Stepped temperature control accumulative deformation method for high-modulus magnesium-based composite material

Abstract

The invention belongs to the technical field of magnesium-based composite material forming, and particularly relates to a stepped temperature control accumulative deformation method of a high-modulus magnesium-based composite material, which comprises the following steps: step 1, carrying out homogenization treatment on a cast ingot at the temperature T1 for 6-8 hours; 2, the cast ingot is transferred into a sine arc mold, the mold temperature is T2, T2 is larger than T1, rapid accumulated deformation is conducted N1 times to obtain a blank, N1 is larger than or equal to 5 and smaller than or equal to 10, the blank is transferred and returned to the furnace for heat preservation, the heat preservation temperature is T3, and T3 is smaller than T1; 3, the blank is transferred into a cosine arc-shaped mold, the mold temperature is T4, T4 is larger than T1, rapid accumulated deformation is conducted N2 times to obtain a forging stock, N2 is larger than or equal to 5 and smaller than or equal to 15, and after one-time deformation, the blank needs to be inverted by 180 degrees and placed into the cosine arc-shaped mold for next-time deformation; and 4, the forging stock is cooled through water at the temperature of 50-80 DEG C. The problems that a large-size high-modulus magnesium-based composite material is serious in deformation and cracking and poor in structure uniformity are solved.

Description

Technical Field

[0001] The invention belongs to the technical field of magnesium-based composite material forming, and in particular relates to a step-temperature-controlled cumulative deformation method for a high-modulus magnesium-based composite material. Background Art

[0002] With the rapid development of the aerospace field, more stringent requirements have been put forward for lightweight, high precision and large load of equipment. The existing single alloy materials can no longer meet the requirements of lightweight and high performance, so magnesium-based composite materials came into being. Lightweight and high modulus (E≥60GPa) magnesium-based composite materials are common requirements for key parts of equipment in the aerospace field. At present, how to achieve high-quality deformation of large-scale high modulus magnesium-based composite materials is a key problem that needs to be solved in the development and production of high modulus magnesium-based composite components. The close-packed hexagonal structural properties of magnesium alloys lead to poor deformation performance. At the same time, the high modulus reinforcement phase and the matrix are not coordinated during the deformation process, which makes the deformation structure uniformity of high modulus magnesium-based composite materials poor and the cracking phenomenon is very serious.

[0003] Existing methods of magnesium alloy deformation blanking include multi-directional free forging, forward extrusion, etc. Since the deformation of the blank in the X and Y directions during the multi-directional free forging process is unconstrained and the deformation behavior of the high modulus magnesium-based composite material is poor, the cracking and scrapping rate of the blank remains high. Although forward extrusion blanking can realize the deformation of the high modulus magnesium-based composite material under three-dimensional compressive stress conditions, the microstructure after blanking is a single extruded microstructure, and it is difficult to ensure the uniformity of the performance of the blank in the three directions of X, Y, and Z. At the same time, the extrusion of large-sized ingots (diameter ≥500mm) requires extra-large tonnage extrusion equipment, which increases the deformation processing cost of the ingot. Document CN113560362B discloses a process for processing and refining the grains of magnesium alloy materials and weakening the texture of magnesium alloys by means of composite variable cross-section extrusion, spiral extrusion and twisting, and equal channel angular extrusion. In this process, the cross-sectional diameter of the magnesium alloy ingots is a small-sized sample of less than 100 mm, which is not suitable for the blanking deformation of large-sized magnesium-based composite ingots with a diameter of ≥500 mm; Document CN114713654B discloses a method for dramatic plastic deformation of large-sized rare earth magnesium alloy ingots, which realizes the dramatic plastic deformation of rare earth magnesium alloys by large-tonnage extrusion equipment and complex molds. This process is a giant plastic deformation one-time forming process, which is suitable for rare earth magnesium alloy materials with relatively excellent plastic properties, but is difficult to be applied to high modulus magnesium-based composite materials with poor deformation properties. Summary of the invention

