Heat treatment method for enabling cast aluminum alloy to obtain linear separation characteristic

Abstract

The invention provides a heat treatment method for enabling cast aluminum alloy to obtain a linear separation characteristic, which comprises the following steps of: 1, putting an aluminum alloy casting into a hot isostatic pressing furnace, raising the temperature and the pressure, and keeping the temperature and the pressure at the temperature lower than the grain growth temperature; 2, after heat preservation and pressure maintaining in the step 1 are finished, reducing the pressure, meanwhile, raising the temperature, and completing heat preservation and pressure maintaining at the temperature higher than the grain growth temperature; and thirdly, after heat preservation and pressure maintaining in the second step are finished, the pressure is increased, meanwhile, cooling is conducted, the first step and the second step are repeated, and 4-6 cycles of low-temperature high-pressure and high-temperature low-pressure heat treatment are completed. According to the method, on the basis of hot isostatic pressing, the local grain growth rate of the aluminum alloy is affected by the solute segregation effect under the pressure and temperature cycle regulation effect, the grain distribution characteristic of a quasi double-peak structure is formed in the alloy, and a cast aluminum alloy casting has the linear separation characteristic; the problem that a traditional aluminum alloy material cannot achieve controllable linear separation under dynamic impact on the premise that quasi-static high toughness is met can be solved, and the lightweight level of a multi-stage aircraft is further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum alloy heat treatment, and in particular relates to a heat treatment method for aluminum to enable a cast aluminum alloy to obtain linear separable characteristics. Background Art

[0002] Linear separation is the main form of separation for high-performance multi-stage aircraft. In addition to maintaining the aerodynamic shape and load-bearing requirements of the conventional cabin, some sections of the aircraft must also be separated during flight to meet the design requirements. However, under the premise of meeting the quasi-static high strength and toughness of large maneuvers and large overloads, traditional aluminum alloy materials have a high separation charge and a large impact response, which has a serious impact on the lightweight and performance of high-performance multi-stage aircraft: when the impact charge is large, various mounting brackets need to be significantly thickened to ensure rigidity. This process will significantly reduce the lightweight level of the aircraft. In addition, the large impact response will deteriorate the flight environment in the cabin, and in severe cases, it may even cause the failure of brittle components and lead to flight loss of control. At this time, a large number of buffer structures have to be added, and some high-precision instruments and equipment cannot be used. It is also difficult to carry out integrated electrical design, and the performance of the equipment is significantly reduced.

[0003] Among the most widely used high-strength and tough light alloys, aluminum alloys such as ZL114A meet the quasi-static toughness requirements, but the high cutting amount leads to a large separation impact response, which cannot take into account both quasi-static toughness and high-speed impact brittleness. Therefore, while maintaining the quasi-static toughness of cast aluminum alloys, improving their high-speed impact brittleness is the key to improving the lightweight level and performance of multi-stage aircraft. Summary of the invention

[0004] Aiming at the problems that traditional light alloy materials have high separation amount and large impact response, high-performance multi-stage aircraft are lightweight and suffer performance loss, and high-speed impact brittleness is insufficient while meeting the quasi-static high strength and toughness requirements of large maneuverability and large overload, a method for making aluminum alloy have both quasi-static strength and toughness and high-speed impact brittleness through heat treatment is provided, and a microstructure with a "double-peak structure" distribution of casting grains is obtained through pressure and temperature regulation. When subjected to high-speed impact, the large-sized grains of the alloy's "double-peak structure" will be conducive to the generation of crack sources and crack propagation, so that the alloy has the characteristics of high-speed impact brittleness, while taking into account strength and toughness, further improving the lightweight level of the aircraft.

[0005] The technical solution provided by the present invention is as follows:

[0006] In a first aspect, a heat treatment method for making a cast aluminum alloy obtain linear separability characteristics comprises:

[0007] Step 1: placing the aluminum alloy casting into a hot isostatic pressing furnace, increasing the temperature and pressure, and maintaining the temperature and pressure at a temperature lower than the grain growth temperature;

[0008] Step 2: After the heat preservation and pressure holding in step 1 is completed, the pressure is reduced and the temperature is increased at the same time, and the heat preservation and pressure holding is completed at a temperature higher than the grain growth temperature;

[0009] Step 3: After the heat preservation and pressure maintenance in step 2 is completed, the pressure is increased and the temperature is reduced at the same time, and steps 1 and 2 are repeated to complete a total of 4 to 6 cycles of low-temperature high-pressure and high-temperature low-pressure heat treatment.

