Alloy high-throughput preparation and characterization method

Abstract

The application relates to an alloy high-flux preparation and characterization method, which comprises the following steps: preparing a first alloy rod material with a carbon content gradient in a radial direction; gradient heat treating the first alloy rod material, so that the first alloy rod material has a temperature gradient in the axial direction during the heat treatment process, and a second alloy rod material is obtained; cutting the second alloy rod material into a half cylinder along the carbon content gradient direction, performing Vickers hardness tests on different positions of the rectangular cross section of the half cylinder, and determining boundary conditions for one-dimensional steady-state heat conduction calculation and division of regions with different characteristic microstructures; and respectively adopting synchronous X-ray diffraction and high-speed nanoindentation tests to characterize phase compositions and phase characteristics of different positions of the rectangular cross section of the half cylinder. By adopting the above method, a UniSteel alloy composition-heat treatment process-microstructure-mechanical property relationship can be quickly established, and data support is provided for subsequent rapid screening of optimized alloy compositions (carbon contents) and heat treatment processes (isothermal holding temperatures), so that the work amount is greatly reduced, the research efficiency is improved, and the application has important significance.

Description

Technical Field

[0001] This invention relates to the field of alloy production technology, and in particular to a high-throughput preparation and characterization method for alloys. Background Technology

[0002] Currently, the steel industry accounts for approximately 15% of my country's total carbon emissions, making it the second largest emitter after the energy industry. Over 80% of these emissions occur in the pre-iron stage. Reducing the use of primary resources such as iron ore, coal, and limestone mined from geological resources, and significantly increasing the recycling rate of scrap steel, are among the most direct and effective sustainable methods to reduce energy consumption and emissions. With the rapid development of the automotive industry, the number of steel-made car bodies in my country is gradually reaching saturation, resulting in a large amount of scrap steel. Utilizing this scrap steel effectively and promoting recycling can significantly reduce carbon emissions and fuel consumption. Therefore, to promote the recycling of car body steel, the UniSteel concept was proposed, which uses a single alloy composition and different heat treatment processes to produce all types of steel, offering advantages such as ease of welding and remanufacturing. Furthermore, the main difference between DP steel, Q&P steel, and PHS steel lies in carbon content; therefore, controlling the carbon content is extremely crucial for the composition. Therefore, how to simultaneously control the carbon content (key alloying element) and isothermal holding temperature (heat treatment process) of steel, and construct the relationship between UniSteel alloy composition, heat treatment process, microstructure, and mechanical properties, and systematically optimize the alloy composition (carbon content) and heat treatment process (isothermal holding temperature) is a major problem. If the traditional research method of "one experiment, one sample" is followed, the workload will be large and the research cycle will be long.

[0003] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a high-throughput preparation and characterization method for alloys, which aims to solve the problems of large workload and long research cycle required by the traditional "one experiment, one sample" research method.

[0005] This invention, based on a selected alloy system, systematically studies the effects of carbon (a key alloying element) content and isothermal holding temperature on the microstructure (phase composition, phase characteristics, etc.) and mechanical properties (hardness, etc.) of UniSteel. It establishes the relationship between UniSteel alloy composition, heat treatment process, microstructure, and mechanical properties, providing data support for the subsequent rapid selection of optimized alloy compositions (carbon content) and heat treatment processes (isothermal holding temperatures). This method effectively solves the problem of large experimental workload and long research cycles required to construct the relationship between UniSteel alloy composition, heat treatment process, microstructure, and mechanical properties using traditional processing, characterization, and testing methods.

[0006] The technical solution of the present invention is as follows:

[0007] The present invention provides a high-throughput preparation and characterization method for alloys, comprising:

[0008] Step 1: Prepare a first alloy rod, wherein the first alloy rod has a carbon content gradient along a diameter direction;

[0009] Step 2: The first alloy rod is subjected to gradient heat treatment in a vacuum directional solidification equipment to create a temperature gradient along the axial direction, thereby obtaining the second alloy rod.

