CN114505427A - Thermal mechanical densification device for brittle high-entropy alloy hot-pressing sintering body and using method thereof - Google Patents
Thermal mechanical densification device for brittle high-entropy alloy hot-pressing sintering body and using method thereof Download PDFInfo
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- CN114505427A CN114505427A CN202210210235.8A CN202210210235A CN114505427A CN 114505427 A CN114505427 A CN 114505427A CN 202210210235 A CN202210210235 A CN 202210210235A CN 114505427 A CN114505427 A CN 114505427A
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- 239000000956 alloy Substances 0.000 title claims abstract description 90
- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 88
- 238000007731 hot pressing Methods 0.000 title claims abstract description 40
- 238000000280 densification Methods 0.000 title claims abstract description 38
- 238000000034 method Methods 0.000 title claims abstract description 37
- 238000005245 sintering Methods 0.000 title claims abstract description 15
- 238000010438 heat treatment Methods 0.000 claims abstract description 50
- 230000000930 thermomechanical effect Effects 0.000 claims abstract description 25
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 8
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 4
- 229910052786 argon Inorganic materials 0.000 claims description 4
- 230000006835 compression Effects 0.000 claims description 4
- 238000007906 compression Methods 0.000 claims description 4
- 229910002804 graphite Inorganic materials 0.000 claims description 4
- 239000010439 graphite Substances 0.000 claims description 4
- 238000012546 transfer Methods 0.000 claims description 4
- 238000005336 cracking Methods 0.000 abstract description 9
- 239000011148 porous material Substances 0.000 abstract description 5
- 238000012545 processing Methods 0.000 abstract description 4
- 229920001169 thermoplastic Polymers 0.000 abstract description 4
- 239000004416 thermosoftening plastic Substances 0.000 abstract description 4
- 238000012360 testing method Methods 0.000 description 9
- 238000005452 bending Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 238000005242 forging Methods 0.000 description 2
- 238000005098 hot rolling Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000003672 processing method Methods 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 238000001192 hot extrusion Methods 0.000 description 1
- 238000004663 powder metallurgy Methods 0.000 description 1
- 238000004886 process control Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J1/00—Preparing metal stock or similar ancillary operations prior, during or post forging, e.g. heating or cooling
- B21J1/02—Preliminary treatment of metal stock without particular shaping, e.g. salvaging segregated zones, forging or pressing in the rough
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J1/00—Preparing metal stock or similar ancillary operations prior, during or post forging, e.g. heating or cooling
- B21J1/06—Heating or cooling methods or arrangements specially adapted for performing forging or pressing operations
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J13/00—Details of machines for forging, pressing, or hammering
- B21J13/02—Dies or mountings therefor
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J3/00—Lubricating during forging or pressing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J9/00—Forging presses
- B21J9/02—Special design or construction
- B21J9/06—Swaging presses; Upsetting presses
- B21J9/08—Swaging presses; Upsetting presses equipped with devices for heating the work-piece
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Abstract
A thermo-mechanical densification device for a brittle high-entropy alloy hot-pressing sintering body and a using method thereof relate to a thermo-mechanical densification device for an alloy hot-pressing sintering body and a using method thereof. The invention aims to solve the technical problems that the compact pair of the brittle high-entropy alloy hot-pressing sintered body is relatively low, and the sintered body is easy to generate unstable cracking in the thermal mechanical processing and compacting process. The closed die cavity consisting of the compact male die, the compact female die and the compact ejector rod realizes that a three-dimensional pressure stress state is quickly established in the medium alloy under the action of the die cavity in the thermal mechanical deformation process of small-deformation upsetting, and the instability and cracking are avoided. The low-plasticity high-entropy alloy realizes pore closure through thermoplastic deformation flow by proper blank temperature and heating of the die, and can effectively improve the density of the brittle high-entropy alloy hot-pressing sintered body.
Description
Technical Field
The invention relates to a thermomechanical densification device for an alloy hot-pressing sintering body and a using method thereof.
Background
The block high-entropy alloy obtained by adopting a sintering process through a powder metallurgy path has the advantages of fine structure, high strength and the like. The high-entropy alloy with the body-centered cubic or close-packed hexagonal as the main phase structure has high strength and low plasticity (high brittleness). The alloy powder with high hardness and low plasticity has small plastic deformation degree in the unidirectional pressure sintering process, and is more difficult to compact compared with plastic powder. Meanwhile, the strength of the sintering mold is limited, and the unidirectional pressure is usually not more than 70 MPa. The sintered bulk alloy inevitably has some porosity. The existence of pores causes the compactness of a microstructure to be limited, and the mechanical property of the sintered alloy is reduced to a certain extent.