[0010] Furthermore, the aluminum alloy casting is a sand-cast Al-Si aluminum alloy casting, and its composition, by mass percentage, is: Si 4.0-10.0%, Mg 0.30-0.75%, Cu 0-4.5%, Ti 0-0.25%, Be 0-0.4%, and the rest is Al.

[0011] Furthermore, in the step of placing the aluminum alloy casting into a hot isostatic pressing furnace, increasing the temperature and pressure, and maintaining the temperature and pressure below the grain growth temperature, the hot isostatic pressing furnace is evacuated before increasing the temperature and pressure, and an inert gas is introduced as a protective gas and a pressure medium.

[0012] Furthermore, in the step of placing the aluminum alloy casting into a hot isostatic pressing furnace, increasing the temperature and pressure, and maintaining the temperature and pressure at a temperature below the grain growth temperature, the pressure is increased to 160-180 MPa and the temperature is increased to 480-500°C at a heating rate of 0.03-0.06°C / s, and then the temperature is maintained and pressure maintained for 30-60 minutes.

[0013] Furthermore, after the step 1 of heat preservation and pressure holding is completed, the pressure is reduced and the temperature is increased at the same time. In the step of completing heat preservation and pressure holding at a temperature higher than the grain growth temperature, after the pressure is reduced to 120-140 MPa and the temperature is increased to 520-540°C at a heating rate of 0.03-0.06°C / s, the heat preservation and pressure holding is performed for 5-10 minutes.

[0014] Furthermore, after the heat preservation and pressure maintenance in step 2 is completed, the pressure is increased and the temperature is reduced at the same time, and steps 1 and 2 are repeated to complete a total of 4 to 6 cycles of low-temperature and high-pressure and high-temperature and low-pressure heat treatment steps, with a cooling rate of 0.05 to 0.2°C / s.

[0015] Furthermore, after the cyclic heat treatment is completed, the pressure reducing valve is opened and the temperature is naturally reduced along with the hot isostatic pressing furnace, and the end point is normal temperature and pressure.

[0016] Furthermore, the heat treatment method also includes: performing aging treatment on the casting after hot isostatic pressing, the aging temperature is 165-180° C., and the aging time is 8-12 hours.

[0017] In the second aspect, the grain size of the cast aluminum alloy treated by the heat treatment method for obtaining linear separability of the cast aluminum alloy according to the first aspect presents a "bimodal structure" distribution.

[0018] A heat treatment method for making a cast aluminum alloy obtain linear separability according to the present invention has the following beneficial effects:

[0019] (1) The present invention provides a heat treatment method for making a cast aluminum alloy obtain linear separability. The heat treatment process utilizes the solute segregation effect under the action of pressure and temperature to effectively inhibit the growth of some grains and preferentially grow the grains, ultimately making the grain size of the casting have a "double-peak structure" distribution characteristic. After the casting is subjected to high-speed impact, the cracks generated at the penetration front can easily expand along the direction of the large-size grains of the casting. Therefore, under the same cutting charge dosage, the casting with a "double-peak structure" has a deeper overall penetration depth, and low charge dosage separation can be achieved;

[0020] (2) The present invention provides a heat treatment method for making a cast aluminum alloy obtain linear separability. Through heat treatment, the aluminum alloy has both quasi-static toughness and high-speed impact brittleness. The high-speed impact brittleness reduces the amount of cutting wire. The reduction of the impact response of the low amount of wire ensures the use environment of high-level precision instruments and the conditions for integrated electrical design. The low impact response can greatly reduce the installation of various brackets and thickening designs, thereby improving the lightweight level.

[0021] (3) The present invention provides a heat treatment method for obtaining linear separable characteristics of cast aluminum alloys. The aluminum alloy has a small "Hall-Petch" coefficient, and its mechanical properties are less sensitive to changes in grain size. Although the large grain components in the "double-peak structure" of the casting cause the average grain size to increase to a certain extent, it can still maintain high strength and toughness under quasi-static conditions.