[0010] Step 3: Cut the second alloy rod into a semi-cylinder along the diameter direction (which is the carbon content gradient direction). Perform hardness tests at predetermined positions along the diameter and axis of the rectangular cross-section of the semi-cylinder to obtain multiple hardness values, which are used to determine the boundary conditions for one-dimensional steady-state heat conduction calculation and the division of regions with different characteristic structures.

[0011] Step 4: Based on the multiple hardness values ​​obtained from the test, calculate the temperature gradient along the axial direction of the second alloy bar using the one-dimensional steady-state heat conduction formula;

[0012] Step 5: Simultaneous X-ray diffraction and high-speed nanoindentation techniques are used to characterize the phase composition and phase properties at predetermined positions along the radial and axial directions of the rectangular cross-section of the semi-cylinder.

[0013] It should be noted that the carbon content gradient of the first alloy rod along a diameter direction in step one specifically means that the carbon content of the first alloy rod decreases from the center to the edge along a diameter direction, that is, the carbon content of the first alloy rod is high in the middle and low on both sides along a diameter direction.

[0014] This invention introduces carbon content gradients and temperature gradients in two orthogonal directions of the alloy rod, and combines synchronous X-ray diffraction and high-throughput characterization with high-speed nanoindentation to study the microstructure and mechanical properties of the second alloy rod with carbon content gradients and temperature gradients. This allows for the rapid establishment of the relationship between UniSteel alloy composition, heat treatment process, microstructure, and mechanical properties, thus providing data support for the subsequent rapid screening of optimized alloy composition (carbon content) and heat treatment process (isothermal holding temperature). This significantly reduces workload, improves research efficiency, and is of great importance.

[0015] Optionally, step one specifically includes:

[0016] Three alloy plates of the same shape and size are stacked together; the alloy plate in the middle has a higher carbon content than the alloy plates on both sides, and the alloy plates on both sides have the same carbon content (the alloy plate in the middle is called the high carbon alloy plate, and the alloy plates on both sides are called the low carbon alloy plates).

[0017] The three alloy plates stacked together are placed in a vacuum hot press furnace, and after vacuuming (preferably to below 20 Pa), they are vacuum hot pressed for 2 hours at a pressure of 30 Pa and a temperature of 950 °C.

[0018] The alloy sheet after vacuum hot pressing is hot rolled at 950°C to obtain an alloy sheet with a carbon content gradient along the thickness direction.

[0019] The first alloy bar is machined from the alloy sheet having a carbon content gradient along the thickness direction.

[0020] Optionally, step two specifically includes:

[0021] First, the entire first alloy bar is inserted into the heater of the vacuum directional solidification equipment and heated to 950°C at a rate of 10°C / s, and then held at that temperature for 30 minutes to make it completely austenitic.

[0022] Then, the first alloy rod is moved downward (57 mm) using the drive device of the vacuum directional solidification equipment, so that the upper part (upper length can be 20 mm) of the first alloy rod remains in the heater and continues to be heated at 950°C, while the lower part (lower length can be 22 mm) is immersed in liquid GaIn alloy for cooling. The part located between the bottom of the heater and the top of the liquid GaIn alloy is in a vacuum state and is maintained for 30 minutes, so that the first alloy rod has a temperature gradient along the axial direction.

[0023] Finally, the entire first alloy rod is placed in liquid GaIn alloy and quenched to room temperature to obtain the second alloy rod.

[0024] In this step, the upper part (in a heating environment of 950°C) and the lower part (immersed in liquid GaIn alloy for cooling) of the first alloy rod form a temperature field through axial heat conduction. The part located between the bottom of the heater and the top of the liquid GaIn alloy is in a vacuum state. Under the condition of neglecting radiation heat dissipation, the one-dimensional steady-state heat conduction condition is satisfied, thereby generating a temperature gradient.