The hot-mechanical processing of the hot-pressed sintered body is a commonly used technique for improving the density of the alloy sintered body. Thermomechanical working typically includes unidirectional hot upsetting, hot rolling, multidirectional hot forging, hot extrusion, and the like. During hot working, the pores inside the sintered body are closed by thermoplastic deformation. However, in the case of a high-entropy alloy having high strength and low plasticity (high brittleness), when it is subjected to thermomechanical working by a method such as unidirectional hot upsetting, hot rolling, or multidirectional hot forging, the stress state inside the alloy is not a three-dimensional compressive stress state, and the alloy is very likely to undergo unstable cracking during working. The amount of deformation in thermomechanical working is also difficult to control.
Therefore, when the high-strength, low-plasticity (brittleness) and high-entropy alloy hot-pressed sintered body is subjected to thermomechanical densification, the control of alloy instability cracking is the key point of research and innovation of the professional. The current thermomechanical densification of such alloys requires reasonable mold apparatus and process control to achieve a sintered body in a state of three-dimensional compressive stress during densification to prevent buckling cracking. Meanwhile, the reasonable die device and the reasonable process method can improve the efficiency and controllability of the densification process.
Disclosure of Invention
The invention provides a hot-pressing sintered body hot-pressing device for a brittle high-entropy alloy and a using method thereof, aiming at solving the technical problems that the density of the current hot-pressing sintered body for the brittle high-entropy alloy is relatively low, the material is easy to unstably crack in the process of compacting the high-strength low-plasticity high-entropy alloy by the current hot-pressing method, and the compacting process is difficult to control.
The invention relates to a hot mechanical compacting device for a brittle high-entropy alloy hot-pressing sintering body, which consists of an upper template 1, a compact male die fixing block 2, a compact male die 3, a male die heating sleeve 4, a compact female die 5, a female die sleeve 6, a lower template 7, a compact ejector rod 8 and a die sleeve heating sleeve 10;
the compact male die 3 is formed by coaxially fixing four cylinders from top to bottom, and the diameters of the four cylinders are gradually reduced from top to bottom; the four cylinders are a first cylinder 3-1, a second cylinder 3-2, a third cylinder 3-3 and a fourth cylinder 3-4 from top to bottom in sequence; the third cylinder 3-3 improves the rigidity of the compact male die 3 and prevents unstable bending in the compact pressurizing process;
the center of the compact male die fixing block 2 is a through hole, the inner wall of the through hole is of a stepped structure, and the stepped structure is matched with a first cylinder 3-1 and a second cylinder 3-2 of the compact male die 3; a first cylinder 3-1 and a second cylinder 3-2 of the compact male die 3 are arranged in a stepped structure of the compact male die fixing block 2, and the compact male die fixing block 2 is fixed on the lower surface of the upper die plate 1 through a plurality of bolts; the third cylinder 3-3 and the fourth cylinder 3-4 of the compact male die 3 are both arranged below the compact male die fixing block 2; a male die heating sleeve 4 is fixed on the outer wall of a third cylinder 3-3 of the compact male die 3, and the male die heating sleeve 4 is connected with an external power supply; the upper end surface of the upper template 1 is connected with a movable cross beam of the press machine;
the outer wall of the compact female die 5 is of a round table-shaped structure, the diameter of the upper end of the compact female die 5 is smaller, the center of the compact female die 5 is provided with a through hole, the inner wall of the through hole is of a stepped structure, and the diameter of the upper end of the stepped structure is smaller; the shape of the inner cavity of the female die sleeve 6 is matched with the outer wall of the compact female die 5, the female die sleeve 6 is tightly sleeved on the outer wall of the compact female die 5, a die sleeve heating sleeve 10 is fixed on the side wall of the female die sleeve 6, and the die sleeve heating sleeve 10 is connected with an external power supply;
a circular groove 7-2 is formed in the center of the lower template 7, an annular groove 7-1 is formed in the outer ring of the circular groove 7-2, and the upper surface of the annular groove 7-1 is lower than the upper surface of the circular groove 7-2; a plurality of bolt holes 7-3 are uniformly formed in the outer edge of the circular groove 7-2; the bottom of the female die sleeve 6 is fixed in the circular groove 7-2 through a plurality of bolts; the lower end face of the lower template 7 is connected with a lower cross beam of the press;
the compact ejector rod 8 is of a stepped structure, the diameter of the upper end of the compact ejector rod is smaller, and the lower end of the compact ejector rod is used for improving the rigidity of the compact ejector rod 8 and preventing unstable bending in the process of compact pressurization; the compact ejector rod 8 is arranged in a central through hole of the compact female die 5 and is in sliding connection with the compact female die; the bottom of the compact ejector rod 8 is placed on the ejection end face of an ejection cylinder of the press; a fourth cylinder 3-4 of the compact male die 3 is arranged in a central through hole of the compact female die 5, a male die heating sleeve 4 is arranged above the compact female die 5, and a compact ejector rod 8 is positioned below the compact male die 3; the upper end of the compact mandril 8, the lower end surface of the compact convex die 3 and the side wall of the central through hole of the compact concave die 5 form a cavity 9.
