A method for preparing an alloy member for a study of a probability of detection of a seaworthiness certification defect

Abstract

The application provides a preparation method of an alloy component for airworthiness certification defect detection probability research, and relates to the technical field of airworthiness certification evaluation of an aero-engine, and comprises the following steps: cutting treatment is performed on an alloy test piece to be implanted, a hole is punched at a predetermined position of a cutting surface to obtain an implantation hole; an inclusion defect is placed in the implantation hole; then, the cutting surface is subjected to sealing welding treatment; the alloy test piece after the sealing welding treatment is subjected to hot isostatic pressing treatment to obtain the alloy component for airworthiness certification defect detection probability research; wherein the hot isostatic pressing treatment comprises a first stage and a second stage performed in sequence. Considering the influence of the geometric configuration of the disc piece on the detection probability, the alloy test piece with a circular cross section and provided with a step or a groove is adopted, and no forging treatment is required after implantation, so that the size and shape of the defects caused by the forging treatment are not controllable, and thus the accuracy of detection is ensured. Meanwhile, only one hot isostatic pressing treatment is required in the whole process, and errors are reduced.

Description

Technical Field

[0001] This invention belongs to the field of airworthiness certification evaluation technology for aero-engines, specifically relating to a method for preparing alloy components for studying the probability of detecting defects in airworthiness certification. Background Technology

[0002] Inclusions are a common smelting defect in life-limited components. Their presence severely reduces the mechanical properties of engine structural components, especially fatigue performance, leading to premature failure and significant personnel and economic losses. Therefore, to improve the overall safety level of the engine, the failure probability of inclusions during the wheel's lifespan must be assessed during wheel design and life-limiting processes. This is also one of the compliance requirements that must be demonstrated during engine airworthiness certification. Since the late 20th century, the Southwest Research Institute, with the support of the FAA and several major engine manufacturers, has systematically conducted theoretical and methodological research on probabilistic risk assessment, combining defective wheel component testing with verification. This method, based on the concept of discrete region risk calculation, has gradually developed and improved corresponding risk assessment analysis tools based on fracture mechanics, non-destructive testing, and probabilistic calculation methods. Currently, this analysis method has been approved by the FAA.

[0003] Currently, the life management system for domestic aero-engine rotors is still based on the assumption of ideal materials free of defects, without considering the impact of inclusions. However, the presence of inclusions inevitably leads to changes in material crack initiation, crack propagation, and fracture mechanisms, thus affecting the rotor's lifespan. This necessitates the inclusion of probabilistic failure risk assessment in the rotor's life management system to evaluate the impact of inclusions on the probability of failure during the rotor's lifespan. Defect detection probability data is a key input for probabilistic failure risk assessment; however, there is a lack of systematic research in China on methods for obtaining the detection probability of inclusions inside life-limited components, which has become one of the bottlenecks restricting the establishment of my country's independent airworthiness system. At present, the methods for obtaining the defect detection probability of life-limited components mainly refer to relevant foreign research methods, but these methods are not suitable for my country's industrial base. First, due to the lack of basic data related to defect detection probability in China, and the incompatibility between relevant foreign research data and methods and the domestic industrial system, foreign research results cannot be directly copied. Second, a review of relevant literature reveals that foreign defect detection probability analysis methods can no longer meet the current airworthiness regulations' requirements for the safety of life-limited components. If the above problems cannot be solved, it will be difficult to obtain defect detection probability acquisition methods and data that are compatible with my country's industrial system, which will affect the establishment of my country's independent airworthiness regulations, leaving my country's independent airworthiness in a state of being subject to others and making it difficult to gain international influence.

[0004] Currently, foreign countries have mastered the fabrication technology of high-throughput multi-factor coupled alloy components specifically for airworthiness certification defect detection probability studies. However, due to technological blockades, China has not yet made breakthroughs in related fabrication technologies. Existing alloy components (containing defective discs) specifically for airworthiness certification defect detection probability studies are prepared by first fabricating alloy bars containing inclusion defects, followed by forging. However, the forging process causes internal defects to fracture, resulting in uncontrollable defect size and morphology, which fails to meet the requirements of airworthiness certification studies. Summary of the Invention

[0005] Therefore, the present invention provides a method for preparing alloy components for airworthiness certification defect detection probability research, the main purpose of which is to precisely control the size of the inclusion defects in the prepared alloy components for airworthiness certification defect detection probability research.

[0006] To address the aforementioned problems, this invention provides a method for preparing alloy components for airworthiness certification defect detection probability studies, comprising the following steps:

[0007] Step 1): Cut the alloy specimen to be implanted, and drill holes at predetermined positions on the cut surfaces to obtain implantation holes; place the inclusion defects into the implantation holes;

[0008] The alloy specimen has a circular cross-section and is provided with steps or grooves;

[0009] Step 2): After inserting the inclusion defect, the cut surface is sealed by welding to obtain the alloy specimen after sealing by welding.

[0010] Step 3): The alloy specimen after the sealing and welding treatment is subjected to hot isostatic pressing to obtain an alloy component for the airworthiness certification defect detection probability study.

[0011] The hot isostatic pressing process includes a first stage and a second stage performed sequentially. The first stage is used to form a metallurgical bond between the alloy specimen and the interface of inclusion defects and to promote the diffusion of elements at the interface. The second stage reduces the difference in mechanical properties between the interface and the base material of the alloy specimen.

[0012] Furthermore, in the hot isostatic pressing process:

[0013] The temperature in the first stage is higher than the temperature in the second stage, and the duration of the first stage is shorter than the duration of the second stage.

[0014] Preferably, after the first stage, the interfacial bonding rate between the alloy specimen and the inclusion defects is ≥70%.

[0015] Furthermore, in the hot isostatic pressing process:

[0016] The temperature of the first stage is T0-15℃, the pressure is 140~160MPa, and the time is 0.5~1h;

[0017] Wherein, T0 is the critical temperature of the microstructure of the alloy specimen.

[0018] Furthermore, in the hot isostatic pressing process:

[0019] The temperature of the second stage is T β -30℃, pressure 170~200MPa, time 2~6h;

[0020] Wherein, T0 is the critical temperature of the microstructure of the alloy specimen.

