Die-casting aluminum alloy material and strengthening and toughening method and application thereof

Abstract

The invention discloses a die-casting aluminum alloy material and a strengthening and toughening method and application thereof, and belongs to the technical field of aluminum alloy casting. The strengthening and toughening method of the die-casting aluminum alloy material comprises the following steps that a die-casting aluminum alloy material base body is subjected to heat preservation for the first time at the temperature of 100-180 DEG C, and the heat preservation time ranges from 10 min to 40 min; and the die-casting aluminum alloy material base body subjected to first-time heat preservation is subjected to second-time heat preservation at the temperature of 180-220 DEG C, and the heat preservation time ranges from 120 min to 300 min. According to the strengthening and toughening method for the die-casting aluminum alloy material, through the two-step low-temperature heat treatment process, the yield strength of the die-casting aluminum alloy material is improved by 30%, and the elongation at break is kept unchanged, so that the strength and plasticity of the shell material are improved, and the worse use working condition is met.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum alloy casting, and in particular to a die-casting aluminum alloy material and a strengthening and toughening method and application thereof. Background Art

[0002] Die-cast aluminum alloy is the most commonly used lightweight metal material for railway signal lamp housings. Compared with ordinary steel, it can achieve a 20%-30% weight reduction effect, and the use of this material can realize the one-piece molding of the housing, reducing the manufacturing workload. However, the current die-cast aluminum alloy materials are mainly Al-Si alloys, which have mechanical property disadvantages such as low strength and poor plasticity, which will cause hidden dangers to the normal operation of the signal machine. In addition, due to the existence of problems such as air entrainment during the high-pressure casting process, there are many defects inside the aluminum alloy material, which is prone to macroscopic defects such as blistering and deformation under high-temperature heat treatment conditions, affecting the qualified rate of parts and components. Therefore, it is necessary to select appropriate heat treatment for the die-cast material to meet service requirements.

[0003] For die-cast Al-Si alloy materials, the most commonly used heat treatment method is T6 heat treatment, that is, solid solution + aging heat treatment process. Although higher strength and toughness can be obtained through this heat treatment process, the temperature of solid solution treatment is usually 400℃-500℃, and die-cast parts are prone to macro defects such as blistering under this temperature condition, which affects the production qualification rate and leads to poor mechanical properties of parts. In order to solve this problem, two methods are usually used to improve the strength and toughness of die-cast aluminum alloy parts. One way is high vacuum die casting combined with T6 heat treatment. This method has a complex process and high production cost; the other is ordinary die casting combined with aging treatment. Although this method improves the strength of the material, it greatly sacrifices the toughness of the material and cannot meet the service requirements of the parts.

[0004] The patent with publication number CN112281091A discloses a heat treatment method for Al-Si-Cu die-cast aluminum alloy, which specifically discloses improving the Rockwell hardness of die-cast aluminum alloy parts by two-stage aging, 50℃-120℃ / 20min-60min and 150℃-200℃ / 180min-600min. However, the patent only analyzes the effect of the two-step heat treatment on the hardness of the material, and is unable to clarify the effect of the two-step heat treatment on the comprehensive mechanical properties of the material.

[0005] Therefore, in view of the existing aluminum alloy heat treatment problems, there is an urgent need for a method to comprehensively improve the strength and toughness of die-cast parts and ensure that the parts do not undergo macroscopic deformation. Summary of the invention

[0006] The purpose of the present invention is to provide a die-cast aluminum alloy material and a strengthening and toughening method and application thereof, so as to solve the technical problem in the prior art that the die-cast aluminum alloy has poor strength and toughness and is difficult to meet the mechanical property requirements of the shell material.

[0007] To achieve the above object, an embodiment of the present invention provides a method for strengthening and toughening a die-cast aluminum alloy material, comprising the following steps:

[0008] The die-cast aluminum alloy material substrate is firstly kept at 100°C-180°C for 10min-40min;

[0009] After the first heat preservation, the die-cast aluminum alloy material matrix is ​​subjected to a second heat preservation at 180° C.-220° C., and the heat preservation time is 120 min-300 min.

[0010] In one of the preferred solutions of the present invention, the temperature of the first insulation is 120° C.-180° C., and the insulation time is 15 min-40 min.

[0011] In one of the preferred solutions of the present invention, the temperature of the first insulation is 120° C.-150° C., and the insulation time is 15 min-40 min.

[0012] In one of the preferred solutions of the present invention, the temperature of the second insulation is 180° C.-200° C., and the insulation time is 120 min-180 min.

[0013] In one of the preferred solutions of the present invention, cooling is performed after the first heat preservation and the second heat preservation are completed.