The use method of the thermo-mechanical densification device for the brittle high-entropy alloy hot-pressing sintered body comprises the following steps:
firstly, putting the high-entropy alloy hot-pressing sintered body 11 into an atmosphere resistance furnace protected by argon, and preserving heat for 1-1.2 h at 900-1050 ℃; meanwhile, the mold is heated by the male mold heating sleeve 4 and the mold sleeve heating sleeve 10, and when the temperature of the cavity 9 reaches 150 ℃, graphite is uniformly sprayed on the surface of the cavity 9, so that the purpose of reducing the friction on the surface of the mold and facilitating ejection after densification is finished is achieved; then, the temperature of the device is continuously increased to ensure that the temperatures of the upper end surfaces of the compact female die 5 and the movable compact ejector rod 8 reach 450-500 ℃, the temperature of the compact male die 3 reaches 400-450 ℃, and the temperature is detected by using a general thermocouple;
secondly, starting a press machine to control the compact male die 3 to move upwards, transferring the high-entropy alloy sintered body 11 heated in the step one into the cavity 9, and controlling the transfer time to be 5-8 s; a gap is reserved between the side wall of the high-entropy alloy hot-pressing sintered body 11 and the inner wall of the compact female die 5;
thirdly, controlling the compacting male die 3 to move downwards through a press machine to pressurize the high-entropy alloy sintered body 11 to a height reduced by compression of the high-entropy alloy hot-pressed sintered body, wherein the height is 15% -20% of the original height, and then maintaining the pressure for 50 s;
fourthly, after the pressure maintaining is finished, controlling the compact male die 3 to move upwards to open the die;
and fifthly, starting a press ejection cylinder to control the compact ejector rod 8 to ascend, ejecting the compact high-entropy alloy block 11 out of the compact female die 5, and taking out.
The device is suitable for high-entropy alloy hot-pressing sintered bodies of systems such as AlCoCrCuFeNi, AlCoCrCuNi, AlCoCrFeNi, AlCoCrFeMnNi, AlCrCuFeNi and the like which mainly use a body-centered cubic structure phase.
Compared with the prior art, the invention has the following beneficial effects:
1. according to the invention, through a thermal mechanical processing method, the pores of the brittle high-entropy alloy hot-pressed sintered body are closed through thermoplastic deformation, so that the density and the mechanical property are effectively improved;
2. the invention effectively avoids the unstable cracking of the brittle high-entropy alloy hot-pressing sintering body in the thermal mechanical processing process through the action of three-dimensional compressive stress of the die cavity;
3. according to the invention, after densification is finished, the densified alloy material is conveniently taken out through the ejection mechanism, so that the efficiency of the densification process is improved.
Drawings
FIG. 1 is a schematic view of a hot-pressed sintered compact thermomechanical densification apparatus of a brittle high-entropy alloy according to a first embodiment;
FIG. 2 is an enlarged view of a portion of area A of FIG. 1;
FIG. 3 is a top view of the lower platen 7 of FIG. 1;
FIG. 4 is a schematic view of the compacting punch 3 of FIG. 1;
FIG. 5 is a schematic view of the compaction die 5 of FIG. 1;
FIG. 6 is a schematic view of the thermo-mechanical densification apparatus for the hot-pressed sintered body of the brittle high-entropy alloy after step two of the seventh embodiment is completed;
FIG. 7 is an enlarged view of a portion of area B of FIG. 6;
FIG. 8 is an enlarged partial view of the thermo-mechanical densification apparatus of the hot-pressed sintered body of brittle high-entropy alloy at the same location as in FIG. 7 after step three of the seventh embodiment;
fig. 9 is a schematic view of the thermo-mechanical densification apparatus for the hot-pressed sintered body of the brittle high-entropy alloy after step five of embodiment seven is completed;
fig. 10 is a schematic view of the densification mandrel 8 of fig. 1.
