CN114507770B - Twinning induced plasticity steel with stacking fault energy gradient distribution and preparation method thereof - Google Patents
Twinning induced plasticity steel with stacking fault energy gradient distribution and preparation method thereof Download PDFInfo
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- 238000009826 distribution Methods 0.000 title claims abstract description 45
- 229910000937 TWIP steel Inorganic materials 0.000 title claims abstract description 44
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- 238000003756 stirring Methods 0.000 claims abstract description 134
- 238000012545 processing Methods 0.000 claims abstract description 91
- 238000000034 method Methods 0.000 claims abstract description 61
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- 229910000831 Steel Inorganic materials 0.000 claims abstract description 42
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- 230000008569 process Effects 0.000 claims description 27
- 239000000758 substrate Substances 0.000 claims description 27
- 238000010438 heat treatment Methods 0.000 claims description 20
- 239000002826 coolant Substances 0.000 claims description 15
- 238000003466 welding Methods 0.000 claims description 11
- 239000013078 crystal Substances 0.000 claims description 10
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- 229910052751 metal Inorganic materials 0.000 claims description 4
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- 238000004519 manufacturing process Methods 0.000 claims 2
- 238000001514 detection method Methods 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
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- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- 229910001566 austenite Inorganic materials 0.000 description 4
- 230000007547 defect Effects 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 229910000734 martensite Inorganic materials 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
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- 238000009864 tensile test Methods 0.000 description 2
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- 229910018125 Al-Si Inorganic materials 0.000 description 1
- 229910018520 Al—Si Inorganic materials 0.000 description 1
- 229910000617 Mangalloy Inorganic materials 0.000 description 1
- 229910000914 Mn alloy Inorganic materials 0.000 description 1
- 208000016285 Movement disease Diseases 0.000 description 1
- 244000137852 Petrea volubilis Species 0.000 description 1
- 229910000794 TRIP steel Inorganic materials 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
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- C21D11/00—Process control or regulation for heat treatments
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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Abstract
The invention provides a twining induced plasticity steel with a gradient distribution of stacking fault energy and a preparation method thereof, wherein the twining induced plasticity steel is taken as a base material, and the technological parameters for friction stir processing of the base material are determined according to the stacking fault energy regulation and control range of the twining induced plasticity steel; and according to the determined technological parameters, alternately carrying out normal-temperature friction stir processing and rapid cooling friction stir processing on the heat-treated base material according to the pass to obtain the twin induced plasticity steel with the gradient distribution of the stacking fault energy. The twinning induced plasticity steel with the transverse stacking fault energy gradient distribution or the longitudinal stacking fault energy gradient distribution prepared by the method provided by the invention has the advantage that the stacking fault energy of the twinning induced plasticity steel between different friction stir processing passes is graded, so that the purpose of locally increasing the strength and plasticity of the twinning induced plasticity steel is achieved.
Description
Technical Field
The invention belongs to the technical field of steel material processing, and particularly relates to twin induced plasticity steel with stacking fault energy gradient distribution and a preparation method thereof.
Background
The twinning induced plasticity steel is a high manganese alloy austenitic steel, has the characteristics of high strength and high plasticity compared with common steel, belongs to second-generation ultrahigh-strength steel, has the strength of 800-1000MPa, and has the elongation after fracture of 65-85%. The high-manganese twinning induced plasticity steel has high energy absorption capacity, high rigidity and high plasticity, and is often used in the fields of transportation, national defense and military industry, energy exploration and the like. .