[0014] In one of the preferred solutions of the present invention, the cooling is air cooling after exiting the furnace.

[0015] One of the preferred solutions of the present invention is to place the die-cast aluminum alloy material substrate in a constant temperature oil bath furnace for a first heat preservation and a second heat preservation.

[0016] Based on the strengthening and toughening method of a die-casting aluminum alloy material disclosed in the present invention, the present invention also discloses a die-casting aluminum alloy material, which is prepared by applying the strengthening and toughening method of the die-casting aluminum alloy material mentioned above.

[0017] In one of the preferred solutions of the present invention, the die-casting aluminum alloy material comprises the following chemical components in proportion by mass percentage:

[0018] Si: 6%-9%, Mg: 0.4%-0.6%, Mn: 0.3%-0.7%, Zn: ≤0.05%, Fe: ≤0.02%. The balance is Al and impurities.

[0019] The invention also discloses an application of the die-cast aluminum alloy material, and the die-cast aluminum alloy material is used for a railway signal lamp housing.

[0020] In summary, the beneficial effects of the present invention are:

[0021] 1. The toughening method of the die-cast aluminum alloy material of the present invention adopts a toughening method of low-temperature short-time annealing + artificial aging. On the one hand, a large number of nano-Si particles are precipitated in the Al matrix through the low-temperature annealing process. During the plastic deformation process, these nano-Si can act as dislocation sources to release dislocations to the matrix during dislocation interaction, thereby increasing the density of movable dislocations and improving the plasticity of the material; on the other hand, through the artificial aging process, needle-shaped strengthening phase β is precipitated. ” This strengthening phase can hinder the movement of dislocations and improve the strength of the material. The combination of the two-step heat treatment process can improve the comprehensive mechanical properties of the die-cast aluminum alloy material. At the same time, due to the low heat treatment temperature, the material does not deform during the heat treatment process, thus ensuring the dimensional accuracy of the parts.

[0022] 2. The die-cast aluminum alloy material prepared by the present invention has a yield strength of not less than 140 MPa, a tensile strength of not less than 260 MPa, and an elongation of not less than 8%; compared with the die-cast alloy, the strength can be increased by at least 25% while the elongation remains unchanged; compared with the single-stage aged alloy, the elongation can be increased by at least 50% while the strength remains unchanged.

[0023] 3. The aluminum alloy material treated by the toughening method of the die-cast aluminum alloy material of the present invention has good comprehensive mechanical properties and can be applied to railway signal lamp housings.

[0024] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by implementing the present invention. The purpose and other advantages of the present invention can be described by the effects described in the description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of a heat treatment process for strengthening and toughening a die-cast aluminum alloy material according to the present invention;

[0026] Figure 2 It is a schematic diagram of the dimensions of the tensile specimen in the embodiment of the present invention;

[0027] Figure 3 This is the microstructure diagram of the die-cast aluminum alloy material prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0030] The present invention provides a method for strengthening and toughening a die-cast aluminum alloy material, comprising two steps of heat treatment, such as Figure 1 As shown, the specific steps include:

[0031] Step (1): the die-cast aluminum alloy material matrix is ​​firstly kept at 100°C-180°C for a holding time of 10min-40min; specifically, the temperature of the constant temperature oil bath furnace is set to 100°C-180°C, and then the die-cast aluminum alloy material matrix is ​​placed in the constant temperature oil bath furnace for heating and measuring the surface temperature of the sample, and after the surface temperature of the sample reaches the set temperature of the constant temperature oil bath furnace, it is kept for 10min-40min, and then taken out of the furnace and air-cooled to room temperature, and further, the holding temperature is 120°C-180°C, and the holding time is 15min-40min, and preferably, the holding temperature is 120°C-150°C;

[0032] Step (2): After the first insulation, the die-cast aluminum alloy material substrate is subjected to a second insulation at 180°C-220°C, and the insulation time is 120min-300min; specifically, the temperature of the constant temperature oil bath furnace is set to 180°C-220°C, the die-cast aluminum alloy material substrate treated in step (1) is placed in the constant temperature oil bath furnace for heating and the surface temperature of the sample is measured, and after the surface temperature of the sample reaches the set temperature of the constant temperature oil bath furnace, the sample is kept warm for 120min-300min, and after the insulation is completed, the sample is taken out of the furnace and air-cooled to room temperature. Furthermore, the insulation temperature is 180°C-200°C, and the insulation time is 120min-180min.

