A method for predicting cracks in an aluminum alloy extrusion profile and a production method for an aluminum alloy extrusion profile

Abstract

The present invention relates to a method for predicting cracks in aluminum alloy extruded profiles and a method for producing aluminum alloy extruded profiles. The prediction method is used to predict whether cracks will occur in the profiles during extrusion molding under the extrusion parameters to be predicted. By using the prediction method, the extrusion parameters under which the extruded profiles will not have cracks are determined, and then the aluminum alloy is extruded and produced under these extrusion parameters to obtain aluminum alloy extruded profiles. The prediction method of the present invention has high prediction accuracy and is simple and easy to implement. This method can effectively optimize the extrusion process and extrusion tooling, thereby greatly improving the deficiencies existing in the extrusion process and extrusion tooling, effectively avoiding the occurrence of profile cracks, and thus greatly increasing the yield of extruded profiles of difficult-to-extrude aluminum alloys.

Description

Technical Field

[0001] The present invention belongs to the field of deep processing of aluminum alloy materials and is applied to the extrusion production technology of aluminum alloy profiles. Specifically, it relates to a method for predicting cracks in aluminum alloy extruded profiles and a production method for aluminum alloy extruded profiles. Background Art

[0002] This section aims to provide background or context for the embodiments of the present invention described in the claims. The description herein is not admitted to be prior art merely because it is included in this section.

[0003] Since high-strength and high-toughness 5xxx, 6xxx, and 7xxx series aluminum alloys contain relatively high contents of strengthening elements such as Mg, Si, Cu, Zn, Mn, and Cr, the flow stress of such aluminum alloys is relatively high, the fluidity is poor, and extrusion cracks are extremely likely to occur, resulting in the failure or scrapping of profiles.

[0004] Currently, the prediction of cracks in such difficult-to-extrude profiles is mostly based on the trial-and-error method. However, since this type of aluminum alloy is more sensitive to process parameters, usually more tests are required for optimization, and the experience of the operator has a very large impact on the number of optimizations. Therefore, the trial-and-error method is time-consuming, laborious, and inefficient. The simulation software for predicting profile cracks is mostly based on traditional damage and fracture criteria, without considering the special working conditions during the extrusion process. There is a large error between the prediction results and the actual on-site results, and it cannot effectively guide the optimization of on-site processes and die tooling.

[0005] Therefore, there is an urgent need for a method for predicting cracks in extruded profiles. Through this method, the generation of profile crack defects can be effectively avoided, and the extrusion process and extrusion tooling can be effectively optimized, which can further increase the possibility of avoiding the generation of profile crack defects. Summary of the Invention

[0006] One object of the present invention is to provide a method for predicting cracks in aluminum alloy extruded profiles with high prediction accuracy.

[0007] Another object of the present invention is to provide a production method for aluminum alloy profiles, and production is carried out according to the extrusion parameters predicted by this prediction method.

[0008] To achieve the above objects, the technical solutions adopted by the present invention are as follows:

[0009] In the first aspect of the present invention, a method for predicting cracks in aluminum alloy extruded profiles is provided. The prediction method is used to predict whether cracks will appear in the profile when extrusion forming is carried out under the extrusion parameters to be predicted. The prediction method includes the following steps:

[0010] (1) Conduct extrusion production tests on aluminum alloy under multiple groups of different extrusion parameters, and determine the extrusion parameters when the profile just starts to crack in the test as the critical extrusion parameters;

[0011] (2) Numerically simulate the extrusion process under the critical extrusion parameters by using the crack prediction model to obtain the effective plastic strain rate, rheological stress σ and time t under the critical extrusion parameters, and then calculate the critical plastic strain energy density C according to the formula ; selectively correct the critical plastic strain energy density C cr according to the results of multiple tests to improve the accuracy of model prediction; cr

[0012] (3) Numerically simulate the extrusion process under the extrusion parameters to be predicted by using the crack prediction model to obtain the effective plastic strain rate , rheological stress σ, time t, temperature T of the profile and stress triaxiality η under the extrusion parameters to be predicted;

[0013] (4) According to the results of the numerical simulation in step (3), judge whether the profile has cracks according to the following crack criterion formula. If H = 1, the predicted result is that there are cracks; if H = 0, the predicted result is that there are no cracks;

[0014] , where T cr is the low melting point phase temperature of the aluminum alloy.

[0015] According to some specific embodiments, the method for determining the critical extrusion parameters is as follows: for the profiles obtained under two adjacent sets of extrusion parameters, one group has cracks and the other group has no cracks, then the extrusion parameters of the group with cracks are used as the critical extrusion parameters.

[0016] According to some specific embodiments, in step (1), the number of groups of the multiple sets of different extrusion parameters is 2 - 6 groups.

[0017] According to some specific embodiments, the crack prediction model includes the constitutive equation of the aluminum alloy and finite element analysis software.

[0018] Further, the constitutive equation of the aluminum alloy is pre - constructed in the following manner:

[0019] (a) Conduct a hot simulation compression test on the aluminum alloy ingot to obtain the true stress - true strain data of the aluminum alloy under different deformation conditions;

[0020] (b) Substitute the true stress - true strain data into the Arrhenius equation to establish the constitutive equation of the aluminum alloy; where the formula of the Arrhenius equation is:

[0021] , where σ is the rheological stress; where $\dot{\varepsilon}$ is the strain rate, $T$ is the deformation temperature; $Q$ is the activation energy of deformation; $R$ is the universal gas constant; $A$ and $\beta$ are coefficients related to the material.

[0022] According to some specific embodiments, the calculation formula of the stress triaxiality $\eta$ is as follows:

[0023] , where $\sigma_1$, $\sigma_2$ and $\sigma_3$ are the three principal stresses obtained by simulation calculation of the crack prediction model, and $\sigma$ m is the mean stress, and $\sigma_{eq}$ is the effective stress.