Detailed Description
The first embodiment is as follows: the embodiment is a hot-pressing sintering body thermal mechanical compacting device for brittle high-entropy alloy, and as shown in fig. 1-10, the device specifically comprises an upper template 1, a compact male die fixing block 2, a compact male die 3, a male die heating sleeve 4, a compact female die 5, a female die sleeve 6, a lower template 7, a compact ejector rod 8 and a die sleeve heating sleeve 10;
the compact male die 3 is formed by coaxially fixing four cylinders from top to bottom, and the diameters of the four cylinders are gradually reduced from top to bottom; the four cylinders are a first cylinder 3-1, a second cylinder 3-2, a third cylinder 3-3 and a fourth cylinder 3-4 from top to bottom in sequence;
the center of the compact male die fixing block 2 is a through hole, the inner wall of the through hole is of a stepped structure, and the stepped structure is matched with a first cylinder 3-1 and a second cylinder 3-2 of the compact male die 3; a first cylinder 3-1 and a second cylinder 3-2 of the compact male die 3 are arranged in a stepped structure of the compact male die fixing block 2, and the compact male die fixing block 2 is fixed on the lower surface of the upper die plate 1 through a plurality of bolts; the third cylinder 3-3 and the fourth cylinder 3-4 of the compact male die 3 are both arranged below the compact male die fixing block 2; a male die heating sleeve 4 is fixed on the outer wall of a third cylinder 3-3 of the compact male die 3, and the male die heating sleeve 4 is connected with an external power supply; the upper end surface of the upper template 1 is connected with a movable cross beam of the press machine;
the outer wall of the compact female die 5 is of a round table-shaped structure, the diameter of the upper end of the compact female die 5 is smaller, the center of the compact female die 5 is provided with a through hole, the inner wall of the through hole is of a stepped structure, and the diameter of the upper end of the stepped structure is smaller; the shape of the inner cavity of the female die sleeve 6 is matched with the outer wall of the compact female die 5, the female die sleeve 6 is tightly sleeved on the outer wall of the compact female die 5, a die sleeve heating sleeve 10 is fixed on the side wall of the female die sleeve 6, and the die sleeve heating sleeve 10 is connected with an external power supply;
a circular groove 7-2 is formed in the center of the lower template 7, an annular groove 7-1 is formed in the outer ring of the circular groove 7-2, and the upper surface of the annular groove 7-1 is lower than the upper surface of the circular groove 7-2; a plurality of bolt holes 7-3 are uniformly formed in the outer edge of the circular groove 7-2; the bottom of the female die sleeve 6 is fixed in the circular groove 7-2 through a plurality of bolts; the lower end face of the lower template 7 is connected with a lower cross beam of the press;
the compact ejector rod 8 is of a stepped structure, the diameter of the upper end of the compact ejector rod is smaller, the compact ejector rod 8 is arranged in a central through hole of the compact female die 5, and the compact ejector rod and the compact female die are in sliding connection; the bottom of the compact ejector rod 8 is placed on the ejection end face of an ejection cylinder of the press; a fourth cylinder 3-4 of the compact male die 3 is arranged in a central through hole of the compact female die 5, a male die heating sleeve 4 is arranged above the compact female die 5, and a compact ejector rod 8 is positioned below the compact male die 3; the upper end of the compact mandril 8, the lower end surface of the compact convex die 3 and the side wall of the central through hole of the compact concave die 5 form a cavity 9.
The second embodiment is as follows: the first difference between the present embodiment and the specific embodiment is: the unilateral clearance between the second cylinder 3-2 of the compact male die 3 and the inner hole part of the compact male die fixing block 2 is 0.03-0.05 mm, the unilateral clearance between the first cylinder 3-1 and the inner hole part of the compact male die fixing block 2 is 0.5-0.8 mm, and the upper end surface of the compact male die 3 is 0.5-1 mm higher than the upper end surface of the compact male die fixing block 2. The rest is the same as the first embodiment.
The third concrete implementation mode: the present embodiment differs from the first or second embodiment in that: the included angle between the outer side wall of the compact female die 5 and the vertical direction is 4-5 degrees, the upper end face of the compact female die 5 is 1-2 mm lower than the upper end face of the female die sleeve 6, and the lower end face of the compact female die 5 is 2-3 mm lower than the lower end face of the female die sleeve 6. The others are the same as in the first or second embodiment.
The fourth concrete implementation mode: the difference between this embodiment mode and one of the first to third embodiment modes is: the side wall of the annular groove 7-1 is matched with the side surface of the female die sleeve 6 to realize the positioning of the compact female die 5, and the single-side gap between the side wall of the annular groove 7-1 and the side surface of the female die sleeve 6 is 0.5-0.8 mm; the diameter of the central inner hole of the lower template 7 is 10 mm-15 mm larger than that of the inner hole at the bottom of the compact female die 5. The rest is the same as one of the first to third embodiments.
The fifth concrete implementation mode: the fourth difference between this embodiment and the specific embodiment is that: the height L2 of the upper end of the compact mandril 8 is 1.8-2.2 times of the height L1 of the upper end of the central hole of the compact concave die 5 (as shown in figures 5 and 10), so that the lower end of the compact mandril 8 does not interfere with the compact concave die 5 when the compact mandril 8 is ejected. The rest is the same as the fourth embodiment.
The sixth specific implementation mode: the difference between this embodiment mode and one of the first to third embodiment modes is: the compact male die 3, the compact ejector rod 8 and the side wall of the inner cavity of the compact female die 5 are in clearance fit, and the fit clearance is 0.1 mm. The rest is the same as one of the first to third embodiments.