[0021] Furthermore, the alloy specimen is one of the following shapes: cake-shaped, dog-bone-shaped, or spiral-shaped;

[0022] Preferably, the predetermined location includes the corner of the alloy specimen; when multiple inclusion defects are implanted at the corner, the included angle between the centers of any two adjacent inclusion defects along the circumference of the alloy specimen is ≥35°.

[0023] Preferably, the distance between any two adjacent inclusion defects is ≥30mm;

[0024] Preferably, the distance between the inclusion defect and the outer surface of the alloy specimen is ≥2mm.

[0025] Furthermore, the alloy specimen is one of titanium alloy, high-temperature alloy, and aluminum alloy; and / or

[0026] The inclusion defects are one or more of TiN, MgO, SiO2, and dirty white spots.

[0027] Furthermore, before step 1), the following is also included:

[0028] Based on the need for defect detection probability research, the influencing factors of inclusions are determined, and the characteristic information of inclusions is determined according to the influencing factors. Then, the inclusion defects are prepared according to the characteristic information.

[0029] Furthermore, the influencing factors include one or more of the following: inclusion size, element content, and inclusion type.

[0030] Furthermore, when the influencing factors include inclusion size, the feature information includes the extreme size and size distribution of the inclusions;

[0031] Preferably, the extreme values ​​and size distribution of inclusions are determined by a function formula; wherein the function formula is one of the logarithmic distribution function, the exponential distribution function, and the Weibull distribution.

[0032] Furthermore, the inclusion defects are prepared using powder metallurgy, forging, or casting.

[0033] Compared with the prior art, the present invention has at least the following beneficial effects:

[0034] 1. The present invention provides a method for preparing an alloy component for airworthiness certification defect detection probability research, comprising the following steps: cutting an alloy specimen to be implanted, drilling holes at predetermined positions on the cut surface to obtain implantation holes; placing inclusion defects into the implantation holes; wherein the cross-section of the alloy specimen is circular and has steps or grooves; after placing the inclusion defects, sealing the cut surface to obtain a sealed alloy specimen; subjecting the sealed alloy specimen to hot isostatic pressing to obtain an alloy component for airworthiness certification defect detection probability research; wherein the hot isostatic pressing includes a first stage and a second stage performed sequentially; the first stage is used to form a metallurgical bond between the alloy specimen and the inclusion defects and to promote the diffusion of elements at the interface; the second stage reduces the difference in mechanical properties between the interface and the base material of the alloy specimen. Considering the influence of disc geometry on detection probability, this invention uses an alloy specimen with a circular cross-section and steps or grooves. This means the alloy specimen has the same or similar geometric features as the actual disc and eliminates the need for post-implantation forging, avoiding the uncontrollable size and shape of defects caused by forging, thus ensuring detection accuracy. Furthermore, the entire process requires only one hot isostatic pressing (HIP) treatment, reducing errors (two HIP treatments are unnecessary; while two HIP treatments would reduce defects, they would not conform to the actual component manufacturing process and would result in larger errors), further ensuring detection accuracy.

[0035] 2. Furthermore, the first stage of the hot isostatic pressing process of the present invention employs high-temperature short-time hot pressing to eliminate the influence of diffusion interfaces (between alloy matrices, between alloy matrices and inclusions) on the test results and to prevent the alloy and inclusion structures from coarsening, which would not match the actual situation and lead to a decrease in test accuracy. The second stage employs low-temperature long-time hot pressing to ensure that the performance at the interface of the base material is restored to the state before implantation and to prevent excessive diffusion of inclusions and the matrix at high temperatures, forming a diffusion zone that would cause changes in the actual size of the defect implantation. Attached Figure Description

[0036] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0037] Figure 1A schematic diagram of multiple rods containing inclusions prepared by existing methods;

[0038] Figure 2 This is a schematic diagram of the inclusion implantation in Example 1 and a schematic diagram of the cake-shaped alloy specimen;

[0039] Figure 3 The image shows the Ti60 high-temperature titanium alloy component containing TiN inclusions prepared in Example 1 and the test results.

[0040] Figure 4 This is a schematic diagram of the inclusion implantation in Example 2 and a schematic diagram of the dog bone-shaped alloy specimen;

[0041] Figure 5 The image shows the 7050 aluminum alloy component containing MgO inclusions prepared in Example 2 and the test results.

[0042] Figure 6 This is a schematic diagram of the inclusion implantation in Example 3 and a schematic diagram of the spiral alloy specimen;

[0043] Figure 7 Figure 3 shows the GH4065A high-temperature alloy component containing SiO2 inclusions prepared in Example 3 and the test results.

[0044] Figure 8 For the following Figure 9 and Figure 10 The dimensions of the inclusions are shown in the diagram; the left side shows an implantation defect size of 1.96 mm, and the right side shows an implantation defect size of 2.01 mm; it can be seen that the implantation inclusions are of two different sizes, proving that the method of the present invention can be used for implantation of defects of different sizes;

[0045] Figure 9 The images show a comparison of the morphology of inclusions after implantation according to the technical solution of this patent. The defect size on the left is 1.92 mm, and the defect size on the right is 2.0 mm. It can be seen that the morphology of the inclusions changes little, which demonstrates that the method of this application can effectively control the size of the inclusions, thereby ensuring the accuracy of the detection.

[0046] Figure 10 The images show a comparison of the morphology of the inclusions after implantation in the comparative example. The defect size on the left is 2.25 mm, while the defect size on the right is 3.44 mm. It can be seen that the morphology of the inclusions changes significantly, indicating that the comparative example method cannot effectively control the inclusion size, leading to a significant deviation in detection accuracy. Detailed Implementation

[0047] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the specific embodiments, structures, features, and effects according to the present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. In the following description, different "an embodiment" or "an embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0048] The applicant also discovered that the prior art uses rods (regular cylinders, such as...) Figure 1 When studying the effect of defect implantation depth on detection probability, the inclusion defects are usually implanted at a fixed depth without considering the impact of the defect implantation depth. If multiple different rods are used to study the effect of defect implantation depth, the preparation processes cannot be completely consistent, resulting in differences in the prepared rods containing inclusions, which leads to large fluctuations and errors in the obtained detection probability.

