Method for rapidly determining heat treatment strength of TC4 titanium alloy

Abstract

The application discloses a kind of methods for quickly determining the strength of TC4 titanium alloy heat treatment, comprising the following steps: S1: establishing lookup database: by pairing test, establish the lookup database about aging temperature-Brinell hardness-tensile strength;S2: clear target strength requirement: according to the requirement from design drawing or technical specification, clear target strength requirement;S3: to be tested sample heat treatment;S4: sample hardness detection: with the range value of hardness in lookup database as reference standard, the hardness of TC4 titanium alloy sample after heat treatment is detected;S5: tensile test strength detection.The application process replaces destructive tensile test by non-destructive or micro-loss hardness test, reduces material cost and manufacturing cost of quality detection;Through sample hardness detection, provide technical basis for the strength qualification determination of each heat treated part, through the feedback of quick micro-loss hardness detection, adjust and improve the reliability of product heat treatment quality, reduce quality hidden danger.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy heat treatment technology, specifically relating to a method for rapidly determining the heat treatment strength of TC4 titanium alloy. Background Technology

[0002] TC4 (Ti-6Al-4V) titanium alloy is a typical (α+β) dual-phase titanium alloy. Due to its high specific strength, excellent corrosion resistance, and good comprehensive mechanical properties, it is known as "space metal" and "marine metal," and is an indispensable key structural material in high-end equipment fields such as aerospace, shipbuilding, biomedicine, and chemical energy. Heat treatment is the core process for controlling the final mechanical properties of TC4 titanium alloy. Through different solution treatments (temperature, time) and aging treatments, the morphology, size, content, and distribution of its internal α and β phases can be precisely adjusted, thereby obtaining the desired balance of strength, plasticity, toughness, and fatigue properties.

[0003] Currently, the most mainstream and authoritative method for determining the performance of TC4 titanium alloy after heat treatment in industrial production is the "direct destructive testing method based on standard tensile tests." The specific process is as follows: First, design target strength indicators (such as tensile strength σ) based on the service conditions of the part. b Yield strength σ 0.2 Then, corresponding heat treatment processes (such as solution temperature, time, cooling method, and aging regime) are formulated. After heat treatment, samples must be taken from parts of the same batch or from specially prepared test bars prepared with the furnace, and room temperature tensile tests must be conducted according to national standards (such as GB / T 228.1) to test their strength. Only when the tensile test results meet the design specifications can the batch of parts be deemed qualified.

[0004] Current standards recommending heat treatment regimes lack corresponding strength or hardness indicators, and there is no industry-wide correlation between titanium alloy parameters, hardness, and strength. This makes it impossible to determine solution treatment and aging parameters based on strength and hardness during heat treatment process design. Instead, process parameters must be selected within the standard range for heat treatment, followed by destructive tensile testing to test strength. If the strength test results are outside the design specifications, production workers must continuously adjust parameters within the process range, reworking the process and then performing tensile tests and pass / fail judgments on the reworked bars from the same furnace, repeating the process until the strength meets the design specifications. Multiple reworks result in wasted materials, energy, and time, and cause irreversible deterioration of the material's microstructure (more than three solution treatments can easily lead to severe material performance degradation, resulting in product scrap). In short, existing process technologies require multiple adjustments, lack operability, have low production efficiency, and high production costs.

[0005] The existing method of "determining the strength of TC4 titanium alloy after heat treatment by preparing furnace-loaded samples and conducting destructive tensile tests" has the following main drawbacks, which directly restrict production efficiency, increase costs, and introduce quality risks: Low testing efficiency and lengthy production cycles: Tensile testing itself is cumbersome. From sample cooling, sampling, and machining after heat treatment to testing on a universal testing machine, the entire process can take several hours or even days. This means that the entire batch of parts must remain in the inspection area, waiting for the test results before being released to the next process, which seriously slows down the overall production pace and cannot meet the requirements of modern manufacturing for high efficiency and rapid response.

[0006] High testing costs lead to significant resource waste: each test requires the destruction of one or more furnace-batch samples. Sample preparation and machining also incur costs. This waste is particularly pronounced for small batches of high-value parts. If a test result is unsatisfactory, the entire batch of parts may face scrapping or rework, resulting in substantial economic losses. This is a "post-test verification" model, unable to intervene before damage occurs.

[0007] The destructive nature of testing inherently prevents 100% inspection, posing a quality risk: because the testing method is destructive, it fundamentally prevents strength verification of every part leaving the factory, allowing only sampling inspection (usually one or a few samples taken with the furnace). This "sample-for-part" model carries inherent quality risks: the actual performance of a single part may not perfectly match the sample. Therefore, there is a risk of non-conforming products being missed and entering the downstream market, posing a potential threat to the reliability and safety of products (especially high-end equipment such as aerospace).