[0025] Optionally, in step four, the one-dimensional steady-state heat conduction formula is Φ=-λAdT / dx, where Φ is the heat flow rate; λ is the thermal conductivity of the material; A is the cross-sectional area perpendicular to the heat conduction direction; dT / dx is the temperature gradient; and - indicates that the heat flow direction is opposite to the temperature gradient direction.

[0026] The temperature gradient can be calculated using the one-dimensional steady-state heat conduction formula described above.

[0027] Optionally, step four specifically includes:

[0028] Two alloy blocks of the same size and material (with the same composition as the high-carbon alloy plate) were prepared. The two alloy blocks were subjected to phase transformation instrument experiments, and then the hardness of the two alloy blocks after the phase transformation instrument experiment was tested to obtain the hardness of the two alloy blocks.

[0029] Then, among the multiple hardness values ​​obtained in step three, find the value that is the same as the hardness value of the two alloy blocks, determine the distance from the top of the second alloy rod corresponding to these two hardness values, and calculate dT / dx;

[0030] Based on the obtained dT / dx, the numerical value of the temperature gradient along the axial direction of the second alloy bar is calculated.

[0031] Optionally, the heat treatment step of the phase change instrument experiment includes:

[0032] An alloy block is heated to 950°C at a rate of 10°C / s, held for 30 min, then cooled to 780°C at a rate of 40°C / s, held for 30 min, and finally quenched to room temperature.

[0033] Another alloy block is heated to 950°C at a rate of 10°C / s, held for 30 min, then cooled to 720°C at a rate of 40°C / s, held for another 30 min, and finally quenched to room temperature.

[0034] Optionally, the phase characteristics in step five include phase distribution, phase fraction, and phase hardness.

[0035] Optionally, the synchrotron X-ray diffraction test uses high-energy X-rays with an energy of 88 keV and a spot size of 0.3 × 0.3 mm. 2 The exposure time was 3s; the high-speed nanoindentation test adopted the displacement control mode, the loading rate was 0.1μm / s, and the maximum indentation depth was 50nm.

[0036] Optionally, the alloy bar is a steel bar.

[0037] Compared with the prior art, the present invention has the following technical advantages:

[0038] Achieving a carbon content gradient: This invention successfully achieves a carbon content gradient along the diameter of alloy bars, with a high carbon content in the middle and low carbon content at both ends, using a combination of vacuum hot pressing and hot rolling. The vacuum hot pressing furnace used in this invention can precisely regulate temperature and pressure, and the high vacuum level effectively reduces harmful substances in the atmosphere, such as water vapor, oxygen, nitrogen, and other impurities, thereby avoiding a series of reactions such as decarburization, carburization, oxidation, and reduction. Furthermore, hot rolling is performed after vacuum hot pressing, resulting in a tighter bond between the plates. Without this method, it would be difficult to tightly bond high-carbon and low-carbon alloy plates together, making it difficult to achieve the desired effect of this invention.

[0039] Realization of the temperature gradient: This invention uses a vacuum directional solidification device to perform gradient heat treatment on a first alloy rod with a carbon content gradient along a diameter direction, thereby introducing a temperature gradient along the axial direction of the first alloy rod. Finally, carbon content gradients and temperature gradients are introduced in the diameter direction and axial direction of the alloy rod, respectively, resulting in a second alloy rod. In the study of the gradient heat treatment process of this invention, it was found that directly measuring the temperature gradient value is difficult. By analyzing the heat transfer during the gradient heat treatment process, it was found that the alloy rod between the bottom of the heater and the top of the liquid GaIn alloy is in a vacuum state. Under the condition of neglecting radiative heat dissipation, it meets the one-dimensional steady-state heat conduction condition. Therefore, the temperature gradient value can be calculated using the one-dimensional steady-state heat conduction formula, successfully solving the above problem.