[0024] According to some specific embodiments, the temperature of the low melting point phase of the aluminum alloy is obtained by DSC detection.

[0025] According to some specific embodiments, the aluminum alloy is a 5xxx series aluminum alloy, a 6xxx series aluminum alloy or a 7xxx series aluminum alloy.

[0026] According to some specific embodiments, the prediction method further includes step (5) performed when the prediction result is that there is a crack, and step (5) includes the following steps:

[0027] (i) Adjust the extrusion parameters to be predicted;

[0028] (ii) Obtain the numerical simulation result under the adjusted extrusion parameters to be predicted according to the method of step (3);

[0029] (iii) Judge whether the profile has cracks according to the method of step (4). If $H = 0$, the prediction result of the profile extruded under the adjusted extrusion parameters to be predicted is that there is no crack; otherwise, repeat steps (i) to (iii).

[0030] According to some specific embodiments, the extrusion parameters include extrusion temperature and extrusion speed.

[0031] According to some specific embodiments, in step (2), the number of test results for correcting the critical plastic strain energy density $C$ cr is 2 to 5.

[0032] According to some specific embodiments, in step (2), the multiple test results are the critical extrusion speeds corresponding to multiple different extrusion temperatures, and the multiple critical plastic strain energy densities $C$ obtained by numerical simulation according to the method of step (2) cr .

[0033] According to some specific embodiments, in step (2), the steps for correcting the critical plastic strain energy density $C$ cr are as follows:

[0034] 1) Conduct extrusion production tests on aluminum alloy at multiple different extrusion temperatures to determine the critical extrusion speeds at which cracks first appear in the profiles obtained from the tests at multiple different temperatures;

[0035] 2) Respectively obtain the critical plastic strain energy density C at multiple different extrusion temperatures and corresponding multiple critical extrusion speeds according to the method in step (2), cr and then calculate the modified critical plastic strain energy density C' according to the following formula for multiple said critical plastic strain energy densities C: cr cr ':

[0036] ;

[0037] 3) Substitute the modified critical plastic strain energy density C' for the critical plastic strain energy density C in the crack criterion formula. cr cr .

[0038] On the other hand, the present invention provides a production method for aluminum alloy extruded profiles, including the following steps:

[0039] I) Determine the extrusion parameters at which the profiles formed by extrusion will not crack, where the extrusion parameters are predicted according to the prediction method described above;

[0040] II) Extrude the aluminum alloy according to the extrusion parameters determined in step I) to obtain aluminum alloy extruded profiles.

[0041] According to some specific embodiments, the extrusion parameter in step I) is the fastest extrusion speed at which the profile does not crack at a specific extrusion temperature.

[0042] According to some specific embodiments, the extrusion parameter in step I) is the fastest achievable extrusion speed and the corresponding extrusion temperature on the premise of ensuring that the quality of the aluminum alloy profile meets the technical requirements of the standard specifications and the load-bearing capacity of the extrusion equipment. Thus, the production efficiency is maximized on the premise of ensuring the forming quality of the material and the safety of the equipment.

[0043] Due to the application of the above technical solutions, the present invention has the following advantages compared with the prior art:

[0044] The prediction method of the present invention has high prediction accuracy and is simple and easy to implement. This method can effectively optimize the extrusion process and extrusion tooling, thereby greatly improving the deficiencies in the extrusion process and extrusion tooling, effectively avoiding the occurrence of profile cracks, and thus greatly increasing the yield of extruded profiles of difficult-to-extrude aluminum alloys. Description of the Drawings

[0045] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only some embodiments recorded in the present application. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on these drawings.

[0046] Figure 1 It is the DSC diagram of a certain 6-series aluminum alloy;

[0047] Figure 2 It is the comparison diagram of the photo of the 6-series aluminum alloy extrusion profile produced at an extrusion temperature of 490°C and an extrusion speed of 1.5 mm / s and the simulated crack distribution;

[0048] Figure 3 It is the distribution diagram of the stress triaxiality of the simulated 6-series aluminum alloy extrusion profile at an extrusion temperature of 490°C and an extrusion speed of 1.5 mm / s;

[0049] Figure 4 It is the comparison diagram of the photo of the 6-series aluminum alloy extrusion profile produced at an extrusion temperature of 490°C and an extrusion speed of 1 mm / s and the simulated crack distribution;

[0050] Figure 5 It is the comparison diagram of the photo of the 6-series aluminum alloy extrusion profile produced at an extrusion temperature of 490°C and an extrusion speed of 2.5 mm / s and the simulated crack distribution. Detailed implementation manners

[0051] In order to enable those in the technical field to better understand the solution of the present invention, the following will clearly and completely describe the technical solution of the present invention in combination with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0052] It should be noted that the terms "first", "second", etc. in the description, claims and above-described drawings of the present invention are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. It should be understood that such data used can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, device, product or equipment comprising a series of steps or units does not necessarily limit to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or equipment. The term "plurality" means two or more, such as two, three, four, five or more.

[0053] Due to the great difficulty in extruding aluminum alloys such as high-strength and high-toughness 5xxx, 6xxx and 7xxx series aluminum alloys, there are problems such as time-consuming, laborious, low efficiency and low prediction accuracy in predicting cracks based on methods such as the trial-and-error method, traditional damage and fracture criteria.

[0054] Therefore, based on the deficiencies of the prior art, the present invention provides a method for predicting cracks. First, a material equation of aluminum alloy and a constitutive equation of profile cracks are established, and then through numerical calculation, combined with test data, the cumulative critical plastic strain energy density at which cracks appear is determined. Based on this, combined with the stress triaxiality and the low-temperature phase melting point temperature, the prediction of extrusion profile cracks or the control of profile crack defects is carried out.