[0004] The purpose of the present invention is to provide a step-by-step temperature control cumulative deformation method for high modulus magnesium-based composite materials, at least to solve the problems of severe deformation and cracking and poor structural uniformity of large-sized high modulus magnesium-based composite materials.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A stepped temperature-controlled cumulative deformation method for a high-modulus magnesium-based composite material, comprising the following steps:

[0007] Step 1, homogenize the high-modulus magnesium-based composite ingot, the homogenization temperature is T1, and the time is 6-8h;

[0008] Step 2, transfer the homogenized ingot to a sine arc-shaped mold, the temperature of the sine arc-shaped mold is T2, T2>T1, rapidly accumulate deformation N1 times to obtain a blank, 5≤N1≤10, after the deformation is completed, transfer the blank back to the furnace for heat preservation, and the heat preservation temperature is T3, T3<T1;

[0009] Step 3, transfer the blank after heat preservation to a cosine arc-shaped mold, the temperature of the cosine arc-shaped mold is T4, T4>T1, rapidly accumulate deformation N2 times to obtain a forging blank, 5≤N2≤15, after one deformation, the blank needs to be inverted 180° and put into the cosine arc-shaped mold for the next deformation;

[0010] Step 4, quickly take out the forging blank after the deformation is completed, and cool the forging blank with water at 50-80°C.

[0011] Preferably, in the step 2, the ingot transfer time does not exceed 2 minutes, T2=T1+20°C, T3=T1-10N1, the deformation rate of the i-th deformation is v(i), that is, v(i) is calculated according to the following formula (2),

[0012]

[0013] Preferably, the sine arc-shaped mold in the step 2 includes a first punch, a first guide sleeve and a first die, the first die is a split opening and closing structure, the first die is in a sine arc shape, and the shape function of the sine arc is y1, that is, y1 is calculated according to the following formula (2),

[0014]

[0015] Among them, D1 is the diameter of the ingot, the diameter of the first guide sleeve, and the diameter of the upper and lower mouths of the first die, and H1 is the height of the first die.

[0016] Preferably, in the step 3, the blank transfer time does not exceed 2 minutes, T4=T1+20°C, the deformation rate of the n-th deformation is f(n), that is, f(n) is calculated according to the following formula (3),

[0017]

[0018] Preferably, the cosine arc-shaped die in step 3 includes a blank ejector block, a second punch, a second guide sleeve, and a second die. The blank ejector block is used to eject the blank. The second die is of an integral structure. The upper half of the second die is linear, and the lower half of the second die is cosine arc-shaped. The shape function of the cosine arc is y2, that is, the shape of the cosine arc is determined according to the following formula (4).

[0019]

[0020] where D2 is the maximum diameter of the blank, the diameter of the second guide sleeve, and the diameter of the upper mouth of the second die, and H2 is the height of the second die.

[0021] Compared with the prior art, the present invention has the following technical effects: adopting the solution of the present invention can gradually refine the grains, avoid local stress concentration or cracking caused by single large deformation, and is applicable to large-size (diameter ≥ 500 mm) ingots, breaking through the size limitation of the traditional deformation process; by controlling the temperature of different deformation passes, it can not only ensure the deformation ability but also avoid the recrystallized grain growth caused by traditional repeated heating, maintaining the stability of the structure; adopting the solution of the present invention can ensure that the deformation is evenly transmitted to the core of the ingot, coordinate the deformation heat effect, and reduce the tissue inhomogeneity caused by the temperature gradient; under the synergistic effect of the multi-pass cumulative deformation process, stepped temperature control, and uniform speed control method, the problem of macro-micro tissue inhomogeneity existing in the plastic deformation process of large-size magnesium alloy ingots is effectively solved. After the ingot is cogged, the uniformity and consistency of the structure and mechanical properties are greatly improved; the present invention cleverly adopts the mutual cooperation of the sine arc-shaped die and the cosine arc-shaped die, so that the blank can be subjected to a more uniform and continuous stress distribution during the deformation process, reducing the risk of uneven deformation and cracking, and enabling the ingot to have good surface quality after deformation and cogging. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a forming process diagram using a sine arc-shaped die;