[0022] (4) The present invention provides a heat treatment method for enabling a cast aluminum alloy to obtain linear separability. The heat treatment of the casting completes the solid solution treatment in a hot isostatic pressing furnace. The pores existing inside the casting can also be closed at this stage, thereby improving the qualified rate of the casting. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the grain size distribution diagram before and after heat treatment of Example 1;

[0024] Figure 2 This is the grain size distribution diagram before and after heat treatment of Example 2;

[0025] Figure 3 This is the grain size distribution diagram before and after heat treatment of Example 3;

[0026] Figure 4 This is the grain size distribution diagram before and after heat treatment of Example 4;

[0027] Figure 5 This is the grain size distribution diagram before and after heat treatment of Comparative Example 1;

[0028] Figure 6 This is a physical picture of the cutting simulation structural parts. DETAILED DESCRIPTION

[0029] The following detailed description of the present invention will make the features and advantages of the present invention more clear and explicit.

[0030] The word “exemplary” is used exclusively herein to mean “serving as an example, example, or illustration.” Any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments.

[0031] In order to simulate the linear separation of multi-stage aircraft, experiments on melting, pouring, heat treatment and energy-focusing cutting of cutting simulation structural castings were carried out.

[0032] Aluminum alloy castings are prepared by sand mold anti-gravity casting process, and alloy smelting is carried out in a high-purity graphite crucible (>99.9wt.%). The alloy preparation adopts the following smelting and casting process: preheat the raw materials at 300℃, and place the preheated raw materials in the crucible furnace in order for smelting; use a graphite rotor for degassing and slag refining; add the preheated modifier (Al-10Sr) and refiner (Al-5Ti-1B) to the 730-750℃ alloy liquid, and sprinkle the covering agent and slag after standing for 15 minutes. The pouring temperature is 690-700℃, the holding pressure is 240MPa, and the holding time is 500s.

[0033] The aluminum alloy casting is subjected to hot isostatic pressing treatment in a hot isostatic pressing device.

[0034] The heat treatment method for making a cast aluminum alloy obtain linear separability characteristics specifically comprises the following steps:

[0035] Step 1: Place the aluminum alloy casting into a hot isostatic pressing furnace, evacuate the furnace, and then introduce an inert gas such as argon protective gas, while starting to increase the temperature and pressure. When the pressure rises to 160-180 MPa, and the temperature rises to 480-500°C at a heating rate of 0.03-0.06°C / s, keep the temperature and pressure for 30-60 minutes. During the heat and pressure holding process, the divorced eutectic phase at the grain boundary begins to slowly dissolve, and the solute elements are concentrated near the grain boundary under the action of high pressure.

[0036] In particular, in the temperature range of 480-500°C, the eutectic phase at the grain boundary can be slowly decomposed and the grains will not grow; the pressure of 160-180 MPa can inhibit the diffusion of solutes near the grain boundary into the crystal.

[0037] Step 2: Reduce the pressure and increase the temperature at the same time. After the pressure is reduced to 120-140MPa and the temperature is increased to 520-540℃ at a heating rate of 0.03-0.06℃ / s, keep the temperature and pressure for 5-10 minutes. During the heat preservation and pressure holding process, due to the large amount of solute elements segregated near some grains, they grow preferentially under the action of temperature and solute segregation, and the solute begins to diffuse from the grain boundary to the grain.

[0038] In particular, short-term heat treatment at 520-540℃ can promote the rapid preferential growth of some grains, and the pressure of 120-140MPa can not only realize the uniform diffusion of solutes near the grain boundary into the crystal, but also shorten the time required for the next stage of pressure increase. Too long heat preservation and pressure holding time will lead to excessive growth of the entire grain, while too short time will lead to unclear preferential growth of some grains, so the control time is 5-10 minutes.

[0039] Step 3: Increase the pressure and reduce the temperature at the same time. After the pressure is increased to 160-180MPa and the temperature is reduced to 480-500℃ at a cooling rate of 0.05-0.2℃ / s, keep the temperature and pressure for 30-60min. Repeat steps 1 and 2 to complete a total of five cycles of long-term low-temperature and high-pressure heat treatment and short-term high-temperature and low-pressure heat treatment. Figure 1 , cooling and reducing pressure to room temperature and pressure. 4 to 6 cycles of heat treatment complete the solution treatment of the casting, the solute is evenly distributed, and the grain size is distributed in a "bimodal structure". The small grain size of the "bimodal structure" is 40 to 110 μm, and the large grain size is 200 to 250 μm. Small grains contain a larger grain boundary area, which can effectively hinder dislocation slip and improve strength. At the same time, small grains can also coordinate dislocation movement during plastic deformation of the alloy, ensuring the quasi-static toughness of the alloy. Large grains will initiate microcracks when the alloy is impacted, and the cracks can easily extend along the grain boundaries, ensuring the high-speed impact brittleness of the alloy. And large grains will not cause the overall average grain size of the alloy to increase excessively, so that the alloy has both quasi-static toughness and high-speed impact brittleness.

