Alloy high-flux mechanical testing method

Abstract

The invention relates to an alloy high-flux mechanical testing method, and belongs to the technical field of alloy production. The method comprises the following steps that a single alloy bar is placed in vacuum directional solidification equipment to be subjected to gradient heat treatment, so that the single alloy bar has a heat treatment process which continuously changes in the axis direction; processing a plurality of hundred-micron micro-columns in parallel on a single alloy bar subjected to gradient heat treatment to form a micro-column array; and performing a compression test on the micro-column array by using a mechanical test platform to obtain mechanical data of different micro-columns. The core of the method is that a macroscopic scale continuous gradient sample library is converted into hundreds of independent test units with macroscopic mechanical representativeness through a parallel micro-nano manufacturing technology, and rapid and accurate performance screening and mapping are realized by using an autonomously built test platform.

Description

Technical Field

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

[0002] Currently, the automotive industry is facing global challenges of energy conservation, emission reduction, and sustainable development, and vehicle lightweighting is one of the core technological paths to address these challenges. Against this backdrop, high-strength, low-density steel, due to its comprehensive advantages in specific strength, manufacturing cost, and process maturity, is considered an ideal material for achieving lightweight vehicle body structures. However, those skilled in the art know that the traditional research and development paradigm for steel materials heavily relies on trial and error and experience-based guidance. This involves separately melting alloys of different compositions and preparing macroscopic standard samples through multiple processes such as forging, rolling, and heat treatment before conducting mechanical property tests. This method has inherent and pressing technical bottlenecks: firstly, the research and development cycle is extremely long, often taking months or even years from design to performance data acquisition for a single material, which cannot meet the demands of modern industry for rapid iteration; secondly, the research and development costs are high, with a large amount of raw materials, energy, and equipment time consumed in the preparation and testing of individual samples; and thirdly, the research and development efficiency is low, as limited experimental data points make it difficult to systematically reveal the intrinsic relationships between composition, process, microstructure, and properties, thus hindering the design and optimization process of new materials. Therefore, developing a high-throughput experimental method that can achieve rapid, parallel, and low-cost material preparation and performance characterization has become a prominent technical challenge in this field.

[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 mechanical testing method for alloys, specifically a high-throughput method that can achieve rapid, parallel and low-cost material preparation and performance characterization, thereby significantly accelerating the research and development process of advanced high-strength steel and solving the technical problems of long development cycles and high costs of traditional discrete sample research and development. The technical solution of the present invention is as follows: A high-throughput mechanical testing method for alloys, comprising: Step 1: Place the single alloy bar in a vacuum directional solidification equipment for gradient heat treatment, so that the single alloy bar has a continuously changing heat treatment process along the axial direction. Step 2: Multiple micropillars of hundreds of micrometers in size are machined in parallel from a single alloy bar that has undergone gradient heat treatment to form a micropillar array; Step 3: Perform compression tests on the micropillar array using a mechanical testing platform to obtain mechanical data for different micropillars.

[0005] Optionally, step one specifically includes: Insert the entire single alloy rod into the heater of the vacuum directional solidification equipment, heat it to 900℃ and hold it for 30 minutes; Then, the drive mechanism of the vacuum directional solidification equipment is used to move the single alloy rod downward at a speed of 5 mm / s, so that one end of the single alloy rod is heated at 900°C and the other end is immersed in the 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. The two ends of the single alloy rod form a temperature field through axial heat conduction, generating a temperature gradient. Finally, the entire single alloy bar is placed in liquid GaIn alloy and quenched to room temperature to obtain a single alloy bar with a continuously varying heat treatment process along the axial direction.

[0006] Optionally, in step two, each micropillar has a length of 150-200 μm, a width of 150-200 μm, and a height of 300-500 μm.

[0007] Optionally, in step two, multiple micropillars of hundreds of micrometers in size are machined in parallel from a single alloy rod that has undergone gradient heat treatment using wire electrical discharge machining (EDM) technology.