[0023] Figure 2 is a forming process diagram using a cosine arc-shaped die;

[0024] Figure 3 is a forming process diagram using a cosine arc-shaped die;

[0025] In the figure: the first punch 1, the first guide sleeve 2, the first die 3, the ingot 4, the blank 5, the second punch 6, the second guide sleeve 7, the second die 8. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] The following is further detailed through specific embodiments:

[0027] Example 1

[0028] A stepped temperature-controlled cumulative deformation method for a high modulus magnesium matrix composite material. In this embodiment, a 5wt% SiCp / Mg-3Al-2Ca-1Y-0.4Mn magnesium matrix composite ingot with a diameter of 500 mm is used for deformation, which specifically includes the following steps:

[0029] Step 1: The 5wt% SiCp / Mg-3Al-2Ca-1Y-0.4Mn magnesium matrix composite ingot with a diameter of 500 mm is subjected to homogenization treatment. The temperature of the homogenization treatment is T1, T1 = 480 °C, and the time is 6 h;

[0030] Step 2: As shown in Figure 1 , the homogenized ingot is transferred to a sine arc-shaped die within 2 minutes for cumulative deformation. The temperature of the sine arc-shaped die is T2, T2 = T1 + 20 °C = 480 + 20 = 500 °C;

[0031] The ingot is rapidly cumulatively deformed N1 times to obtain a blank, N1 = 8. The deformation rate of the i-th deformation is v(i),

[0032]

[0033] According to formula (1), it can be calculated that the deformation rates of the first 5 times are 2 mm / s, and the deformation rates of the 6th to 8th times are 3 mm / s, 4 mm / s, and 5 mm / s in sequence. After the deformation is completed, the blank is transferred back to the furnace and kept warm for 30 minutes. The holding temperature is T3, T3 = T1 - 10N1 = 480 - 10×8 = 400 °C;

[0034] The sine arc-shaped die includes a first punch, a first guide sleeve, and a first die. The first die is a split-open structure, and the first die is in a sine arc shape. The shape function of the sine arc is y1,

[0035]

[0036] where D1 is the diameter of the ingot, the diameter of the first guide sleeve, and the diameters of the upper and lower mouths of the first die, and H1 is the height of the first die.

[0037] The temperature of the sine arc-shaped die is higher than that of the ingot. Through the reverse temperature field of "high-temperature die - low-temperature ingot", the temperature loss of the blank during multi-pass deformation is effectively reduced, ensuring the continuity and uniformity of deformation. The deformation rate is controlled according to the number of deformation passes. The first 5 passes are at a low speed to ensure uniform deformation, and subsequent acceleration improves the deformation efficiency, refines the grains, makes the deformation process more stable, and reduces defects such as blank cracking caused by too fast deformation rate. The return temperature of the blank is lower than the initial forging temperature of the ingot, which can not only release the internal stress generated by multi-pass cumulative deformation to prevent blank cracking, but also prevent the rapidly growing of the refined grains of the blank and maintain the stability of the structure. Through the waveform constraint of the sine arc-shaped die, the blank flows along a specific path during deformation, promoting uniform strain distribution, reducing the risk of non-uniform deformation and cracking, and eliminating the coarse-grained area in the center of the as-cast state.