[0033] The heat treatment in step (1) of the present invention is intended to coarsen the morphology of eutectic Si and precipitate nano-Si particles, so that the plasticity of the material is greatly improved within a shorter heat treatment time, thereby improving the toughness of the die-casting material.

[0034] The present invention also discloses a die-cast aluminum alloy material, which is prepared by applying the above-mentioned method for strengthening and toughening a die-cast aluminum alloy material. The die-cast aluminum alloy material includes the following chemical components in proportion by mass percentage:

[0035] Si: 6%-9%, Mg: 0.4%-0.6%, Mn: 0.3%-0.7%, Zn: ≤0.05%, Fe: ≤0.02%. The balance is Al and impurities.

[0036] The invention also discloses an application of the die-cast aluminum alloy material, and the die-cast aluminum alloy material is used for a railway signal lamp housing.

[0037] Example 1

[0038] A method for strengthening and toughening a die-cast aluminum alloy material comprises the following steps:

[0039] Step (1): the die-cast aluminum alloy is kept in a constant temperature oil bath furnace at 120° C. for 15 minutes for low temperature annealing, and then taken out of the furnace and air-cooled to room temperature;

[0040] Step (2): the low temperature annealed alloy is kept in a constant temperature oil bath furnace at 180° C. for 120 min for isothermal artificial aging, and then taken out of the furnace and air-cooled to room temperature.

[0041] A die-cast aluminum alloy material is prepared by using a method for strengthening and toughening a die-cast aluminum alloy material in this embodiment. The die-cast aluminum alloy material includes the following chemical components in proportion by mass percentage:

[0042] Si: 6.58%, Mg: 0.43%, Mn: 0.47%, Zn: 0.05%, Fe: 0.02%, and the balance is Al and impurities.

[0043] Example 2

[0044] A method for strengthening and toughening a die-cast aluminum alloy material comprises the following steps:

[0045] Step (1): the die-cast aluminum alloy is kept in a constant temperature oil bath furnace at 150° C. for 15 minutes for low temperature annealing, and then taken out of the furnace and air-cooled to room temperature;

[0046] Step (2): the low temperature annealed alloy is kept in a constant temperature oil bath furnace at 180° C. for 120 min for isothermal artificial aging, and then taken out of the furnace and air-cooled to room temperature.

[0047] A die-cast aluminum alloy material is prepared by using a method for strengthening and toughening a die-cast aluminum alloy material in this embodiment. The die-cast aluminum alloy material includes the following chemical components in proportion by mass percentage:

[0048] Si: 6.58%, Mg: 0.43%, Mn: 0.47%, Zn: 0.05%, Fe: 0.02%, and the balance is Al and impurities.

[0049] Example 3

[0050] A method for strengthening and toughening a die-cast aluminum alloy material comprises the following steps:

[0051] Step (1): the die-cast aluminum alloy is kept in a constant temperature oil bath furnace at 180° C. for 15 minutes for low temperature annealing, and then taken out of the furnace and air-cooled to room temperature;

[0052] Step (2): the low temperature annealed alloy is kept in a constant temperature oil bath furnace at 180° C. for 120 min for isothermal artificial aging, and then taken out of the furnace and air-cooled to room temperature.

[0053] A die-cast aluminum alloy material is prepared by using a method for strengthening and toughening a die-cast aluminum alloy material in this embodiment. The die-cast aluminum alloy material includes the following chemical components in proportion by mass percentage:

[0054] Si: 6.58%, Mg: 0.43%, Mn: 0.47%, Zn: 0.05%, Fe: 0.02%, and the balance is Al and impurities.

[0055] Comparative Example 1

[0056] A die-cast alloy having the chemical composition described in Example 1 was used (ie, the chemical composition of the die-cast alloy was: Si: 6.58%, Mg: 0.43%, Mn: 0.47%, Zn: 0.05%, Fe: 0.02%, and the remainder was Al and impurities).

[0057] Comparative Example 2

[0058] The die-cast alloy with the chemical composition described in Example 1 (i.e., the chemical composition of the die-cast alloy is: Si: 6.58%, Mg: 0.43%, Mn: 0.47%, Zn: 0.05%, Fe: 0.02%, and the balance is Al and impurities) is kept in a constant temperature oil bath furnace at 180°C for 2 hours for isothermal artificial aging, and then taken out of the furnace and air-cooled to room temperature.

[0059] Test and Inspection

[0060] The die-cast aluminum alloy materials prepared in Examples 1-3 and Comparative Examples 1-2 were made into tensile specimens. The specific dimensions of the tensile specimens are as follows: Figure 2 The tensile test specimens were subjected to a tensile test on an Instron 5967 tensile tester at a tensile rate of 0.3 mm / min. A CCD camera was used to capture images during the experiment, and a video extensometer was used to perform digital image analysis to measure the strain of the specimens during the tensile test. The experiment was performed at least three times in each state, and the experimental values ​​obtained were the average values. The mechanical properties are shown in Table 1.