[0055] Specifically, the method for predicting cracks in aluminum alloy extruded profiles includes the following steps:

[0056] (1) Conduct extrusion production tests on aluminum alloy under multiple groups of different extrusion parameters, and determine the extrusion parameters at which cracks just appear in the profiles obtained from the tests as the critical extrusion parameters.

[0057] Wherein, the extrusion production test refers to using a small-scale test model to conduct a production test with the set extrusion parameters.

[0058] The aluminum alloy extruded profile refers to an aluminum alloy profile obtained by forming an aluminum alloy blank through an extrusion die.

[0059] In some embodiments, the method for determining the critical extrusion parameters is as follows: for the profiles obtained under two adjacent groups of extrusion parameters, if one group has cracks and the other group has no cracks, then the extrusion parameters of the group with cracks are taken as the critical extrusion parameters.

[0060] Further, when the extrusion temperature is determined, the difference in extrusion speed between two adjacent sets of extrusion parameters is 0.05 mm / s to 0.3 mm / s, such as 0.05 mm / s, 0.1 mm / s, 0.15 mm / s, 0.2 mm / s, 0.25 mm / s, 0.3 mm / s. For example, when the extrusion temperature is 490 °C, the extrusion speed of one set is 1.4 mm / s, and the extrusion speed of the other set is 1.5 mm / s. The smaller the difference in extrusion speed between two adjacent sets, the more accurate the obtained critical extrusion parameters, but the more extrusion production tests are required. The larger the difference in extrusion speed between two adjacent sets, the fewer extrusion production tests are required, but the accuracy of the obtained critical extrusion parameters is poor.

[0061] In some embodiments, the determination of the critical extrusion parameters can be carried out by the golden section method for sequential experimental design to gradually approach the critical extrusion parameters. It is also possible to combine production experience to further reduce the number of extrusion production tests while obtaining the critical extrusion parameters.

[0062] In some embodiments, in step (1), the number of sets of the multiple different extrusion parameters is 2 to 6 sets.

[0063] In some embodiments, the extrusion parameters are extrusion temperature and extrusion speed.

[0064] For example, when producing a certain 6-series aluminum alloy, first, extrusion production is carried out at an extrusion temperature of 490 °C and an extrusion speed of 1 mm / s, and no cracks appear in the extruded profile. Then, extrusion production is carried out at an extrusion temperature of 490 °C and an extrusion speed of 2.5 mm / s, and cracks appear in the extruded profile. Then, extrusion production is carried out at an extrusion temperature of 490 °C and an extrusion speed of 1.5 mm / s, and cracks appear in the extruded profile. Then, extrusion production is carried out at an extrusion temperature of 490 °C and an extrusion speed of 1.3 mm / s, and no cracks appear in the extruded profile. Continuing to carry out extrusion production at an extrusion temperature of 490 °C and an extrusion speed of 1.4 mm / s, no cracks appear in the extruded profile. Then, it is determined that at an extrusion temperature of 490 °C, when the extrusion speed is less than 1.5 mm / s, no cracks appear in the profile, and 490 °C and 1.5 mm / s are used as the critical extrusion parameters.

[0065] (2) Numerically simulate the extrusion process under the critical extrusion parameters by using the crack prediction model to obtain the effective plastic strain rate , the flow stress σ and the time t under the critical extrusion parameters, and then according to the formula calculate the critical plastic strain energy density C cr , and selectively correct the critical plastic strain energy density C cr according to the results of multiple tests to improve the accuracy of model prediction.

[0066] In some embodiments, the crack prediction model is pre-constructed.

[0067] In some embodiments, the crack prediction model includes the constitutive equation of aluminum alloy and finite element analysis software.

[0068] In some embodiments, the constitutive equation of aluminum alloy is pre-constructed in the following manner:

[0069] (a) Conduct a hot simulation compression test on an aluminum alloy ingot to obtain true stress-true strain data of the aluminum alloy under different deformation conditions;

[0070] (b) Substitute the true stress-true strain data into the Arrhenius equation, and use the Arrhenius equation to describe the relationship between the flow stress σ, the strain rate and the deformation temperature T (K). After fitting, the constitutive equation of the aluminum alloy is obtained; wherein, the formula of the Arrhenius equation is:

[0071] , where σ is the flow stress; is the strain rate, T is the deformation temperature; Q is the deformation activation energy; R is the universal gas constant; A and β are coefficients related to the material.

[0072] Substituting the true stress-true strain data into the Arrhenius equation can obtain the specific values of Q, R, A, and β for this aluminum alloy, and further obtain the constitutive equation of this aluminum alloy.

[0073] Among them, the hot simulation compression test can be carried out on a Gleeble-3500 hot simulation testing machine.

[0074] The finite element analysis software performs numerical simulation of the extrusion process under the input extrusion parameters according to the constitutive equation of the aluminum alloy, and obtains a series of numerical values during the extrusion process.

[0075] In some embodiments, the calculation formula of the stress triaxiality η is as follows:

[0076] , where σ1, σ2, and σ3 are the three principal stresses obtained by simulation calculation of the crack prediction model, and σ m is the mean stress, is the effective stress.

[0077] In some embodiments, the temperature of the low melting point phase of the aluminum alloy is detected by DSC (differential scanning calorimeter). The temperature of the low melting point phase refers to the temperature at which some components in the aluminum alloy undergo a phase change from solid to liquid when heated to a certain temperature.

[0078] In some embodiments, in step (2), for the critical plastic strain energy density C cr The number of test results for correction is 2 to 5, such as 2, 3, 4, or 5.