[0008] It hinders the rapid optimization and iteration of production processes: During product development, process debugging, or quality problem investigation, it is necessary to repeatedly adjust heat treatment parameters and observe their effects. The lengthy testing cycle of existing technologies means that each process modification requires a long wait for performance feedback. This significantly delays the R&D progress, increases trial-and-error costs, and is detrimental to technological innovation and the rapid improvement of process technology.

[0009] In alloy processing technology, Chinese Patent No. CN107723458A discloses an online monitoring method for the aging process of heat-treated aluminum alloys, which is an online monitoring method for the resistivity of aluminum alloys during the aging process; while Chinese Patent No. CN105973708A discloses an evaluation method for the tensile strength of high alloy heat-resistant steel, which is an evaluation method based on the linear formula of hardness-strength for high alloy heat-resistant steel, lacking a rapid determination method for the heat treatment strength of TC4 titanium alloy.

[0010] The patent (CN107723458A) is applicable to heat-treatable aluminum alloys (Al-Cu, Al-Mg-Si, Al-Zn-Mg). Its strengthening mechanism is precipitation strengthening, where solute atoms precipitate to form a second phase. The aging process only requires controlling the degree of solute precipitation. This technology uses resistivity as a performance-related indicator, predicting the mechanical properties of aluminum alloys through online resistivity measurement. However, the relationship between the α / β phase transformation and resistivity in titanium alloys is complex and lacks mature applications.

[0011] The patent (CN105973708A) is applicable to martensitic high-alloy heat-resistant steel. Its strengthening mechanism is martensitic phase transformation strengthening through quenching and high-temperature tempering, and its hardness and tensile strength show a stable linear relationship. This technology has derived a single linear formula (Rm=3.57, HB-90.2) through extensive experiments, because the hardness and strength of heat-resistant steel have a stable linear relationship.

[0012] Neither of the two disclosed technologies mentioned above provides a method for rapidly determining the heat treatment strength of TC4 titanium alloy. Summary of the Invention

[0013] The purpose of this invention is to provide a method for rapidly determining the heat treatment strength of TC4 titanium alloy, addressing the technical problems mentioned in the background section.

[0014] The technical solution of this invention: A method for rapidly determining the heat-treated strength of TC4 titanium alloy includes the following steps: S1: Establish a lookup database: Through paired tests, compile the strength and Brinell hardness values ​​of TC4 titanium alloy samples at different aging temperatures, and establish a lookup database on aging temperature-Brown hardness-tensile strength. S2: Define target strength requirements: Define target strength requirements based on the requirements from design drawings or technical specifications; S3: Heat treatment of the test sample: Based on the target strength requirements, the database is consulted to determine the aging temperature and the range of Brinell hardness values, and the TC4 titanium alloy sample to be tested is then heat-treated. S4: Sample hardness test: After completing step S3, the hardness of the heat-treated TC4 titanium alloy sample is tested using the range of hardness values ​​in the database as a reference standard. If the Brinell hardness test is qualified, proceed to step S5. If the Brinell hardness test is unqualified, return to step S3 for rework. S5: Tensile strength test: After the Brinell hardness value is qualified in step S4, a tensile strength test is performed. If it is not qualified, proceed to step S3 again. If it is qualified, the finished product sample is obtained.

[0015] In step S1, the aging temperature ranges from 440℃ to 680℃, with each 30℃ interval being a measurement range.

[0016] In step S3, the specifications of the TC4 titanium alloy sample to be tested are as follows: 25×100.

[0017] In step S3, the TC4 titanium alloy sample to be tested is subjected to heat treatment, including solution treatment and aging treatment after solution treatment.

[0018] The solution treatment process includes the following steps: a1: Take the TC4 titanium alloy sample to be tested, heat the sample to 925℃-935℃, and then hold it at that temperature for 70-80 minutes. a2: After completing step a1, cool the sample to room temperature with water to complete the solution treatment process.

[0019] The aging process includes the following steps: b1: Based on the target strength requirements, refer to the database to determine the aging temperature and Brinell hardness range. Take the TC4 titanium alloy sample to be tested after solution treatment, heat the sample to the corresponding aging temperature, and hold for 140-160 min. b2: After completing step b1, air-cool the sample to room temperature to complete the aging process.