In the plastic deformation process, the deformation mechanism of the twinning induced plastic steel is mainly carried out in a twinning mode, because a large number of dislocation and stacking fault defects are generated in austenite grains with low stacking fault energy during deformation, under the action of shear stress, a large number of dislocation generated by a dislocation source is blocked during movement along the sliding direction, dislocation is pinned to cause dislocation accumulation and entanglement, the dislocation is continuously stacked along with the increase of the stress, the stress concentration is larger, and the sliding system is difficult to move in a sliding mode. When the stress concentrates in the twinning direction to reach the critical stress value, twins are formed. As the amount of strain increases, a large amount of high-density deformation twins appear in the material, and secondary twins are generated. The primary twin crystal and the secondary twin crystal cross and cut the matrix alternately, thereby increasing movement disorder, playing a role of refining grains and greatly improving the strength of the twinning induced plastic steel. The twin boundary formed by the high strain region firstly prevents dislocation sliding, other regions with lower strain are caused to deform through sliding until twin is formed, necking is obviously delayed, the material maintains high processing strain rate, high strength is further shown, and a larger extension effect is obtained.
Although dislocation movement makes the twinning induced plasticity steel have high plasticity, the twinning induced plasticity steel reinforced by the dislocation product only has the defects of low yield strength and easy deformation, and limits the application range of the twinning induced plasticity steel. At present, methods for regulating and controlling the tensile strength and the yield strength of the twinning induced plasticity steel mainly comprise alloying and grain refinement. The alloying improvement effect is limited, and meanwhile, the preparation cost of the material is increased, which is unfavorable for resource environmental protection. The grain refinement can better improve the tensile strength and the yield strength of the material, and the existing large plastic deformation technology, such as rolling, equal channel angular extrusion, forging and high-pressure torsion, can effectively refine the grain size, improve the strength of the material, but can greatly reduce the plasticity of the material. Thus, how to improve the strength of twinning induced plasticity steel while maintaining its high plasticity is a problem to be solved.
Disclosure of Invention
The invention aims to overcome the defects of the traditional technology, and simultaneously enriches a preparation method of twinning induced plasticity steel with gradient distribution of stacking fault energy.
In order to achieve the above purpose, the technical scheme of the invention is as follows:
the invention provides a preparation method of twining induced plasticity steel with gradient distribution of stacking fault energy, which takes twining induced plasticity steel as a base material, and determines technological parameters for friction stir processing of the base material according to the stacking fault energy regulation and control range of the twining induced plasticity steel; and according to the determined technological parameters, alternately carrying out normal-temperature friction stir processing and rapid cooling friction stir processing on the heat-treated base material according to the pass to obtain the twin induced plasticity steel with the gradient distribution of the stacking fault energy.
The invention also has the following technical characteristics:
specifically, the stacking fault energy gradient distribution comprises a stacking fault energy transverse gradient distribution and a stacking fault energy longitudinal gradient distribution.
Furthermore, the control range of the stacking fault energy of the twinning induced plasticity steel is 12-35mJ/m 2 。
Further, the rotating speed of the stirring head in the friction stir processing is 100-2000 r/min, and the advancing speed of the stirring head is 50-600 mm/min.
Further, the rapid cooling friction process uses a coolant to cool the substrate, the coolant comprising liquid CO 2 Or liquid C 5 H 12 。
Further, in the friction stir processing, the diameter of the coolant injection pipeline is 1-2 mm, the number of the coolant injection pipelines is 1-4, and the pressure of the coolant bottle is 5-10 Pa.
Further, the heating temperature of the heat treatment is 500-1100 ℃, and the heat preservation time is 10-35 min.
Further, the method specifically comprises the following steps:
step 1, using twinning induced plasticity steel as a base material, and determining a grain size regulation range of the base material according to a fault energy regulation range of the twinning induced plasticity steel; determining the ratio of the rotation speed of the stirring head to the advancing speed of the stirring head in the stirring friction processing process according to the obtained grain size regulation range, wherein the regulation range of the stacking fault energy of the twinning induced plasticity steel is 12-35mJ/m 2 ；
Step 2, performing heat treatment on the substrate, and regulating the grain size of the substrate to be higher than the maximum value of the grain size regulating range determined in the step 1, so as to obtain a heat treated substrate;
and 3, determining technological parameters of friction stir processing according to the ratio of the rotation speed of the stirring head to the advancing speed of the stirring head in the friction stir processing process determined in the step 1, and then alternately performing normal-temperature friction stir processing and rapid cooling friction stir processing on the heat-treated base material according to the pass to obtain the twin induced plasticity steel with the gradient distribution of the stacking fault energy.
