Preparation method of high-toughness in-situ TiB2 particle reinforced aluminum-based composite material

Abstract

According to the preparation method of the high-toughness in-situ TiB2 particle reinforced aluminum-based composite material, an improved molten salt reaction process, a hot extrusion process and a heat treatment process are combined, casting defects such as pores and cracks in a composite material blank can be effectively eliminated, and the density of the composite material blank is improved; and the size and the distribution state of the TiB2 reinforced particles in the matrix are further improved, so that the in-situ TiB2 particle reinforced aluminum-based composite material with high strength and high toughness is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum matrix composites, and specifically to a preparation method of a high-strength and tough in-situ TiB2 particle-reinforced aluminum matrix composite material. Background Art

[0002] In-situ particle-reinforced aluminum matrix composites have the characteristics of low density, high specific strength, high specific stiffness, high wear resistance, and good interfacial bonding with the aluminum alloy matrix, and have extensive application requirements in many fields such as aerospace, automotive, energy, and military industry. They are lightweight and high-strength composites with great application potential. Currently, the second-phase particles commonly used for in-situ reinforcement of aluminum matrix composites mainly include TiB2, TiC, B4C, and Al2O3, etc. Among them, TiB2 particles exhibit excellent reinforcement characteristics due to their high hardness, high elasticity, and the fact that they are not easy to generate interfacial reactants with aluminum.

[0003] Existing in-situ TiB2 particle-reinforced aluminum matrix composites are generally prepared by the high-temperature reaction of a mixed salt of KBF4 and K2TiF6 with an aluminum melt. This method has a simple process and low preparation cost, and is suitable for batch industrial production. However, the in-situ TiB2 particle-reinforced aluminum matrix composites prepared by the molten salt reaction method have problems such as relatively large sizes of the reinforcement particles, uneven dispersion, and serious agglomeration phenomena. This will inevitably reduce the mechanical properties of the material and ultimately have an adverse impact on the comprehensive performance of the product. In recent years, researchers have been committed to optimizing the original process or developing new preparation processes for aluminum matrix composites to solve the above problems. By pressing the mixed salt into the form of a prefabricated block and pressing it into the molten metal, the contact area between the mixed salt and the aluminum melt is enlarged, the reaction efficiency is improved, and the recovery rate of the reaction elements is thereby increased. In addition, the size and distribution state of TiB2 particles in the melt are controlled through the combined action of yttrium, gadolinium, neodymium rare earth elements and electromagnetic stirring. However, the TiB2 particle-reinforced aluminum matrix composites prepared by the above method still have the following two problems: (1) The raw materials of rare earth elements such as yttrium, gadolinium, and neodymium required for the preparation of the above composites are expensive, which is not conducive to mass industrial production; (2) The molten salt reaction temperature is mostly selected in the high-temperature range of 850-920 °C, which will exacerbate the burning loss of alloy elements in the aluminum alloy melt, resulting in unstable tissue composition of the final composite material.

[0004] As can be seen from the above, in-situ particle-reinforced aluminum matrix composites have broad application prospects, but the methods reported currently cannot effectively solve the problems of relatively large sizes and uniform distribution of TiB2 particles. At the same time, in-situ particle-reinforced aluminum matrix composites also have problems such as easy burning loss of alloy elements during the melting process, low tissue density, and insufficient room temperature elongation rate, which have a serious impact on the final comprehensive mechanical properties of the material. Summary of the Invention

[0005] In view of this, the present invention aims to provide a preparation method for a high-strength and high-toughness in-situ TiB2 particle-reinforced aluminum matrix composite material. This method combines an improved molten salt reaction process, a hot extrusion process, and a heat treatment process, which can effectively eliminate casting defects such as pores and cracks in the composite billet, improve its density, and further improve the size and distribution state of TiB2 reinforcing particles in the matrix, thereby obtaining an in-situ TiB2 particle-reinforced aluminum matrix composite material with excellent properties.

[0006] To achieve the above object, the technical solution of the present invention is realized as follows:

[0007] A preparation method for a high-strength and high-toughness in-situ TiB2 particle-reinforced aluminum matrix composite material, comprising the steps of:

[0008] Step (1): Configure industrial pure aluminum, aluminum-silicon master alloy, copper, aluminum-chromium master alloy, aluminum-manganese master alloy, zinc, and magnesium furnace charges according to the mass percentage of 6061 aluminum alloy material, and preheat all the furnace charges.

[0009] Step (2): Configure reaction salts (KBF4, K2TiF6) and a reaction promoter Na3AlF6 powder according to the proportion of TiB2 particles required for the in-situ TiB2 particle-reinforced aluminum matrix composite material, and then pour them into a V-type mixer and mix evenly.