[0079] Furthermore, in step (2), the multiple test results are the critical extrusion speeds corresponding to multiple different extrusion temperatures. The multiple critical plastic strain energy densities C cr .

[0080] Furthermore, in step (2), the steps for correcting the critical plastic strain energy density C cr are as follows:

[0081] 1) Conduct extrusion production tests on the aluminum alloy at multiple different extrusion temperatures to determine the critical extrusion speeds at which cracks just appear in the profiles obtained from the tests at multiple different temperatures;

[0082] 2) Respectively obtain the critical plastic strain energy densities C cr at multiple different extrusion temperatures and the corresponding multiple critical extrusion speeds according to the method in step (2). Then, calculate the multiple critical plastic strain energy densities C cr according to the following formula to obtain the corrected critical plastic strain energy density C cr ’:

[0083] ;

[0084] 3) Replace the critical plastic strain energy density C cr ’ in the crack criterion formula with the critical plastic strain energy density C cr .

[0085] By correcting the critical plastic strain energy density C cr for the same type of aluminum alloy, especially by correcting according to the above formula, the accuracy of crack prediction for this type of aluminum alloy under different extrusion parameters can be better predicted. The reason is that the correction of the critical plastic strain energy density can reduce the interference of temperature factors on it.

[0086] In some embodiments, multiple different extrusion temperatures adopt a multi-temperature gradient system, and at least the extrusion parameters for high, medium, and low temperature intervals are set to effectively weaken the interference of temperature variables on the prediction accuracy.

[0087] Among them, the effective plastic strain rate refers to that under complex stress states, the strain contributions in different directions of the material are different. The effective plastic strain rate is the strain rate in the plastic stage of the material, and it is closely related to the generation of extrusion cracks in the profiles.

[0088] The flow stress refers to the stress generated during the deformation of a material due to internal microstructural changes (such as dislocation movement, grain deformation, etc.). It reflects the flow resistance of the material during deformation.

[0089] In the production of aluminum alloy extrusion, time usually refers to the time during which the material participates in hot deformation during the extrusion process.

[0090] The temperature of the profile refers to the real-time temperature during the actual extrusion process of the aluminum alloy profile during extrusion.

[0091] The stress triaxiality refers to the relationship between the three principal stresses in a three-dimensional stress state of a material, and its calculation formula is as described above.

[0092] The three principal stresses refer to the stress at any point inside the material in a three-dimensional stress state, which can be decomposed into three mutually perpendicular principal stresses, denoted by σ1, σ2, and σ3 respectively.

[0093] The strain rate refers to the amount of strain change of a material per unit time, reflecting the speed of material deformation.

[0094] The deformation temperature refers to the temperature at which the ingot is heated in preparation for extrusion.

[0095] (3) Use the crack prediction model to perform numerical simulation on the extrusion process under the extrusion parameters to be predicted, and obtain the effective plastic strain rate , the flow stress σ, the time t, the temperature T of the profile, and the stress triaxiality η under the extrusion parameters to be predicted.

[0096] Among them, the crack prediction model is the model pre-constructed according to the above method, and the construction method is as described above, which will not be elaborated here.

[0097] In some embodiments, a series of numerical values during the extrusion process simulated using the crack prediction model can be used to calculate the critical plastic strain energy density C cr or the plastic strain energy density C through software or a program according to the formula.

[0098] (4) According to the results of the numerical simulation in step (3), judge whether the profile has cracks according to the following crack criterion formula. If H = 1, the predicted result is that there are cracks; if H = 0, the predicted result is that there are no cracks;

[0099] , where T cr is the low melting point phase temperature of the aluminum alloy.

[0100] Among them, in the above crack criterion formula, if the result of the numerical simulation under the extrusion parameters to be predicted is calculated according to the formula The calculated plastic strain energy density C ≥ the critical plastic strain energy density C cr or the modified critical plastic strain energy density C cr ’, and η ≥ 0, and T > T cr , then H = 1; if the result of the numerical simulation under the extrusion parameters to be predicted is calculated according to the formula and the calculated plastic strain energy density C < the critical plastic strain energy density C cr or the modified critical plastic strain energy density C cr ’, or η < 0, or T ≤ T cr , then H = 0.

[0101] In some embodiments, by combining the critical plastic strain energy density C cr , the stress triaxiality η, and the temperature T of the profile, it is also possible to predict the location where cracks occur in the extruded profile, so as to provide a basis for process improvement and related research.

[0102] In some embodiments, the prediction method further includes step (5) performed when the prediction result is that there are cracks, and step (5) includes the following steps:

[0103] (i) Adjust the extrusion parameters to be predicted;

[0104] (ii) Obtain the effective plastic strain rate, rheological stress σ, time t, temperature T of the profile, and stress triaxiality η under the adjusted extrusion parameters to be predicted according to the method of step (3);

[0105] (iii) Judge whether cracks appear in the profile according to the method of step (4). If H = 0, the prediction result of the profile extruded under the adjusted extrusion parameters to be predicted is that there are no cracks; otherwise, repeat steps (i) to (iii).

[0106] The prediction method of the present invention has a wide range of applications, and is particularly suitable for high-strength and difficult-to-extrude aluminum alloys such as 5xxx series aluminum alloys, 6xxx series aluminum alloys, or 7xxx series aluminum alloys. Among them, the 5xxx series aluminum alloys include but are not limited to 5052, 5083, 5754, etc. The 6xxx series aluminum alloys include but are not limited to 6061, 6A82, 6082, etc. The 7xxx series aluminum alloys include but are not limited to 7075, 7A04, 7050, etc.

[0107] When calculating the critical plastic strain energy density C cr and the plastic strain energy density C of the present invention, using the rheological stress for calculation is beneficial to improving the prediction accuracy. The reason is that it is the true stress corresponding to the instantaneous plastic flow, and can better reflect the cause of crack generation during the profile extrusion process.