[0049] In addition, defective discs used in airworthiness certification studies must meet the following six requirements to ensure the accuracy and validity of the test results: 1) The interface structure of the defect implantation should not affect the test results; 2) The mechanical properties at the interface must be comparable to those of the base material; 3) The morphology and size of the internal defects must remain consistent with those at the time of implantation; 4) The internal defects must form a good metallurgical bond with the base material; 5) The prepared defective discs must have a typical structure; 6) The internal defects of the prepared discs must possess multiple characteristics (type, size, location, angle, etc.). The applicant also found that there are three main existing methods for preparing defective discs or bars: "hot isostatic pressing + forging," "hot isostatic pressing + heat treatment," and "surface roughness control + hot isostatic pressing + heat treatment." For the "hot isostatic pressing + forging" method, the prepared discs do not meet the third requirement of the airworthiness requirements. Because the forging process causes the internal defects to fracture, the size and morphology of the defects become uncontrollable, failing to meet the requirements of the airworthiness certification study. For the "hot isostatic pressing + heat treatment" method, the resulting discs do not meet the requirements of Articles 3, 5, and 6 of the airworthiness requirements. First, this method can only produce bars with inherent defects, thus failing to produce a typical structure. Second, this method cannot simultaneously reflect multiple characteristics of defects (such as defect location and defect angle). Finally, if this method is used to produce discs, the bars must be forged, which leads to uncontrollable defect size and morphology, failing to meet the airworthiness certification study requirements. For the "surface roughness control + hot isostatic pressing + heat treatment" method, the resulting discs do not meet the requirements of Articles 3, 5, and 6 of the airworthiness requirements. The specific reasons are the same as for "hot isostatic pressing + heat treatment".

[0050] This invention enables high-throughput, multi-factor coupled fabrication, allowing for the detection of inclusions under various complex conditions within a single component. This eliminates the inaccuracy issues caused by differences in fabrication processes when using multiple components for detection in traditional methods. In other words, this invention ensures the accuracy of subsequent experimental results and the reliability of detection probability data. The specific solution is as follows:

[0051] This invention provides a method for preparing alloy components for airworthiness certification defect detection probability studies, comprising the following steps:

[0052] Step 1): Cut the alloy specimen to be implanted, drill holes at predetermined positions on the cut surface to obtain implantation holes; place the inclusion defects into the implantation holes;

[0053] The alloy specimen has a circular cross-section and is provided with steps or grooves.

[0054] Step 2): After inserting the inclusion defect, the cut surface is sealed by welding to obtain the alloy specimen after sealing by welding.

[0055] Step 3): The alloy specimen after sealing and welding is subjected to hot isostatic pressing to obtain the alloy component for the airworthiness certification defect detection probability study;

[0056] The hot isostatic pressing process includes a first stage and a second stage performed sequentially. The first stage is used to form a metallurgical bond between the alloy specimen and the interface of inclusion defects and to promote the diffusion of elements at the interface. The second stage reduces the difference in mechanical properties between the interface and the base material of the alloy specimen.

[0057] Since geometric features such as protrusions and corners in actual discs can affect the probability of defect detection, this invention uses alloy specimens with a circular cross-section and steps or grooves, meaning the alloy specimens have the same or similar geometric features as the actual discs. Furthermore, it eliminates the need for forging after implantation to obtain the disc, avoiding the uncontrollable size and shape of defects caused by forging, thus ensuring detection accuracy. Simultaneously, the entire process requires only one hot isostatic pressing (HIP) treatment, so the defect morphology and size after implantation remain consistent with those before implantation (eliminating the need for two HIP treatments, which would reduce defects and deviate from the actual component manufacturing process, leading to larger errors), further ensuring detection accuracy.

[0058] In some implementations, during hot isostatic pressing: the temperature of the first stage is higher than that of the second stage, and the time of the first stage is shorter than that of the second stage.

[0059] The first stage of the hot isostatic pressing process of this invention employs high-temperature short-time hot pressing to eliminate the influence of diffusion interfaces (between alloy matrix (i.e., the matrix of the alloy specimen) and between the alloy matrix and inclusions) on the test results, and to prevent the coarsening of the alloy specimen and inclusion structure, which would not match the actual situation and lead to a decrease in test accuracy. The second stage employs low-temperature long-time hot pressing to ensure that the performance at the interface of the base material is restored to the state before implantation, and to prevent excessive diffusion of inclusions and matrix at high temperatures, forming a diffusion zone, which would cause changes in the actual size of the defect implantation.

[0060] Furthermore, the temperature of the first stage is T0-15℃, the pressure is 140~160MPa, and the time is 0.5~1h; where T0 is the critical temperature of the microstructure of the alloy specimen.

[0061] The second stage has a temperature of T0-30℃, a pressure of 170~200MPa, and a time of 2~6h; where T0 is the critical temperature for the microstructure of the alloy specimen.

[0062] The alloy specimen can be a titanium alloy, an aluminum alloy, or a high-temperature alloy, etc. When it is a titanium alloy, T0 is the β phase transformation temperature of the titanium alloy specimen; when it is an aluminum alloy or a high-temperature alloy, T0 is the critical temperature for abnormal grain growth of the corresponding alloy specimen.

[0063] In the first stage, higher temperatures enhance atomic diffusion, facilitating interfacial bonding. However, excessively high temperatures lead to coarsening of the alloy specimen and inclusion microstructure, resulting in a coarsened specimen matrix that differs from the actual disk, thus reducing detection accuracy. Conversely, excessively low temperatures result in insufficient atomic diffusion, preventing the formation of a good metallurgical bond at the interface, and residual gaps that affect detection accuracy. Therefore, this invention, through precise control of temperature, time, and pressure, ensures metallurgical bonding between the alloy specimen and inclusion defects while avoiding microstructure coarsening, achieving an interfacial bonding rate ≥70%. In the second stage, although the interface heals after the high-temperature treatment in the first stage, the material itself may exhibit residual stress or a tendency towards microstructure coarsening. The second stage uses a lower temperature, which can effectively eliminate stress without significantly changing the grain size, ensuring that the mechanical properties at the interface are restored to a level comparable to the base material (the tensile properties (tensile strength, yield strength, and elongation) at the inclusion defect implantation interface reach more than 95% of the base material's properties). Simultaneously, it avoids excessively high temperatures, which could cause intense interdiffusion between elements in the inclusions and the matrix, forming a diffusion zone with a transitional composition, blurring the inclusion boundaries, and making it difficult to accurately define their "effective size." Furthermore, the slower atomic migration rate at low temperatures requires a longer time to complete property recovery. The pressure of hot isostatic pressing ensures good interfacial contact.