[0061] Table 1: Tensile test mechanical properties of die-cast aluminum alloy materials obtained in Examples and Comparative Examples

[0062]

[0063] It can be seen from Table 1 that the tensile strength of the die-cast aluminum alloy materials prepared in Examples 1-3 is above 260 MPa, the yield strength reaches 150 MPa, and the elongation exceeds 8.5%; compared with the die-cast alloy in Comparative Example 1, the yield strength is increased by about 25%, while the tensile strength and elongation at break remain basically unchanged; compared with the artificially aged alloy in Comparative Example 2, the yield strength is basically unchanged, but the elongation at break is increased by 54.5%, which greatly improves the plasticity of the material.

[0064] The die-cast aluminum alloy material prepared in Example 2 was subjected to metallographic microstructural observation, and the results are as follows: Figure 3 As shown, (a) is the microstructure of the die-cast aluminum alloy material, Si is the microstructure of the nano-Si particles, β ” β ” The microstructure diagram of the phase. Figure 3 It can be seen that after two-step heat treatment, a large number of nano-scale Si particles are precipitated on the aluminum matrix. The nano-Si particles dispersed in the matrix reduce the stress concentration phenomenon at the dendrites and improve the plastic deformation ability of the material; artificial aging treatment makes β ” Precipitation, the needle-shaped precipitation phase is the main precipitation strengthening phase of Al-Mg-Si alloy, and has a coherent relationship with the aluminum matrix. Its precipitation will cause lattice distortion of the aluminum matrix. The stress field generated by the lattice distortion interacts with the dislocation, hindering the movement of the dislocation, thereby producing a strengthening effect. Through the effective combination of the two-step heat treatment process, the material can maintain good plasticity while improving strength.

[0065] In summary, the toughening method of the die-cast aluminum alloy material of the present invention increases the yield strength of the die-cast aluminum alloy material by 30% through a two-step low-temperature heat treatment process, and maintains the elongation at break unchanged, thereby improving the strength and plasticity of the shell material to meet more severe operating conditions.

[0066] The embodiments described above are merely descriptions of preferred implementations of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary engineering and technical personnel in the field should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for strengthening and toughening a die-cast aluminum alloy material, characterized in that: The following steps are involved: The die-cast aluminum alloy material substrate is firstly kept at 100°C-180°C for 10min-40min; After the first heat preservation, the die-cast aluminum alloy material matrix is ​​subjected to a second heat preservation at 180° C.-220° C., and the heat preservation time is 120 min-300 min.

2. A method for strengthening and toughening a die-cast aluminum alloy material according to claim 1, characterized in that: The temperature of the first insulation is 120° C.-180° C., and the insulation time is 15 min-40 min.

3. A method for strengthening and toughening a die-cast aluminum alloy material as claimed in claim 2, characterized in that: The temperature of the first insulation is 120° C.-150° C., and the insulation time is 15 min-40 min.

4. A method for strengthening and toughening a die-cast aluminum alloy material as claimed in claim 1, characterized in that: The temperature of the second insulation is 180° C.-200° C., and the insulation time is 120 min-180 min.

5. The method for strengthening and toughening a die-cast aluminum alloy material according to claim 1, characterized in that: After the first heat preservation and the second heat preservation are completed, cooling is performed.

6. A method for strengthening and toughening a die-cast aluminum alloy material as claimed in claim 5, characterized in that: The cooling is air cooling after leaving the furnace.

7. A method for strengthening and toughening a die-cast aluminum alloy material as claimed in claim 1, characterized in that: The die-cast aluminum alloy material substrate is placed in a constant temperature oil bath furnace for the first and second insulation.

8. A die-casting aluminum alloy material, characterized in that: The die-cast aluminum alloy material is prepared by the strengthening and toughening method described in any one of claims 1 to 7.

9. A die-cast aluminum alloy material as claimed in claim 8, characterized in that: The die-casting aluminum alloy material includes the following chemical components in proportion by mass percentage: Si: 6%-9%, Mg: 0.4%-0.6%, Mn: 0.3%-0.7%, Zn: ≤0.05%, Fe: ≤0.02%. The balance is Al and impurities.

10. An application of a die-casting aluminum alloy material according to any one of claims 8 to 9, characterized in that: Die-cast aluminum alloy materials are used for railway signal lamp housings.

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