[0020] The beneficial effects of this invention are: This invention replaces destructive tensile testing with non-destructive or minimally destructive hardness testing, reducing material and manufacturing costs for quality inspection. Hardness testing of samples provides a technical basis for determining the strength compliance of each heat-treated part. Rapid, minimally destructive hardness testing provides feedback on the suitability of the heat treatment process, allowing for precise adjustments to improve the reliability of product heat treatment quality and reduce potential quality issues. Screening through sample hardness testing saves the time required for tensile strength testing of numerous samples that do not meet hardness and strength standards, reducing the strength determination cycle from several hours to several days to within minutes. This enables rapid, on-site determination of heat treatment strength, providing immediate and quantitative data feedback for optimizing the heat treatment process, thereby significantly improving production efficiency. Attached Figure Description

[0021] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0022] refer to Figure 1 A method for rapidly determining the heat treatment strength of TC4 titanium alloy includes the following steps: S1: Establish a lookup database: Through paired tests, compile the strength and Brinell hardness values ​​of TC4 titanium alloy samples at different aging temperatures, and establish a lookup database on aging temperature-Brown hardness-tensile strength. This step primarily involves conducting numerous paired experiments to compile the strength and Brinell hardness values ​​of TC4 titanium alloy samples at different aging temperatures, thereby establishing a database for searching aging temperature, Brinell hardness, and tensile strength. The aging temperature range is 440℃-680℃, with each 30℃ interval being a measurement range, as detailed in Table 1.

[0023] Table 1. Aging Temperature, Brinell Hardness, and Tensile Strength of TC4 Titanium Alloy (Database Search)

[0024] S2: Define target strength requirements: Define target strength requirements based on the requirements from design drawings or technical specifications; S3: Heat treatment of the test sample: Based on the target strength requirements, the database is consulted to determine the aging temperature and the range of Brinell hardness values, and the TC4 titanium alloy sample to be tested is then heat-treated. The specifications of the TC4 titanium alloy sample to be tested are as follows: 25×100.

[0025] The TC4 titanium alloy sample to be tested was subjected to heat treatment, including solution treatment and aging treatment after solution treatment.

[0026] The solution treatment process includes the following steps: a1: Take the TC4 titanium alloy sample to be tested, heat the sample to 925℃-935℃, and then hold it at that temperature for 70-80 minutes. a2: After completing step a1, cool the sample to room temperature with water to complete the solution treatment process.

[0027] The aging process includes the following steps: b1: Based on the target strength requirements, refer to the database to determine the aging temperature and Brinell hardness range. Take the TC4 titanium alloy sample to be tested after solution treatment, heat the sample to the corresponding aging temperature, and hold for 140-160 min. b2: After completing step b1, air-cool the sample to room temperature to complete the aging process.

[0028] S4: Sample hardness test: After completing step S3, the hardness of the heat-treated TC4 titanium alloy sample is tested using the range of hardness values ​​in the database as a reference standard. If the Brinell hardness test is qualified, proceed to step S5. If the Brinell hardness test is unqualified, return to step S3 for rework. S5: Tensile strength test: After the Brinell hardness value is qualified in step S4, a tensile strength test is performed. If it is not qualified, proceed to step S3 again. If it is qualified, the finished product sample is obtained.

[0029] The invention will be illustrated by the following examples: Case 1: Material is TC4, dimensions are... Heat treatment of 25×100 blank parts (strength requirement ≥ 1140 MPa) a1: Database query: Table 1 shows that tensile strength ≥ 1140 MPa corresponds to the first three aging temperature ranges (440-530℃). Among them, the 470-500℃ range has the highest strength (1142-1154 MPa) and also the highest hardness (377-383 HBW). This range is selected as the target.

[0030] a2: Define the objective: The design drawings require a tensile strength ≥ 1140 MPa.

[0031] a3: Heat treatment: Solution treatment: 930℃ / 75min, water cooling.

[0032] Aging treatment: To achieve peak strength, select the midpoint of the range, 485℃ (within the range of 470-500℃), keep warm for 150 minutes, and then air cool.

[0033] a4: Hardness test (quick determination): Acceptable path: The measured Brinell hardness of the end face is HBW 380. This value falls within the predicted range of 377-383 HBW in the database, and is therefore judged as "hardness test qualified", proceed to a5.

[0034] a5: Tensile test (final verification): The blank with qualified hardness is machined from the core and surface separately. Eight standard pull bars were subjected to tensile testing. The tensile strength measured in the core was 1148 MPa, and the tensile strength measured on the surface was 1152 MPa. Both met the requirement of ≥1140 MPa, and were therefore deemed to be finally qualified.

[0035] Case 2: Material is TC4, dimensions are... Heat treatment of 25×100 blank parts (strength requirement 1100-1120MPa) b1: Database query: Table 1 shows that the tensile strength range of 1100-1120 MPa corresponds to 560-590℃ (1110-1132 MPa) and 590-620℃ (1094-1110 MPa). To ensure the lower limit of strength, the 560-590℃ range is selected.

[0036] b2: Define the objective: The technical specifications require a strength of 1100-1120 MPa.

[0037] b3: Heat treatment: Solution treatment: 925°C / 80 min, water cooling.

