CN114505427B - Thermomechanical densification device for brittle high-entropy alloy hot-pressed sintering body and use method thereof - Google Patents
Thermomechanical densification device for brittle high-entropy alloy hot-pressed sintering body and use method thereof Download PDFInfo
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- CN114505427B CN114505427B CN202210210235.8A CN202210210235A CN114505427B CN 114505427 B CN114505427 B CN 114505427B CN 202210210235 A CN202210210235 A CN 202210210235A CN 114505427 B CN114505427 B CN 114505427B
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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
- 238000000280 densification Methods 0.000 title claims abstract description 69
- 238000000034 method Methods 0.000 title claims abstract description 37
- 230000000930 thermomechanical effect Effects 0.000 title claims abstract description 32
- 238000005245 sintering Methods 0.000 title claims abstract description 24
- 238000010438 heat treatment Methods 0.000 claims abstract description 50
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 4
- 229910002804 graphite Inorganic materials 0.000 claims description 4
- 239000010439 graphite Substances 0.000 claims description 4
- 238000005336 cracking Methods 0.000 abstract description 9
- 239000011148 porous material Substances 0.000 abstract description 6
- 229920001169 thermoplastic Polymers 0.000 abstract description 4
- 239000004416 thermosoftening plastic Substances 0.000 abstract description 4
- 238000003754 machining Methods 0.000 abstract 1
- 238000012360 testing method Methods 0.000 description 9
- 238000012545 processing Methods 0.000 description 6
- 238000010586 diagram Methods 0.000 description 3
- 238000012546 transfer Methods 0.000 description 3
- 238000005452 bending Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000000694 effects Effects 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
- 238000001192 hot extrusion Methods 0.000 description 1
- 238000004663 powder metallurgy Methods 0.000 description 1
- 238000003825 pressing 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 thermomechanical densification device of a brittle high-entropy alloy hot-pressed sintering body and a use method thereof relate to an alloy hot-pressed sintering body thermomechanical densification device and a use method thereof. The invention aims to solve the technical problems that the compact pair of the brittle high-entropy alloy hot-pressed sintered body is relatively low, and instability and cracking are easy to occur in the hot machining compact process of the sintered body. The closed cavity formed by the compact male die, the compact female die and the compact ejector rod realizes that the three-dimensional compressive stress state is quickly built in the middle alloy by the action of the die cavity in the thermo-mechanical deformation process of small-deformation upsetting, and instability cracking is avoided. The pore closure of the low-plasticity high-entropy alloy is realized through thermoplastic deformation flow by proper blank temperature and heating of a die, so that the compactness of the brittle high-entropy alloy hot-pressed sintered body can be effectively improved.
Description
Technical Field
The invention relates to a thermomechanical densification device of an alloy hot-pressed sintering body and a use method thereof.
Background
The bulk high-entropy alloy obtained by adopting the sintering process through the powder metallurgy path has the advantages of fine structure, high strength and the like. High-entropy alloys with body-centered cubic or close-packed hexagonal structure as the main phase structure have high strength and low plasticity (large brittleness). In the unidirectional pressure sintering process, the alloy powder with high hardness and low plasticity has small plastic deformation degree, and is more difficult to compact than plastic powder. While the sintering mold strength is limited, the unidirectional pressure is typically no more than 70MPa. Therefore, a part of the pores of the sintered bulk alloy is unavoidable. The existence of pores leads to the limitation of the density of the microstructure, and the mechanical property of the sintered alloy is reduced to a certain extent.
The thermo-mechanical processing of the hot pressed sintered body is a technique which is more commonly used for improving the density of the alloy sintered body. Thermomechanical processing typically includes unidirectional hot upsetting, hot rolling, multi-directional hot forging, hot extrusion, and the like. During the hot working process, 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 (large brittleness), when the alloy is subjected to thermal mechanical processing by unidirectional hot upsetting, hot rolling, multi-directional hot forging, or the like, the stress state in the alloy is not a three-dimensional compressive stress state, and the alloy is very likely to be unstable and cracked during processing. The amount of deformation of the thermomechanical process is also difficult to control.