[0040] High-throughput characterization methods: This invention employs synchronous X-ray diffraction and high-speed nanoindentation to rapidly characterize an alloy rod with a carbon content gradient along its diameter and a temperature gradient along its axis. Both synchronous X-ray diffraction and high-speed nanoindentation are high-throughput characterization methods that can be automated. The synchronous X-ray diffraction test performed in this invention uses 88 keV high-energy X-rays with a spot size of 0.3 × 0.3 mm. 2The exposure time is 3 seconds, and 75 tests can be performed in only about 5 minutes. The high-speed nanoindentation test of this invention adopts a displacement control mode, with a loading rate of 0.1 μm / s and a maximum indentation depth of 50 nm. It can perform 9600 indentation tests in about 6 hours, with each indentation test taking only about 2.11 seconds. In addition, the speed of a single indentation test can be even faster. Therefore, the synchronous X-ray diffraction and high-speed nanoindentation test technology used in this invention can characterize a large number of samples in a short time. Furthermore, the high-speed nanoindentation test technology used in this invention can quickly obtain the phase characteristics of each phase in the sample and distinguish phases with similar morphologies by hardness. It is also an imaging method that can obtain the distribution of each phase. If traditional characterization methods such as secondary electron imaging and EBSD are used to determine phase composition, phase characteristics, and distinguish phases with similar morphologies, it is very difficult, and the testing efficiency is low and cannot be automated. Therefore, the use of synchronous X-ray diffraction and high-speed nanoindentation test, two high-throughput characterization methods, successfully solves the above problems. If this method is not used, more traditional characterization methods need to be combined to characterize each sample individually in order to determine the phase composition and characteristics of each phase and to distinguish phases with similar morphologies. This requires a large amount of work and a long time, which makes it difficult for the process of this invention to achieve the target effect. Attached Figure Description

[0041] Figure 1 This is a process flow diagram of steps one and two in a specific embodiment.

[0042] Figure 2 This is a schematic diagram before and after the cutting in step three of a specific embodiment.

[0043] Figure 3 This is a Vickers hardness diagram of the entire alloy bar along both the diameter direction (i.e., the carbon content gradient direction) and the axial direction.

[0044] Figure 4 This is a schematic diagram of the heat treatment process of a phase change instrument.

[0045] Figure 5 This is a two-dimensional Vickers hardness diagram of the entire alloy bar in the radial and axial directions.

[0046] Figure 6 The diffraction patterns are obtained from sampling locations under different temperatures and carbon contents within the range of 590-735℃.

[0047] Figure 7 The diffraction patterns are obtained from sampling locations under different temperatures and carbon contents within the range of 287-399℃.

[0048] Figure 8 This is a distribution map of nanoindentation hardness at various sampling locations under different temperatures and carbon contents within the range of 590-735℃.

[0049] Figure 9 The area fraction of each phase (a) and the average hardness (b) at each sampling location under different temperatures and carbon contents within the range of 590-735℃ are given.

[0050] Figure 10 The image shows the distribution of nanoindentation hardness at various sampling locations under different temperatures and carbon contents within the range of 287-399℃.

[0051] Figure 11 The volume fraction of each phase (a) and average hardness (b) at each sampling location under different temperatures and carbon contents within the range of 287-399℃ are given.

[0052] In the figure: 1, 2, and 3 represent radial distances of 0.6 mm, 1.2 mm, and 1.8 mm from the edge, respectively. The carbon content increases with the distance from the edge. M represents martensite, P represents pearlite, FM represents fresh martensite, B / TM represents bainite / tempered martensite (where bainite / tempered martensite means that there is bainite above the martensite transformation start temperature (Ms) but no tempered martensite, and there is both bainite and tempered martensite below the Ms temperature), and RA represents retained austenite. Detailed Implementation

[0053] This invention provides a high-throughput preparation and characterization method for alloys. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0054] This invention provides a high-throughput preparation and characterization method for alloys, comprising the following steps:

[0055] like Figure 1 As shown, step one specifically involves:

[0056] Three steel plates of the same shape and size are provided, including one high-carbon steel plate and two low-carbon steel plates. The carbon content of the high-carbon steel plate is 0.425 wt.% and the carbon content of the low-carbon steel plate is 0.306 wt.%.