[0008] Optionally, the mechanical testing platform integrates a universal testing machine, an XY-axis precision moving platform, a flat-end indenter, and a lateral high-resolution optical microscope.

[0009] Optionally, the diameter of the flat-end indenter is 800 μm.

[0010] Optionally, the mechanical data in step three includes yield strength data.

[0011] Optionally, the alloy can be an iron-based alloy or a nickel-based alloy.

[0012] Compared with the prior art, the present invention has the following technical advantages: 1. A fundamental innovation in the principle of sample library preparation: from "discrete samples" to "continuous gradients" Prior art generally employs the preparation of multiple independent samples with discrete composition or process parameters to construct a sample library, essentially a "one sample, one data point" model, offering limited efficiency improvements. The core difference of this invention lies in utilizing directional solidification and gradient heat treatment techniques to actively construct a continuously varying microstructure gradient along the axial direction on a single rod-shaped sample. This achieves a leap from "discrete points" to a "continuous spectrum," making a single sample itself a "material database" containing continuous process parameters, laying the physical foundation for truly high-throughput characterization.

[0013] 2. Strategic Choices in Testing Scale and Concept: From "Microscopic Mechanism Exploration" to "Macroscopic Performance Screening" Existing high-throughput mechanical testing of materials, especially micropillar compression, largely focuses on the micro-nano scale (characteristic size <1μm). Its primary goal is to study size effects and microscopic deformation mechanisms. However, due to the extremely small testing scale, the measured properties (such as yield strength) deviate significantly from macroscopic eigenvalues, making them unsuitable for direct application in engineering material selection. The key innovation of this invention lies in explicitly designing the micropillar size to be at the "hundred-micrometer level" (preferably 150-200μm in length and width, and 300-500μm in height). This scale selection strategically avoids significant size effects, ensuring a high degree of consistency between test results (such as yield strength) and the macroscopic mechanical properties of the material. This successfully shifts the application goal of high-throughput testing from "mechanism research" to "rapid screening of macroscopic properties for engineering material selection."

[0014] 3. Integrated Construction of the Technology System: A High-Throughput Solution to Achieve a Closed Loop Between Preparation and Testing Prior art often treats sample preparation and performance testing as relatively independent steps, resulting in throughput bottlenecks or data disconnect. This invention combines the aforementioned gradient sample library preparation with the parallel fabrication of a hundred-micron-scale micropillar array (e.g., wire EDM) and a matching dedicated compression testing device, forming a complete and integrated technical system. This system enables the rapid extraction of a large number of macroscopically representative mechanical testing units from a continuous gradient sample library and performs efficient and accurate testing, ultimately resolving the long-standing contradiction between "macroscopic performance testing" and "high throughput efficiency." Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the vacuum directional solidification equipment and the temperature distribution of the sample.

[0016] Figure 2 This is a schematic diagram of the specific process of gradient heat treatment.

[0017] Figure 3 This is a graph showing the continuous change in axial position and hardness value of a single alloy bar after gradient heat treatment.

[0018] Figure 4 A schematic diagram of the micro-pillar cross-section measured by a white light interferometer.

[0019] Figure 5 This is a characterization of the micropillar surface using a white light interferometer.

[0020] Figure 6 It serves as a mechanical testing platform.

[0021] Figure 7 for Figure 6 Enlarged view of image 4.

[0022] Figure 8 The graph shows the continuous relationship between yield strength and strain obtained from the compression test of martensitic steel micropillars.

[0023] Figure 9 This is a graph showing the continuous relationship between yield strength and strain obtained from micropillar compression tests.

[0024] Figure 10 This is an image of the morphology of a compressed martensitic steel micropillar observed by white light interference.

[0025] Figure 11 A graph showing the continuous relationship between the equivalent yield strength calculated from the hardness test and the axial distance. Detailed Implementation

[0026] This invention provides a high-throughput mechanical testing 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.