[0064] It should be noted that during solid-state phase transitions in metallic materials, the diffusion temperature is the primary factor influencing the diffusion interface. Higher diffusion temperatures result in more intense elemental activity at the interface and a larger diffusion region. Its main function is to achieve interface healing (the mechanism is as follows: the diffusion bonding process can be divided into three stages. The first stage is the physical contact stage: under pressure, the grooved and ridge-like regions on the alloy bonding surfaces come into contact and undergo limited plastic deformation. Under continuous pressure, the contact area between the materials continuously increases, forming local physical contact. The second stage is the interface migration stage: after the physical contact in the first stage, the contact area between the materials continuously increases due to the local plastic deformation caused by continuous pressure. Under a certain period of high-temperature insulation, atoms at the material bonding interface diffuse and migrate, further reducing the gaps between the materials. The third stage is the interface healing stage: under continuous high temperature and pressure, atoms at the bonding interface diffuse with each other, and the pores between the material bonding interfaces gradually heal and eventually disappear, achieving material bonding). Diffusion time plays a supporting role, mainly in regulating the microstructure and mechanical properties at the interface. In this application, high-temperature short-time hot isostatic pressing (HIP) is used to achieve interface healing while preventing excessive diffusion of elements at the interface that could cause changes in inclusion size. However, the properties at the interface cannot reach the state of the parent material after high-temperature short-time heat treatment. Therefore, low-temperature long-time heat treatment is used to regulate the properties of the interface structure and restore the properties at the interface, thereby meeting the requirements of discs used in airworthiness certification research.

[0065] In some embodiments, the alloy specimen is one of the following shapes: cake-shaped, dog-bone-shaped, or spiral-shaped.

[0066] Among them, such as Figure 2 and 3 As shown, the cake-shaped alloy specimen is a circular disc-shaped structure with varying thickness in its radial cross-section, forming multiple steps. This structure is identical to that of typical life-limiting components (such as centrifugal impellers) and can reflect real test results. The diameter difference between adjacent steps is no less than 60 mm, and the height difference between adjacent steps is no less than 30 mm. The dimensions of the cake structure avoid mutual interference during ultrasonic testing. Furthermore, by implanting inclusions of different sizes and depths in different step areas on the same cake-shaped alloy specimen, multiple sets of comparative data can be obtained simultaneously in a single test, meeting the needs of high-throughput defect detection probability studies.

[0067] like Figure 4 and 5As shown, the dog-bone-shaped alloy specimen has a dumbbell-shaped structure, wider at both ends and narrower in the middle. The central recess forms a groove or channel, with numerous corners. The depth-to-width ratio of the recess is not less than 1 / 10, and the diameter of the recess is 1 / 3 to 2 / 3 of the overall diameter. This structure allows for simultaneous comparison of inclusions at different sizes and depths. According to the research requirements for airworthiness certification, non-destructive testing is required on billets, semi-finished forgings, and finished forgings. The dog-bone structure is identical to the typical structure of semi-finished life-limited parts, and can reflect the true test results at the semi-finished forging stage.

[0068] like Figure 6 and 7 As shown, the described spiral alloy specimen has a bent or helical structure with a wall thickness not exceeding 20 mm and multiple stress concentration areas (such as structural inflection points). This structure is the same as the typical structure of actual life-limited components (such as centrifugal impeller over-rotation rupture simulation components) and can reflect the actual test results.

[0069] It should be noted that the cake-shaped, dog bone-shaped, and spiral-shaped alloy specimens of the present invention can be obtained by forging and machining the billet.

[0070] Since the formed alloy specimen is a circular disc, multiple inclusion defects can be implanted at the corners of the specimen (at the inner fillet of the variable cross-section transition). Along the circumference of the alloy specimen, the included angle between the centers of any two adjacent inclusion defects should be ≥35° to ensure no interference during testing. If multiple defects are implanted along the height of the component, the defects must not be on the same straight line, and there should be at least a 30mm interval between any two defects. When implanted at a thin-walled location, the defect should be at least 2mm away from the specimen surface.

[0071] It should be noted that the present invention performs cutting processing in the transverse direction (radial direction) perpendicular to the component axis (height), which can implant defects at any interface, and the implantation location and number are not limited.

[0072] Because components often have complex structures, such as varying cross-sections and thicknesses, internal cavities, slender channels or closed cavities, sharp corners, abrupt changes in curvature, and large dimensions, these factors make the hot pressing process extremely sensitive to the selection of the "temperature-pressure-time" window. This drastically amplifies the inherent limitations of the conventional one-step hot isostatic pressing method (referred to as the "one-step method"), making it unsuitable for fabricating complex components. The specific reasons are as follows:

[0073] (1) Interfacial contact mismatch caused by temperature field inhomogeneity

[0074] One-step method: During the heating process of complex components, the thicker parts exhibit significant thermal lag, while the temperature of thin-walled regions reaches the set value first. To ensure sufficient creep closure even at the coldest point, the one-step method necessitates a longer holding time to gradually reduce the temperature gradient. However, this means that the thin-walled and surface areas remain at high temperatures for an extended period, leading to severe grain coarsening and precipitation of harmful phases. Even if the temperature difference eventually decreases, prolonged high-temperature creep causes undesirable plastic flow at the thin-walled areas, altering the component's shape and position accuracy. If an internal cavity exists, the high temperature outside the cavity and the lag inside cause asynchronous contact at the cavity wall interfaces. While the outer wall has already begun diffusion bonding, the inner wall may not yet have adhered, ultimately forming a "hard shell" defect with a hollow interior and a solid exterior.

[0075] The two-step hot isostatic pressing (HTPC) method (referred to as the "two-step method"): The first step involves a short period of high temperature. Although a temperature difference still exists, the goal is not complete homogenization, but rather rapid creep that can be initiated by localized high temperatures. The high temperature at thin-walled areas causes the interface to close rapidly, while at thick-walled areas, due to slightly lower temperatures and slightly higher strength, the closure is slightly delayed, but the deformation difference is not significant within a very short time. The second step involves lowering the temperature and holding it at a long time. At this point, the temperature difference is minimal, and the interface is further homogenized through short-range diffusion. Furthermore, the material strength is high at low temperatures, preventing the inhomogeneity from being triggered by new non-uniform rheological processes. This compensates for the non-uniformity of the first step and avoids the accumulation of differences caused by prolonged high temperatures at varying thicknesses and interior / exterior surfaces.

