the inner diameter is 100mm, the outer diameter is 120mm, the height is 100mm, and the industrial pure iron is completely immersed in liquid nitrogen and kept for 30 min;
2) after cooling the industrial pure iron, immediately taking out the industrial pure iron and placing the industrial pure iron into a Q235B carbon structural steel sheath placed on a workbench, simultaneously carrying out unidirectional single-pass high-speed impact on the industrial pure iron and the Q235B carbon structural steel sheath by a 4000kg air hammer, wherein the impact speed is 7.35m/s, and finally obtaining the high-distortion industrial pure iron with the strain capacity of 0.50;
3) removing the sheath of the impact treatment material, processing the impact treatment material into a tensile sample and a Charpy V-notch standard impact sample according to the national standard, putting the tensile sample and the Charpy V-notch standard impact sample into a uniform temperature field heat treatment furnace for heat treatment, wherein the annealing temperature is 580 ℃, the heat preservation time is 1h, and cooling the impact treatment material to room temperature along with the furnace after the heat treatment;
4) the mechanical property experiment is carried out, and the tensile strength is 600MPa, the elongation after fracture is 30 percent, and the impact toughness is 130J/cm2Compared with the raw material (tensile strength 430MPa, elongation after fracture 25.75%, impact toughness 47.5J/cm)2) The tensile strength, the elongation after fracture and the impact toughness of the composite material are higher and are respectively improved by 40.0 percent, 16.5 percent and 173.7 percent.
Example 2
1) The industrial pure iron (original crystal grains are equiaxial and have the size of 25 mu m) is a solid cylindrical sample with the diameter of 99.5mm and the height of 100mm, the sheath material is a Q235B carbon structural steel hollow cylinder, the inner diameter is 100mm, the outer diameter is 120mm, the height is 100mm, and the industrial pure iron sample is completely immersed in liquid nitrogen and kept for 30 min;
2) after cooling, the industrial pure iron is immediately taken out and placed into a Q235B carbon structural steel sheath which is placed on a workbench, and unidirectional single-pass high-speed impact is simultaneously carried out on the industrial pure iron and the Q235B carbon structural steel sheath by a 4000kg air hammer, wherein the impact speed is 7.35m/s, and finally the high-distortion industrial pure iron with the strain capacity of 0.48 is obtained;
3) removing the sheath of the impact treatment material, processing the impact treatment material into a tensile sample and a Charpy V-notch standard impact sample according to the national standard, putting the tensile sample and the Charpy V-notch standard impact sample into a uniform temperature field heat treatment furnace for heat treatment, wherein the annealing temperature is 600 ℃, the heat preservation time is 1h, and cooling the impact treatment material to room temperature along with the furnace after the heat treatment;
4) the mechanical property experiment is carried out, and the tensile strength is 570MPa, the elongation after fracture is 32 percent, and the impact toughness is 120J/cm2Compared with the raw material (tensile strength 430MPa, elongation after fracture 25.75%, impact toughness 47.5J/cm)2) The tensile strength and the impact toughness of the material are high, and the elongation after fracture is high, and are respectively improved by 32.6 percent, 24.3 percent and 152.6 percent.
Embodiment 3
1) The industrial pure iron (original crystal grains are equiaxial and have the size of 25 mu m) is a solid cylindrical sample with the diameter of 99.5mm and the height of 100mm, the sheath material is a Q235B carbon structural steel hollow cylinder, the inner diameter is 100mm, the outer diameter is 120mm, the height is 100mm, and the industrial pure iron sample is completely immersed in liquid nitrogen and kept for 30 min;
2) after cooling, the industrial pure iron is immediately taken out and placed into a Q235B carbon structural steel sheath which is placed on a workbench, and unidirectional single-pass high-speed impact is simultaneously carried out on the industrial pure iron and the Q235B carbon structural steel sheath by a 4000kg air hammer, wherein the impact speed is 7.35m/s, and finally the high-distortion industrial pure iron with the strain capacity of 0.45 is obtained;
3) removing the sheath of the impact treatment material, processing the impact treatment material into a tensile sample and a Charpy V-notch standard impact sample according to the national standard, putting the tensile sample and the Charpy V-notch standard impact sample into a uniform temperature field heat treatment furnace for heat treatment, wherein the annealing temperature is 620 ℃, the heat preservation time is 1h, and cooling the impact treatment material to room temperature along with the furnace after the heat treatment;
4) the mechanical property experiment is carried out, and the tensile strength is 540MPa, the elongation after fracture is 35 percent, and the impact toughness is 150J/cm2Compared with the raw material (tensile strength 430MPa, elongation after fracture 25.75%, impact toughness 47.5J/cm)2) Tensile strength thereofThe impact toughness and the elongation after fracture are respectively improved by 25.5 percent, 25.9 percent and 215.8 percent.