[0010] Step (3): Put the powder obtained in step (2) into an oven and dry it to remove excess moisture.

[0011] Step (4): Add industrial pure aluminum to a resistance furnace, heat it to melt, and heat it to 800 - 820 °C.

[0012] Step (5): Skim the oxide skin on the surface of the melt, and then use a powder spraying machine to evenly sprinkle the mixed powder in step (3) on the surface of the melt, and keep it warm at a reaction temperature of 830 - 850 °C for 30 - 90 min.

[0013] Step (6): Skim the molten salt after the reaction on the surface layer of the melt is complete, and then mechanically stir the melt.

[0014] Step (7): Add aluminum-silicon master alloy, copper, aluminum-chromium master alloy, aluminum-manganese master alloy, zinc, and magnesium to the resistance furnace in sequence, and then keep it warm at 720 - 750 °C until all the component furnace charges are completely melted.

[0015] Step (8): Use a powder spraying machine to evenly sprinkle the slag cleaning agent on the surface of the melt, then introduce high-purity argon for degassing and refining while mechanically stirring. After degassing and mechanical stirring are completed, skim the scum on the surface of the melt, and let it stand at 710 - 740 °C for 5 - 30 min.

[0016] Step (9): Pour the melt obtained in step (8) into a preheated metal mold.

[0017] Step (10) performs homogenization treatment on the composite material cast rod obtained in step (9);

[0018] Step (11) performs hot extrusion processing on the composite material cast rod obtained in step (10);

[0019] Step (12) performs heat treatment on the composite material hot extrusion rod obtained in step (11) to obtain an in-situ TiB2 particle-reinforced aluminum matrix composite material.

[0020] In some embodiments, the mass percentages of the various elements in the 6061 aluminum alloy material in step (1) are as follows: 0.4 - 0.8% of Si, not more than 0.7% of Fe, 0.15 - 0.40% of Cu, not more than 0.15% of Mn, 0.8 - 1.2% of Mg, 0.04 - 0.35% of Cr, not more than 0.25% of Zn, not more than 0.15% of Ti, not more than 0.05% of other single impurity elements, not more than 0.15% of the total of other impurity elements, and the balance of Al.

[0021] In some embodiments, the preheating temperature of the 6061 aluminum alloy material in step (1) is 300 - 400 °C.

[0022] In some embodiments, in step (2), the mass content of TiB2 particles in the in-situ TiB2 particle-reinforced aluminum matrix composite material is 2 - 6%, the ratio of K2TiF6 to KBF4 is 1:2, and the addition amount of the reaction assistant Na3AlF6 powder is 10 - 20% of the mass of the reaction salt.

[0023] In some embodiments, in step (3), the powder drying temperature is 250 - 300 °C, and the heat preservation time is 2 - 3 h.

[0024] In some embodiments, in step (6), the mechanical stirring speed is 250 - 350 r / min, and the stirring time is 3 - 10 min.

[0025] In some embodiments, in step (7), the aluminum-silicon master alloy, aluminum-chromium master alloy, and aluminum-manganese master alloy are respectively AlSi20, AlCr10, and AlMn10 master alloys, and copper, zinc, and magnesium are all pure metals.

[0026] In some embodiments, the homogenization treatment in step (10) includes heat preservation at a temperature of 535 - 545 °C for 8 - 10 h, and then immediately water cooling to room temperature.

[0027] In some embodiments, in step (11), the hot extrusion temperature is 400 - 420 °C, the extrusion rate is 1 - 3 mm / s, and the extrusion ratio is 30 - 60.

[0028] In some embodiments, the heat treatment in step (12) includes solution treatment and artificial aging. The solution treatment is carried out at 540 - 560 °C for 1 - 4 h, and the artificial aging is carried out at 170 - 180 °C for 2 - 5 h.

[0029] Compared with the prior art, the method for preparing the high-strength and high-toughness in-situ TiB2 particle-reinforced aluminum matrix composite of the present invention has the following advantages:

[0030] The method for preparing the high-strength and high-toughness in-situ TiB2 particle-reinforced aluminum matrix composite disclosed in the present invention develops a method of first preparing an in-situ TiB2 / Al master alloy liquid by reacting a fluoride salt with commercially pure aluminum, and then remelting other furnace charges to prepare an in-situ TiB2 particle-reinforced 6061 aluminum matrix composite, effectively solving problems such as alloy element burning loss, composition ratio imbalance, and poor cleanliness during the preparation of aluminum matrix composites. By means of the high-temperature and high-pressure process of hot extrusion, the distribution state of the reinforcing particles and their interfacial bonding with the matrix are further improved, and at the same time, casting defects such as pores and cracks in the composite are eliminated, and the tissue density is increased. The heat treatment process after hot extrusion can further adjust the matrix microstructure and improve the final mechanical properties of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0032] Figure 1 It is the metallographic image of Comparative Example 2.