[0076] (2) Non-coordinated deformation and dimensional accuracy maintenance

[0077] One-step method: To ensure the closure of all interfaces, it is often necessary to increase the pressure or extend the time. However, prolonged high temperature and pressure can cause unsupported thin walls and cavities to creep, buckle, or collapse excessively, altering the cross-sectional area of ​​the flow channels and even causing welding. Especially at the joints of dissimilar materials, the difference in creep resistance between the different materials can lead to asymmetric deformation, resulting in component distortion.

[0078] Two-step method: In the first step, the material's rheological stress is extremely low at high temperatures, requiring only a small amount of pressure to rapidly plastically yield the rough peaks at the interface to be welded. At this point, the total creep is minimal, having almost no impact on the macroscopic profile of the component. In the second step, at low temperatures, diffused stress relaxation is mainly achieved through short-range atomic migration rather than dislocation creep. Therefore, almost no macroscopic plastic deformation occurs, and the fine structure of complex components is completely preserved, resulting in dimensional accuracy far superior to the one-step method.

[0079] (3) Residual stress and interface integrity

[0080] Complex shapes lead to uneven temperature fields during cooling, and the mismatch in thermal expansion between dissimilar materials generates severe residual stress. In the one-step method, the entire component is homogenized at high temperature for a long time and then directly cooled from the high temperature. This results in large temperature differences, asynchronous shrinkage in different parts, and the formation of tensile stress peaks at the interfaces. Microcracks can also be initiated at stress concentration points such as sharp corners.

[0081] The second step of the two-step process involves a prolonged holding at a lower temperature, which can essentially be considered as online stress-relief annealing. Although the temperature is not high, it is sufficient to activate interstitial atomic diffusion and dislocation climb. Under the constraint of holding pressure, the micro-stress gradient at the interface can be relaxed through atomic rearrangement. In addition, the temperature difference from this temperature to room temperature is much smaller than the temperature difference from the high temperature of the one-step process, resulting in a significant decrease in the intrinsic value of thermal stress. Moreover, a stable bond has been formed at the interface at a low temperature, with good plasticity reserves, which significantly reduces the residual stress level of complex components after welding and improves fatigue resistance.

[0082] (4) Densification of "pressure shadow" areas such as narrow gaps and blind holes

[0083] Complex component assembly interfaces often have narrow wedge-shaped gaps and blind hole bottoms caused by local misfitting. While isostatic pressure is theoretically isobaric, in narrow gaps, gas entry is obstructed, and pressure transmission is delayed, creating a "pressure shadow." One-step long-term insulation methods attempt to force the material into the shadow area through overall creep, but often result in excessive deformation of the already contacted areas, while the shadow area remains incompletely closed.

[0084] In the first high-temperature step of the two-step process, the material's rheological stress is extremely low. Even with slightly insufficient pressure in the shaded area, the material at the interface is in a flowable state, and surface tension and capillary action also contribute to pore shrinkage. Furthermore, the difference in material volume expansion caused by short-term high temperatures can also promote local contact. In the subsequent low-temperature stage, surface diffusion and grain boundary diffusion can "draw in" atoms to fill remaining pores, avoiding dependence on overall deformation. This is particularly crucial for microstructures with large aspect ratios.

[0085] Hot isostatic pressing (HIP) of complex components essentially adds two new dimensions to the original contradiction of interface contact and diffusion: "thermal-mechanical field inhomogeneity" and "geometric constraints." The one-step method requires simultaneously satisfying the following conditions at a single temperature: 1) sufficient creep closure under uniform temperature across all parts; 2) no excessive harmful deformation; 3) no excessive structural degradation; 4) no uncontrolled growth of harmful interface phases; and 5) controllable residual stress. However, it is almost impossible to simultaneously satisfy these conditions for complex components, inevitably leading to a trade-off. The two-step method, by separating the "high-temperature, short-time" physical contact from the "low-temperature, long-time" diffusion-enhanced process, more naturally adapts to the inhomogeneity of complex structures: 1) High temperature is only responsible for rapid bonding; the short duration tolerates temperature differences and uneven deformation because the goal is only rough peak yielding, not overall rheology; 2) Low temperature is responsible for consolidating the bond and stress relaxation; the long duration complements temperature homogenization, using diffusion to "fine-tune" interface integrity without causing new deformation or structural damage.

[0086] Therefore, the more complex the component, the greater the process tolerance obtained by decoupling the two-step hot isostatic pressing, and the higher the retention of interface quality and base material properties. This is not only an optimization in mechanics and metallurgy, but also a qualitative improvement in the engineering feasibility of complex components.

[0087] In some embodiments, the alloy specimen is one of titanium alloy, high-temperature alloy, and aluminum alloy; the inclusion defect is one or more of TiN, MgO, and SiO2.

[0088] In some implementations, before step 1), the method further includes: determining the influencing factors of inclusions based on the needs of defect detection probability research, determining the characteristic information of inclusions based on the influencing factors, and then preparing inclusion defects according to the characteristic information.

[0089] Furthermore, influencing factors include one or more of the following: inclusion size, element content, and inclusion type.

[0090] Furthermore, when the influencing factor includes inclusion size, the characteristic information includes the extreme size and size distribution of the inclusion; the extreme size and size distribution of the inclusion are determined using a function formula; wherein the function formula is one of the logarithmic distribution function, exponential distribution function, and Weibull distribution. When the influencing factor includes element content, the characteristic information includes the elemental composition and content of the inclusion; when the influencing factor includes inclusion type, the characteristic information includes the material type of the inclusion.

[0091] The requirements for defect detection probability studies include: the defect itself, and its characteristics (such as size and location). When studying a single factor, such as the impact of inclusion size on detection probability, the core influencing factor is the size of the inclusion defect. If the study needs to investigate the impact of inclusion composition on detection probability, then the core influencing factor is composition, and so on. When studying multiple influencing factors, if the study simultaneously investigates the impact of inclusion size and location, then the core influencing factors are size and location. The specific requirements depend on which clause of the airworthiness regulations the study is focusing on.