[0108] The numbers of steps (1) to (4) described in this application are only used to clarify the logical relationship of the technical solutions and do not constitute a mandatory limitation on the process operation sequence. Specifically, for example, the implementation order of step (2) and step (3) can be adjusted according to the optimization requirements of actual process parameters, and such adjustment does not affect the overall implementation effect of the technical solution.

[0109] The production method of the aluminum alloy extruded profile includes the following steps:

[0110] I) Determine the extrusion parameters at which the extruded profile will not crack, where the extrusion parameters are predicted by the prediction method as described above;

[0111] II) Extrude the aluminum alloy according to the extrusion parameters determined in step I) to obtain the aluminum alloy extruded profile.

[0112] In some embodiments, the extrusion parameter in step I) is the fastest extrusion speed at which the profile does not crack at a specific extrusion temperature.

[0113] In some embodiments, the extrusion parameter in step I) is the fastest extrusion speed and the corresponding extrusion temperature that can be achieved on the premise of ensuring that the quality of the aluminum alloy profile meets the standard specifications and the technical requirements of the extrusion equipment's bearing capacity. Thus, the production efficiency is maximized while ensuring the material forming quality and equipment safety.

[0114] Example 1: Crack prediction of a high-strength and high-toughness 6-series aluminum alloy, where the composition of this high-strength and high-toughness 6-series aluminum alloy includes: Al, 1.05 wt.% Si, 0.85 wt.% Mg, 0.45 wt.% Cu, 0.3 wt.% Cr, 0.6 wt.% Mn.

[0115] In this example, the pre-construction method of the crack prediction model is as follows: A thermal simulation compression test is carried out using Gleeble-3500, and the test scheme is deformation temperatures of 300 °C, 400 °C, 450 °C, 500 °C; strain rates are 0.01 s -1 , 0.1 s -1 , 1 s -1 , 10 s -1 , the heating rate of the specimen is 10 °C / s, the holding time is 5 min, the deformation amount is 70%, the true strain is 1.2, and the Arrhenius equation is used to describe the relationship between the flow stress σ and the strain rate and the deformation temperature T (K). After fitting, the Arrhenius constitutive equation is obtained, and the constitutive equation of this high-strength and high-toughness 6-series aluminum alloy is constructed. The finite element analysis software is Qform.

[0116] The constitutive equation of this high-strength and high-toughness 6-series aluminum alloy is as follows:

[0117] .

[0118] In this embodiment, the low melting point phase temperature T of the high-strength and high-toughness 6-series aluminum alloy detected by DSC cr is 542 °C, and the test results are as Figure 1 shown.

[0119] In this embodiment, after 5 extrusion production tests of aluminum alloy, it is determined that when the extrusion temperature of the aluminum alloy is 490 °C and the extrusion speed is less than 1.5 mm / s, no cracks will appear in the profile. At the extrusion temperature of 490 °C, the critical extrusion speed is 1.5 mm / s. The critical plastic strain energy density C under this critical extrusion parameter cr1 is 2e7 J / m 3 , and a photo of the aluminum alloy profile produced under this critical extrusion parameter is as shown in part a of Figure 2 , and the comparison diagram of the simulated crack distribution is as shown in part b of Figure 2 , and the distribution of the stress triaxiality is as shown in Figure 3 shown.

[0120] After 5 extrusion production tests of aluminum alloy, it is determined that when the extrusion temperature of the aluminum alloy is 400 °C and the extrusion speed is less than 2.5 mm / s, no cracks will appear in the profile. At the extrusion temperature of 400 °C, the critical extrusion speed is 2.5 mm / s. The critical plastic strain energy density C under this critical extrusion parameter cr2 is 1.9e7 J / m 3 .

[0121] After 5 extrusion production tests of aluminum alloy, it is determined that when the extrusion temperature of the aluminum alloy is 300 °C and the extrusion speed is less than 3 mm / s, no cracks will appear in the profile. At the extrusion temperature of 300 °C, the critical extrusion speed is 3 mm / s. The critical plastic strain energy density C under this critical extrusion parameter cr3 is 2.1e7 J / m 3 .

[0122] In this embodiment, the corrected critical plastic strain energy density C cr ' is 2.0e7 J / m 3 .

[0123] Result verification:

[0124] During the extrusion process, the crack is predicted according to the extrusion temperature of 490 °C and the extrusion speed of 1 mm / s. The plastic strain energy density C under this extrusion parameter is 1e7 J / m 3 , which is less than the corrected critical plastic strain energy density C cr', at this time H = 0. Therefore, the prediction result under this extrusion parameter is no crack. According to this extrusion parameter, the extrusion production test was carried out, and the photo of the obtained profile is as follows Figure 4 As shown in part a, it can be seen that the profile has no cracks, and the simulated crack distribution comparison diagram is as follows Figure 4 As shown in part b, it can be seen that the predicted results are consistent with the actual production results.

[0125] The cracks in the extrusion process are predicted according to the extrusion temperature of 490℃ and the extrusion speed of 1.4mm / s. The plastic strain energy density C under this extrusion parameter is 1.9e7 J / m 3 , which is less than the modified critical plastic strain energy density C cr ', at this time H = 0. Therefore, the predicted result under this extrusion parameter is no crack. According to the extrusion parameters, the extrusion production test was carried out, and the obtained profile had no cracks. It can be seen that the predicted result is consistent with the actual production result.