[0038] Step 3, as Figure 3 shown, transfer the well-insulated blank to the cosine arc-shaped die within 2 minutes for cumulative deformation. The temperature of the cosine arc-shaped die is T4, T4 = T1 + 20°C = 480 + 20 = 500°C. Perform upset extrusion deformation on the blank, and rapidly accumulate deformation N2 times to obtain the forging blank. N2 = 10. After one deformation, the blank needs to be inverted 180° and placed in the cosine arc-shaped die for the next deformation (as Figure 3 shown);

[0039] The deformation rate of the nth deformation is f(n),

[0040]

[0041] Calculated according to formula (3), the deformation rates of the first 5 deformations are all 4 mm / s, and the deformation rates of the 6th - 10th times are 4.5 mm / s, 5 mm / s, 5.5 mm / s, 6 mm / s, and 6.5 mm / s in sequence;

[0042] The cosine arc-shaped die includes a blank ejector block, a second punch, a second guide sleeve, and a second die cavity. The blank ejector block is used to eject the blank. The second die cavity is of an integral structure. The upper half of the second die cavity is linear, and the lower half of the second die cavity is cosine arc-shaped. The shape function of the cosine arc is y2,

[0043]

[0044] where D2 is the maximum diameter of the blank, the diameter of the second guide sleeve, and the diameter of the upper mouth of the second die cavity, and H2 is the height of the second die cavity;

[0045] Increase the deformation rate stage by stage according to the number of deformations to avoid too fast deformation rate, making the deformation process smoother and avoiding problems such as billet cracking; the straight-arc transition of the cosine arc-shaped die causes greater radial compression in the lower part of the die, further crushing the coarse grains of the billet. Moreover, after each deformation, the billet is flipped 180° and deformed again, which can change the direction of the principal strain, eliminate anisotropy, and improve the overall uniformity.

[0046] Step 4, quickly take out the forged billet after deformation is completed, and cool the forged billet with water at 60°C; inhibit the growth of recrystallized grains and retain the fine grain structure.

[0047] The grain size and mechanical properties of the ingot and forged billet of the magnesium matrix composite material in this example were tested respectively, and the results are shown in Table 1.

[0048] Table 1 Microstructure and properties of ingot and forged billet of 5wt% SiCp / Mg-3Al-2Ca-1Y-0.4Mn magnesium matrix composite

[0049]

[0050] Example 2

[0051] A stepped temperature-controlled cumulative deformation method for a high-modulus magnesium matrix composite material. In this example, a 5wt% TiB2 / AZ91-1Y magnesium matrix composite material ingot with a diameter of 600 mm was used for deformation, which specifically included the following steps:

[0052] Step 1, homogenize the 5wt% TiB2 / AZ91-1Y magnesium matrix composite material ingot with a diameter of 600 mm. The homogenization temperature is T2, T1 = 420°C, and the time is 7 hours.

[0053] Step 2, as Figure 1 shown, transfer the homogenized ingot to a sine arc-shaped die within 2 minutes. The structure of the sine arc-shaped die is the same as that in Example 1. The temperature of the sine arc-shaped die is T2, T2 = T1 + 20°C = 420 + 20 = 440°C. The ingot is rapidly and cumulatively deformed N1 times to obtain a billet, N1 = 10. The deformation rate of the i-th deformation is v(i), and the calculation formula of v(i) is the same as that in Example 1. According to the calculation by formula (1), the deformation rates of the first 5 times are all 2 mm / s, and the deformation rates of the 6th to 10th times are 3 mm / s, 4 mm / s, 5 mm / s, 6 mm / s, and 7 mm / s in sequence. After the deformation is completed, transfer the billet back to the furnace and keep it warm for 30 minutes. The holding temperature is T3, T3 = T1 - 10N1 = 420 - 10×10 = 320°C.

[0054] Step 3, as Figure 2As shown, transfer the well-insulated blank to the cosine arc-shaped die within 2 minutes. The structure of the cosine arc-shaped die is the same as that in Example 1, and the temperature of the cosine arc-shaped die is T4, where T4 = T1 + 20°C = 420 + 20 = 440°C. Perform upset extrusion deformation on the blank, and quickly accumulate the deformation N2 times to obtain a forging blank. N2 = 6. After each deformation, the blank needs to be inverted 180° and placed back into the cosine arc-shaped die for the next deformation (as Figure 3 shown). The deformation rate of the nth deformation is f(n), and the calculation formula of f(n) is the same as that in Example 1. According to formula (3), it can be calculated that the deformation rates of the first 5 times are all 4 mm / s, and the deformation rate of the 6th time is 4.5 mm / s;

[0055] Step 4: Quickly take out the deformed forging blank and cool it with water at 60°C.