Therefore, when the hot pressed sintered body of the high-strength, low-plasticity (brittleness) and high-entropy alloy is subjected to thermo-mechanical densification, the control of cracking of the alloy Jin Shiwen is the focus of research and innovation of the expert. At present, the thermomechanical densification of the alloy requires reasonable die device and process control to realize that the sintered body is in a three-dimensional compressive stress state in the densification process so as to prevent unstable cracking. Meanwhile, the reasonable die device and the process method can improve the efficiency and controllability of the densification process.
Disclosure of Invention
The invention aims to solve the technical problems that the density of the existing brittle high-entropy alloy hot-pressed sintered body is relatively low, and the existing thermomechanical densification method is easy to cause material instability cracking in the densification process of high-strength and low-plasticity high-entropy alloy and the densification process is difficult to control, and provides a thermomechanical densification device for the brittle high-entropy alloy hot-pressed sintered body and a use method thereof.
The invention relates to a thermomechanical densification device of a brittle high-entropy alloy hot-pressed sintering body, which consists of an upper template 1, a densification male die fixing block 2, a densification male die 3, a male die heating sleeve 4, a densification female die 5, a female die sleeve 6, a lower template 7, a densification 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 in sequence from top to bottom; the third cylinder 3-3 has the advantages that the rigidity of the compacting male die 3 is improved, and unstable bending is prevented in the compacting pressurization 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 the first cylinder 3-1 and the second cylinder 3-2 of the compact male die 3; the first cylinder 3-1 and the 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 arranged below the compact male die fixing block 2; the outer wall of the third cylinder 3-3 of the compact male die 3 is fixed with a male die heating sleeve 4, 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 truncated cone-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 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, the 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;
The center of the lower die plate 7 is provided with a circular groove 7-2, the outer ring of the circular groove 7-2 is provided with an annular groove 7-1, and the upper surface of the annular groove 7-1 is lower than the upper surface of the circular groove 7-2; the outer edge of the circular groove 7-2 is uniformly provided with a plurality of bolt holes 7-3; 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 stepped structure, the diameter of the upper end is smaller, and the lower end has the function of improving the rigidity of the compact ejector rod 8 and preventing unstable bending in the compact pressurizing process; the compact ejector rod 8 is arranged in the central through hole of the compact female die 5 and is in sliding connection with the compact female die 5; the bottom of the compact ejector rod 8 is placed on the ejection end face of an ejection cylinder of the press; the fourth cylinder 3-4 of the compact male die 3 is arranged in the central through hole of the compact female die 5, the male die heating sleeve 4 is arranged above the compact female die 5, and the compact ejector rod 8 is arranged below the compact male die 3; the upper end of the compact ejector rod 8, the lower end surface 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.
The application method of the thermomechanical densification device of the brittle high-entropy alloy hot-pressed sintering body comprises the following steps:
1. Placing the high-entropy alloy hot-pressed sintered body 11 in an argon-protected atmosphere resistance furnace, and preserving heat for 1-1.2 h at 900-1050 ℃; simultaneously, the die is heated by the male die heating sleeve 4 and the die sleeve heating sleeve 10, and graphite is uniformly sprayed on the surface of the die cavity 9 when the temperature of the die cavity 9 reaches 150 ℃, so as to reduce friction on the surface of the die and facilitate ejection after densification is finished; then the device is continuously heated up to ensure that the temperature 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;
2. starting a press machine to control the compact male die 3 to ascend, and transferring the high-entropy alloy hot-pressed sintered body 11 heated in the step one into the cavity 9, wherein the transfer time is controlled to be 5-8 s; the side wall of the high-entropy alloy hot-pressed sintered body 11 and the inner wall of the compact female die 5 are provided with gaps;
3. Controlling the compact male die 3 to move downwards through a press machine to press the high-entropy alloy hot-pressed sintered body 11 until the compressed height of the high-entropy alloy hot-pressed sintered body is 15-20% of the original height, and then maintaining the pressure for 50s;
4. after the pressure maintaining is finished, controlling the compact male die 3 to ascend to open the die;
5. and starting a press ejection cylinder to control the compact ejector rod 8 to move upwards, ejecting the compact high-entropy alloy hot-pressed sintered body 11 out of the compact female die 5, and taking out.