Further, the grain size regulation range described in step 1 determines the ratio of the rotation speed of the stirring head to the advancing speed of the stirring head in the friction stir processing process, and is realized by the following formula:
wherein:
V rotation The rotation speed of the stirring head is rap/min; v (V) Welding process The unit is mm/min for the advancing speed of the stirring head; d is the diameter between axes, and the unit is mm; t is the temperature of friction stir processing, and the unit is DEG C; v (V) 0.5 Is the maximum recrystallization rate of metal grains, and has the unit of s -1 The method comprises the steps of carrying out a first treatment on the surface of the L is the width of the friction stir processing area, and the unit is mm; ρ is the grain size in μm; n is the number of crystal grains in the width direction in the friction stir processing area, and n is a positive integer; f is the coefficient of friction; t is the friction stir processing timeThe unit is s.
The invention relates to a preparation method of a twinning induced plasticity steel with the stacking fault energy gradient distribution, which is the twinning induced plasticity steel with the stacking fault energy gradient distribution;
the twining induced plasticity steel with the gradient distribution of the stacking fault energy comprises the steps of taking the twining induced plasticity steel as a base material, and determining the technological parameters for friction stir processing of the base material according to the stacking fault energy regulation and control range of the twining induced plasticity steel; and (3) according to the determined technological parameters, alternately carrying out normal-temperature friction stir processing and rapid cooling friction stir processing on the heat-treated base material according to the pass.
Compared with the prior art, the invention has the following technical effects:
(1) The transverse stacking fault energy gradient distribution or the longitudinal stacking fault energy gradient distribution of the twinning induced plasticity steel prepared by the method of the invention has the stacking fault energy of 12-35mJ/m 2 In the range, the prepared twin induced plasticity steel has gradient of the stacking fault energy among different friction stir processing passes, and the stacking fault energy in a welding zone, a mechanical heat affected zone and a heat affected zone of each friction stir processing pass also has gradient, so that the purpose of locally increasing the strength and plasticity of the twin induced plasticity steel is achieved, and the prepared twin induced plasticity steel with the gradient distribution of the stacking fault energy is more suitable for being used under the condition of complex working conditions.
(2) The capability of the twinning induced plasticity steel with the gradient distribution of the stacking fault energy prepared by the method for resisting local shrinkage is improved, meanwhile, the higher processing conversion rate is maintained, and the strong plastic product of the material is effectively improved.
(3) The method provided by the invention has strong regulation and control capability, does not limit the size of the material, is environment-friendly, can be directly applied to metastable state material modification and the like, and has strong popularization and application values.
Drawings
FIG. 1 is a schematic diagram of the process of the present invention for producing a plastic steel by transverse stacking fault energy gradient twinning induction;
FIG. 2 is a graph of the grain size of the substrate after heat treatment in example 1.
The present invention will be described in detail with reference to the following specific embodiments.
Detailed Description
Hereinafter, only certain exemplary embodiments are briefly described. As will be recognized by those skilled in the art, the described embodiments may be modified in various different ways, including by adding, deleting, modifying, etc., without departing from the spirit or scope of the invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not as restrictive.
The following describes specific embodiments of the present invention in detail with reference to the drawings. It should be understood that the detailed description and specific examples, while indicating and illustrating the invention, are not intended to limit the invention.
The following terms of art in the present invention are explained:
the stacking fault energy gradient distribution: meaning that the material exhibits a gradient distribution in the stacking fault energy in a certain direction.
Twinning induced plasticity steel: the high strength and toughness of the alloy come from the formation of twin crystals in the deformation process, and the product of the tensile strength (Rm) and the elongation (A) is more than 50000MPa percent, which is twice that of the TRIP steel with high strength and toughness. The main component of the twinning induced plasticity steel is Fe-Mn-C or Fe-Mn-Al-Si. The thickness of the twinning-induced plasticity steel base material is usually 1 to 5mm.