[0092] In some embodiments, inclusion defects are prepared using powder metallurgy. Specifically, this involves mixing, shaping, and sintering the raw material powder for the inclusion (defect) to obtain inclusion defects of the desired composition and size. It should be noted that the inclusion should also be as consistent as possible with the actual inclusion. For example, the actual inclusion is not completely dense and contains pores or cracks; therefore, the prepared inclusion should also be as consistent as possible.

[0093] Furthermore, when implanting inclusion defects at predetermined locations, the locations are determined based on research needs. For example, if the impact of structural abrupt changes on detection probability needs to be characterized, then the defect needs to be implanted at a right angle; if the impact of depth on detection probability needs to be studied, then it needs to be implanted at different depths; or if the impact of stress on detection probability needs to be studied, then the defect needs to be implanted at the stress concentration point of the alloy specimen. The predetermined locations must also meet airworthiness certification research requirements, and the defects must not interfere with each other during testing. It should be noted that: for cake structures, the selection of predetermined locations ensures accurate implantation depth while maintaining a spacing of at least 30mm between defects to prevent interference during testing; for dog bone structures, the selection of predetermined locations ensures that defects are implanted at abrupt changes while maintaining a spacing of at least 30mm between defects to prevent interference during testing; for spiral structures, the selection of predetermined locations must ensure implantation at both abrupt changes and areas of maximum stress concentration. The depth difference should be greater than 20mm, and the defect spacing should be no less than 30mm. It is not necessary to implant defects at all right angle locations.

[0094] During the inclusion implantation process, the hot isostatic pressing treatment we use does not affect the macroscopic dimensions of the component; therefore, the inclusion implantation location is the predetermined location. To verify the accuracy of the implantation, the component after implantation can be dissected according to the implantation location to determine whether the defect implantation was accurate.

[0095] The present invention also has the following advantages:

[0096] (1) This invention is not limited by alloy materials and inclusion types, and can be applied to the preparation of various alloy components containing inclusions involved in aero-engines according to airworthiness certification requirements. The method of this invention can prepare any defective disc, and therefore is applicable to all materials of aero-engines. The types of inclusions in different materials correspond to the alloy materials (in reality, inclusions in high-temperature alloys rarely appear in titanium alloys), so the type of inclusions contained in the material is determined, and therefore it is not limited by alloy materials and inclusions.

[0097] (2) The method provided by the present invention can realize the artificial control of the type, size, position, etc. of inclusions. It can simulate the internal defects of various components according to the airworthiness certification requirements of different types of components, lay the material foundation for carrying out the probability analysis of the detection of alloy components with internal defects, and provide technical support for the airworthiness certification of domestic aero engines.

[0098] (3) The present invention can realize high-throughput multi-factor coupled preparation, realize the detection of inclusions under various complex conditions in one component, eliminate the problem of inaccurate detection results due to the difference in preparation process when multiple components are used for detection in the traditional way, and the present invention can ensure the accuracy of subsequent experimental results and the reliability of detection probability data.

[0099] The present invention will be further described below with reference to specific embodiments and comparative examples.

[0100] Example 1

[0101] This embodiment provides a method for preparing alloy components for airworthiness certification defect detection probability studies, including the following steps:

[0102] Step 1): Cut the alloy specimen to be implanted, and drill holes at predetermined positions on the cut surface to obtain implantation holes; place inclusion defects of multiple sizes into the corresponding implantation holes;

[0103] Among them, such as Figure 2 The right side of the image and Figure 3 As shown in the top left figure, the alloy specimen is a cake-shaped Ti60 high-temperature titanium alloy specimen, consisting of four layers. The diameters of each layer, from bottom to top, are 350 mm, 290 mm, 230 mm, and 170 mm, respectively. The inclusion defects in each layer are randomly distributed (spaced more than 30 mm apart), as shown in the figure. Figure 2 As shown in the left figure; the inclusion defect is TiN inclusion; the core elements of the inclusion are the size and location of the TiN inclusion;

[0104] Based on the requirements of defect detection probability research, the extreme sizes of TiN inclusions are 0.7 mm and 2.6 mm (too small a size makes them difficult to process and detect, while too large a size may cause them to fail before detection). The Weibull distribution function formula is used to determine the size distribution of TiN inclusions as 0.7 mm, 1 mm, 1.4 mm, 1.9 mm, and 2.6 mm, as follows:

[0105]

[0106] C i For the size of which defect; C 10 The minimum value; C 90 is the maximum value, n is the number of inclusion sizes distributed; i is the nth defect.

[0107] The specific calculation process is as follows:

[0108] 1) The first defect (minimum value) = 0.7 × (2.6 / 1.7) 1-1 / 5-1 =0.7×3.71 0 =0.7mm;

[0109] 2) The second defect = 0.7 × (2.6 / 1.7) 2-1 / 5-1 =0.7×3.71 1 / 4 =1.0mm;

[0110] 3) The third defect = 0.7 × (2.6 / 1.7) 3-1 / 5-1 =0.7×3.71 2 / 4 =1.4mm;

[0111] 4) The fourth defect = 0.7 × (2.6 / 1.7) 4-1 / 5-1 =0.7×3.71 3 / 4 =1.9mm;

[0112] 5) The fifth defect (maximum value) = 0.7 × (2.6 / 1.7) 5-1 / 5-1 =0.7×3.71 4 / 4 =2.6mm.

[0113] Step 2): After inserting the inclusion defect, the cut surface is sealed by welding to obtain the alloy specimen after sealing by welding.

[0114] Step 3): The alloy specimen after sealing and welding is subjected to hot isostatic pressing to obtain the alloy component for the airworthiness certification defect detection probability study; wherein, the hot isostatic pressing includes a first stage and a second stage performed sequentially; the first stage process is 1035℃ / 160MPa / 1h, and the second stage process is 1020℃ / 200MPa / 6h.