[0040] Step 4: Perform conventional aging treatment on the casting after hot isostatic pressing, the aging temperature is 165-180°C, and the aging time is 8-12h.

[0041] The "double-peak structure" casting obtained by the present invention has a high sensitivity to high-speed impact due to the presence of some large grains. Therefore, when the thickness of the structural parts is the same, less cutting wire is required to achieve linear separation, and the separation impact response is lower. In addition, since the heat treatment process is completed in a hot isostatic pressing furnace, if defects such as looseness and pores occasionally appear in the casting, they can be closed during the heat treatment process, thereby improving the yield rate.

[0042] The energy-focused cutting performance test was carried out on the cutting simulation structural castings to find out the minimum cutting charge amount of the structural parts obtained by different heat treatment methods under the same thickness.

[0043] Example

[0044] Example 1

[0045] This embodiment provides a heat treatment method for making a cast aluminum alloy obtain linear separability, comprising:

[0046] Step 1: Cut the simulated structural casting (see Figure 6 ) After the hot isostatic pressing furnace, the temperature and pressure are increased, and the temperature and pressure are maintained; specifically: the casting is heated from room temperature to 480°C in the hot isostatic pressing furnace, the heating rate is 0.06°C / s, and the temperature and pressure are maintained at 480°C and 180MPa for 50 minutes; the cutting simulation structure casting is an Al-Si series aluminum alloy, and its alloy composition is Si6.8%, Mg 0.58%, Ti 0.12%, Be 0.04%, and the rest is Al, which is recorded as ZL114A;

[0047] Step 2: Reduce the pressure, increase the temperature, and continue to maintain the temperature and pressure; specifically: increase the temperature to 530°C, the heating rate is 0.06°C / s, reduce the pressure to 140MPa, and maintain the temperature and pressure for 10 minutes;

[0048] Step three: Cool down and increase the pressure, repeat steps one and two, and complete a total of 5 cycles of long-term low-temperature and high-pressure and short-term high-temperature and low-pressure heat treatment. Specifically: lower the temperature to 480°C, the cooling rate is 0.1°C / s, increase the pressure to 180MPa, and keep the temperature and pressure for 50 minutes. Repeat the above two steps, and after completing five cycles of heat treatment, cool down naturally with the hot isostatic pressing equipment, open the pressure reducing valve to reduce the pressure, and the end point of cooling and pressure reduction is room temperature and pressure. The castings after hot isostatic pressing are subjected to conventional aging treatment, with an aging temperature of 165°C and an aging time of 10 hours. The grain distribution test of the cut simulation structure castings after heat treatment was carried out. The grains of the castings showed a "double-peak structure" distribution between 40-80μm and 200-250μm. The grain size of the castings before and after hot isostatic pressing can be seen. Figure 1 .

[0049] Carry out concentrated energy cutting performance test and test the minimum cutting charge amount.

[0050] Example 2

[0051] This embodiment provides a heat treatment method for making a cast aluminum alloy obtain linear separability, comprising:

[0052] Step 1: After placing the cutting simulation structure casting into a hot isostatic pressing furnace, the temperature and pressure are increased, and the temperature and pressure are maintained; specifically: the casting is heated from room temperature to 480°C in the hot isostatic pressing furnace, the heating rate is 0.06°C / s, and the temperature and pressure are maintained at 480°C and 160MPa for 50 minutes; the cutting simulation structure casting is an Al-Si series aluminum alloy, and its alloy composition is Si 6.8%, Mg 0.58%, Ti 0.12%, Be 0.04%, and the rest is Al, recorded as ZL114A;