Transverse gradient distribution: it means that the stacking fault energy is distributed in a gradient along the direction perpendicular to the rolling direction.
Longitudinal gradient distribution: refers to the gradient distribution of the stacking fault energy along the rolling direction.
It should be noted that, only plasticity can be ensured by single twin deformation of the steel, high strength cannot be ensured, and two methods exist for improving strength, one is to reduce the stacking fault energy to 12-18 mJ/m 2 Within the phase transition and twinning mechanism of (a); the other is 18-35 mJ/m 2 The error energy is reduced in the range of (1) and the strength is improved by delaying the twin opening, so that the regulation and control range of the error energy in the scheme of the invention is set to be 12-35mJ/m 2 。
The method for alternately performing normal-temperature friction stir processing and rapid cooling friction stir processing on the heat-treated base material according to the pass in the invention specifically comprises the following steps: and carrying out normal-temperature friction stir processing in the former pass, and carrying out rapid cooling friction stir processing on the substrate in the latter pass under the condition of spraying a coolant on the surface of the substrate. The aim of alternately carrying out normal-temperature friction stir processing and rapid cooling friction stir processing according to the pass is as follows: the gradient grain size is formed, and when the friction stir welding is assisted by rapid cooling, the rapid cooling can reduce the heat input, improve the cooling speed and achieve the refinement effect of 1-2 mu m of the grains.
The heat-insulating friction stir processing and the rapid cooling friction stir processing can be alternately performed on the heat-treated base material according to the working condition requirement, namely, the heat-insulating friction stir processing is performed on the base material after the former pass is heated to a certain temperature by the heating device, and the rapid cooling friction stir processing is performed on the latter pass under the condition that the coolant is sprayed to the surface of the base material.
The rapid cooling friction stir processing technique can regulate and control the grain size and the local dislocation density.
Specifically, in the heat treatment process, when the base material is heated at high temperature, dislocation inside the crystal grains is annihilated, and crystal boundaries migrate and are mutually swallowed under the action of heat activation energy, so that the growth of the crystal grains is realized; the grains may grow long enough for a sufficient holding time that, upon cooling, dislocations accumulate at the grain boundaries, slowing down grain boundary movement to prevent grain growth, and thus the grain size of the substrate may be altered by heat treatment.
The raw materials in the present invention are all commercially available unless otherwise specified.
Example 1
The embodiment provides a preparation method of twin induced plasticity steel with the gradient distribution of the stacking fault energy, which takes the twin induced plasticity steel as a base material, and determines the technological parameters for friction stir processing of the base material according to the stacking fault energy regulation and control range of the twin induced plasticity steel; and according to the determined technological parameters, alternately carrying out normal-temperature friction stir processing and rapid cooling friction stir processing on the heat-treated base material according to the pass to obtain the twin induced plasticity steel with the gradient distribution of the stacking fault energy.
The method specifically comprises the following steps:
step 1, using twinning induced plasticity steel as a base material, determining the adjustment and control range of the stacking fault energy of the base material according to the deformation mechanism and the stacking fault energy classification of the twinning induced plasticity steel, and further determining the adjustment and control range of the grain size of the base material; determining the ratio of the rotation speed of the stirring head to the advancing speed of the stirring head in the stirring friction processing process according to the obtained grain size regulation range;
in this embodiment, with twinning induced plasticity steel as a base material, first, a substrate with chemical composition percentages of 0.6% of C, 0.1% of Si, 17% of Mn, 1.5% of Al and 80.8% of Fe, and dimensions of 210mm×96mm×2mm is selected, and then the substrate is pretreated, specifically: polishing the surface of the metal plate by using sand paper before processing to ensure that the surface roughness Ra is less than or equal to 10 mu m, cleaning the polished surface by using acetone, removing greasy dirt, oxide and impurities on the surface of the substrate, and drying;