[0126] The cracks in the extrusion process are predicted according to the extrusion temperature of 490℃ and the extrusion speed of 2.5mm / s. The plastic strain energy density C under this extrusion parameter is 2.5e7 J / m 3 , which is greater than the modified critical plastic strain energy density C cr ', there is a position where the stress triaxiality η result is greater than 0, and the temperature T of the profile is greater than 542℃, at this time H=1. Therefore, the prediction result under this extrusion parameter is that there is a crack and the location where the crack occurs is predicted. According to the extrusion parameters, the extrusion production test is carried out, and the photos of the obtained profiles are shown in Figure 5 As shown in part a, it can be seen that the profile has cracks, and the simulated crack distribution comparison diagram is as follows Figure 5 As shown in part b, it can be seen that the predicted results are consistent with the actual production results.

[0127] The crack prediction during the extrusion process is carried out according to the extrusion temperature of 490℃ and the extrusion speed of 1.50mm / s. The plastic strain energy density C under this extrusion parameter is 2.0e7 J / m 3 , which is equal to the modified critical plastic strain energy density C cr ', there is a stress triaxiality η>0 position, and the temperature T of the profile is greater than 542℃, at this time H=1. According to the extrusion parameters, the extrusion production test was carried out, and the obtained profile had cracks. It can be seen that the prediction results are consistent with the actual production results.

[0128] Aluminum alloy extrusion molding production is carried out under the extrusion parameters of extrusion temperature 490℃ and extrusion speed 1.4mm / s. Under this condition, the aluminum alloy extruded profiles produced are of good quality, free of cracks, high production efficiency, and the yield rate can reach more than 90%.

[0129] The cracks in the extrusion process are predicted according to the extrusion temperature of 450℃ and the extrusion speed of 2.3mm / s. The plastic strain energy density C under this extrusion parameter is 1.9e7 J / m 3 , which is less than the modified critical plastic strain energy density C cr ', but equal to C cr2 , there is a position where the stress triaxiality η>0, and the temperature T of the profile is greater than 542℃. At this time, according to the modified critical plastic strain energy density C cr ', H = 0, indicating that the profile will not crack under this extrusion parameter. cr2 To judge, H = 1, it means that the profile will crack under the extrusion parameters. According to the extrusion parameters, the extrusion production test was carried out, and the obtained profile had no cracks, indicating that the modified critical plastic strain energy density C cr 'It can effectively avoid the interference of extrusion temperature on the profile crack judgment criteria.

[0130] The cracks in the extrusion process are predicted according to the extrusion temperature of 450℃ and the extrusion speed of 2.4mm / s. The plastic strain energy density C under this extrusion parameter is 2.2e7 J / m 3 , which is greater than the modified critical plastic strain energy density C cr ', there is a position where the stress triaxiality η>0, and the temperature of the profile is greater than 542℃, at this time H=1. According to the extrusion parameters, the extrusion production test was carried out, and the obtained profile had cracks. It can be seen that the prediction results are consistent with the actual production results.

[0131] Aluminum alloy extrusion molding production is carried out under the extrusion parameters of extrusion temperature 450℃ and extrusion speed 2.3mm / s. The aluminum alloy extruded profiles produced under this condition are of good quality, free of cracks, and have extremely high production efficiency. The yield rate can reach more than 90%, but the tonnage requirements of the extrusion equipment are relatively high.

[0132] The cracks in the extrusion process are predicted according to the extrusion temperature of 350℃ and the extrusion speed of 2.8mm / s. The plastic strain energy density C under this extrusion parameter is 1.89e7 J / m 3 , which is less than the modified critical plastic strain energy density C cr ', there is a position where the stress triaxiality η>0, the temperature T of the profile is less than 542℃, and H=0. According to the extrusion parameters, the extrusion production test was carried out, and the obtained profile had no cracks. It can be seen that the prediction results are consistent with the actual production results.

[0133] The cracks in the extrusion process are predicted according to the extrusion temperature of 350℃ and the extrusion speed of 2.9mm / s. The plastic strain energy density C under this extrusion parameter is 2.2e7 J / m 3 , which is greater than the modified critical plastic strain energy density Ccr ’, there is a position where the stress triaxiality η > 0, and the result of the temperature T of the profile is greater than 542 °C. At this time, H = 1. Extrusion production tests were carried out according to this extrusion parameter, and cracks appeared in the produced profiles. It can be seen that the prediction result is consistent with the actual production result.

[0134] Aluminum alloy extrusion forming production was carried out under the extrusion parameters of an extrusion temperature of 350 °C and an extrusion speed of 2.8 mm / s. Under this condition, the quality of the produced aluminum alloy extruded profiles is good and there are no cracks, but the requirement for the tonnage of the extrusion equipment is extremely high, which is not suitable for large-scale industrial production.

[0135] Example 2: Crack prediction of a 5-series aluminum alloy. The composition of this 5-series aluminum alloy includes: Al, 4 wt.%, Mg, 0.15 wt.%, Cr, 0.6 wt.%, Mn.

[0136] In this example, the pre-construction method of the crack prediction model is as follows: A hot simulation compression test was carried out using Gleeble-3500. The test scheme was a deformation temperature of 300 °C, 400 °C, 450 °C, 500 °C; the strain rate was 0.01 s -1 , 0.1 s -1 , 1 s -1 , 10 s -1 , the heating rate of the specimen was 10 °C / s, the holding time was 5 min, the deformation amount was 70%, the true strain was 1.2, and the Arrhenius equation was used to describe the relationship between the flow stress σ and the strain rate and the deformation temperature T (K). After fitting, the Arrhenius constitutive equation was obtained, and the constitutive equation of this 5-series aluminum alloy was constructed. The finite element analysis software was Qform.

[0137] In this example, the low melting point phase temperature T of the 5-series aluminum alloy detected by DSC cr was 482 °C.