[0038] Aging treatment: Select 575°C (within 560 - 590°C), hold for 150 min, air cooling.

[0039] b4: Hardness testing: The Brinell hardness of the end face is measured as HBW 360. Looking up Table 1, the hardness range corresponding to this temperature range is 358 - 367 HBW. 360 HBW is within this range, judged as qualified, and proceed to b5.

[0040] b5: Tensile test: Standard tensile bars are machined from the core and surface of the billets with qualified hardness for tensile testing. The strength measured at the core is 1110 MPa, and the strength measured on the surface is 1115 MPa, which exactly falls within the target range of 1100 - 1120 MPa, qualified.

[0041] In the conventional process, when performing lengthwise tensile testing on TC4 titanium alloy specimens, the tensile test strength detection takes a large amount of time. In practical applications, there is a linear relationship between the specimen hardness and strength. When the specimen hardness meets the conditions, the tensile test strength detection basically meets the qualified requirements, based on searching the database.

[0042] From the above case, it can be seen that in this invention, by first detecting the hardness of the test specimens after the heat treatment process, the unqualified specimens are returned for re - heat treatment, and the qualified specimens are subjected to tensile test strength detection. The specimens produced by this process can basically meet the requirements of tensile test strength detection, not only improving the yield rate but also saving a large amount of time and reducing time waste.

[0043] The process of this invention replaces the destructive tensile test with non - destructive or slightly destructive hardness testing, reducing the material cost and manufacturing cost of quality inspection; through specimen hardness detection, it provides a technical basis for judging the strength qualification of each heat - treated part. By quickly detecting the slightly destructive hardness, it feedbacks the adaptability of the heat treatment regime, precisely adjusts and improves the reliability of product heat treatment quality, and reduces quality risks. Through specimen hardness detection for screening, it saves the time for tensile test strength detection of a large number of specimens with unqualified hardness and strength in traditional technology, shortening the strength judgment cycle from several hours to several days to within a few minutes, realizing rapid and on - site judgment of heat treatment strength, providing immediate and quantitative data feedback for the optimization of heat treatment process, thereby greatly improving production efficiency.

Claims

1. A method for rapidly determining the heat-treated strength of TC4 titanium alloy, characterized in that... Includes the following steps: S1: Establish a lookup database: Through paired tests, compile the strength and Brinell hardness values ​​of TC4 titanium alloy samples at different aging temperatures, and establish a lookup database on aging temperature-Brown hardness-tensile strength. S2: Define target strength requirements: Define target strength requirements based on the requirements from design drawings or technical specifications; S3: Heat treatment of the test sample: Based on the target strength requirements, the database is consulted to determine the aging temperature and the range of Brinell hardness values, and the TC4 titanium alloy sample to be tested is then heat-treated. S4: Sample hardness test: After completing step S3, the hardness of the heat-treated TC4 titanium alloy sample is tested using the range of hardness values ​​in the database as a reference standard. If the Brinell hardness test is qualified, proceed to step S5. If the Brinell hardness test is unqualified, return to step S3 for rework. S5: Tensile strength test: After the Brinell hardness value is qualified in step S4, a tensile strength test is performed. If it is not qualified, proceed to step S3 again. If it is qualified, the finished sample is obtained.

2. The method for rapidly determining the heat treatment strength of TC4 titanium alloy according to claim 1, characterized in that: In step S1, the aging temperature ranges from 440℃ to 680℃, with each 30℃ interval being a measurement range.

3. The method for rapidly determining the heat treatment strength of TC4 titanium alloy according to claim 1, characterized in that: In step S3, the specifications of the TC4 titanium alloy sample to be tested are as follows: 25×100.

4. The method for rapidly determining the heat treatment strength of TC4 titanium alloy according to claim 1, characterized in that: In step S3, the TC4 titanium alloy sample to be tested is subjected to heat treatment, including solution treatment and aging treatment after solution treatment.

5. The method for rapidly determining the heat treatment strength of TC4 titanium alloy according to claim 4, characterized in that: The solution treatment process includes the following steps: a1: Take the TC4 titanium alloy sample to be tested, heat the sample to 925℃-935℃, and then hold it at that temperature for 70-80 minutes. a2: After completing step a1, cool the sample to room temperature with water to complete the solution treatment process.

6. The method for rapidly determining the heat treatment strength of TC4 titanium alloy according to claim 4, characterized in that: The aging process includes the following steps: b1: Based on the target strength requirements, refer to the database to determine the aging temperature and Brinell hardness range. Take the TC4 titanium alloy sample to be tested after solution treatment, heat the sample to the corresponding aging temperature, and hold for 140-160 min. b2: After completing step b1, air-cool the sample to room temperature to complete the aging process.

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