The device is suitable for high-entropy alloy hot-pressed sintered bodies of AlCoCrCuFeNi, alCoCrCuNi, alCoCrFeNi, alCoCrFeMnNi, alCrCuFeNi systems and the like which mainly adopt the body-centered cubic structure phase.
Compared with the prior art, the invention has the following beneficial effects:
1. According to the invention, the pores of the brittle high-entropy alloy hot-pressed sintered body are closed through thermoplastic deformation by a thermo-mechanical processing method, so that the density and the mechanical property are effectively improved;
2. According to the invention, through the three-dimensional compressive stress effect of the die cavity, the unstable cracking of the brittle high-entropy alloy hot-pressed sintered body in the thermo-mechanical processing process is effectively avoided;
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 diagram of a hot mechanical densification apparatus for brittle high entropy alloy hot pressed sintering bodies according to one embodiment;
FIG. 2 is an enlarged view of a portion of the area A of FIG. 1;
fig. 3 is a top view of the lower die plate 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 dense female die 5 of fig. 1;
FIG. 6 is a schematic diagram of a thermomechanical densification apparatus for brittle high-entropy alloy hot-pressed sintering after completion of step two of the seventh embodiment;
FIG. 7 is an enlarged view of a portion of region B of FIG. 6;
FIG. 8 is a schematic view of a part of the hot mechanical densification apparatus of a brittle high-entropy alloy hot press sintered body at the same location as that of FIG. 7 after the completion of step three of the seventh embodiment;
FIG. 9 is a schematic diagram of a thermomechanical densification apparatus for brittle high-entropy alloy hot-pressed sintering after completion of step five of the seventh embodiment;
Fig. 10 is a schematic view of the dense ejector rod 8 of fig. 1.
Detailed Description
The first embodiment is as follows: the embodiment is a thermomechanical densification device of a brittle high-entropy alloy hot-pressed sintering body, as shown in fig. 1-10, and specifically comprises an upper template 1, a densification male die fixing block 2, a densification male die 3, a male die heating sleeve 4, a densification female die 5, a female die sleeve 6, a lower template 7, a densification 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 in sequence from top to bottom;
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 the first cylinder 3-1 and the second cylinder 3-2 of the compact male die 3; the first cylinder 3-1 and the 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 arranged below the compact male die fixing block 2; the outer wall of the third cylinder 3-3 of the compact male die 3 is fixed with a male die heating sleeve 4, 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 truncated cone-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 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, the 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;
The center of the lower die plate 7 is provided with a circular groove 7-2, the outer ring of the circular groove 7-2 is provided with an annular groove 7-1, and the upper surface of the annular groove 7-1 is lower than the upper surface of the circular groove 7-2; the outer edge of the circular groove 7-2 is uniformly provided with a plurality of bolt holes 7-3; 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 stepped structure, the diameter of the upper end of the compact ejector rod is smaller, the compact ejector rod 8 is arranged in the central through hole of the compact female die 5, and the compact ejector rod 8 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; the fourth cylinder 3-4 of the compact male die 3 is arranged in the central through hole of the compact female die 5, the male die heating sleeve 4 is arranged above the compact female die 5, and the compact ejector rod 8 is arranged below the compact male die 3; the upper end of the compact ejector rod 8, the lower end surface 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.