Comparing the comparative example 1 with the comparative example 2, it can be found that the tensile strength, the elongation after fracture and the impact toughness of the industrial pure iron can be regulated and controlled under the action of heat treatment. The main mechanism is fine grain strengthening and defect generation after impact deformation, but the mechanical property is changed due to the reduction of internal defects under the action of heat treatment.
Comparing comparative example 2 and example 1, it can be found that as the annealing temperature is increased to 580 c, deformed industrial pure iron having strength, plasticity and toughness superior to those of the raw material can be obtained. The main mechanism is that the crystal grains are refined in the process of recrystallization, so that the tensile strength is still higher than that of the raw material, the internal stress is completely released in the process of recrystallization, and the lath-shaped cementite is converted into the spherical cementite. Compared with lath-shaped cementite, the spherical cementite has more excellent plasticity and toughness, so that the strength, the plasticity and the impact toughness of the impact deformation industrial pure iron can be simultaneously improved after the annealing at 580 ℃.
Comparing comparative example 4, comparative example 5 and the embodiment, it was found that the recrystallization temperature decreased when the amount of strain was higher because more dislocations were accumulated inside and the distortion energy was higher and the potential energy required for recrystallization decreased.
As can be seen from comparison of cases 4 and 5, the impact deformation causes grain refinement and an increase in tensile strength, and although the recrystallization phenomenon occurs, the lath-shaped cementite is not transformed into a spherical cementite during the recrystallization, resulting in an insignificant increase in plasticity and impact toughness, even lower than that of the raw material.
Comparing comparative example 3 and embodiment example 3, it can be found that when the annealing temperature is increased to 660 ℃, the strength is decreased below the raw material. The main mechanism is that when annealing is carried out at 660 ℃, crystal grains grow, the strengthening effect of fine grains is weakened, the internal stress is completely released, the distortion energy is reduced, and the tensile strength is reduced.
Claims (2)
1. A modification method for simultaneously improving the strength, the plasticity and the toughness of industrial pure iron is characterized by comprising the following steps:
1) cryogenic treatment of industrial pure iron: completely immersing cylindrical industrial pure iron into liquid nitrogen and keeping the temperature at-196 ℃ for more than 30 min;
2) and (3) impact treatment under a large load: immediately putting the cooled industrial pure iron into a normal-temperature carbon steel sheath, and performing unidirectional high-speed impact on the industrial pure iron by a 4000kg air hammer, wherein the impact speed of the unidirectional high-speed impact is 7.35m/s, and the impact frequency is once to obtain the industrial pure iron with the deformation amount of 0.45-0.50;
3) heat treatment in a uniform temperature field: placing the impact treatment material into a uniform temperature field heat treatment furnace for heat treatment, wherein the temperature range is 580-620 ℃, the heat preservation time is 1h, and cooling the impact treatment material to room temperature along with the furnace after heat treatment;
4) removing the sheath: after the carbon steel sheath is removed by heat treatment of the material, the cylindrical industrial pure iron with high strength, high plasticity and high impact toughness can be obtained.
2. The method as claimed in claim 1, wherein the carbon steel sheath is hollow cylindrical and has the same height as the cylindrical industrial pure iron in step 1), and the industrial pure iron is just completely embedded in the sheath core.
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| SU1420059A1 (en) * | 1987-02-16 | 1988-08-30 | Производственное Объединение "Гомсельмаш" | Malleable cast iron |
| JPH03244108A (en) * | 1990-02-22 | 1991-10-30 | Nippon Steel Corp | Manufacture of bulk alpha'' iron nitride with high saturated magnetic flux density |
| CN104690205A (en) * | 2015-01-27 | 2015-06-10 | 浙江大学 | Die and method for preparing large-size three-dimensional full-density nanocrystalline iron body material |
| CN104593572B (en) * | 2014-12-22 | 2016-08-24 | 浙江大学 | A kind of full-compact nanometer crystalline pure iron block materials preparation method |
| CN108754103A (en) * | 2018-06-07 | 2018-11-06 | 浙江大学 | A kind of superfine crystalline pure iron functionally gradient material (FGM) preparation method |
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2019
- 2019-03-12 CN CN201910185980.XA patent/CN109913627B/en active Active
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| SU1420059A1 (en) * | 1987-02-16 | 1988-08-30 | Производственное Объединение "Гомсельмаш" | Malleable cast iron |
| JPH03244108A (en) * | 1990-02-22 | 1991-10-30 | Nippon Steel Corp | Manufacture of bulk alpha'' iron nitride with high saturated magnetic flux density |
| CN104593572B (en) * | 2014-12-22 | 2016-08-24 | 浙江大学 | A kind of full-compact nanometer crystalline pure iron block materials preparation method |
| CN104690205A (en) * | 2015-01-27 | 2015-06-10 | 浙江大学 | Die and method for preparing large-size three-dimensional full-density nanocrystalline iron body material |
| CN108754103A (en) * | 2018-06-07 | 2018-11-06 | 浙江大学 | A kind of superfine crystalline pure iron functionally gradient material (FGM) preparation method |
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