the (111) plane molar surface density of the substrate obtained by referring to the data was 2.94×10 5 mol/m 2 The driving force at the time of austenite to martensite transformation was 2.295 ×10 5 mJ/mol; the grain size of the substrate is measured by experiments to 5 mu m, the values are brought into the existing Olson-Cohen model, and the stacking fault energy of the substrate is calculated to be 35mJ/m 2 According to the deformation mechanism and the stacking fault energy classification of the twinning induced plasticity steel, the base plate belongs to 18-35 mJ/m 2 Is a twin deformation mechanism of (a). Two ways to increase the strength are: 1. the stacking fault energy is reduced to 12-18 mJ/m 2 Within the phase transition and twinning mechanism of (a); 2. at 18-35 mJ/m 2 The stacking fault energy is reduced in the range of (2), and the strength is improved by delaying the twin opening. Therefore, the regulation and control range of the substrate stacking fault energy is 12-35mJ/m 2 The method comprises the steps of carrying out a first treatment on the surface of the Then the determined substrate stacking fault energy regulating and controlling range is 12-35mJ/m 2 Carrying out the method into the existing Olson-Cohen model, and calculating the grain size regulation range of the base material to be 5-30 mu m;
in the Olson-Cohen model, the relationship of the stacking fault energy and grain size is as follows:
Γ＝2ρ(ΔG γ→ε +170.06exp(-d/18.55))+2σ γ/ε
wherein Γ is the stacking fault energy in mJ/m 2 ρ is the (111) crystal plane of the substrateMolar surface Density in mol/m 2 ，ΔG γ→ε The unit of the driving force is mJ/mol, the unit of d is the grain size, and the unit is mu m and sigma when austenite is transformed into epsilon martensite γ/ε The unit is mJ/mol for austenite and martensite interfacial energy.
Substituting a threshold value of the grain size regulating range into the following formula according to the obtained grain size regulating range, and determining the ratio of the rotation speed of the stirring head to the advancing speed of the stirring head in the stirring friction processing process;
wherein:
V rotation The unit is r/min for the rotation speed of the stirring head; v (V) Welding process The unit is mm/min for the advancing speed of the stirring head; d is the diameter between axes, and the unit is mm; t is the temperature of friction stir processing, and the unit is DEG C; v (V) 0.5 Is the maximum recrystallization rate of metal grains, and has the unit of s -1 The method comprises the steps of carrying out a first treatment on the surface of the L is the width of the friction stir processing area, and the unit is mm; ρ is the grain size in μm; n is the number of crystal grains in the width direction in the friction stir processing area, and n is a positive integer; f is the coefficient of friction; t is the time of friction stir processing in s.
In this embodiment: under the condition that the grain refinement degree is 5-30 mu m, calculating the ratio V of the rotation speed of the stirring head to the advancing speed of the stirring head in the stirring friction processing process Rotation /V Welding process ＝1～4.5。
Step 2, heat treatment is carried out on the base material, in the heat treatment process, the base material is heated to 1000 ℃ firstly, the heat is preserved for 30min, and then air cooling is carried out; regulating the grain size of the base material to be higher than the maximum value of the grain size regulating range determined in the step 1, so as to obtain the grain size of the base material after heat treatment to be 30 mu m;
and 3, determining technological parameters of friction stir processing according to the ratio of the rotation speed of the stirring head to the advancing speed of the stirring head in the friction stir processing process determined in the step 1, and then alternately performing normal-temperature friction stir processing and rapid cooling friction stir processing on the heat-treated base material according to the pass to obtain the twin induced plasticity steel with the gradient distribution of the stacking fault energy.
The friction stir processing apparatus used in the present embodiment includes: the shaft shoulder is cylindrical, and the diameter of the shaft shoulder is 12mm; the stirring pin is in a truncated cone shape. The diameter of the root of the truncated cone-shaped stirring pin is 5mm, the diameter of the top of the truncated cone-shaped stirring pin is 4mm, and the length of the truncated cone-shaped stirring pin is 1.5mm.
In the friction stir processing, the diameter of the coolant injection pipeline is 1.5mm, the number of the coolant injection pipelines is 2, the pressure of the coolant bottle is 8Pa, and liquid carbon dioxide is used as the quick cooling liquid.