[0033] Figure 2 It is the scanning electron microscope image of Comparative Example 2.

[0034] Figure 3 It is the metallographic image of the microstructure of the cross-section perpendicular to the extrusion direction of Example 4 of the present invention.

[0035] Figure 4 It is the metallographic image of the microstructure along the extrusion direction of Example 4 of the present invention.

[0036] Figure 5 It is the electron microscope image of the microstructure of the cross-section perpendicular to the extrusion direction of Example 4 of the present invention.

[0037] Figure 6 It is the electron microscope image of the microstructure along the extrusion direction of Example 4 of the present invention.

[0038] Figure 7 It is the comparison chart of the tensile mechanical properties of the composites prepared in Examples 1 - 4 of the present invention and the materials prepared in Comparative Examples 1 - 3. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0040] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and in combination with embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present invention without making creative efforts belong to the scope of protection of the present invention.

[0041] Reference is made below Figures 1 to 7 and in combination with embodiments to describe the preparation method of a high-strength and high-toughness in-situ TiB2 particle-reinforced aluminum matrix composite material according to an embodiment of the present invention.

[0042] A preparation method of a high-strength and high-toughness in-situ TiB2 particle-reinforced aluminum matrix composite material, comprising the following steps: (1) configuring industrial pure aluminum, aluminum-silicon master alloy, copper, aluminum-chromium master alloy, aluminum-manganese master alloy, zinc, and magnesium charge according to the mass percentage of 6061 aluminum alloy material, and preheating all the charge; (2) configuring reaction salts (KBF4, K2TiF6) and reaction auxiliary agent Na3AlF6 powder according to the proportion of TiB2 particles required for the in-situ TiB2 particle-reinforced aluminum matrix composite material, and then pouring them into a V-type mixer and mixing evenly; (3) putting the powder obtained in step (2) into an oven to remove excess moisture; (4) adding industrial pure aluminum to a resistance furnace for heating and melting and superheating to 800-820 °C; (5) skimming the oxide skin on the surface of the melt, and then evenly spraying the mixed powder in step (3) on the surface of the melt with a powder spraying machine, and keeping it warm for a certain time at a certain reaction temperature; (6) skimming the molten salt after the reaction on the surface layer of the melt is complete, and then mechanically stirring the melt for a certain time; (7) sequentially adding aluminum-silicon master alloy, copper, aluminum-chromium master alloy, aluminum-manganese master alloy, zinc, and magnesium to the resistance furnace, and then keeping it warm at a certain temperature until all the component charges are completely melted; (8) using a powder spraying machine to evenly sprinkle a slag cleaning agent on the surface of the melt, then introducing high-purity argon for degassing and refining and simultaneously performing mechanical stirring, skimming the floating slag on the surface of the melt after degassing and mechanical stirring are completed, and standing for a certain time at a certain temperature; (9) pouring the melt obtained in step (8) into a preheated metal mold; (10) performing homogenization treatment on the composite material casting rod obtained in step (9); (11) performing hot extrusion processing on the composite material casting rod obtained in step (10); (12) performing heat treatment on the composite material hot extrusion rod obtained in step (11) to obtain an in-situ TiB2 particle-reinforced aluminum matrix composite material.

[0043] In the 6061 wrought aluminum alloy described in step (1), the mass percentage composition of each element is as follows: 0.4 - 0.8% of Si, no more than 0.7% of Fe, 0.15 - 0.40% of Cu, no more than 0.15% of Mn, 0.8 - 1.2% of Mg, 0.04 - 0.35% of Cr, no more than 0.25% of Zn, no more than 0.15% of Ti, no more than 0.05% of other single impurity elements, no more than 0.15% of the total of other impurity elements, and the balance of Al. The preheating of the furnace charge is to keep the furnace charge at 300 - 400 °C for 3 - 5 h.

[0044] In step (2), the mass content of the TiB2 reinforcing particles to be generated is 2 - 6%, preferably 3 - 5%. The atomic ratio of K2TiF6 and KBF4 powders is preferably 1:2. The addition amount of the reaction assistant Na3AlF6 powder is 10 - 20% of the mass of the reaction salts, and the mixing time is 50 - 80 min.

[0045] In step (3), the drying temperature of the powder is 250 - 300 °C, and the heat preservation time is 2 - 3 h.

[0046] In step (5), the molten salt reaction temperature is 830 - 850 °C, and the reaction time is 30 - 90 min.

[0047] In step (6), the rotation speed of the mechanical stirring graphite rotor is 250 - 350 r / min, and the stirring time is 3 - 10 min.