[0057] Three steel plates of the same shape and size are stacked together with the middle plate being high carbon and the two sides being low carbon.

[0058] The three steel plates stacked together were placed in a vacuum hot press furnace of model ZT-40-21Y, and after being evacuated to 20Pa, they were vacuum hot pressed for 2 hours at a pressure of 30MPa and a temperature of 950℃.

[0059] Then it is taken out and hot-rolled at 950℃ to obtain the product along the thickness direction ( Figure 1 ND in the middle indicates steel plates with a carbon content gradient in the thickness direction;

[0060] A steel bar with a length of 77 mm and a diameter of 3.8 mm is machined from a steel plate with a carbon content gradient along its thickness direction, wherein the carbon content is high in the middle and low on both sides in one diameter direction.

[0061] like Figure 1 As shown, step two specifically involves:

[0062] The entire steel bar (i.e. Figure 1 The sample was inserted into the heater of a DHN400 vacuum directional solidification apparatus and heated to 950°C at a rate of 10°C / s, and held for 30 minutes to fully austenitize it.

[0063] Then, using the drive device of the vacuum directional solidification equipment, the steel bar is moved downwards by 57mm at a speed of 5mm / s, so that the upper 20mm of the steel bar remains in the heater and continues to be heated at 950℃, while the lower 22mm of the steel bar is immersed in liquid GaIn alloy for cooling. The part between the bottom of the heater and the top of the liquid GaIn alloy is in a vacuum state, which is maintained for 30min. In this step, the upper part of the steel bar (in a heating environment of 950℃) and the lower part (immersed in liquid GaIn alloy for cooling) form a temperature field through axial heat conduction. The part between the bottom of the heater and the top of the liquid GaIn alloy is in a vacuum state. Under the condition of neglecting radiation heat dissipation, the one-dimensional steady-state heat conduction condition is satisfied, thereby generating a temperature gradient.

[0064] Finally, the entire steel bar is placed in liquid GaIn alloy at a speed of 5 mm / s, and the entire steel bar is quenched to room temperature to obtain a steel bar with a carbon content gradient in the diameter direction and a temperature gradient in the axial direction (e.g., Figure 2 As shown in (a), Figure 2 In (a), the radial direction is the same as the radial direction, where the radius refers to half of the diameter.

[0065] like Figure 2 As shown, step three specifically involves:

[0066] A steel bar with a carbon content gradient along its diameter and a temperature gradient along its axis was cut into four cylindrical specimens with dimensions of Φ3.8×15mm and one cylindrical specimen with dimensions of Φ3.8×17mm using a diamond wire cutting machine. Then, semi-cylindrical specimens were obtained by cutting along the carbon content gradient direction (e.g., ...). Figure 2 As shown in (b), the subsequent high-throughput characterization is mainly performed on the rectangular cross-section of the semi-cylindrical sample.

[0067] To determine the boundary conditions for the one-dimensional steady-state heat conduction formula and to delineate regions with different microstructures, Vickers hardness was measured on a rectangular cross-section from top to bottom of the steel bar. Four Vickers hardness tests were performed at 0.6 mm intervals along both the diameter and axial directions of the rectangular cross-section of the semi-cylinder, and the average value was taken as the Vickers hardness value at that location. The results are as follows: Figure 3 As shown, the hardness along the axial direction of the steel bar changes significantly with different distances from the top of the steel bar, indicating that the steel bar has different microstructures along the axial direction with different distances from the top of the steel bar. Furthermore, since the carbon content is high in the middle and low at both ends of the steel bar along its diameter, its hardness is characterized by being high in the middle and low at both ends.