As shown in the figure, the S-type friction stir is used in the friction stir processing, that is, after one pass of processing is completed, the friction stir processing of the next pass is performed by only laterally shifting without resetting. The first pass adopts normal temperature friction stir processing: the rotation speed of the stirring head is 400r/min, and the advancing speed of the stirring head is 50mm/min. The second pass adopts quick cooling friction stir processing: the rotation speed of the stirring head is 400r/min, and the advancing speed of the stirring head is 50mm/min. And adopting normal-temperature friction stir processing for the third time: the rotation speed of the stirring head is 400r/min, and the advancing speed of the stirring head is 200mm/min. And the fourth pass adopts rapid cooling friction stir processing: the rotation speed of the stirring head is 400r/min, and the advancing speed of the stirring head is 200mm/min. Finally preparing the twinning induced plasticity steel plate with the transverse gradient distribution of the fault energy.
Experimental results:
the first-pass local tensile test sample and the second-pass local tensile test sample, which are both 4mm×2mm in size, are cut from the produced twin induced plasticity steel plate with the stacking fault energy laterally gradient distribution, and the performance test is performed respectively, and the results are shown in the following table:
| substrate treatment process | Heat treatment of | 1 pass | 2 passes of | 3 passes of | 4 passes of |
| Grain size (mum) | 35 | 17 | 10 | 9 | 6 |
| The energy of the fault (mJ/m) 2 ) | 26 | 28.18 | 30.01 | 30.33 | 31.40 |
Mechanical property detection results:
the experimental results show that: the mechanical properties of the steel sheet subjected to simple heat treatment are poor without friction stir processing. The grain size of the first pass of the prepared twin induced plasticity steel plate with the transverse gradient distribution of the stacking fault energy is 17 mu m, and the stacking fault energy is 28.18mJ/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The grain size of the second pass is 10 μm, and the stacking fault energy is 30.01mJ/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The grain size of the third pass is 9 μm, and the stacking fault energy is 30.33mJ/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The grain size in the fourth pass was 6 μm,the stacking fault energy is 31.40mJ/m 2 。
Because the first pass adopts the processing parameter of 400r/min of rotational speed, 50mm/min of welding speed and the ratio of rotational speed to welding speed is not between 1 and 4.5, overheat phenomenon occurs in the friction stir processing process, and the tensile strength, the yield strength and the elongation are poor. Under the same parameters (the rotating speed of the stirring head is 400r/min, the advancing speed of the stirring head is 200 mm/min), the third time of plasticity after normal-temperature friction stir processing is low, and the strength is high; the fourth pass after the rapid cooling friction stir processing has low strength and high plasticity. The whole plate realizes the transverse gradient of grain size and stacking fault energy along the transverse direction, and the performance also achieves the gradient effect.
Example 2
The substrate of the embodiment is the same as that of the embodiment 1, wherein the first pass adopts the rotating speed of 400rpm/min and the welding speed of 260mm/min; the second pass adopts the rotating speed of 400rpm/min and the welding speed of 50mm/min; this comparative example did not have a heat treatment to regulate grain size. The effect of the heat treatment step and the importance of the parameter proportion are shown by comparing the grain size, the stacking fault energy, the dislocation density distribution and the mechanical property of different partitions of each pass.
Detection results of different partitions in the first pass:
detection results of different partitions in the second pass:
| HAZ | TMAZ | SZ | |
| grain size | 4.2 | 4.5 | 3.7 |
| Energy of stacking fault | 29.9 | 29 | 33 |
| Dislocation density | 4.1×10 13 | 4.8×10 13 | 2.5×10 14 |
Mechanical property detection results:
the grain sizes of the different subareas of the first pass and the second pass and the stacking fault energy and dislocation density are changed in a gradient way. Comparing the mechanical properties of the first pass and the second pass to obtain that the first pass performance of which the rotating speed and the welding speed ratio belong to the range of the invention is far higher than that of the second pass which is not in the range of the parameters of the invention; comparing the properties of the second pass with those of the first pass of example 1, it was found that the first pass of example 1, which passed the heat treatment step of the present invention, had a higher plasticity than the second pass of this example.