[0048] In step (7), the aluminum-silicon master alloy, aluminum-chromium master alloy, and aluminum-manganese master alloy are AlSi20, AlCr10, and AlMn10 master alloys respectively. Copper, zinc, and magnesium are all pure metals. The heat preservation temperature is controlled at 720 - 750 °C.

[0049] In step (8), the argon flow rate is controlled at 3 L / h, the mechanical stirring speed is 250 - 350 r / min, the degassing and stirring times are both controlled within 3 - 10 min, and then the melt temperature is adjusted to 710 - 740 °C and left to stand for 5 - 30 min.

[0050] In step (9), the metal mold is preheated by keeping it at 250 - 300 °C for 2 - 3 h, the pouring temperature is 705 - 710 °C, and the specifications of the obtained composite material ingot blank are φ90 mm × 600 mm.

[0051] In step (10), the homogenization treatment process is to keep it at 535 - 545 °C for 8 - 10 h, and then immediately water-cool it to room temperature.

[0052] In step (11), the hot extrusion temperature is 400 - 420 °C, the extrusion rate is 1 - 3 mm / s, the extrusion ratio is 30 - 60, and the cooling method is air cooling.

[0053] The heat treatment process described in step (12) is solution treatment and artificial aging. The solution treatment is carried out at 540 - 560 °C for 1 - 4 h, and the cooling method after solution treatment is water cooling. The artificial aging is carried out at 170 - 180 °C for 2 - 5 h.

[0054] Example 1:

[0055] Step (1): Prepare 9 kg of 6061 aluminum alloy furnace charges including industrial pure aluminum, aluminum - silicon master alloy, copper, aluminum - chromium master alloy, aluminum - manganese master alloy, zinc, and magnesium according to the mass percentages of 0.65% Si, 0.25% Cu, 0.09% Mn, 1.1% Mg, 0.08% Cr, 0.1% Zn, and the balance Al. Then pre - heat all the furnace charges in an oven at 350 °C for 3 h.

[0056] Step (2): Prepare 962 g of K2TiF6, 1009 g of KBF4, and 296 g of Na3AlF6 according to the requirement of generating 3 wt.% TiB2 reinforcing particles. Then pour them into a V - type mixer and mix for 60 min.

[0057] Step (3): Put the powder from step (2) into an oven to dry. The oven temperature is 250 °C and the drying time is 2 h.

[0058] Step (4): Add the industrial pure aluminum in step (1) into a resistance furnace for heating and melting, and superheat to 810 °C.

[0059] Step (5): Skim the oxide skin on the surface of the melt. Then use a powder spraying machine to evenly spray the mixed powder in step (3) on the surface of the melt, control the reaction temperature at 850 °C, and the reaction time at 30 min.

[0060] Step (6): Skim the molten salt after the reaction on the surface layer of the melt is complete. Then use a graphite rotor with a rotation speed of 250 r / min to stir the melt for 5 min.

[0061] Step (7): Add aluminum - silicon master alloy, copper, aluminum - chromium master alloy, aluminum - manganese master alloy, zinc, and magnesium into the melt in step (6) in sequence. Ensure that the melt temperature is lower than 765 °C when adding the furnace charges, and then keep it at 750 °C until all the component furnace charges are completely melted.

[0062] Step (8): Use a powder spraying machine to evenly sprinkle the slag - cleaning agent on the surface of the melt. Then introduce high - purity argon with a flow rate of 3 L / h for degassing and refining, and apply mechanical stirring with a rotation speed of 300 r / min at the same time. After degassing and mechanical stirring are completed, skim the floating slag on the surface of the melt. Then adjust the melt temperature to 730 °C and let it stand for 10 min.

[0063] Step (9): Pour the melt obtained in step (8) into a pre - heated metal mold, and the pouring temperature is 710 °C.

[0064] Step (10): Subject the composite material casting rod obtained in step (9) to homogenization treatment (540 °C × 10 h, water cooling).

[0065] Step (11): Perform hot extrusion processing on the composite material casting rod obtained in step (10), with an extrusion temperature of 400 °C, an extrusion rate of 1.5 mm / s, an extrusion ratio of 35, and an air cooling method for cooling.

[0066] Step (12): Subject the hot extruded rod of the composite material obtained in step (11) to heat treatment (550 °C × 3 h + water cooling + 175 °C × 2 h) to obtain an in-situ TiB2 particle-reinforced aluminum matrix composite material.

[0067] Example 2:

[0068] Step (1): Configure 9 kg of 6061 aluminum alloy furnace charges including industrial pure aluminum, aluminum-silicon master alloy, copper, aluminum-chromium master alloy, aluminum-manganese master alloy, zinc, and magnesium according to 0.65% Si, 0.25% Cu, 0.09% Mn, 1.1% Mg, 0.08% Cr, 0.1% Zn, and the balance of Al by mass percentage, and then preheat all the furnace charges in an oven at 350 °C for 3 h.