[0053] Step 2: Reduce the pressure, increase the temperature, and continue to maintain the temperature and pressure; specifically: increase the temperature to 530°C, the heating rate is 0.06°C / s, reduce the pressure to 140MPa, and maintain the temperature and pressure for 10 minutes;

[0054] Step three: Cool down and increase the pressure, repeat steps one and two, and complete a total of five cycles of long-term low-temperature and high-pressure and short-term high-temperature and low-pressure heat treatment. Specifically: lower the temperature to 480°C, the cooling rate is 0.1°C / s, increase the pressure to 160MPa, and keep the temperature and pressure for 50 minutes. Repeat the above two steps, and after completing 5 cycles of heat treatment, let the hot isostatic pressing equipment cool down naturally, open the pressure reducing valve to reduce the pressure, and the end point of cooling and pressure reduction is room temperature and pressure. The castings after hot isostatic pressing are subjected to conventional aging treatment, with an aging temperature of 165°C and an aging time of 10 hours. The grain distribution test of the cut simulation structure castings after heat treatment was carried out. The grains of the castings showed a "double peak structure" distribution between 40-80μm and 200-250μm. The grain size of the castings before and after hot isostatic pressing can be seen. Figure 2 .

[0055] Carry out concentrated energy cutting performance test and test the minimum cutting charge amount.

[0056] Example 3

[0057] This embodiment provides a heat treatment method for making a cast aluminum alloy obtain linear separability, comprising:

[0058] Step 1: After placing the cutting simulation structure casting into a hot isostatic pressing furnace, the temperature and pressure are increased, and the temperature and pressure are maintained; specifically: the casting is heated from room temperature to 480°C in the hot isostatic pressing furnace, the heating rate is 0.06°C / s, and the temperature and pressure are maintained at 480°C and 180MPa for 30 minutes; the cutting simulation structure casting is an Al-Si series aluminum alloy, and its alloy composition is Si 6.8%, Mg 0.58%, Ti 0.12%, Be 0.04%, and the rest is Al, recorded as ZL114A;

[0059] Step 2: Reduce the pressure, increase the temperature, and continue to maintain the temperature and pressure; specifically: increase the temperature to 530°C, the heating rate is 0.06°C / s, reduce the pressure to 140MPa, and maintain the temperature and pressure for 5 minutes;

[0060] Step three: Cool down and increase the pressure, repeat steps one and two, and complete a total of five cycles of long-term low-temperature and high-pressure and short-term high-temperature and low-pressure heat treatment. Specifically: lower the temperature to 480°C, the cooling rate is 0.1°C / s, increase the pressure to 180MPa, and keep warm and pressurized for 30 minutes. Repeat the above two steps, and after completing 5 cycles of heat treatment, let the hot isostatic pressing equipment cool down naturally, open the pressure reducing valve to reduce the pressure, and the end point of cooling and pressure reduction is room temperature and pressure. The castings after hot isostatic pressing are subjected to conventional aging treatment, with an aging temperature of 165°C and an aging time of 10 hours. The grain distribution test of the cut simulation structure castings after heat treatment was carried out. The grains of the castings showed a "double-peak structure" distribution between 40-80μm and 200-250μm. The grain size of the castings before and after hot isostatic pressing can be seen. Figure 3 .

[0061] Carry out concentrated energy cutting performance test and test the minimum cutting charge amount.

[0062] Example 4

[0063] This embodiment provides a heat treatment method for making a cast aluminum alloy obtain linear separability, comprising:

[0064] Step 1: After placing the cutting simulation structure casting into a hot isostatic pressing furnace, the temperature and pressure are increased, and the temperature and pressure are maintained; specifically, the casting is heated from room temperature to 480°C in the hot isostatic pressing furnace, the heating rate is 0.06°C / s, and the temperature and pressure are maintained at 500°C and 160MPa for 30 minutes; the cutting simulation structure casting is an Al-Si series aluminum alloy, and its alloy composition is Si 6.8%, Mg 0.58%, Ti 0.12%, Be 0.04%, and the rest is Al, recorded as ZL114A;

[0065] Step 2: Reduce the pressure, increase the temperature, and continue to maintain the temperature and pressure; specifically: increase the temperature to 540°C, the heating rate is 0.06°C / s, reduce the pressure to 120MPa, and maintain the temperature and pressure for 10 minutes;