[0138] In this example, after 5 extrusion production tests of the aluminum alloy, it was determined that at an extrusion temperature of 450 °C, the critical extrusion speed of this aluminum alloy was 0.8 mm / s. The critical plastic strain energy density C under this critical extrusion parameter cr was 1.8e7 J / m 3 .

[0139] After 5 extrusion production tests of the aluminum alloy, it was determined that at an extrusion temperature of 430 °C, the critical extrusion speed of this aluminum alloy was 1 mm / s. The critical plastic strain energy density C under this critical extrusion parameter cr was 1.79e7 J / m 3 .

[0140] After 5 extrusion production tests of aluminum alloy, it is determined that at an extrusion temperature of 400 °C, the critical extrusion speed of this aluminum alloy is 1.5 mm / s. The critical plastic strain energy density C under this critical extrusion parameter cr is 1.81e7 J / m 3 .

[0141] In this embodiment, the corrected critical plastic strain energy density C cr ’ is 1.8e7 J / m 3 .

[0142] Result verification:

[0143] During the extrusion process, the prediction of cracks is carried out according to an extrusion temperature of 420 °C and an extrusion speed of 1.2 mm / s. The plastic strain energy density C under this extrusion parameter is 1.78e7 J / m 3 , which is less than the corrected critical plastic strain energy density C cr ’. At the position where the stress triaxiality η > 0, the temperature T of the profile is greater than 482 °C, and at this time H = 0. According to this extrusion parameter, an extrusion production test is carried out, and the produced profile has no cracks. It can be seen that the prediction result is consistent with the actual production result.

[0144] During the extrusion process, the prediction of cracks is carried out according to an extrusion temperature of 420 °C and an extrusion speed of 1.3 mm / s. The plastic strain energy density C under this extrusion parameter is 1.82e7 J / m 3 , which is greater than the corrected critical plastic strain energy density C cr ’. At the position where the stress triaxiality η > 0, and the temperature T of the profile is greater than 482 °C, and at this time H = 1. According to this extrusion parameter, an extrusion production test is carried out, and the produced profile has cracks. It can be seen that the prediction result is consistent with the actual production result.

[0145] Example 3: Crack prediction of a 7-series aluminum alloy. The composition of this 7-series aluminum alloy includes: Al, 6.5 wt.% Zn, 2.0 wt.% Mg, 0.2 wt.% Cu, 0.10 wt.% Cr, 0.15 wt.% Zr.

[0146] In this embodiment, the pre-construction method of the crack prediction model is as follows: A thermal simulation compression test is carried out using Gleeble-3500. The test scheme is deformation temperatures of 300 °C, 400 °C, 450 °C, 500 °C; strain rates are 0.01 s -1 , 0.1 s -1 , 1 s -1 , 10 s -1 , the heating speed of the specimen is 10 °C / s, the holding time is 5 min, the deformation amount is 70%, the true strain is 1.2, and the Arrhenius equation is used to describe the flow stress σ and the strain rate The relationship between the strain rate and the deformation temperature T (K) was obtained by fitting to get the Arrhenius constitutive equation, and the constitutive equation of this 7-series aluminum alloy was constructed. The finite element analysis software was Qform.

[0147] In this embodiment, the low melting point phase temperature T of the 7-series aluminum alloy detected by DSC cr is 475 °C.

[0148] In this embodiment, after 5 extrusion production tests of the aluminum alloy, it was determined that at an extrusion temperature of 450 °C, the critical extrusion speed of the aluminum alloy is 0.5 mm / s. The critical plastic strain energy density C under this critical extrusion parameter cr is 1.6e7 J / m 3 .

[0149] After 5 extrusion production tests of the aluminum alloy, it was determined that at an extrusion temperature of 400 °C, the critical extrusion speed of the aluminum alloy is 0.8 mm / s. The critical plastic strain energy density C under this critical extrusion parameter cr is 1.62e7 J / m 3 .

[0150] After 5 extrusion production tests of the aluminum alloy, it was determined that at an extrusion temperature of 350 °C, the critical extrusion speed of the aluminum alloy is 1 mm / s. The critical plastic strain energy density C under this critical extrusion parameter cr is 1.61e7 J / m 3 .

[0151] In this embodiment, the corrected critical plastic strain energy density C cr ’ is 1.61e7 J / m 3 .

[0152] Result verification:

[0153] During the prediction of cracks during extrusion at an extrusion temperature of 420 °C and an extrusion speed of 0.6 mm / s, the plastic strain energy density C under this extrusion parameter is 1.58e7 J / m 3 , which is less than the corrected critical plastic strain energy density C cr ’. At the position where the stress triaxiality η > 0, the temperature T of the profile > 475 °C, and at this time H = 0. According to this extrusion parameter, an extrusion production test was carried out, and the produced profile has no cracks. It can be seen that the prediction result is consistent with the actual production result.

[0154] During the prediction of cracks during extrusion at an extrusion temperature of 420 °C and an extrusion speed of 0.7 mm / s, the plastic strain energy density C under this extrusion parameter is 1.63e7 J / m 3 , which is greater than the corrected critical plastic strain energy density C cr', there is a position where the stress triaxiality η>0, and the temperature of the profile T>475℃, at this time H=1. According to the extrusion parameters, the extrusion production test was carried out, and the obtained profile had cracks. It can be seen that the prediction results are consistent with the actual production results.

[0155] It can be seen from the above embodiments that the prediction results of the prediction method of the present invention are basically consistent with the results of actual production, indicating that the method of the present invention is reliable and effective, and can accurately predict the production process parameters with the fastest production efficiency under the premise of meeting the performance requirements of aluminum alloys, avoid the occurrence of cracks, and thus improve the alloy yield rate, reduce production costs, and provide technical guarantee for the production of high-performance aluminum alloy extruded profiles.