[0069] Step (2): Configure 962 g of K2TiF6, 1009 g of KBF4, and 296 g of Na3AlF6 according to the requirement of generating 3 wt.% TiB2 reinforcing particles, and then pour them into a V-type mixer and mix for 60 min.

[0070] Step (3): Put the powder obtained in step (2) into an oven for drying, with the oven temperature at 250 °C and the drying time of 2 h.

[0071] Step (4): Add the industrial pure aluminum in step (1) to an electric resistance furnace for heating and melting and superheat it to 810 °C.

[0072] Step (5): Skim the oxide skin on the surface of the melt, and then use a powder spraying machine to evenly spray the mixed powder in step (3) on the surface of the melt, controlling the reaction temperature at 850 °C and the reaction time at 30 min.

[0073] Step (6): Skim the molten salt after the reaction on the surface layer of the melt is complete, and then stir the melt with a graphite rotor rotating at 250 r / min for 5 min.

[0074] Step (7): Add aluminum-silicon master alloy, copper, aluminum-chromium master alloy, aluminum-manganese master alloy, zinc, and magnesium to the melt in step (6) in sequence, ensuring that the melt temperature is lower than 765 °C when adding the furnace charges, and then keep it at 750 °C until all the component furnace charges are completely melted.

[0075] Step (8): Use a powder spraying machine to evenly sprinkle the dross cleaning agent on the surface of the melt, then introduce high-purity argon gas with a flow rate of 3 L / h for degassing and refining while applying mechanical stirring at a rotational speed of 300 r / min. After degassing and mechanical stirring are completed, skim the scum on the surface of the melt, and then adjust the temperature of the melt to 730 °C and let it stand for 10 min;

[0076] Step (9): Pour the melt obtained in step (8) into a preheated metal mold, and the pouring temperature is 710 °C;

[0077] Step (10): Carry out homogenization treatment (540 °C × 10 h, water cooling) on the composite material cast rod obtained in step (9);

[0078] Step (11): Carry out hot extrusion processing on the composite material cast rod obtained in step (10), the extrusion temperature is 400 °C, the extrusion rate is 1.5 mm / s, the extrusion ratio is 35, and the cooling method is air cooling;

[0079] Step (12): Carry out heat treatment (550 °C × 3 h + water cooling + 175 °C × 4 h) on the composite material hot extrusion rod obtained in step (11) to obtain an in-situ TiB2 particle-reinforced aluminum matrix composite material.

[0080] Example 3:

[0081] Step (1): Configure a total of 9 kg of 6061 aluminum alloy furnace charges such as industrial pure aluminum, aluminum-silicon master alloy, copper, aluminum-chromium master alloy, aluminum-manganese master alloy, zinc, and magnesium according to 0.65% Si, 0.25% Cu, 0.09% Mn, 1.1% Mg, 0.08% Cr, 0.1% Zn, and the balance of Al by mass percentage, and then preheat all the furnace charges in an oven at 350 °C for 3 h;

[0082] Step (2): Configure 1637 g of K2TiF6, 1717 g of KBF4, and 503 g of Na3AlF6 according to the required 5 wt.% TiB2 reinforcing particles, and then pour them into a V-type mixer and mix for 60 min;

[0083] Step (3): Put the powder in step (2) into an oven for drying, the oven temperature is 250 °C, and the drying time is 2 h;

[0084] Step (4): Add the industrial pure aluminum in step (1) to an electric resistance furnace for heating and melting and superheat to 810 °C;

[0085] Step (5): Skim the oxide scale on the surface of the melt, and then use a powder spraying machine to evenly spray the mixed powder in step (3) on the surface of the melt, control the reaction temperature at 850 °C, and the reaction time at 30 min;

[0086] Step (6): Remove the molten salt after the reaction on the surface of the melt is complete, and then stir the melt with a graphite rotor at a speed of 250 r / min for 5 min;

[0087] Step (7): Add aluminum-silicon master alloy, copper, aluminum-chromium master alloy, aluminum-manganese master alloy, zinc, and magnesium into the melt obtained in step (6) in sequence. Ensure that the melt temperature is lower than 765 °C when adding the furnace charge, and then keep it at 750 °C until all the component furnace charges are completely melted;

[0088] Step (8): Use a powder spraying machine to evenly sprinkle the slag cleaning agent on the surface of the melt, and then introduce high-purity argon with a flow rate of 3 L / h for degassing and refining while applying mechanical stirring at a speed of 300 r / min. After degassing and mechanical stirring are completed, remove the floating slag on the surface of the melt, and then adjust the melt temperature to 730 °C and let it stand for 10 min;

[0089] Step (9): Pour the melt obtained in step (8) into a preheated metal mold, and the pouring temperature is 710 °C;

[0090] Step (10): Perform homogenization treatment (540 °C × 10 h, water cooling) on the composite material casting rod obtained in step (9);

[0091] Step (11): Perform hot extrusion processing on the composite material casting rod obtained in step (10). The extrusion temperature is 400 °C, the extrusion rate is 1.5 mm / s, the extrusion ratio is 35, and the cooling method is air cooling;

[0092] Step (12): Perform heat treatment (550 °C × 3 h + water cooling + 175 °C × 2 h) on the composite material hot extrusion rod obtained in step (11) to obtain an in-situ TiB2 particle-reinforced aluminum matrix composite material.