[0056] Test the grain size and mechanical properties of the ingot and forging blank of the magnesium matrix composite material in this example respectively. The results are shown in Table 2.

[0057] Table 2 Microstructure and properties of 5wt% TiB2 / AZ91-1Y magnesium matrix composite ingot and forging blank

[0058]

[0059] In the present invention, through the collaborative control of multi-pass cumulative deformation, reverse temperature field, strain rate, and path optimization, the problems of deformation cracking, uneven microstructure, and performance anisotropy of large-size magnesium matrix composite materials are solved. Combining the test data in Table 1 and Table 2, it can be seen that the performance of the magnesium matrix composite material can be significantly improved by using this method: the grain size is refined from >100 μm in the as-cast state to 20 - 28 μm, and the distribution of the reinforcement is uniform; the tensile strength reaches 352 - 390 MPa (an increase of 112 - 160% compared with the as-cast state), the elastic modulus breaks through 63 - 64 GPa, the elongation after fracture is increased to 6.5 - 8%, the mechanical properties are excellent, the strength deviation between the edge and the core is <5%, and the performance difference between the edge and the core is small. It is suitable for the preparation of large-size components, can meet the high-performance and lightweight requirements of high-modulus magnesium matrix composite components in the aerospace field, and has the value of large-scale industrial promotion.

Claims

1. A step-by-step temperature control cumulative deformation method for a high modulus magnesium-based composite material, characterized in that: The following steps are involved: Step 1, homogenizing the high modulus magnesium-based composite material ingot, the homogenization temperature is T1, and the time is 6 to 8 hours; Step 2, transferring the homogenized ingot to a sinusoidal arc mold for roughening deformation, the temperature of the sinusoidal arc mold is T2, T2>T1, and the billet is quickly accumulated for N1 times of deformation to obtain a billet, 5≤N1≤10, and after the deformation is completed, the billet is transferred back to the furnace for heat preservation, and the heat preservation temperature is T3, T3<T1; Step 3, after the insulation is completed, the blank is transferred to a cosine arc mold for roughing deformation, the temperature of the cosine arc mold is T4, T4>T1, and the forging blank is quickly accumulated for N2 times, 5≤N2≤15. After one deformation, the blank is turned 180° and placed in the cosine arc mold for the next deformation; Step 4, quickly take out the forging blank after deformation, and cool it with water at 50-80°C.

2. The method according to claim 1, characterized in that In the step 2, the ingot transfer time does not exceed 2 minutes, T2=T1+20°C, T3=T1-10N1, and the rate of the i-th deformation is v(i).

3. The method according to claim 2, characterized in that The sinusoidal arc mold in step 2 includes a first male mold, a first material guide sleeve and a first female mold. The first female mold is a double-petal opening and closing structure. The first female mold is in a sinusoidal arc shape. The shape function of the sinusoidal arc is y1. Among them, D1 is the ingot diameter, the first guide sleeve diameter, the diameter of the upper and lower openings of the first die, and H1 is the height of the first die.

4. The method according to claim 3, characterized in that In the step 3, the blank transfer time does not exceed 2 minutes, T4 = T1 + 20°C, and the rate of the nth deformation is f(n).

5. The method according to claim 4, characterized in that The cosine arc mold in step 3 includes a ejector block, a second convex mold, a second guide sleeve and a second concave mold. The ejector block is used to eject the blank. The second concave mold is an integral structure. The upper half of the second concave mold is straight, and the lower half of the second concave mold is cosine arc-shaped. The shape function of the cosine arc is y2. Among them, D2 is the maximum diameter of the blank, the diameter of the second guide sleeve, the diameter of the upper opening of the second die, and H2 is the height of the second die.

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