[0156] Furthermore, the prediction method of the present invention can effectively optimize the extrusion process and extrusion tooling to further improve the possibility of avoiding the generation of profile crack defects, reduce the number of trial production and debugging, and improve efficiency.

[0157] The above detailed description of the present invention is intended to enable persons familiar with the art to understand the contents of the present invention and implement them. It does not limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for predicting cracks in aluminum alloy extrusion profiles, characterized in that: The prediction method is used to predict whether cracks will occur in the profile during extrusion forming under the extrusion parameters to be predicted. The prediction method includes the following steps: (1) Conduct extrusion production tests on aluminum alloy under multiple groups of different extrusion parameters, and determine the extrusion parameters at which cracks just appear in the profiles obtained from the tests as the critical extrusion parameters; (2) Use the crack prediction model to numerically simulate the extrusion process under the critical extrusion parameters to obtain the effective plastic strain rate, the flow stress σ, and the time t under the critical extrusion parameters, and then calculate the critical plastic strain energy density C according to the formula , and selectively correct the critical plastic strain energy density C according to the results of multiple tests to improve the prediction accuracy; cr , selectively correct the critical plastic strain energy density C cr according to the results of multiple tests to improve the prediction accuracy; (3) Use the crack prediction model to perform numerical simulation on the extrusion process under the extrusion parameters to be predicted, and obtain the effective plastic strain rate under the extrusion parameters to be predicted , flow stress σ, time t, temperature T of the profile, and stress triaxiality η; the calculation formula of the stress triaxiality η is as follows: ， Among them, σ1, σ2, and σ3 are the three principal stresses obtained by simulation calculation of the crack prediction model, and σ m is the mean stress, is the effective stress; (4) According to the results of the numerical simulation in step (3), judge whether cracks occur in the profile according to the following crack criterion formula. If H = 1, the prediction result is that there are cracks; if H = 0, the prediction result is that there are no cracks; , where T cr is the temperature of the low melting point phase of the aluminum alloy.

2. The prediction method of the crack of the aluminum alloy extrusion profile according to claim 1, characterized in that: The method for determining the critical extrusion parameters is as follows: for the profiles obtained under two adjacent groups of extrusion parameters, one group has cracks and the other group has no cracks, then the extrusion parameters of the group with cracks are used as the critical extrusion parameters.

3. The method for predicting cracks in the aluminum alloy extrusion profile according to claim 1, characterized in that: In step (1), the number of groups of the multiple groups of different extrusion parameters is 2 - 6 groups.

4. The method for predicting cracks in aluminum alloy extrusion profiles according to claim 1, characterized in that: The crack prediction model includes the constitutive equation of aluminum alloy and finite element analysis software.

5. The method for predicting cracks in aluminum alloy extrusion profiles according to claim 4, wherein: The constitutive equation of the aluminum alloy is pre - constructed in the following way: (a) Conduct hot simulation compression tests on aluminum alloy ingots to obtain true stress - true strain data of the aluminum alloy under different deformation conditions; (b) Substitute the true stress - true strain data into the Arrhenius equation to establish the constitutive equation of the aluminum alloy; where the formula of the Arrhenius equation is: , where σ is the flow stress; is the strain rate, T is the deformation temperature; Q is the deformation activation energy; R is the universal gas constant; A and β are coefficients related to the material.

6. The prediction method for cracks in aluminum alloy extrusion profiles according to claim 1, characterized in that: The prediction method further includes step (5) when the prediction result is that there are cracks. Step (5) includes the following steps: (i) Adjust the extrusion parameters to be predicted; (ii) Obtain the numerical simulation results under the adjusted extrusion parameters to be predicted according to the method in step (3); (iii) Judge whether cracks occur in the profile according to the method in step (4). If H = 0, the prediction result of the profile extruded under the adjusted extrusion parameters to be predicted is that there are no cracks; otherwise, repeat steps (i) to (iii).

7. The prediction method for cracks in aluminum alloy extrusion profiles according to claim 1, characterized in that: The extrusion parameters include extrusion temperature and extrusion speed.

8. The method for predicting cracks in aluminum alloy extrusion profiles according to claim 1 or 7, characterized in that: In step (2), multiple test results are the corresponding critical extrusion speeds under multiple different extrusion temperatures, and multiple critical plastic strain energy densities C obtained by numerical simulation according to the method in step (2) cr .

9. The method for predicting cracks in aluminum alloy extruded profiles according to claim 1 or 7, characterized in that: In step (2), the steps for correcting the critical plastic strain energy density C cr are as follows: 1) Conduct extrusion production tests on aluminum alloy at multiple different extrusion temperatures, and determine the critical extrusion speeds at which cracks just appear in the profiles obtained from the tests at multiple different temperatures; 2) Obtain the critical plastic strain energy density C at multiple different extrusion temperatures and corresponding multiple critical extrusion speeds respectively according to the method in step (2). cr , and then calculate the multiple critical plastic strain energy densities C cr to obtain the corrected critical plastic strain energy density C cr ' according to the following formula: ； 3) Substitute the corrected critical plastic strain energy density C cr ’ for the critical plastic strain energy density C in the crack criterion formula cr .

10. A production method of an aluminum alloy extrusion profile, characterized in that: It includes the following steps: I) Determine the extrusion parameters under which the extruded profile will not have cracks, where the extrusion parameters are predicted according to the prediction method described in any one of claims 1 to 9; II) Conduct extrusion production on aluminum alloy according to the extrusion parameters determined in step I) to obtain aluminum alloy extruded profiles.

11. The production method of the aluminum alloy extrusion profile according to claim 10, characterized in that: The extrusion parameters in step I) are the fastest extrusion speeds at which the profile does not have cracks at a specific extrusion temperature.

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