[0093] Example 4:

[0094] Step (1): Configure 9 kg of 6061 aluminum alloy furnace charges such as industrial pure aluminum, aluminum-silicon master alloy, copper, aluminum-chromium master alloy, aluminum-manganese master alloy, zinc, and magnesium according to 0.65% Si, 0.25% Cu, 0.09% Mn, 1.1% Mg, 0.08% Cr, 0.1% Zn, and the balance of Al by mass percentage. Then preheat all the furnace charges in an oven at 350 °C for 3 h;

[0095] Step (2): Configure 1637 g of K2TiF6, 1717 g of KBF4, and 503 g of Na3AlF6 according to the required generation of 5 wt.% TiB2 reinforcing particles, and then pour them into a V-type mixer and mix for 60 min;

[0096] Step (3): Put the powder obtained in step (2) into an oven for drying. The oven temperature is 250 °C, and the drying time is 2 h;

[0097] Step (4): Add commercially pure aluminum in step (1) into a resistance furnace for heating and melting, and superheat it to 810 °C.

[0098] Step (5): Skim off the oxide scale on the surface of the melt, and then evenly sprinkle the mixed powder in step (3) on the surface of the melt with a powder spraying machine, control the reaction temperature at 850 °C, and the reaction time at 30 min.

[0099] Step (6): Skim off the molten salt after the reaction on the surface layer of the melt is complete, and then stir the melt with a graphite rotor rotating at 250 r / min for 5 min.

[0100] Step (7): Add aluminum-silicon master alloy, copper, aluminum-chromium master alloy, aluminum-manganese master alloy, zinc, and magnesium into the melt in step (6) in sequence. Ensure that the melt temperature is lower than 765 °C when adding the furnace charge, and then keep it at 750 °C until all components of the furnace charge are completely melted.

[0101] Step (8): Use a powder spraying machine to evenly sprinkle the slag cleaning agent on the surface of the melt, then introduce high-purity argon with a flow rate of 3 L / h for degassing and refining, and apply mechanical stirring with a rotation speed of 300 r / min at the same time. After degassing and mechanical stirring are completed, skim off the floating slag on the surface of the melt, and then adjust the melt temperature to 730 °C and let it stand for 10 min.

[0102] Step (9): Pour the melt obtained in step (8) into a preheated metal mold, and the pouring temperature is 710 °C.

[0103] Step (10): Perform homogenization treatment (540 °C × 10 h, water cooling) on the composite material cast rod obtained in step (9).

[0104] Step (11): Perform hot extrusion processing on the composite material cast rod obtained in step (10), the extrusion temperature is 400 °C, the extrusion rate is 1.5 mm / s, the extrusion ratio is 35, and the cooling method is air cooling.

[0105] Step (12): Perform heat treatment (550 °C × 3 h + water cooling + 175 °C × 4 h) on the hot-extruded rod of the composite material obtained in step (11) to obtain an in-situ TiB2 particle-reinforced aluminum matrix composite material.

[0106] After the preparation is completed according to the above method, the TiB2 / 6061 aluminum matrix composite materials described in Examples 1-4 are obtained respectively.

[0107] Comparative Example 1 (6061 aluminum alloy without TiB2 reinforcing particles, extruded and heat-treated):

[0108] The difference between Comparative Example 1 and the Example is that in the preparation process of the material of Comparative Example 1, steps (2), (3), (5), and (6) in Example 1 are omitted, and the heat treatment parameters in step (12) are set as 550 °C × 3 h + water cooling + 175 °C × 4 h.

[0109] Comparative Example 2 (5 wt.% TiB2 particle-reinforced aluminum matrix composite, not extruded but heat-treated):

[0110] The difference between Comparative Example 2 and the Example is that in the preparation process of the material of Comparative Example 2, step (11) in Example 1 is omitted, and in step (2), 1637 g of K2TiF6, 1717 g of KBF4, and 503 g of Na3AlF6 are configured according to the requirement of generating 5 wt.% TiB2 reinforcing particles, and the heat treatment parameters in step (12) are set as 550 °C × 3 h + water cooling + 175 °C × 4 h.