The second embodiment is as follows: the first difference between this embodiment and the specific embodiment is that: the unilateral gap between the second cylinder 3-2 of the compact punch 3 and the inner hole part of the compact punch fixing block 2 is 0.03-0.05 mm, the unilateral gap between the first cylinder 3-1 and the inner hole part of the compact punch fixing block 2 is 0.5-0.8 mm, and the upper end face of the compact punch 3 is 0.5-1 mm higher than the upper end face of the compact punch fixing block 2. The other is the same as in the first embodiment.
And a third specific embodiment: this 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 surface of the compact female die 5 is 1-2 mm lower than the upper end surface of the female die sleeve 6, and the lower end surface of the compact female die 5 is 2-3 mm lower than the lower end surface of the female die sleeve 6. The other embodiments are the same as those of the first or second embodiment.
The specific embodiment IV is as follows: this embodiment differs from one of the first to third embodiments in that: the side wall of the annular groove 7-1 is matched with the side surface of the die sleeve 6 to realize the positioning of the compact die 5, and the unilateral clearance between the side wall of the annular groove 7-1 and the side surface of the die sleeve 6 is 0.5 mm-0.8 mm; the diameter of the central inner hole of the lower die plate 7 is 10 mm-15 mm larger than that of the inner hole at the bottom of the compact female die 5. The other is the same as in one of the first to third embodiments.
Fifth embodiment: the fourth difference between this embodiment and the third embodiment is that: the height L2 of the upper end of the compact ejector rod 8 is 1.8-2.2 times of the height L1 of the upper end of the central hole of the compact female die 5 (as shown in fig. 5 and 10), so as to ensure 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 other is the same as in the fourth embodiment.
Specific embodiment six: this embodiment differs from one of the first to third embodiments in that: 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 0.1mm. The other is the same as in one of the first to third embodiments.
Seventh embodiment: the embodiment is a use method of the thermomechanical densification device of the brittle high-entropy alloy hot-pressed sintering body in the embodiment, and the specific process is as follows:
1. Placing the high-entropy alloy hot-pressed sintered body 11 in an argon-protected atmosphere resistance furnace, and preserving heat for 1-1.2 h at 900-1050 ℃; simultaneously, the die is heated by the male die heating sleeve 4 and the die sleeve heating sleeve 10, and graphite is uniformly sprayed on the surface of the die cavity 9 when the temperature of the die cavity 9 reaches 150 ℃, so as to reduce friction on the surface of the die and facilitate ejection after densification is finished; then the device is continuously heated up to ensure that the temperature 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;
2. starting a press machine to control the compact male die 3 to ascend, and transferring the high-entropy alloy hot-pressed sintered body 11 heated in the step one into the cavity 9, wherein the transfer time is controlled to be 5-8 s; the side wall of the high-entropy alloy hot-pressed sintered body 11 and the inner wall of the compact female die 5 are provided with gaps;
3. Controlling the compact male die 3 to move downwards through a press machine to press the high-entropy alloy hot-pressed sintered body 11 until the compressed height of the high-entropy alloy hot-pressed sintered body is 15-20% of the original height, and then maintaining the pressure for 50s;
4. after the pressure maintaining is finished, controlling the compact male die 3 to ascend to open the die;
5. and starting a press ejection cylinder to control the compact ejector rod 8 to move upwards, ejecting the compact high-entropy alloy hot-pressed sintered body 11 out of the compact female die 5, and taking out.
Eighth embodiment: the present embodiment is different from the seventh embodiment in that: in the first step, the heating power of the male 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 other is the same as in the seventh embodiment.
Detailed description nine: the present 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 2 mm-3 mm larger than that of the high-entropy alloy hot-pressed sintered body 11, so that the contact between the side wall of the high-entropy alloy hot-pressed sintered body 11 and the inner wall of the compact female die 5 is ensured when the high-entropy alloy hot-pressed sintered body is deformed under a small pressing force, and three-dimensional compressive stress is applied to the high-entropy alloy hot-pressed sintered body, so that unstable cracking is avoided. The other is the same as in the seventh embodiment.