[0066] Step three: Cool down and increase the pressure, repeat steps one and two, and complete a total of 5 cycles of long-term low-temperature and high-pressure and short-term high-temperature and low-pressure heat treatment. Specifically: lower the temperature to 480°C, the cooling rate is 0.1°C / s, increase the pressure to 180MPa, and keep the temperature and pressure for 50 minutes. Repeat the above two steps, and after completing five cycles of heat treatment, cool down naturally with the hot isostatic pressing equipment, open the pressure reducing valve to reduce the pressure, and the end point of cooling and pressure reduction is room temperature and pressure. The castings after hot isostatic pressing are subjected to conventional aging treatment, with an aging temperature of 165°C and an aging time of 10 hours. The grain distribution test of the cut simulation structure castings after heat treatment was carried out. The casting grains were distributed in a "double-peak structure" between 50-110μm and 200-250μm. The grain size of the casting before and after hot isostatic pressing can be seen. Figure 4 .

[0067] Carry out concentrated energy cutting performance test and test the minimum cutting charge amount.

[0068] Example 5

[0069] This embodiment provides a heat treatment method for making a cast aluminum alloy obtain linear separability, comprising:

[0070] Step 1: After the cutting simulation structure casting is placed in a hot isostatic pressing furnace, the temperature and pressure are increased, and the temperature and pressure are maintained; specifically: the casting is heated from room temperature to 480°C in the hot isostatic pressing furnace, the heating rate is 0.06°C / s, and the temperature and pressure are maintained at 480°C and 180MPa for 50 minutes; the cutting simulation structure casting is an Al-Si series aluminum alloy, and its alloy composition is Si 7.6%, Mg 0.45%, Ti 0.16%, Be 0.06%, and the rest is Al in terms of mass percentage;

[0071] Step 2: Reduce the pressure, increase the temperature, and continue to maintain the temperature and pressure; specifically: increase the temperature to 530°C, the heating rate is 0.06°C / s, reduce the pressure to 140MPa, and maintain the temperature and pressure for 10 minutes;

[0072] Step 3: Cool down and increase the pressure, repeat steps 1 and 2, and complete a total of 5 cycles of long-term low-temperature and high-pressure and short-term high-temperature and low-pressure heat treatment. Specifically: reduce the temperature to 480°C, the cooling rate is 0.1°C / s, increase the pressure to 180MPa, and keep the temperature and pressure for 50 minutes. Repeat the above two steps, and after completing five cycles of heat treatment, cool down naturally with the hot isostatic pressing equipment, open the pressure reducing valve to reduce the pressure, and the end point of cooling and pressure reduction is room temperature and pressure. The castings after hot isostatic pressing are subjected to conventional aging treatment, with an aging temperature of 165°C and an aging time of 10 hours. The grain distribution test of the cut simulation structure casting after heat treatment was carried out, and the casting grains were distributed in a "bimodal structure" between 40-80μm and 200-250μm.

[0073] Carry out concentrated energy cutting performance test and test the minimum cutting charge amount.

[0074] Example 6

[0075] This embodiment provides a heat treatment method for making a cast aluminum alloy obtain linear separability, comprising:

[0076] Step 1: After the cutting simulation structure casting is put into a hot isostatic pressing furnace, the temperature and pressure are increased, and the temperature and pressure are maintained; specifically: the casting is heated from room temperature to 480°C in the hot isostatic pressing furnace, the heating rate is 0.06°C / s, and the temperature and pressure are maintained at 480°C and 180MPa for 50 minutes; the cutting simulation structure casting is an Al-Si series aluminum alloy, and its alloy composition is Si 7.8%, Mg0.55%, Ti 0.20%, Be 0.08%, and the rest is Al in terms of mass percentage;

[0077] Step 2: Reduce the pressure, increase the temperature, and continue to maintain the temperature and pressure; specifically: increase the temperature to 530°C, the heating rate is 0.06°C / s, reduce the pressure to 140MPa, and maintain the temperature and pressure for 10 minutes;

[0078] Step 3: Cool down and increase the pressure, repeat steps 1 and 2, and complete a total of 5 cycles of long-term low-temperature and high-pressure and short-term high-temperature and low-pressure heat treatment. Specifically: reduce the temperature to 480°C, the cooling rate is 0.1°C / s, increase the pressure to 180MPa, and keep the temperature and pressure for 50 minutes. Repeat the above two steps, and after completing five cycles of heat treatment, cool down naturally with the hot isostatic pressing equipment, open the pressure reducing valve to reduce the pressure, and the end point of cooling and pressure reduction is room temperature and pressure. The castings after hot isostatic pressing are subjected to conventional aging treatment, with an aging temperature of 165°C and an aging time of 10 hours. The grain distribution test of the cut simulation structure casting after heat treatment was carried out, and the casting grains were distributed in a "bimodal structure" between 40-80μm and 200-250μm.