The seventh embodiment: the embodiment is a use method of a hot-pressing sintered body thermomechanical densification device of a brittle high-entropy alloy, and the specific process is as follows:
firstly, putting the high-entropy alloy hot-pressing sintered body 11 into an atmosphere resistance furnace protected by argon, and preserving heat for 1-1.2 h at 900-1050 ℃; meanwhile, the mold is heated by the male mold heating sleeve 4 and the mold sleeve heating sleeve 10, and when the temperature of the cavity 9 reaches 150 ℃, graphite is uniformly sprayed on the surface of the cavity 9, so that the purpose of reducing the friction on the surface of the mold and facilitating ejection after densification is finished is achieved; then, the temperature of the device is continuously increased to ensure that the temperatures of the upper end surfaces of the compact female die 5 and the movable compact ejector rod 8 reach 450-500 ℃, the temperature of the compact male die 3 reaches 400-450 ℃, and the temperature is detected by using a general thermocouple;
secondly, starting a press machine to control the compact male die 3 to move upwards, transferring the high-entropy alloy sintered body 11 heated in the step one into the cavity 9, and controlling the transfer time to be 5-8 s; a gap is reserved between the side wall of the high-entropy alloy hot-pressing sintered body 11 and the inner wall of the compact female die 5;
thirdly, controlling the compacting male die 3 to move downwards through a press machine to pressurize the high-entropy alloy sintered body 11 to a height reduced by compression of the high-entropy alloy hot-pressed sintered body, wherein the height is 15% -20% of the original height, and then maintaining the pressure for 50 s;
fourthly, after the pressure maintaining is finished, controlling the compact male die 3 to move upwards to open the die;
and fifthly, starting a press ejection cylinder to control the compact ejector rod 8 to ascend, ejecting the compact high-entropy alloy block 11 out of the compact female die 5, and taking out.
The specific implementation mode is eight: the seventh embodiment is different from the seventh embodiment in that: in the first step, the heating power of the convex die heating sleeve 4 is 3 kW-5 kW, and the heating power of the die sleeve heating sleeve 10 is 8 kW-10 kW. The rest is the same as the seventh embodiment.
The specific implementation method nine: the seventh embodiment is different from the seventh embodiment in that: as shown in fig. 7, the diameter of the cavity 9 in the second step is 2mm to 3mm larger than that of the high-entropy alloy hot-pressing sintered body 11, so that the design ensures that the side wall of the high-entropy alloy hot-pressing sintered body 11 is in contact with the inner wall of the compact female die 5 when the high-entropy alloy hot-pressing sintered body is deformed under a small pressure, and three-dimensional compressive stress is applied to the high-entropy alloy hot-pressing sintered body, thereby avoiding unstable cracking. The rest is the same as the seventh embodiment.
The detailed implementation mode is ten: the seventh embodiment is different from the seventh embodiment in that: the high-entropy alloy hot-pressing sintered body 11 in the third step is subjected to the pressure of 250 MPa-300 MPa in the pressure holding process. The rest is the same as the seventh embodiment.
The invention was verified with the following tests:
test one: the test is a hot mechanical compacting device for a brittle high-entropy alloy hot-pressing sintering body, and as shown in figures 1-10, the hot mechanical compacting device specifically comprises an upper template 1, a compacting male die fixing block 2, a compacting male die 3, a male die heating sleeve 4, a compacting female die 5, a female die sleeve 6, a lower template 7, a compacting ejector rod 8 and a die sleeve heating sleeve 10; all die materials are forged H13 hot work die steel and are subjected to modulation heat treatment;
the compact male die 3 is formed by coaxially fixing four cylinders from top to bottom, and the diameters of the four cylinders are gradually reduced from top to bottom; the four cylinders are a first cylinder 3-1, a second cylinder 3-2, a third cylinder 3-3 and a fourth cylinder 3-4 from top to bottom in sequence;
the center of the compact convex die fixing block 2 is provided with a through hole, the inner wall of the through hole is of a stepped structure, and the stepped structure is matched with the first cylinder 3-1 and the second cylinder 3-2 of the compact convex die 3; a first cylinder 3-1 and a second cylinder 3-2 of the compact male die 3 are arranged in a stepped structure of the compact male die fixing block 2, and the compact male die fixing block 2 is fixed on the lower surface of the upper die plate 1 through a plurality of bolts; the third cylinder 3-3 and the fourth cylinder 3-4 of the compact male die 3 are both arranged below the compact male die fixing block 2; a male die heating sleeve 4 is fixed on the outer wall of a third cylinder 3-3 of the compact male die 3, and the male die heating sleeve 4 is connected with an external power supply; the upper end surface of the upper template 1 is connected with a movable cross beam of the press machine;
the outer wall of the compact female die 5 is of a round table-shaped structure, the diameter of the upper end of the compact female die 5 is smaller, the center of the compact female die 5 is provided with a through hole, the inner wall of the through hole is of a stepped structure, and the diameter of the upper end of the stepped structure is smaller; the shape of the inner cavity of the female die sleeve 6 is matched with the outer wall of the compact female die 5, the female die sleeve 6 is tightly sleeved on the outer wall of the compact female die 5, a die sleeve heating sleeve 10 is fixed on the side wall of the female die sleeve 6, and the die sleeve heating sleeve 10 is connected with an external power supply;