[0027] First, it should be noted that the alloy of the present invention can be an iron-based alloy. For example, the main components of an iron-based alloy are: Fe-0.4 / 0.3C-1.5Mn-2.0Cr-(Si+Al:1.5-2)-0.4(V+Mo)-0.003B (wt.%). That is, by weight percentage, Fe is the matrix, C is 0.4% or 0.3%, Mn is 1.5%, Cr is 2.0%, the total amount of Si+Al is 1.5-2%, the total amount of V+Mo is 0.4%, and B is 0.003%.

[0028] The high-throughput preparation and characterization method used in this invention can also be applied to the high-throughput design of other alloys (such as high-temperature nickel-based alloys) and is applicable to alloys of any composition. The following section uses an iron-based alloy with the following composition as an example to elaborate on the high-throughput mechanical testing method for alloys provided by this invention: The alloy composition is Fe-0.4 / 0.3C-1.5Mn-2.0Cr-(Si+Al:1.5-2)-0.4(V+Mo)-0.003B (wt.%). When C is 0.3%, the corresponding alloy is called low-carbon steel plate; when C is 0.4%, the corresponding alloy is called high-carbon steel plate.

[0029] This invention provides a high-throughput mechanical testing method for alloys, comprising: Step 1: Place a single alloy rod (not limited to rod shape, but can be any shape) in a vacuum directional solidification equipment for gradient heat treatment, so that the single alloy rod has a continuously changing heat treatment process along the axial direction. Step 2: Multiple micropillars of hundreds of micrometers in size are machined in parallel from a single alloy bar that has undergone gradient heat treatment to form a micropillar array; Step 3: Perform compression tests on the micropillar array using a mechanical testing platform to obtain mechanical data for different micropillars.

[0030] This invention addresses the core pain points of long development cycles and high costs in traditional materials research and development. It successfully developed and validated a high-throughput "macro-micro" linked approach integrating innovative sample design, precision micromachining, and customized testing technologies. The core of this approach lies in transforming a continuous gradient sample library at the macroscopic scale into hundreds of independent test units with macroscopic mechanical representativeness through parallel micro-nano fabrication technology. A self-built testing platform is then used to achieve rapid and accurate performance screening and mapping. The entire technical process is logically rigorous, progressively layered, and cross-validated using systematic experimental data.

[0031] The starting point of this technology is to reconstruct the construction mode of the material sample library. This invention abandons the traditional approach of preparing multiple independent and discrete samples, and instead adopts a gradient heat treatment technology based on the principles of directional solidification and end quenching to create a continuous material property "map" on a single physical entity (i.e., a single alloy rod).

[0032] Specifically, such as Figure 1-2 As shown, step one specifically involves: a. Low-carbon (0.3wt.%C) and high-carbon (0.4wt.%C) steel plates are combined with high-carbon steel in the middle and low-carbon steel on both sides. The plates are placed in a vacuum hot press furnace, and after vacuuming, the temperature is set to 950℃ and the pressure is set to 30MPa. The plates are kept in this environment for 2 hours. The samples are then taken out and hot rolled at 950℃ to create a carbon content gradient in the thickness direction of the plates. Finally, the plates are cut to obtain alloy bars. b. The entire single alloy rod (i.e. Figure 1 The sample (a rod with a length of 77 mm and a diameter of 3.8 mm) was inserted into the heater of a DHN400 vacuum directional solidification device and heated to 900°C at a rate of 10°C / s, and then held at that temperature for 30 min. c. Then, using the drive mechanism of the vacuum directional solidification equipment, the single alloy rod is moved downwards by 57mm at a speed of 5mm / s, so that the upper 20mm of the single alloy rod remains in the heater and continues to be heated at 900℃, while the lower 22mm of the single alloy rod 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, which is maintained for 30min. In this step, the upper part of the single alloy rod (in a heating environment of 900℃) and the lower part (immersed in liquid GaIn alloy for cooling) 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. d. Finally, place the entire single alloy bar into the liquid GaIn alloy at a speed of 5 mm / s, and quench the entire single alloy bar to room temperature to obtain a single alloy bar with a continuously changing heat treatment process along the axial direction.