[0079] Carry out concentrated energy cutting performance test and test the minimum cutting charge amount.

[0080] Comparative Example

[0081] Comparative Example 1

[0082] The same sand casting process was used to prepare ZL114A cutting simulation structure castings with the same composition. The castings were subjected to conventional solution and aging treatment. The solution treatment parameters were 540℃×14h and the aging parameters were 165℃×10h. The grain size of the castings before and after heat treatment is shown in Figure 5 . Carry out concentrated energy cutting performance test and test the minimum cutting charge amount.

[0083] Comparative Example 2

[0084] The casting and heat treatment processes of this comparative example are basically the same as those of Example 1, except that the heat preservation and pressure holding time at 480° C. and 180 MPa is 80 min.

[0085] Comparative Example 3

[0086] The casting and heat treatment processes of this comparative example are basically the same as those of Example 1, except that the heat preservation and pressure holding time at 480° C. and 180 MPa is 20 min.

[0087] Comparative Example 4

[0088] The casting and heat treatment processes of this comparative example are basically the same as those of Example 1, except that the heat preservation and pressure holding time at 530° C. and 140 MPa is 20 min.

[0089] Comparative Example 5

[0090] The casting and heat treatment processes of this comparative example are basically the same as those of Example 1, except that the heat preservation and pressure holding time at 530° C. and 140 MPa is 2 minutes.

[0091] Comparative Example 6

[0092] The casting and heat treatment processes of this comparative example are basically the same as those of Example 1, with the only difference being that in step 1, during the low-temperature and high-pressure heat treatment stage, the casting is heated from room temperature to 420°C in a hot isostatic pressing furnace at a heating rate of 0.06°C / s, and is kept at 420°C and 180MPa for 50 minutes.

[0093] Comparative Example 7

[0094] The casting and heat treatment processes of this comparative example are basically the same as those of Example 1, with the only difference being that in step 1, during the low-temperature and high-pressure heat treatment stage, the casting is heated from room temperature to 520°C in a hot isostatic pressing furnace at a heating rate of 0.06°C / s, and is kept at 520°C and 180MPa for 50 minutes.

[0095] Comparative Example 8

[0096] The casting and heat treatment processes of this comparative example are basically the same as those of Example 1, with the only difference being that in step 2, during the high-temperature and low-pressure heat treatment stage, the temperature is raised to 500°C, the heating rate is 0.06°C / s, the pressure is reduced to 140MPa, and the temperature and pressure are maintained for 10 minutes.

[0097] Comparative Example 9

[0098] The casting and heat treatment processes of this comparative example are basically the same as those of Example 1, with the only difference being that in step 2, during the high-temperature and low-pressure heat treatment stage, the temperature is raised to 580°C at a heating rate of 0.06°C / s, the pressure is reduced to 140MPa, and the temperature and pressure are maintained for 10 minutes.

[0099] Comparative Example 10

[0100] The casting and heat treatment processes of this comparative example are basically the same as those of Example 1, with the only difference being that only three cycles of long-term low-temperature high-pressure and short-term high-temperature low-pressure hot isostatic pressing treatment are performed.

[0101] Effect verification:

[0102] The performance of the alloy castings prepared in the examples and comparative examples was tested, and the test results are shown in Table 1.

[0103] It can be seen from Table 1 that after the ZL114A cutting simulation structure casting is treated by the heat treatment process of the present invention, the strength and toughness are not significantly inferior to those of conventional heat treatment, but the minimum cutting agent amount is significantly reduced, indicating that the ZL114A cutting simulation structure casting has both quasi-static strength and toughness and high-speed impact brittleness.