[0111] Comparative Example 3 (5 wt.% TiB2 particle-reinforced aluminum matrix composite, extruded but not heat-treated):

[0112] The difference between Comparative Example 3 and the Example is that in the preparation process of the material of Comparative Example 3, step (12) in Example 1 is omitted, and in step (2), 1637 g of K2TiF6, 1717 g of KBF4, and 503 g of Na3AlF6 are configured according to the requirement of generating 5 wt.% TiB2 reinforcing particles.

[0113] After the preparation is completed according to the above method, the materials described in Comparative Examples 1 - 3 are obtained respectively.

[0114] Tensile tests are carried out on the TiB2 / 6061 aluminum matrix composites of the 4 groups of Examples and the 3 groups of comparative materials to evaluate their elongation, yield strength, and tensile strength.

[0115] The metallographic phase of the TiB2 / 6061 aluminum matrix composite prepared in Comparative Example 2 is as Figure 1 shown, and the scanning electron microscope microstructural image is as Figure 2 shown. It can be seen from the figure that there is a relatively obvious agglomeration phenomenon of TiB2 particles in the non-extruded TiB2 / 6061 aluminum matrix composite. In addition, it can be seen from Figure 2 that there are also a certain number of pores in the TiB2 / 6061 aluminum matrix composite. The metallographic phase and scanning electron microscope images of the TiB2 / 6061 aluminum matrix composite prepared in Example 4 are as Figures 3 to 6 shown. It can be seen from the figure that hot extrusion can effectively improve the agglomeration phenomenon of TiB2 particles. Combining the cross-section and profile tissues of the sample, it can be seen that recrystallization will occur in the extruded TiB2 / 6061 aluminum matrix composite during the subsequent T6 heat treatment process. At the same time, comparing Figure 2 and Figure 4It can be seen that the hot extrusion process can effectively eliminate the pore defects in the composite material.

[0116] Figure 7 This is the comparison of the tensile properties of the materials in Examples 1-4 and Comparative Examples 1-3 of the present invention. It can be seen from the figure that the TiB2 particle content, hot extrusion process and heat treatment process of the TiB2 / 6061 aluminum matrix composite material all have obvious effects on the strength and toughness of the material. For example, the yield strength and elongation of the 5wt.% TiB2 / 6061 aluminum matrix composite material after only T6 heat treatment (Comparative Example 2) are 279 MPa and 8.3% respectively, while the yield strength and elongation after extrusion and T6 heat treatment (Example 4) are 337 MPa and 13.9% respectively, which are increased by 20.8% and 67.5% respectively.

[0117] Combined with Figures 1 to 7 It can be seen that the coordinated cooperation between the hot extrusion deformation and the heat treatment process plays a very good regulatory role in the microstructure, strength and toughness of the in-situ TiB2 particle-reinforced 6061 aluminum matrix composite material.

[0118] Compared with the prior art, the preparation method of the high-strength and high-toughness in-situ TiB2 particle-reinforced aluminum matrix composite material of the present invention has the following advantages:

[0119] The preparation method of the high-strength and high-toughness in-situ TiB2 particle-reinforced aluminum matrix composite material disclosed by the present invention develops a method of first preparing an in-situ TiB2 / Al master alloy liquid by reacting a fluoride salt with industrial pure aluminum, and then remelting other furnace charges to prepare an in-situ TiB2 particle-reinforced 6061 aluminum matrix composite material, effectively solving problems such as alloy element burning loss, composition ratio imbalance, and poor cleanliness during the preparation process of the aluminum matrix composite material. With the high-temperature and high-pressure process of hot extrusion, the distribution state of the reinforcing particles and their interfacial bonding with the matrix are further improved, and at the same time, casting defects such as pores and cracks in the composite material are eliminated, and the tissue density is increased. The heat treatment process after hot extrusion can further adjust the matrix microstructure and improve the final mechanical properties of the material.

[0120] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation to the protection content of the present invention.

[0121] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise specifically defined.