[0033] In other words, this invention utilizes a vacuum directional solidification device to heat one end of a single alloy rod at 900°C while the other end is slowly drawn into a liquid GaIn alloy for rapid cooling. By precisely controlling the pulling speed, the single alloy rod experiences a continuous cooling rate variation from approximately 0.1°C / s to 1000°C / s at different axial positions, which is equivalent to performing numerous different heat treatment processes in parallel on the single alloy rod. A preliminary Vickers hardness test is then performed on the gradient heat-treated single alloy rod. The test procedure involves dividing the rod sample into regions, for example, 100 micropillars corresponding to 100 regions, each with a different carbon composition and temperature. Subsequently, a fully automated Vickers hardness tester is used to test the hardness of each region, with five test points set in each region to ensure data reliability. The preliminary Vickers hardness scan results are as follows: Figure 3 As shown in the figure, this clearly illustrates the continuous variation trend of hardness with the axial position of the sample (corresponding to different heat treatment processes), providing a physical basis for subsequent high-throughput mechanical testing and other operations; among them, Figure 3 The different curves represent the radial position variation of the rod-shaped sample profile from 600 micrometers to 3600 micrometers (referring to the measurement points at different distances from the center to the edge of the rod-shaped sample cross-section from 600 micrometers to 3600 micrometers), which correspond to the carbon composition gradient; due to symmetry, the 600 and 3600 curves coincide (outermost), the 1200 and 3000 curves coincide, and the 1800 and 2400 curves coincide (center of the axis of symmetry). Figure 3 Regions ①, ②, ③, ④, and ⑤ are defined based on changes in hardness, which is also related to the sample size. Subsequent mechanical testing involved cutting the rod-shaped sample into five parts for testing. In the crucial step of transforming macroscopic gradients into measurable units, this invention involves in-depth process exploration and scale design. The second major innovation of this invention lies in proposing the strategic testing scale of "hundred-micrometer-scale micropillars." Research has found that although compression testing at the micro- and nano-scale has high throughput, its strong "size effect" leads to an abnormally high yield strength, significantly deviating from the macroscopic intrinsic value. The obtained data is only suitable for microscopic mechanism research and cannot be used to guide engineering material selection. Therefore, this invention designs the micropillar scale at the hundred-micrometer level, preferably with a length and width of 150-200 μm and a height of 300-500 μm. This scale is much larger than the critical size at which crystal defects such as dislocations are significantly constrained, thus ensuring that the test results can truly reflect the macroscopic intrinsic mechanical properties of the material. In terms of implementation path, this invention compares and evaluates two methods: laser marking and electrical discharge wire cutting. Experimental data shows that laser marking, as a thermal processing technique, causes significant secondary heat treatment to the surface of the micropillars. Furthermore, the laser-processed micropillars exhibit poor perpendicularity, and their compressive strength reaches as high as 1700 MPa, exceeding the material's actual properties by approximately 200 MPa. This clearly excludes the applicability of this method. Ultimately, this invention employs wire electrical discharge machining (EDM), a cold processing technique, combined with a precision moving platform, to successfully fabricate micropillar arrays with precise dimensions, regular geometric morphology, and excellent sidewall perpendicularity in parallel. This was achieved using a white light interferometer (see...). Figures 4-5 As shown in the figure, rigorous characterization by scanning electron microscopy confirmed that the micropillar surface was smooth and free of remelting layer, and the dimensional tolerance was controlled within a very small range, which fully met the stringent requirements of the precision compression experiment for sample quality.

[0034] To meet the testing requirements of micropillars at the hundred-micrometer scale, this invention independently designed and built a dedicated mechanical testing platform (see...). Figure 6 As shown in the figure, the closed loop from "preparation" to "characterization" is completed. Figure 6 In the diagram, 1 is the upper clamp used to fix the indenter; 2 is the indenter, whose tip is a circular platform with a diameter of 800 micrometers, used to compress the microcolumn; 3 is the purchased XY-axis precision moving platform, used to align the central axis of the microcolumn with the central axis of the indenter to ensure the reliability of the compression test; 4 is a schematic diagram of the sample (its enlarged view is shown below). Figure 7 ); 5 is the lower clamp, used to fix the XY axis precision moving platform.