[0115] The alloy component used in the airworthiness certification defect detection probability study of this embodiment has mechanical properties at the interface after the first stage of hot isostatic pressing (tensile strength of 796 MPa, yield strength of 733 MPa, elongation of 8.3%) and mechanical properties at the interface after the second stage (tensile strength of 1135 MPa, yield strength of 1030 MPa, elongation of 10.5%) that are comparable to those of the base material of the alloy specimen (the base material has tensile strength of 1137 MPa, yield strength of 1026 MPa, and elongation of 10.3%).

[0116] Differences in mechanical properties can reflect metallurgical bonding at the interface and the degree of diffusion promotion. The smaller the difference in data, the smaller the difference. The fact that the mechanical properties in the example recovered to match those of the parent material indicates the formation of metallurgical bonding.

[0117] Figure 3 Other figures show the detection of defects in different locations and sizes. Among them, implanted defects can be detected, and the detection capabilities for defects with different contents and sizes can also be compared.

[0118] Example 2

[0119] This embodiment provides a method for preparing alloy components for airworthiness certification defect detection probability studies, including the following steps:

[0120] Step 1): Cut the alloy specimen to be implanted, and drill holes at predetermined positions on the cut surface to obtain implantation holes; place inclusion defects of multiple sizes into the corresponding implantation holes;

[0121] Among them, such as Figure 5 As shown in the figure on the left, the alloy specimen is a dog-bone shaped 7050 aluminum alloy specimen; the inclusion defect is MgO inclusion. Figure 5 The right-hand image illustrates that some implanted defects (highlighted areas) can be detected; the core elements of inclusions are the oxygen content in MgO (3%, 5%, and 7% respectively) and the location of the MgO inclusions, with specific implantation locations as shown below. Figure 4 As shown;

[0122] Based on the requirements of defect detection probability research, the extreme sizes of MgO inclusions are 1 mm and 1.9 mm, respectively. The Weibull distribution function formula is used to determine the size distribution of MgO inclusions as 1 mm, 1.7 mm, and 1.9 mm, as follows:

[0123]

[0124] C i For the size of which defect; C 10 The minimum value; C 90 is the maximum value, n is the number of inclusion sizes distributed; i is the nth defect.

[0125] The specific calculation process is as follows:

[0126] 1) The first defect (minimum value) = 1.0 × (1.9 / 1.0) 1-1 / 3-1 =1.0 × 1.9 0 =1.0mm;

[0127] 2) The second defect = 1.0 × (1.9 / 1.0) 2-1 / 3-1 =1.0 × 1.9 1 / 2 =1.4mm;

[0128] 3) The third defect (maximum value) = 1.0 × (1.9 / 1.0) 3-1 / 3-1 =1.0 × 1.9 2 / 2 =1.9mm.

[0129] Step 2): After inserting the inclusion defect, the cut surface is sealed by welding to obtain the alloy specimen after sealing by welding.

[0130] Step 3): The alloy specimen after sealing and welding is subjected to hot isostatic pressing to obtain the alloy component for the airworthiness certification defect detection probability study; wherein, the hot isostatic pressing includes a first stage and a second stage performed sequentially; the first stage process is 425℃ / 150MPa / 0.5h, and the second stage process is 410℃ / 180MPa / 4h.

[0131] The alloy component used in the airworthiness certification defect detection probability study of this embodiment exhibits mechanical properties at the interface after the first stage of hot isostatic pressing (tensile strength 411 MPa, yield strength 362 MPa, elongation 5.7%) and at the interface after the second stage of hot isostatic pressing (tensile strength 517 MPa, yield strength 465 MPa, elongation 8%) that are comparable to those of the base material of the alloy specimen (base material tensile strength 513 MPa, yield strength 461 MPa, elongation 8.5%).

[0132] Example 3

[0133] This embodiment provides a method for preparing alloy components for airworthiness certification defect detection probability studies, including the following steps:

[0134] Step 1): Cut the alloy specimen to be implanted, and drill holes at predetermined positions on the cut surface to obtain implantation holes; place inclusion defects of multiple sizes into the corresponding implantation holes;

[0135] Among them, such as Figure 7 The figure on the left shows a gyratory GH4065A high-temperature alloy specimen. Figure 7 The right-hand image illustrates that some implanted defects (highlighted areas) can be detected; the inclusion defect is SiO2 inclusion; the core element of the inclusion is the size of the SiO2 inclusion, and the specific implantation location. Figure 6 As shown;

[0136] Based on the requirements of defect detection probability research, the extreme sizes of SiO2 inclusions are 0.5 mm and 1.4 mm, respectively. The Weibull distribution function formula is used to determine the size distribution of SiO2 inclusions as 0.5 mm, 0.7 mm, 1 mm, and 1.4 mm, as follows:

[0137]

[0138] C i For the size of which defect; C 10 The minimum value; C 90 is the maximum value, n is the number of inclusion sizes distributed; i is the nth defect.

[0139] The specific calculation process is as follows:

[0140] 1) The first defect (minimum value) = 0.5 × (1.4 / 0.5) 1-1 / 4-1 =0.5×2.8 0 =0.7mm;

[0141] 2) The second defect = 0.5 × (1.4 / 0.5) 2-1 / 4-1 =0.5×2.8 1 / 3 =0.7mm;

[0142] 3) The third defect = 0.5 × (1.4 / 0.5) 3-1 / 4-1 =0.5×2.8 2 / 3 =1.0mm;

[0143] 4) The fourth defect (maximum value) = 0.5 × (1.4 / 0.5) 4-1 / 4-1 =0.5×2.8 3 / 3 =1.4mm.

[0144] Step 2): After inserting the inclusion defect, the cut surface is sealed by welding to obtain the alloy specimen after sealing by welding.

[0145] Step 3): The alloy specimen after sealing and welding is subjected to hot isostatic pressing to obtain the alloy component for the airworthiness certification defect detection probability study; wherein, the hot isostatic pressing includes a first stage and a second stage performed sequentially; the first stage process is 1030℃ / 150MPa / 1h, and the second stage process is 1015℃ / 190MPa / 5h.

[0146] The alloy component used in the airworthiness certification defect detection probability study of this embodiment has mechanical properties at the interface after the first stage of hot isostatic pressing (tensile strength of 1064 MPa, yield strength of 853 MPa, elongation of 9.3%) and mechanical properties at the interface after the second stage of hot isostatic pressing (tensile strength of 1281 MPa, yield strength of 992 MPa, elongation of 12.5%) that are comparable to those of the base material of the alloy specimen (the base material has tensile strength of 1289 MPa, yield strength of 996 MPa, and elongation of 12%).