[0122] In the present invention, unless otherwise clearly defined and limited, terms such as "installed", "connected", "coupled", "fixed", etc. shall be construed in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection, an electrical connection, or capable of communicating with each other; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the internal communication of two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0123] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a high-strength and high-toughness in-situ TiB2 particle-reinforced aluminum matrix composite, characterized in that, Including the steps: Step (1): Configure industrial pure aluminum, aluminum-silicon master alloy, copper, aluminum-chromium master alloy, aluminum-manganese master alloy, zinc, and magnesium charge according to the mass percentage of 6061 aluminum alloy material, and preheat it. Step (2): Configure reaction salts (KBF4, K2TiF6) and reaction promoter Na3AlF6 powder according to the proportion of TiB2 particles required for in-situ TiB2 particle-reinforced aluminum matrix composite, and then pour them into a V-type mixer and mix evenly. Step (3): Put the powder obtained in step (2) into an oven and dry it. Step (4): Add industrial pure aluminum to an electric resistance furnace for heating and melting, and heat it to 800 - 820 °C. Step (5): Skim the oxide skin on the surface of the melt, and then use a powder spraying machine to evenly sprinkle the mixed powder in step (3) on the surface of the melt, and keep it warm at a reaction temperature of 830 - 850 °C for 30 - 90 min. Step (6): Skim the molten salt after the reaction on the surface layer of the melt is complete, and then mechanically stir the melt. Step (7): Add aluminum-silicon master alloy, copper, aluminum-chromium master alloy, aluminum-manganese master alloy, zinc, and magnesium to the electric resistance furnace in sequence, and then keep it warm at 720 - 750 °C until all the component charges are completely melted. Step (8): Use a powder spraying machine to evenly sprinkle the slag cleaning agent on the surface of the melt, then introduce high-purity argon for degassing and refining while mechanically stirring. After degassing and mechanical stirring are completed, skim the floating slag on the surface of the melt, and let it stand at 710 - 740 °C for 5 - 30 min. Step (9): Pour the melt obtained in step (8) into a preheated metal mold. Step (10): Perform homogenization treatment on the composite material cast rod obtained in step (9). Step (11): Perform hot extrusion processing on the composite material cast rod obtained in step (10). Step (12): Perform heat treatment on the composite material hot extrusion rod obtained in step (11) to obtain in-situ TiB2 particle-reinforced aluminum matrix composite.

2. The preparation method of the high-strength and tough in-situ TiB2 particle-reinforced aluminum matrix composite according to claim 1, characterized in that, In step (1), the mass percentages of each element in the 6061 aluminum alloy material are as follows: 0.4 - 0.8% of Si, not more than 0.7% of Fe, 0.15 - 0.40% of Cu, not more than 0.15% of Mn, 0.8 - 1.2% of Mg, 0.04 - 0.35% of Cr, not more than 0.25% of Zn, not more than 0.15% of Ti, not more than 0.05% of other single impurity elements, not more than 0.15% of the total of other impurity elements, and the balance of Al.

3. The preparation method of the high-strength and high-toughness in-situ TiB2 particle-reinforced aluminum matrix composite according to claim 1, wherein, The preheating temperature of the 6061 aluminum alloy material in step (1) is 300 - 400 °C.

4. The preparation method of the high-strength and tough in-situ TiB2 particle-reinforced aluminum matrix composite according to claim 1, characterized in that, In step (2), the mass content of TiB2 particles in the in-situ TiB2 particle-reinforced aluminum matrix composite is 2 - 6%, the ratio of K2TiF6 and KBF4 is 1:2, and the addition amount of the reaction promoter Na3AlF6 powder is 10 - 20% of the mass of the reaction salts.

5. The preparation method of the high-strength and high-toughness in-situ TiB2 particle-reinforced aluminum matrix composite according to claim 1, characterized in that, In step (3), the powder drying temperature is 250 - 300 °C, and the heat preservation time is 2 - 3 h.

6. The preparation method of the high-strength and high-toughness in-situ TiB2 particle-reinforced aluminum matrix composite according to claim 1, characterized in that In step (6), the mechanical stirring speed is 250 - 350 r / min, and the stirring time is 3 - 10 min.

7. The preparation method of the high-strength and tough in-situ TiB2 particle-reinforced aluminum matrix composite according to claim 1, characterized in that, In step (7), the aluminum-silicon master alloy, aluminum-chromium master alloy, and aluminum-manganese master alloy are AlSi20, AlCr10, and AlMn10 master alloys respectively, and copper, zinc, and magnesium are all pure metals.

8. The preparation method of the high-strength and tough in-situ TiB2 particle-reinforced aluminum matrix composite according to claim 1, characterized in that, In step (10), the homogenization treatment includes holding at a temperature of 535 - 545 °C for 8 - 10 h, and then immediately water-cooling to room temperature.

9. The preparation method of the high-strength and tough in-situ TiB2 particle-reinforced aluminum matrix composite according to claim 1, characterized in that In step (11), the hot extrusion temperature is 400 - 420 °C, the extrusion rate is 1 - 3 mm / s, and the extrusion ratio is 30 - 60.

10. The preparation method of the high-strength and tough in-situ TiB2 particle-reinforced aluminum matrix composite according to claim 1, characterized in that, In step (12), the heat treatment includes solution treatment and artificial aging. The solution treatment is holding at 540 - 560 °C for 1 - 4 h, and the artificial aging is holding at 170 - 180 °C for 2 - 5 h.

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