Example 3
This embodiment differs from embodiment 1 in that: a commercially available substrate with a thickness of 3mm is used, and the chemical components are Si:4.3%, mn:30.7%, fe:63.5%, al:1.8%.
Determining the grain size of the base material to be 15 mu m by adopting electron back scattering detection, determining the grain size regulation range of the base material to be 5-12 mu m, substituting the threshold value of the grain size regulation range to be 5-12 mu m, namely 5 and 12, into the formula of the invention, and determining the ratio V of the rotation speed of the stirring head to the advancing speed of the stirring head in the stirring friction processing process Rotation /V Welding process ＝1.5～3。
The parameters of friction stir processing were selected as in example 1, and since the substrate grain size was higher than the maximum value of the grain size control range of the substrate, the heat treatment process was not required to enlarge the grain size in this example.
| Number of processes | 1 | 2 | 3 | 4 |
| Grain size (mum) | 8 | 6 | 7 | 5 |
| The energy of the fault (mJ/m) 2 ) | 16.3 | 17.0 | 16.6 | 17.44 |
Mechanical property detection results:
the experimental results show that: the longitudinal gradient twinning induced plasticity steel prepared in the embodiment has the grain size of 8 mu m and the stacking fault energy of 16.3mJ/m in the first pass 2 The method comprises the steps of carrying out a first treatment on the surface of the The grain size of the second pass is 6 μm, and the stacking fault energy is 17mJ/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The grain size of the third pass is 7 μm, and the stacking fault energy is 16.6mJ/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The grain size of the fourth pass is 5 μm, and the stacking fault energy is 17.44mJ/m 2 The method comprises the steps of carrying out a first treatment on the surface of the The strength of the first pass after normal temperature friction stir processing is low; the second pass after the rapid cooling friction stir processing has high strength; the whole plate realizes the gradient of grain size and stacking fault energy along the transverse direction, and the performance also achieves the gradient effect.
Comparative example 1
This comparative example differs from example 1 in that: this comparative example uses a commercially available twinning induced plasticity steel as in example 1, but was not processed by the method of the present invention.
Mechanical property detection results:
experimental results: compared with the example 1, the tensile strength and the yield strength of the commercial similar twinning induced plasticity steel which is not processed by the method are lower than those of the gradient twinning induced plasticity steel prepared by the method.
Comparative example 2
This comparative example differs from example 3 in that: the comparative example used the substrate used in example 3, but was not subjected to friction stir processing by the method of the present invention.
Mechanical property detection results:
experimental results: compared with example 3, the tensile strength, yield strength and plasticity of the twinning induced plasticity steel which is not processed by the method are lower than those of the gradient twinning induced plasticity steel prepared by the method.
The twinning induced plasticity steel with the gradient distribution of the stacking fault energy prepared by the method is suitable for the positions with large difference of the strong plasticity requirements of the automobile body.
The preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the specific details of the above embodiments, and various simple modifications can be made to the technical solution of the present invention within the scope of the technical concept of the present invention, and all the simple modifications belong to the protection scope of the present invention.
[1] Chen Xiguo, zhang Enming, plum eastern, mining machinery ZGMn13 high manganese steel heat treatment process research [ J ]. South agricultural machinery, 2021, 52 (12): 28-30+39.