[0147] Comparative Example

[0148] This comparative example provides a method for preparing an alloy component for studying the probability of detecting defects in airworthiness certification, including the following steps:

[0149] (1) According to the forging process and the size requirements of the internal TiN inclusions, the Ti60 high-temperature titanium alloy bar is cut into the specifications that meet the forging process. The TiN inclusions are cut into a certain size by wire cutting. The size of the TiN inclusion particles is 0.7mm.

[0150] (2) According to the requirements of the TiN inclusions inside the disc, the position of the inclusions inside the forging bar is determined by forming simulation. The bar is sawn along the plane where the position is located. After the sawn surface is ground flat, a hole is drilled at the position of the inclusion. The cut TiN inclusions are placed in the hole. The hole size at the position of the inclusion matches the TiN size.

[0151] (3) Bar welding: The bar is welded along the cut surface using vacuum welding technology, and the weld seam is ground. The welded bar is then hot-pressed and die-forged to produce Ti60 high-temperature titanium alloy discs containing TiN inclusion defects.

[0152] The disk prepared in the comparative example was subjected to water immersion ultrasonic testing, and the detection probability of defects in the disk reached 95%. In Example 1, the detection probability of TiN inclusion defects at the same depth was only 21%. There are two main reasons for this phenomenon: (1) The disk in the comparative example was forged. After forging, the TiN inclusions inside the disk were broken, and a large number of cracks were formed inside, which significantly increased the number of internal interfaces, thus increasing the intensity of the ultrasonic signal and resulting in a higher detection probability. However, there are not a large number of interfaces inside the TiN inclusions in the actual disk. (2) Due to the forging process, the size of the defect has increased and is no longer the preset size when it was implanted. This leads to an increase in the detection result (e.g., the implanted defect is 0.7 mm, and the defect size reaches 1 mm after forging). Based on the above two reasons, the detection result in the comparative example is significantly higher than the actual situation. This leads to an overly ideal detection result, which brings safety hazards to the actual use of the component (if the detection probability of a 0.7 mm defect is 95%, while the actual detection probability is 21%, the defect will be missed, thus bringing hidden dangers).

[0153] It will be readily understood by those skilled in the art that, without conflict, the advantageous technical features of the above-mentioned methods can be freely combined and superimposed.

[0154] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention. The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the protection scope of the present invention.

Claims

1. A method for preparing an alloy component for studying the probability of detecting defects in airworthiness certification, characterized in that, Includes the following steps: Step 1): Cut the alloy specimen to be implanted and drill holes at predetermined positions on the cut surface to obtain implantation holes; The inclusion defect is placed into the implantation hole; The alloy specimen has a circular cross-section and is provided with steps or grooves; Step 2): After inserting the inclusion defect, the cut surface is sealed by welding to obtain the alloy specimen after sealing by welding. Step 3): The alloy specimen after the sealing and welding treatment is subjected to hot isostatic pressing to obtain an alloy component for the airworthiness certification defect detection probability study. The hot isostatic pressing process includes a first stage and a second stage performed sequentially. The first stage is used to form a metallurgical bond between the alloy specimen and the interface of inclusion defects and to promote the diffusion of elements at the interface. The second stage reduces the difference in mechanical properties between the interface and the base material of the alloy specimen.

2. The method for preparing alloy components for airworthiness certification defect detection probability research according to claim 1, characterized in that, In the hot isostatic pressing process: The temperature in the first stage is higher than the temperature in the second stage, and the duration of the first stage is shorter than the duration of the second stage. Preferably, after the first stage, the interfacial bonding rate between the alloy specimen and the inclusion defects is ≥70%.

3. The method for preparing alloy components for airworthiness certification defect detection probability research according to claim 1, characterized in that, In the hot isostatic pressing process: The temperature of the first stage is T0-15℃, the pressure is 140~160MPa, and the time is 0.5~1h; Wherein, T0 is the critical temperature of the microstructure of the alloy specimen.

4. The method for preparing alloy components for airworthiness certification defect detection probability research according to claim 1, characterized in that, In the hot isostatic pressing process: The second stage has a temperature of T0-30℃, a pressure of 170-200MPa, and a time of 2-6 hours; Wherein, T0 is the critical temperature of the microstructure of the alloy specimen.

5. The method for preparing alloy components for airworthiness certification defect detection probability research according to claim 1, characterized in that, The alloy specimen is one of the following shapes: cake-shaped, dog bone-shaped, or spiral-shaped. Preferably, the predetermined location includes the corner of the alloy specimen; when multiple inclusion defects are implanted at the corner, the included angle between the centers of any two adjacent inclusion defects along the circumference of the alloy specimen is ≥35°. Preferably, the distance between any two adjacent inclusion defects is ≥30mm; Preferably, the distance between the inclusion defect and the outer surface of the alloy specimen is ≥2mm.

6. The method for preparing alloy components for airworthiness certification defect detection probability studies according to claim 1, characterized in that, The alloy specimen is one of titanium alloy, high-temperature alloy, and aluminum alloy; and / or The inclusion defects are one or more of TiN, MgO, SiO2, and dirty white spots.

7. The method for preparing alloy components for airworthiness certification defect detection probability studies according to claim 1, characterized in that, Before step 1), the following is also included: Based on the need for defect detection probability research, the influencing factors of inclusions are determined, and the characteristic information of inclusions is determined according to the influencing factors. Then, the inclusion defects are prepared according to the characteristic information.

8. The method for preparing alloy components for airworthiness certification defect detection probability research according to claim 7, characterized in that, The influencing factors include one or more of the following: inclusion size, element content, and inclusion type.

9. The method for preparing alloy components for airworthiness certification defect detection probability research according to claim 8, characterized in that, When the influencing factors include inclusion size, the feature information includes the extreme size and size distribution of the inclusions; Preferably, the extreme values ​​and size distribution of inclusions are determined by a function formula; wherein the function formula is one of the logarithmic distribution function, the exponential distribution function, and the Weibull distribution.

10. The method for preparing alloy components for airworthiness certification defect detection probability research according to claim 7, characterized in that, The inclusion defects are prepared by powder metallurgy, forging or casting.

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