[0068] Step four is as follows:

[0069] The temperature gradient of the steel bar between the bottom of the heater and the top of the liquid GaIn alloy is determined. As shown in step two, the steel bar between the bottom of the heater and the top of the liquid GaIn alloy is in a vacuum state. Ignoring radiative heat dissipation, it satisfies the one-dimensional steady-state heat conduction condition. Therefore, the temperature gradient is calculated using the one-dimensional steady-state heat conduction formula (Φ = -λAdT / dx). The required boundary conditions (boundary temperature values ​​and their spacing) are determined through Vickers hardness testing and related experiments. The determination method is as follows:

[0070] Two samples of identical specifications and materials (consistent with the composition of high-carbon steel plates) were prepared, specifically two samples measuring 10mm × 4mm × 1.8mm (length, width, and height, respectively). Phase change instrument experiments were performed on both samples. The specific heat treatment process for the phase change instrument experiment was similar to that of the gradient heat treatment process (e.g., ...). Figure 4 As shown: One sample was heated to 950℃ at a rate of 10℃ / s, held for 30 min (i.e., 1800 s), then cooled to 780℃ at a rate of 40℃ / s, held for another 30 min, and finally quenched to room temperature; another sample was heated to 950℃ at a rate of 10℃ / s, held for 30 min, then cooled to 720℃ at a rate of 40℃ / s, held for another 30 min, and finally quenched to room temperature.

[0071] Then, Vickers hardness tests were performed on different locations of the two samples that had undergone phase change instrument experiments. The average hardness value was taken as the hardness of each sample to obtain the hardness of the two samples. The hardness of the samples kept at 780℃ and 720℃ were 515.66HV and 335.33HV, respectively.

[0072] Then, Vickers hardness values ​​are plotted along the diameter and axis of the entire steel bar (i.e., Figure 3Find the hardness values ​​that are the same as those of the two samples and their corresponding distances from the top of the steel rod. This allows us to determine that the distances from the top of the steel rod for samples held at 780℃ and 720℃ are 28.19 mm and 31.41 mm, respectively. From this, we can accurately obtain the boundary temperature values ​​and their spacing, and calculate the temperature gradient of the steel rod between the bottom of the heater and the top of the liquid GaIn alloy as 280-933℃. Figure 3 It is known that the hardness of the steel bar is symmetrically distributed along the axis in the diameter direction. Therefore, it is sufficient to study half of the diameter of the steel bar. Thus, two-dimensional Vickers hardness diagrams of the steel bar in the radial and axial directions were drawn (e.g., Figure 5 As shown, Figure 5 The 0.6mm refers to the radial distance from the edge, 1.2mm refers to the radial distance from the edge, and 1.8mm refers to the radial distance from the edge (the horizontal axis represents the distance from the top of the steel bar). Several key temperatures are marked. Based on the analysis, two regions with significant hardness variations (different microstructures) (temperature ranges of 590-735℃ and 287-399℃, respectively) were studied in detail (e.g., Figure 5 (As shown in the shaded area).

[0073] Step five is as follows:

[0074] To determine the phase composition, simultaneous X-ray diffraction tests were performed on regions at two different temperature ranges; high-energy X-rays with an energy of 88 keV and a spot size of 0.3 × 0.3 mm were used. 2 An exposure time of 3 seconds yields a complete Debye ring. This embodiment involved 75 tests over a total of approximately 5 minutes, and the testing process can be automated. Integrating the Debye ring yields the diffraction pattern. Refining the diffraction pattern using the Rietveld refinement method allows for the determination of phase composition at various sampling locations under different temperatures and carbon contents. The diffraction patterns at different sampling locations under different temperatures and carbon contents are shown below. Figure 6 and Figure 7 As shown. Figure 6 Only five BCC diffraction peaks were observed, combined with a two-dimensional Vickers hardness map ( Figure 5 Analysis determined that pearlite transformation occurred in the region within the temperature range of 590-735℃ during the heat preservation process, and the untransformed austenite underwent martensitic transformation during the final quenching. Therefore, the microstructure in this region at room temperature is a mixture of martensite and pearlite. Figure 7 The diffraction peaks include five FCC and five BCC peaks. Combined with a two-dimensional Vickers hardness map (… Figure 5Analysis revealed that isothermal bainitic transformation and one-step quenching-partitioning occurred in the temperature range of 287-399℃. In the higher temperature range, the microstructure consisted of a mixture of fresh martensite and retained austenite; in the medium and low temperature range, the microstructure consisted of a mixture of bainite / tempered martensite, fresh martensite, and retained austenite.