Detailed description ten: the present embodiment is different from the seventh embodiment in that: the pressure applied to the high-entropy alloy hot-pressed sintered body 11 in the pressure maintaining process is 250 MPa-300 MPa. The other is the same as in the seventh embodiment.
The invention was verified with the following test:
test one: the test is a thermomechanical densification device of a brittle high-entropy alloy hot-pressed sintering body, as shown in figures 1-10, and specifically comprises an upper template 1, a densification male die fixing block 2, a densification male die 3, a male die heating sleeve 4, a densification female die 5, a female die sleeve 6, a lower template 7, a densification ejector rod 8 and a die sleeve heating sleeve 10; all the die materials are H13 hot work die steel which is forged, 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 in sequence from top to bottom;
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 the first cylinder 3-1 and the second cylinder 3-2 of the compact male die 3; the first cylinder 3-1 and the 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 arranged below the compact male die fixing block 2; the outer wall of the third cylinder 3-3 of the compact male die 3 is fixed with a male die heating sleeve 4, 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 truncated cone-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 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, the 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;
The center of the lower die plate 7 is provided with a circular groove 7-2, the outer ring of the circular groove 7-2 is provided with an annular groove 7-1, and the upper surface of the annular groove 7-1 is lower than the upper surface of the circular groove 7-2; the outer edge of the circular groove 7-2 is uniformly provided with a plurality of bolt holes 7-3; 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 stepped structure, the diameter of the upper end of the compact ejector rod is smaller, the compact ejector rod 8 is arranged in the central through hole of the compact female die 5, and the compact ejector rod 8 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; the fourth cylinder 3-4 of the compact male die 3 is arranged in the central through hole of the compact female die 5, the male die heating sleeve 4 is arranged above the compact female die 5, and the compact ejector rod 8 is arranged below the compact male die 3; the upper end of the compact ejector rod 8, the lower end surface 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.
The unilateral gap between the second cylinder 3-2 of the compact punch 3 and the inner hole part of the compact punch fixing block 2 is 0.04mm, the unilateral gap between the first cylinder 3-1 and the inner hole part of the compact punch fixing block 2 is 0.7mm, and the upper end face of the compact punch 3 is 0.8mm higher than the upper end face of the compact punch 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 surface of the compact female die 5 is 2mm lower than the upper end surface of the female die sleeve 6, and the lower end surface of the compact female die 5 is 3mm lower than the lower end surface of the female die sleeve 6;
The side wall of the annular groove 7-1 is matched with the side surface of the die sleeve 6 to realize the positioning of the compact 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 7mm; 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 fig. 5 and 10), so as to ensure 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 matching of the compact male die 3 and the compact ejector rod 8 with the side wall of the inner cavity of the compact female die 5 is clearance fit, and the matching clearance is 0.1mm;
The using method of the thermomechanical densification device of the brittle high-entropy alloy hot-pressed sintering body in the test is as follows:
1. Placing the high-entropy alloy hot-pressed sintered body 11 in an argon-protected atmosphere resistance furnace, and preserving heat for 1-1.2 h at 900-1050 ℃; simultaneously, the die is heated by the male die heating sleeve 4 and the die sleeve heating sleeve 10, and graphite is uniformly sprayed on the surface of the die cavity 9 when the temperature of the die cavity 9 reaches 150 ℃, so as to reduce friction on the surface of the die and facilitate ejection after densification is finished; then the device is continuously heated up to ensure that the temperature 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 9kW;
2. Starting a press machine to control the compact male die 3 to ascend, and transferring the high-entropy alloy hot-pressed sintered body 11 heated in the step one into the cavity 9, wherein the transfer time is controlled to be 5-8 s; the side wall of the high-entropy alloy hot-pressed sintered body 11 and the inner wall of the compact female die 5 are provided with gaps; 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-pressed sintered body 11, so that the contact between the side wall of the high-entropy alloy hot-pressed sintered body 11 and the inner wall of the compact female die 5 is ensured when the high-entropy alloy hot-pressed sintered body is deformed under a small pressure, and three-dimensional compressive stress is applied to the high-entropy alloy hot-pressed sintered body, so that unstable cracking is avoided;
3. controlling the compact male die 3 to move downwards through a press machine to press the high-entropy alloy hot-pressed sintered body 11 until the compressed height of the high-entropy alloy hot-pressed sintered body is 15-20% of the original height, and then maintaining the pressure for 50s; the high-entropy alloy hot-pressed sintered body 11 receives 300MPa of pressure in the pressure maintaining process;
4. after the pressure maintaining is finished, controlling the compact male die 3 to ascend to open the die;
5. and starting a press ejection cylinder to control the compact ejector rod 8 to move upwards, ejecting the compact high-entropy alloy hot-pressed sintered body 11 out of the compact female die 5, and taking out.