a circular groove 7-2 is formed in the center of the lower template 7, an annular groove 7-1 is formed in the outer ring of the circular groove 7-2, and the upper surface of the annular groove 7-1 is lower than the upper surface of the circular groove 7-2; a plurality of bolt holes 7-3 are uniformly formed in the outer edge of the circular groove 7-2; the bottom of the female die sleeve 6 is fixed in the circular groove 7-2 through a plurality of bolts; the lower end face of the lower template 7 is connected with a lower cross beam of the press;
the compact ejector rod 8 is of a stepped structure, the diameter of the upper end of the compact ejector rod is smaller, the compact ejector rod 8 is arranged in a central through hole of the compact female die 5, and the compact ejector rod and the compact female die are in sliding connection; the bottom of the compact ejector rod 8 is placed on the ejection end face of an ejection cylinder of the press; a fourth cylinder 3-4 of the compact male die 3 is arranged in a central through hole of the compact female die 5, a male die heating sleeve 4 is arranged above the compact female die 5, and a compact ejector rod 8 is positioned below the compact male die 3; the upper end of the compact mandril 8, the lower end surface of the compact convex die 3 and the side wall of the central through hole of the compact concave die 5 form a cavity 9.
The unilateral clearance between the second cylinder 3-2 of the compact male die 3 and the inner hole part of the compact male die fixing block 2 is 0.04mm, the unilateral clearance between the first cylinder 3-1 and the inner hole part of the compact male die fixing block 2 is 0.7mm, and the upper end surface of the compact male die 3 is 0.8mm higher than the upper end surface of the compact male die fixing block 2;
the included angle between the outer side wall of the compact female die 5 and the vertical direction is 5 degrees, the upper end face of the compact female die 5 is 2mm lower than the upper end face of the female die sleeve 6, and the lower end face of the compact female die 5 is 3mm lower than the lower end face of the female die sleeve 6;
the side wall of the annular groove 7-1 is matched with the side surface of the female die sleeve 6 to realize the positioning of the compact female die 5, and the single-side gap between the side wall of the annular groove 7-1 and the side surface of the female die sleeve 6 is 7 mm; the diameter of the central inner hole of the lower template 7 is 15mm larger than that of the inner hole at the bottom of the compact female die 5;
the height L2 of the upper end of the compact ejector rod 8 is 2.2 times of the height L1 of the upper end of the central hole of the compact female die 5 (as shown in figures 5 and 10), so that the lower end of the compact ejector rod 8 does not interfere with the compact female die 5 when the compact ejector rod 8 is ejected;
the compact male die 3 and the compact ejector rod 8 are in clearance fit with the side wall of the inner cavity of the compact female die 5, and the fit clearance is 0.1 mm;
the using method of the hot-pressing sintering body thermomechanical densification device for the brittle high-entropy alloy in the test is as follows:
firstly, putting the high-entropy alloy hot-pressing sintered body 11 into an atmosphere resistance furnace protected by argon, and preserving heat for 1-1.2 h at 900-1050 ℃; meanwhile, the mold is heated by the male mold heating sleeve 4 and the mold sleeve heating sleeve 10, and when the temperature of the cavity 9 reaches 150 ℃, graphite is uniformly sprayed on the surface of the cavity 9, so that the purpose of reducing the friction on the surface of the mold and facilitating ejection after densification is finished is achieved; then, the temperature of the device is continuously increased to ensure that the temperatures of the upper end surfaces of the compact female die 5 and the movable compact ejector rod 8 reach 450-500 ℃, the temperature of the compact male die 3 reaches 400-450 ℃, and the temperature is detected by using a general thermocouple; the heating power of the male die heating sleeve 4 is 4kW, and the heating power of the die sleeve heating sleeve 10 is 9 kW;
secondly, starting a press machine to control the compact male die 3 to move upwards, transferring the high-entropy alloy sintered body 11 heated in the step one into the cavity 9, and controlling the transfer time to be 5-8 s; a gap is reserved between the side wall of the high-entropy alloy hot-pressing sintered body 11 and the inner wall of the compact female die 5; as shown in fig. 7, the diameter of the cavity 9 in the second step is 3mm larger than that of the high-entropy alloy hot-pressing sintered body 11, so that the design ensures that the side wall of the high-entropy alloy hot-pressing sintered body 11 is in contact with the inner wall of the compact female die 5 when the high-entropy alloy hot-pressing sintered body is deformed under a small pressure, and three-dimensional compressive stress is applied to the high-entropy alloy hot-pressing sintered body, thereby avoiding unstable cracking;
thirdly, controlling the compacting male die 3 to move downwards through a press machine to pressurize the high-entropy alloy sintered body 11 to a height reduced by compression of the high-entropy alloy hot-pressed sintered body, wherein the height is 15% -20% of the original height, and then maintaining the pressure for 50 s; the pressure applied to the high-entropy alloy hot-pressing sintered body 11 in the pressure holding process is 300 MPa;
fourthly, after the pressure maintaining is finished, controlling the compact male die 3 to move upwards to open the die;
and fifthly, starting a press ejection cylinder to control the compact ejector rod 8 to ascend, ejecting the compact high-entropy alloy block 11 out of the compact female die 5, and taking out.