[0075] To further investigate the properties of each phase and to distinguish morphologically similar phases in BCC using hardness differences, high-speed nanoindentation tests were performed on regions within two temperature ranges. The test area at each sampling location was 238 × 158 μm under different temperatures and carbon contents within the range of 590–735 °C. 2 The step size is 2μm, the maximum indentation depth is 50nm, and some test results are as follows: Figure 8 As shown; the test area at each sampling location under different temperatures and carbon contents within the range of 287-399℃ is 39.5 × 59.5 μm. 2 The step size is 0.5 μm, and the maximum indentation depth is 50 nm. Some test results are as follows: Figure 10 As shown, a single hardness distribution map contains 9,600 indentation points and can be completed in 6 hours. Furthermore, this test can be automated.

[0076] Figure 8 The yellowish-green region, with higher hardness, is martensite, while the blue region, with lower hardness, is pearlite. At the same carbon content, as temperature decreases, the martensite content first gradually decreases and then gradually increases, while the pearlite content changes in the opposite direction. At the same temperature but different carbon contents, the content and distribution of each phase differ. By fitting the hardness data using two Gaussian functions to separate the peaks, the area fractions of martensite and pearlite and the average hardness can be obtained, as shown in the results. Figure 9 As shown in (a) and (b), the average hardness and area fraction of martensite and pearlite vary with temperature and carbon content.

[0077] Figure 10 The yellowish-green region represents the hard phase, while the blue region represents the soft phase, which has lower hardness. At the same carbon content, the area fraction of the hard phase gradually decreases while the area fraction of the soft phase gradually increases with decreasing temperature; however, at the same temperature but different carbon contents, the content and distribution of each phase differ. Similarly, two Gaussian functions were used to fit and peak-separate the hardness data to obtain the volume fraction and average hardness of fresh martensite, bainite / tempered martensite, as shown in the results. Figure 11 As shown. Here, the volume fraction of fresh martensite (f) FM ) was determined to be: f FM =(1-f RA )·f hard Volume fraction of bainite / tempered martensite (f) B / TM ) was determined to be: f B / TM =1-f FM -fRA , where f RA f represents the volume fraction of retained austenite obtained from synchrotron X-ray diffraction. hard The area fraction of the hard phase obtained from high-speed nanoindentation. The results show that the average hardness and volume fraction of fresh martensite and bainite / tempered martensite vary with temperature and carbon content.

[0078] In summary, this invention combines vacuum hot pressing, hot rolling, and gradient heat treatment to introduce carbon content gradients and temperature gradients along the diameter and axis of the steel bar, respectively. Furthermore, it utilizes synchronous X-ray diffraction and high-throughput characterization techniques such as high-speed nanoindentation to study the microstructure and mechanical properties of the steel bar. This allows for the rapid establishment of the relationship between UniSteel alloy composition, heat treatment process, microstructure, and mechanical properties. This provides data support for the subsequent rapid selection of optimized alloy composition (carbon content) and heat treatment process (isothermal holding temperature), significantly reducing workload and improving research efficiency, thus possessing significant importance.