[0035] The mechanical testing experimental steps are as follows: 1. Fix the indenter and the XY-axis precision moving platform on the upper and lower fixtures; 2. Attach the sample to the XY-axis precision moving platform with double-sided tape to prevent the sample from slipping during compression; 3. Observe from the X and Y directions using an optical microscope, and make fine adjustments in the X and Y directions to align the central axis of the micropillar with the central axis of the indenter; 4. Start the mechanical test (compression test).

[0036] This platform uses a commercial universal testing machine as its power source and innovatively integrates three major modules: a precision XY-axis moving platform for accurate positioning, a customized flat-end indenter with a diameter of 800 μm (to avoid simultaneous pressure on multiple columns), and a high-resolution lateral optical microscope for real-time observation and alignment. Before applying this testing platform to gradient samples, a rigorous method verification experiment was first conducted using standard martensitic steel as the standard sample. The results are shown in […]. Figures 8-9 The results show that the microcolumn compression curve obtained through this test platform has a typical morphology, and the calculated yield strength is 1.6 GPa, which is consistent with the macroscopic standard compression test data of 1.5 GPa. Meanwhile, the morphological observation of the compressed microcolumns shows that they undergo uniform plastic deformation without any signs of buckling or instability. Figure 10 As shown in the figure. This experiment demonstrates, from both data and morphology perspectives, that the combination of this testing platform and the 100-micron-scale micropillar scheme possesses high reliability and accuracy, and the obtained data can be directly used as a valid basis for macroscopic performance.

[0037] Ultimately, this invention implemented the core process of high-throughput testing and rigorously cross-validated the reliability of massive amounts of data. After systematic micropillar compression testing of specific sections (43,000 μm-58,000 μm) of the sample that underwent gradient heat treatment, a gradient relationship diagram of "yield strength - sample position (sample position corresponds to heat treatment process)" was successfully plotted (see...). Figure 3 and Figure 11 This visually demonstrates the continuous evolution of a material's yield strength under varying heat treatment conditions. By analyzing the strain-yield strength data of micropillars at different locations, the optimal heat treatment process that meets specific strain requirements can be quickly identified, accelerating the iterative development of materials.

[0038] To further confirm the reliability of this high-throughput data, hardness testing, a traditional and widely accepted method, was introduced for comparison. Using the well-established hardness-strength conversion relationship, the hardness gradient data was converted into equivalent yield strength, and then compared point-by-point with the measured values ​​of micropillar compression. Figure 3 and Figure 11 The results show that the performance change trends revealed by both are highly consistent, resembling two curves that follow each other. Figure 11 The changing trend and Figure 3 The fluctuations in region ④ are consistent with those in the standard test; these fluctuations are due to micropillar compression errors and are considered normal. More importantly, the absolute error value is generally controlled within the acceptable range for engineering material testing, below 200 MPa. This crucial cross-validation not only demonstrates the sensitivity of the high-throughput method of this invention in capturing performance trends but also establishes its powerful ability to provide quantitative, accurate, and macroscopically significant mechanical property data.

[0039] In summary, this invention constructs a complete solution, demonstrating significant innovation in its principles, methods, and verification. By organically integrating a macroscopic gradient sample library, parallel testing of micropillars at the hundred-micrometer level, and a dedicated experimental setup, it successfully resolves the long-standing contradiction between high throughput efficiency and macroscopic data accuracy, providing materials scientists with a powerful tool that can significantly accelerate the materials research and development process.

[0040] In summary, the high-throughput mechanical testing method for alloys provided by this invention has the following technical advantages compared to existing methods: 1. A fundamental shift in the principles of sample database construction: from "discrete points" to "continuous spectrum" Unlike traditional methods that prepare discrete samples with multiple independent components or processes, this invention innovatively combines directional solidification with end-quenching principles to actively construct a continuously varying microstructure and property gradient along the axial direction on a single alloy rod (i.e., the sample). This method revolutionizes the traditional "one sample, one data point" model into "one sample, one continuous data spectrum," achieving a qualitative leap in the efficiency of sample library construction and laying the physical foundation for truly high-throughput characterization.