[2]X.C.Liu,Y.F.Sun,T.Nagira,H.Fujii,Investigation of temperature dependent microstructure evolution of pure iron during friction stir welding using liquid CO2 rapid cooling,MaterialsCharacterization,Volume 137,2018,24-38。
Claims (8)
1. The preparation method of the twining induced plasticity steel with the gradient distribution of the stacking fault energy is characterized in that the twining induced plasticity steel is taken as a base material, and the technological parameters for friction stir processing of the base material are determined according to the stacking fault energy regulation and control range of the twining induced plasticity steel; according to the determined technological parameters, alternately carrying out normal-temperature friction stir processing and rapid cooling friction stir processing on the heat-treated base material according to the pass to obtain the twinning induced plasticity steel with the gradient distribution of the stacking fault energy;
the method specifically comprises the following steps:
step 1, using twinning induced plasticity steel as a base material, and according to the twinning induced plasticity steelDetermining a grain size control range of the substrate; determining the ratio of the rotation speed of the stirring head to the advancing speed of the stirring head in the stirring friction processing process according to the obtained grain size regulation range, wherein the adjustment range of the stacking fault energy of the twinning induced plasticity steel is 12-35mJ/m 2 ；
Step 2, performing heat treatment on the substrate, and regulating the grain size of the substrate to be higher than the maximum value of the grain size regulating range determined in the step 1, so as to obtain a heat treated substrate;
step 3, determining technological parameters of friction stir processing according to the ratio of the rotation speed of the stirring head to the advancing speed of the stirring head in the friction stir processing process determined in the step 1, and then alternately performing normal-temperature friction stir processing and rapid cooling friction stir processing on the heat-treated base material according to the pass to obtain the twin induced plasticity steel with the stacking fault energy gradient distribution;
the grain size regulation and control range in the step 1 determines the ratio of the rotation speed of the stirring head to the advancing speed of the stirring head in the friction stir processing process, and is realized by the following formula:
wherein:
V rotation The rotation speed of the stirring head is rap/min; v (V) Welding process The unit is mm/min for the advancing speed of the stirring head; d is the diameter between axes, and the unit is mm; t is the temperature of friction stir processing, and the unit is DEG C; v (V) 0.5 Is the maximum recrystallization rate of metal grains, and has the unit of s -1 The method comprises the steps of carrying out a first treatment on the surface of the L is the width of the friction stir processing area, and the unit is mm; ρ is the grain size in μm; n is the number of crystal grains in the width direction in the friction stir processing area, and n is a positive integer; f is the coefficient of friction; t is the time of friction stir processing in s.
2. The method of producing a twinning-induced plasticity steel having a stacking fault energy gradient profile according to claim 1, wherein the stacking fault energy gradient profile includes a stacking fault energy transverse gradient profile and a stacking fault energy longitudinal gradient profile.
3. The method for preparing the twining-induced plasticity steel with the gradient distribution of the stacking fault energy according to claim 1, wherein the stacking fault energy regulation range of the twining-induced plasticity steel is 12-35mJ/m 2 。
4. The method for preparing the twinning induced plasticity steel with the gradient distribution of the stacking fault energy according to claim 1, wherein the rotating speed of a stirring head in stirring friction processing is 100-2000 r/min, and the advancing speed of the stirring head is 50-600 mm/min.
5. The method for producing a twinning induced plasticity steel having a gradient distribution of stacking fault energy according to claim 1, wherein the substrate is cooled by a coolant during the rapid cooling friction stir processing, the coolant comprising liquid CO 2 Or liquid C 5 H 12 。
6. The method for producing a twinning induced plasticity steel with a gradient distribution of stacking fault energy according to claim 1, wherein the diameter of the coolant injection pipes is 1-2 mm, the number of the coolant injection pipes is 1-4, and the pressure of the coolant bottle is 5-10 pa in the friction stir processing.
7. The method for preparing the twinning induced plasticity steel with the gradient distribution of the stacking fault energy according to claim 1, wherein the heating temperature of the heat treatment is 500-1100 ℃, and the heat preservation time is 10-35 min.
8. The twining-induced plasticity steel with the stacking fault energy gradient distribution, which is prepared by the preparation method of the twining-induced plasticity steel with the stacking fault energy gradient distribution, according to any one of claims 1-7, is characterized in that the twining-induced plasticity steel with the stacking fault energy gradient distribution comprises a twining-induced plasticity steel as a base material, and technological parameters for friction stir processing of the base material are determined according to a stacking fault energy regulation range of the twining-induced plasticity steel; and (3) according to the determined technological parameters, alternately carrying out normal-temperature friction stir processing and rapid cooling friction stir processing on the heat-treated base material according to the pass.
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