[0079] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A high-throughput preparation and characterization method for alloys, characterized in that, include: Step 1: Prepare a first alloy rod, wherein the first alloy rod has a carbon content gradient along a diameter direction; Step 2: The first alloy rod is subjected to gradient heat treatment in a vacuum directional solidification equipment to give the first alloy rod a temperature gradient along the axial direction, thereby obtaining the second alloy rod. Step 3: Cut the second alloy rod into semi-cylinders along the carbon content gradient direction, and perform hardness tests at predetermined positions in the diameter and axial directions of the rectangular cross-section of the semi-cylinders to obtain multiple hardness values. Step 4: Based on the multiple hardness values ​​obtained from the test, calculate the temperature gradient along the axial direction of the second alloy bar using the one-dimensional steady-state heat conduction formula; Step 5: Simultaneous X-ray diffraction and high-speed nanoindentation techniques are used to characterize the phase composition and phase properties at predetermined positions along the radial and axial directions of the rectangular cross-section of the semi-cylinder.

2. The high-throughput alloy preparation and characterization method according to claim 1, characterized in that, Step one specifically includes: Three alloy plates of the same shape and size are stacked together; the alloy plate in the middle has a higher carbon content than the alloy plates on both sides, and the alloy plates on both sides have the same carbon content. The three alloy plates stacked together are placed in a vacuum hot press furnace, and after vacuuming, they are vacuum hot pressed. The alloy sheet that has been vacuum hot-pressed is then hot-rolled to obtain an alloy sheet with a carbon content gradient along the thickness direction. The first alloy bar is machined from the alloy sheet having a carbon content gradient along the thickness direction.

3. The high-throughput alloy preparation and characterization method according to claim 1, characterized in that, Step two specifically includes: First, insert the entire first alloy rod into the heater of the vacuum directional solidification equipment, heat it to 950°C and hold it for 30 minutes. Then, the first alloy rod is moved downward using the drive device of the vacuum directional solidification equipment, so that the upper part remains in the heater and continues to be heated at 950°C, while the lower part is immersed in liquid GaIn alloy for cooling. The part between the bottom of the heater and the top of the liquid GaIn alloy is in a vacuum state for 30 minutes, so that the first alloy rod has a temperature gradient along the axial direction. Finally, the entire first alloy rod is placed in liquid GaIn alloy and quenched to room temperature to obtain the second alloy rod.

4. The high-throughput alloy preparation and characterization method according to claim 1, characterized in that, In step four, the one-dimensional steady-state heat conduction formula is Φ=-λAdT / dx, where Φ is the heat flow rate; λ is the thermal conductivity of the material; A is the cross-sectional area perpendicular to the direction of heat conduction; dT / dx is the temperature gradient; and - indicates that the direction of heat flow is opposite to the direction of temperature gradient.

5. The high-throughput alloy preparation and characterization method according to claim 4, characterized in that, Step four specifically includes: Two alloy blocks of the same size and material were prepared. The two alloy blocks were subjected to phase change instrumentation experiments. Then, the hardness of the two alloy blocks after the phase change instrumentation experiment was tested to obtain the hardness of the two alloy blocks. Then, among the multiple hardness values ​​obtained in step three, find the value that is the same as the hardness value of the two alloy blocks, determine the distance from the top of the second alloy rod corresponding to these two hardness values, and calculate dT / dx; Based on the obtained dT / dx, the numerical value of the temperature gradient along the axial direction of the second alloy bar is calculated.

6. The high-throughput alloy preparation and characterization method according to claim 5, characterized in that, The heat treatment steps for the phase changer experiment include: An alloy block is heated to 950°C, held for 30 minutes, then cooled to 780°C, held for another 30 minutes, and finally quenched to room temperature. Another alloy block was heated to 950°C, held for 30 minutes, then cooled to 720°C, held for another 30 minutes, and finally quenched to room temperature.

7. The high-throughput alloy preparation and characterization method according to claim 1, characterized in that, The phase characteristics in step five include phase distribution, phase fraction, and phase hardness.

8. The high-throughput alloy preparation and characterization method according to claim 1, characterized in that, Synchronous X-ray diffraction testing uses high-energy X-rays; high-speed nanoindentation testing uses displacement control mode.

9. The high-throughput preparation and characterization method for alloys according to claim 1, characterized in that, The alloy rod is a steel rod.

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