[0041] 2. Strategic Selection of Testing Scales: From "Microscopic Mechanism Exploration" to "Macroscopic Performance Screening" Unlike the commonly used approach of using micro- and nano-scale (characteristic size <1μm) micropillars for mechanism research, this invention creatively positions the scale of the test micropillars at the "hundred-micrometer level" (length and width 150-200μm, height 300-500μm). This design cleverly avoids the significant size effect at the micro- and nano-scale, ensuring that the compression test results (such as yield strength) can truly reflect the intrinsic mechanical properties of the material under macroscopic service conditions. Thus, the application goal of high-throughput testing has successfully shifted from exploring microscopic mechanisms to rapidly screening macroscopic engineering properties.

[0042] 3. Integrated innovation of the technology system: a high-throughput solution to achieve a closed loop of "preparation-testing" This invention is not an isolated technological improvement, but rather the construction of a complete technological system. By deeply integrating the preparation of a macroscopic gradient sample library, parallel processing of 100-micron-level micropillars based on electrical discharge wire cutting, and a precisely matched dedicated compression testing device (integrating precision alignment and real-time observation functions), a highly efficient and reliable closed-loop system is formed. This system solves the core contradiction in existing technologies where sample preparation throughput and macroscopic representativeness of test data cannot be simultaneously achieved, realizing ultimate efficiency while ensuring the value of data engineering.

[0043] The high-throughput characterization of this invention generates a large amount of data, which is inefficient to process and filter manually. However, by combining it with programming software, the efficiency of data processing and filtering can be further improved.

[0044] 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 mechanical testing method for alloys, characterized in that, include: Step 1: Place the single alloy bar in a vacuum directional solidification equipment for gradient heat treatment, so that the single alloy bar has a continuously changing heat treatment process along the axial direction. Step 2: Multiple micropillars of hundreds of micrometers in size are machined in parallel from a single alloy bar that has undergone gradient heat treatment to form a micropillar array; Step 3: Perform compression tests on the micropillar array using a mechanical testing platform to obtain mechanical data for different micropillars.

2. The high-throughput mechanical testing method for alloys according to claim 1, characterized in that, Step one specifically includes: Insert the entire single alloy rod into the heater of the vacuum directional solidification equipment, heat it to 900℃ and hold it for 30 minutes; Then, the drive mechanism of the vacuum directional solidification equipment is used to move the single alloy rod downward at a speed of 5 mm / s, so that one end of the single alloy rod is heated at 900°C and the other end is immersed in the 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. The two ends of the single alloy rod form a temperature field through axial heat conduction, generating a temperature gradient. Finally, the entire single alloy bar is placed in liquid GaIn alloy and quenched to room temperature to obtain a single alloy bar with a continuously varying heat treatment process along the axial direction.

3. The high-throughput mechanical testing method for alloys according to claim 1, characterized in that, In step two, each micropillar has a length of 150-200 μm, a width of 150-200 μm, and a height of 300-500 μm.

4. The high-throughput mechanical testing method for alloys according to claim 1, characterized in that, In step two, multiple micropillars of hundreds of micrometers are machined in parallel from a single alloy rod that has undergone gradient heat treatment using wire electrical discharge machining technology.

5. The high-throughput mechanical testing method for alloys according to claim 1, characterized in that, The mechanical testing platform integrates a universal testing machine, an XY axis precision moving platform, a flat end face indenter, and a lateral high-resolution optical microscope.

6. The high-throughput mechanical testing method for alloys according to claim 5, characterized in that, The diameter of the flat-end indenter is 800 μm.

7. The high-throughput mechanical testing method for alloys according to claim 1, characterized in that, The mechanical data in step three includes yield strength data.

8. The high-throughput mechanical testing method for alloys according to claim 1, characterized in that, The alloy is either an iron-based alloy or a nickel-based alloy.

Images