The device for the test is suitable for high-entropy alloy hot-pressed sintered bodies of AlCoCrCuFeNi, alCoCrCuNi, alCoCrFeNi, alCoCrFeMnNi, alCrCuFeNi systems and the like which mainly adopt a body-centered cubic structure phase.
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 hot mechanical processing method, so that the density and the mechanical property are effectively improved;
2. according to the test, through the three-dimensional compressive stress effect of the die cavity, the unstable cracking of the brittle high-entropy alloy hot-pressed sintered body in the thermo-mechanical processing process is effectively avoided;
3. according to the test, 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.
Claims (9)
1. A thermomechanical densification device of a brittle high-entropy alloy hot-pressed sintering body is characterized by comprising an upper template (1), a densification male die fixing block (2), a densification male die (3), a male die heating sleeve (4), a densification female die (5), a female die sleeve (6), a lower template (7), a densification 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) in sequence from top to bottom;
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); the first cylinder (3-1) and the 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 arranged below the compact male die fixing block (2); the outer wall of a third cylinder (3-3) of the compact male die (3) is fixed with a male die heating sleeve (4), 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 concave die (5) is of a truncated cone-shaped structure, the diameter of the upper end of the compact concave die is smaller, the center of the compact concave die (5) is 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 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), the 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;
The center of the lower die plate (7) is provided with a circular groove (7-2), the outer ring of the circular groove (7-2) is provided with an annular groove (7-1), and the upper surface of the annular groove (7-1) is lower than the upper surface of the circular groove (7-2); the outer edge of the circular groove (7-2) is uniformly provided with a plurality of bolt holes (7-3); 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 stepped structure, the diameter of the upper end of the compact ejector rod is smaller, the compact ejector rod (8) is arranged in the 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 arranged on the ejection end surface of an ejection cylinder of the press; the fourth cylinder (3-4) of the compact male die (3) is arranged in the central through hole of the compact female die (5), the male die heating sleeve (4) is arranged above the compact female die (5), and the compact ejector rod (8) is positioned below the compact male die (3); the upper end of the compact ejector rod (8), the lower end surface 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), and the diameter of the die cavity (9) is 2-3 mm larger than that of the high-entropy alloy hot-pressed sintered body to be treated.
2. The thermomechanical densification device of the brittle high-entropy alloy hot-pressed sintering body according to claim 1, wherein the unilateral gap between the second cylinder (3-2) of the densification male die (3) and the inner hole part of the densification male die fixing block (2) is 0.03 mm-0.05 mm, the unilateral gap between the first cylinder (3-1) and the inner hole part of the densification male die fixing block (2) is 0.5 mm-0.8 mm, and the upper end face of the densification male die (3) is 0.5 mm-1 mm higher than the upper end face of the densification male die fixing block (2).