The device for the test is suitable for high-entropy alloy hot-pressing sintered bodies of systems such as AlCoCrCuFeNi, AlCoCrCuNi, AlCoCrFeNi, AlCoCrFeMnNi, AlCrCuFeNi and the like which mainly adopt body-centered cubic structural phases.
Compared with the prior art, the test has the beneficial effects that:
1. according to the test, the pores of the brittle high-entropy alloy hot-pressed sintered body are closed through thermoplastic deformation by a thermal mechanical processing method, so that the density and the mechanical property are effectively improved;
2. the test effectively avoids the unstable cracking of the brittle high-entropy alloy hot-pressing sintering body in the thermal mechanical processing process through the action of three-dimensional compressive stress of the die cavity;
3. according to the test, the densified alloy material is conveniently taken out through the ejection mechanism after densification is finished, and the efficiency of the densification process is improved.
Claims (10)
1. A hot mechanical compacting device for a brittle high-entropy alloy hot-pressing sintering body is characterized by comprising an upper template (1), a compact male die fixing block (2), a compact male die (3), a male die heating sleeve (4), a compact female die (5), a female die sleeve (6), a lower template (7), a compact ejector rod (8) and a die sleeve heating sleeve (10);
the compact male die (3) is formed by coaxially fixing four cylinders from top to bottom, and the diameters of the four cylinders are gradually reduced from top to bottom; the four cylinders are a first cylinder (3-1), a second cylinder (3-2), a third cylinder (3-3) and a fourth cylinder (3-4) from top to bottom in sequence;
the center of the compact male die fixing block (2) is provided with a through hole, the inner wall of the through hole is of a stepped structure, and the stepped structure is matched with a first cylinder (3-1) and a second cylinder (3-2) of the compact male die (3); a first cylinder (3-1) and a second cylinder (3-2) of the compact male die (3) are arranged in a stepped structure of the compact male die fixing block (2), and the compact male die fixing block (2) is fixed on the lower surface of the upper die plate (1) through a plurality of bolts; a third cylinder (3-3) and a fourth cylinder (3-4) of the compact male die (3) are both arranged below the compact male die fixing block (2); a male die heating sleeve (4) is fixed on the outer wall of a third cylinder (3-3) of the compact male die (3), and the male die heating sleeve (4) is connected with an external power supply; the upper end surface of the upper template (1) is connected with a movable cross beam of the press;
the outer wall of the compact female die (5) is of a round table-shaped structure, the diameter of the upper end of the compact female die is smaller, the center of the compact female die (5) is provided with a through hole, the inner wall of the through hole is of a stepped structure, and the diameter of the upper end of the stepped structure is smaller; the shape of the inner cavity of the female die sleeve (6) is matched with the outer wall of the compact female die (5), the female die sleeve (6) is tightly sleeved on the outer wall of the compact female die (5), a die sleeve heating sleeve (10) is fixed on the side wall of the female die sleeve (6), and the die sleeve heating sleeve (10) is connected with an external power supply;
a circular groove (7-2) is formed in the center of the lower template (7), an annular groove (7-1) is formed in the outer ring of the circular groove (7-2), and the upper surface of the annular groove (7-1) is lower than the upper surface of the circular groove (7-2); a plurality of bolt holes (7-3) are uniformly formed in the outer edge of the circular groove (7-2); the bottom of the female die sleeve (6) is fixed in the circular groove (7-2) through a plurality of bolts; the lower end surface of the lower template (7) is connected with a lower cross beam of the press;
the compact ejector rod (8) is of a step-shaped structure, the diameter of the upper end of the compact ejector rod is smaller, the compact ejector rod (8) is arranged in a central through hole of the compact female die (5), and the compact ejector rod and the compact female die are in sliding connection; the bottom of the compact ejector rod (8) is placed on the ejection end face of an ejection cylinder of the press; a fourth cylinder (3-4) of the compact male die (3) is arranged in a central through hole of the compact female die (5), a male die heating sleeve (4) is arranged above the compact female die (5), and a compact ejector rod (8) is positioned below the compact male die (3); the upper end of the compact ejector rod (8), the lower end face of the compact male die (3) and the side wall of the central through hole of the compact female die (5) form a die cavity (9).