[0104] Table 1

[0105]

[0106] The present invention has been described in detail above in conjunction with specific implementation methods and exemplary embodiments, but these descriptions cannot be understood as limiting the present invention. Those skilled in the art understand that, without departing from the spirit and scope of the present invention, a variety of equivalent substitutions, modifications or improvements can be made to the technical solutions and implementation methods of the present invention, all of which fall within the scope of the present invention. The scope of protection of the present invention shall be subject to the attached claims.

[0107] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A heat treatment method for making a cast aluminum alloy obtain linear separability, characterized in that: include: Step 1: placing the aluminum alloy casting into a hot isostatic pressing furnace, increasing the temperature and pressure, and maintaining the temperature and pressure at a temperature lower than the grain growth temperature; Step 2, after the heat preservation and pressure holding in step 1 is completed, the pressure is reduced and the temperature is increased at the same time, and the heat preservation and pressure holding is completed at a temperature higher than the grain growth temperature; Step 3: After the heat preservation and pressure maintenance in step 2 is completed, the pressure is increased and the temperature is reduced at the same time, and steps 1 and 2 are repeated to complete a total of 4 to 6 cycles of low-temperature high-pressure and high-temperature low-pressure heat treatment.

2. The heat treatment method for making a cast aluminum alloy obtain linear separability according to claim 1, characterized in that: The aluminum alloy casting is a sand-cast Al-Si aluminum alloy casting, and its components are as follows by mass percentage: Si 4.0-10.0%, Mg 0.30-0.75%, Cu 0-4.5%, Ti 0-0.25%, Be 0-0.4%, and the rest is Al.

3. The heat treatment method for making a cast aluminum alloy obtain linear separability according to claim 1, characterized in that: In the step of placing the aluminum alloy casting into a hot isostatic pressing furnace, heating and pressurizing, and maintaining the temperature and pressure below the grain growth temperature, the hot isostatic pressing furnace is evacuated and an inert gas is introduced as a protective gas and a pressure medium before heating and pressurizing.

4. The heat treatment method for making a cast aluminum alloy obtain linear separability according to claim 1, characterized in that: In the step of placing the aluminum alloy casting into a hot isostatic pressing furnace, increasing the temperature and pressure, and maintaining the temperature and pressure at a temperature below the grain growth temperature, after the pressure is increased to 160-180 MPa and the temperature is increased to 480-500° C., the temperature and pressure are maintained for 30-60 minutes.

5. The heat treatment method for making a cast aluminum alloy obtain linear separability according to claim 1, characterized in that: In the step of placing the aluminum alloy casting into a hot isostatic pressing furnace, increasing the temperature and pressure, and maintaining the temperature and pressure at a temperature lower than the grain growth temperature, the heating rate is 0.03-0.06° C. / s.

6. The heat treatment method for making a cast aluminum alloy obtain linear separability according to claim 1, characterized in that: After the step 1 of heat preservation and pressure holding is completed, the pressure is reduced and the temperature is increased at the same time. In the step of completing the heat preservation and pressure holding at a temperature higher than the grain growth temperature, after the pressure is reduced to 120-140 MPa and the temperature is increased to 520-540° C., the heat preservation and pressure holding is performed for 5-10 minutes.

7. The heat treatment method for making a cast aluminum alloy obtain linear separability according to claim 1, characterized in that: After the step 1 of heat preservation and pressure holding is completed, the pressure is reduced and the temperature is increased at the same time. In the step of completing the heat preservation and pressure holding at a temperature higher than the grain growth temperature, the heating rate is 0.03-0.06° C. / s.

8. The heat treatment method for making a cast aluminum alloy obtain linear separability according to claim 1, characterized in that: After the heat preservation and pressure maintenance in step 2 is completed, the pressure is increased and the temperature is reduced at the same time, and steps 1 and 2 are repeated to complete a total of 4 to 6 cycles of low-temperature and high-pressure and high-temperature and low-pressure heat treatment steps, with a cooling rate of 0.05 to 0.2°C / s.

9. The heat treatment method for making a cast aluminum alloy obtain linear separability according to claim 1, characterized in that: The heat treatment method further comprises: performing aging treatment on the casting after hot isostatic pressing, the aging temperature is 165-180° C., and the aging time is 8-12 hours.

10. An aluminum alloy casting, characterized in that: The heat treatment method for obtaining linear separability of the cast aluminum alloy as claimed in any one of claims 1 to 9 is used to obtain a "bimodal structure" distribution of grain size.

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