3. The thermomechanical densification device of the brittle high-entropy alloy hot-pressed sinter, according to claim 1, is characterized in that the included angle between the outer side wall of the densification female die (5) and the vertical direction is 4-5 degrees, the upper end surface of the densification female die (5) is 1-2 mm lower than the upper end surface of the female die sleeve (6), and the lower end surface of the densification female die (5) is 2-3 mm lower than the lower end surface of the female die sleeve (6).
4. The thermomechanical densification device of the brittle high-entropy alloy hot-pressed sinter is characterized in that 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 dense female die (5), and the unilateral gap between the side wall of the annular groove (7-1) and the side surface of the female die sleeve (6) is 0.5 mm-0.8 mm; the diameter of the central inner hole of the lower die plate (7) is 10 mm-15 mm larger than that of the inner hole at the bottom of the compact female die (5).
5. The thermomechanical densification device of the brittle high-entropy alloy hot-pressed sintering body according to claim 1, wherein the height L2 of the upper end of the densification ejector rod (8) is 1.8-2.2 times of the height L1 of the upper end of the central hole of the densification female die (5).
6. The thermomechanical densification device for the brittle high-entropy alloy hot-pressed sintering body according to claim 1, wherein the densification male die (3) and the densification ejector rod (8) are in clearance fit with the side wall of the inner cavity of the densification female die (5), and the fit clearance is 0.1mm.
7. The method of using a brittle high-entropy alloy hot-pressed sintering body thermo-mechanical densification device as set forth in claim 1, characterized in that the method of using the brittle high-entropy alloy hot-pressed sintering body thermo-mechanical densification device is as follows:
1. Placing the high-entropy alloy hot-pressed sintered body (11) in an argon-protected atmosphere resistance furnace, and preserving heat for 1-1.2 h at 900-1050 ℃; simultaneously, the die is heated by a male die heating sleeve (4) and a die sleeve heating sleeve (10), and graphite is uniformly sprayed on the surface of the die cavity (9) when the temperature of the die cavity (9) reaches 150 ℃; then the device is continuously heated up to enable the temperature of the upper end surfaces of the compact female die (5) and the movable compact ejector rod (8) to reach 450-500 ℃, and the temperature of the compact male die (3) reaches 400-450 ℃;
2. Starting a press machine to control the compact male die (3) to ascend, and transferring the high-entropy alloy hot-pressed sintered body (11) heated in the step one into the cavity (9) for 5-8 s; a gap is reserved between the side wall of the high-entropy alloy hot-pressed sintered body (11)) and the inner wall of the compact female die (5); the diameter of the cavity (9) is 2 mm-3 mm larger than the diameter of the high-entropy alloy hot-pressed sintered body (11);
3. controlling the compact male die (3) to descend through a press machine to pressurize the high-entropy alloy hot-pressed sintered body (11) until the compressed height of the high-entropy alloy hot-pressed sintered body is 15% -20% of the original height, and then maintaining the pressure for 50s;
4. after the pressure maintaining is finished, controlling the compact male die (3) to ascend to open the die;
5. And (3) starting an ejection cylinder of the press to control the compact ejector rod (8) to move upwards, ejecting the compact high-entropy alloy hot-pressed sintered body (11) out of the compact female die (5), and taking out.
8. The method for using a hot mechanical densification device for brittle high-entropy alloy hot pressed sintering bodies according to claim 7, wherein the heating power of the male die heating sleeve (4) in the step one is 3 kW-5 kW, and the heating power of the die sleeve heating sleeve (10) is 8 kW-10 kW.
9. The method for using a hot mechanical densification device for brittle high-entropy alloy hot pressed sintered bodies according to claim 7, wherein the pressure applied to the hot pressed sintered bodies (11) of the high-entropy alloy in the third step is 250MPa to 300MPa during the pressure maintaining process.
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