2. The thermo-mechanical compacting device for the hot-pressed sintered body of the brittle high-entropy alloy as claimed in claim 1, wherein the unilateral clearance between the second cylinder (3-2) of the compacting punch (3) and the inner hole part of the compacting punch fixed block (2) is 0.03mm to 0.05mm, the unilateral clearance between the first cylinder (3-1) and the inner hole part of the compacting punch fixed block (2) is 0.5mm to 0.8mm, and the upper end surface of the compacting punch (3) is 0.5mm to 1mm higher than the upper end surface of the compacting punch fixed block (2).
3. The thermo-mechanical densification device for the brittle high-entropy alloy hot-pressed sintered body according to claim 1, characterized in that an included angle between the outer side wall of the densification female die (5) and the vertical direction is 4-5 degrees, the upper end face of the densification female die (5) is 1-2 mm lower than the upper end face of the female die sleeve (6), and the lower end face of the densification female die (5) is 2-3 mm lower than the lower end face of the female die sleeve (6).
4. The thermo-mechanical densification device for the hot-pressed sintered body of the brittle high-entropy alloy according to claim 1, wherein the side wall of the annular groove (7-1) is matched with the side surface of the die sleeve (6) to position the densified die (5), and the unilateral gap between the side wall of the annular groove (7-1) and the side surface of the die sleeve (6) is 0.5mm to 0.8 mm; the diameter of the central inner hole of the lower template (7) is 10 mm-15 mm larger than that of the inner hole at the bottom of the compact female die (5).
5. The thermo-mechanical densification device for the hot-pressed sintered body of the brittle high-entropy alloy according to claim 1, wherein the height L2 of the upper end of the densification mandril (8) is 1.8 to 2.2 times of the height L1 of the upper end of the central hole of the densification female die (5).
6. The thermo-mechanical densification device for the brittle high-entropy alloy hot-pressed sintered body according to claim 1, characterized in that the dense male die (3) and the dense ejector rod (8) are in clearance fit with the side wall of the inner cavity of the dense female die (5), and the fit clearance is 0.1 mm.
7. The use method of the thermo-mechanical densification device for the brittle high-entropy alloy hot-pressed sintered body, according to claim 1, is characterized in that the use method of the thermo-mechanical densification device for the brittle high-entropy alloy hot-pressed sintered body is as follows:
firstly, putting the high-entropy alloy hot-pressing sintered body (11) into an atmosphere resistance furnace protected by argon, and preserving heat for 1-1.2 h at 900-1050 ℃; meanwhile, the mold is heated through the male mold heating sleeve (4) and the mold sleeve heating sleeve (10), and when the temperature of the cavity (9) reaches 150 ℃, graphite is uniformly sprayed on the surface of the cavity (9); then, the temperature of the device is continuously increased to ensure that the temperatures of the upper end surfaces of the compact female die (5) and the movable compact ejector rod (8) reach 450-500 ℃, and the temperature of the compact male die (3) reaches 400-450 ℃;
secondly, starting a press machine to control the compact male die (3) to move upwards, transferring the high-entropy alloy sintered body (11) heated in the step one into the cavity (9), and controlling the transfer time to be 5-8 s; a gap is reserved between the side wall of the high-entropy alloy hot-pressing sintered body (11) and the inner wall of the compact female die (5);
thirdly, controlling the compact male die (3) to move downwards through a press machine to pressurize the high-entropy alloy sintered body (11) to a height reduced by compression of the high-entropy alloy hot-pressed sintered body, wherein the height is 15% -20% of the original height, and then maintaining the pressure for 50 s;
fourthly, after the pressure maintaining is finished, controlling the compact male die (3) to move upwards to open the die;
fifthly, starting a press ejection cylinder to control the compact ejector rod (8) to move upwards, ejecting the compact high-entropy alloy block (11) out of the compact female die (5), and taking out the compact high-entropy alloy block.
8. The use method of the thermo-mechanical densification device for the hot-pressed sintered body of the brittle high-entropy alloy, according to claim 1, is characterized in that the heating power of the convex die heating sleeve (4) in the first step is 3kW to 5kW, and the heating power of the die sleeve heating sleeve (10) is 8kW to 10 kW.
9. The use method of the thermo-mechanical densification device for the brittle high-entropy alloy hot-pressed sintered body according to claim 1, wherein the diameter of the cavity (9) in the second step is 2mm to 3mm larger than that of the high-entropy alloy hot-pressed sintered body (11).
10. The use method of the thermo-mechanical densification device for the brittle high-entropy alloy hot-pressed sintered body according to claim 1, characterized in that the pressure applied to the brittle high-entropy alloy hot-pressed sintered body (11) in the pressure maintaining process in the third step is 250MPa to 300 MPa.
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