A method for optimizing composition of titanium alloy for additive manufacturing with low cracking tendency

Abstract

This invention relates to the field of metal additive manufacturing technology, and proposes a method for designing and optimizing the composition of titanium alloys with low cracking tendency suitable for additive manufacturing, comprising the following steps: S1: providing titanium alloys with various different composition systems; S2: obtaining the solid fraction of each titanium alloy component during non-equilibrium solidification using material thermodynamics calculation software. f s With temperature T The relationship is as follows: S3, based on the relationship obtained in step S2, calculate the solidification cracking factor (SCI) value of each titanium alloy component at the end of solidification; S4, according to the SCI value obtained in step S3, screen out titanium alloy components with low cracking tendency. This invention starts from the source of material composition and uses a cracking tendency prediction criterion for titanium alloys to propose a method for optimizing titanium alloy components with low cracking tendency in additive manufacturing, thereby reducing the cracking tendency during the additive manufacturing process.

Description

Technical Field

[0001] This invention relates to the field of metal additive manufacturing technology, and in particular to a method for optimizing the composition of titanium alloys with low cracking tendency suitable for additive manufacturing. Background Technology

[0002] Titanium alloys, due to their high specific strength, high toughness, and excellent corrosion resistance, have become indispensable key structural materials in aerospace and other fields. Additive manufacturing (also known as 3D printing) is an important means of manufacturing complex components in aerospace and other fields because it facilitates integrated design and integral forming of complex components. Therefore, titanium alloy additive manufacturing has been widely used in aerospace and other fields, such as aircraft engine nacelle end frames prepared by directed energy deposition (DED), "Pogo Z-shaped baffles" formed by powder bed fusion (PBF), and "purification pump manifolds" in the International Space Station.

[0003] However, complex titanium alloy systems, especially those containing multiple alloying elements such as Al, Mo, Zr, and Si, are highly prone to cracking during additive manufacturing. Taking the typical TC11 titanium alloy (nominal composition Ti-6.5Al-3.5Mo-1.5Zr-0.3Si, wt.%) as an example, this alloy is one of the main materials selected for load-bearing components in the current and future aerospace industry. However, it is very prone to cracking during additive manufacturing. The complex composition of TC11 titanium alloy undergoes complex phase transformation behavior during rapid solidification, easily forming an extended, mushy region. Under cyclic rapid heating and cooling, it is subjected to concentrated thermal stress and solidification shrinkage, causing tearing of the internal liquid film or weak bonding interfaces. This microscopic damage accumulates and expands continuously during the thermal cycle of layer-by-layer manufacturing, leading to cracks in the component (Acta Materialia 2026, 302: 121668), which is one of the key challenges in the additive manufacturing of complex titanium alloy components.

[0004] Printing complete components that meet dimensional requirements is the primary goal of additive manufacturing. Therefore, solving the cracking problem and obtaining effective suppression methods has always been a key research focus in additive manufacturing. Past solutions mainly focused on process aspects, such as optimizing printing parameters (energy density, scanning speed, etc.), scanning strategies, or performing multiple stress-relief annealing processes on the components. While these methods can alleviate residual stress to some extent, they cannot fundamentally solve the deformation and cracking problems. For example, some complex components develop cracks before stress-relief annealing, leading to printing failures. Therefore, the most fundamental and universal solution is to optimize the alloy composition. However, in engineering, alloy compositions must comply with national and industry standards. Therefore, the most feasible composition optimization strategy is not to design a completely new alloy system, but to scientifically fine-tune and optimize within the existing standard range to obtain a composition that meets the standard requirements while possessing excellent printing performance with low cracking tendency in additive manufacturing. However, how to quickly and accurately screen out the optimal composition combination for crack resistance within a narrow standard-specified composition range, rather than relying on a large number of repeated "trial and error" experiments, remains a key challenge in this field. Summary of the Invention

[0005] In view of this, the present invention proposes a method for compositional optimization design of easily crackable titanium alloys in additive manufacturing based on the solidification cracking factor criterion.

[0006] The technical solution of the present invention is implemented as follows: In a first aspect, the present invention provides a method for optimizing the composition of titanium alloys with low cracking tendency suitable for additive manufacturing, comprising the following steps: S1: Offers a variety of titanium alloys with different composition systems; S2: Obtain the solid fraction of each titanium alloy component during non-equilibrium solidification using materials thermodynamics calculation software. f s With temperature T Relationship; S3. Based on the relationship obtained in step S2, calculate the solidification cracking factor (SCI) value of each titanium alloy component at the end of solidification. S4. Based on the SCI value described in step S3, select titanium alloy components with low cracking tendency.

[0007] Specifically, this invention employs a theoretical tool and composition optimization method capable of predicting the relationship between composition and cracking tendency. This invention is based on the solidification cracking index (SCI) criterion proposed by S. Kou in Acta Materialia 2015, 88:366, which is based on solidification physics. A higher SCI value indicates a greater likelihood of cracking at the end of solidification. f s→1) The steeper the temperature gradient with small changes in solid fraction, the faster the intergranular liquid channels close, the more difficult the liquid metal feeding becomes, and the higher the tendency for hot cracking. This invention applies this to the optimization of titanium alloy composition. Through thermodynamic calculations, the SCI values ​​of different fine-tuned compositions are predicted before the experiment to determine the magnitude of cracking tendency during the printing process, thereby optimizing the design of a titanium alloy composition for additive manufacturing with low cracking tendency.

[0008] Based on the above technical solutions, preferably, the formula for calculating the SCI value in step S3 is as follows: ; in, T For temperature, f s This represents the solid fraction.

[0009] Based on the above technical solution, preferably, in step S3, the SCI value at the end of solidification is the solid fraction. f s The SCI value corresponding to a value of 0.85-0.99.

[0010] Based on the above technical solutions, preferably, the material thermodynamics calculation software mentioned in step S2 includes JMatPro and Thermo-Calc.

[0011] Based on the above technical solutions, preferably, in step S4, an SCI value of <30 indicates a low tendency to crack.

[0012] Based on the above technical solutions, preferably, the titanium alloy mentioned in step S1 is TC11 titanium alloy.

[0013] Based on the above technical solutions, preferably, the composition range of the TC11 titanium alloy is selected according to the range specified in GB / T3620.1-2016. Calculated as 100% by mass, the TC11 titanium alloy includes Al: 5.8%~7.0%, Mo: 2.8%~3.8%, Zr: 0.8%~2.0%, Si: 0.2%~0.35%, and the specified impurity element content, with the balance being Ti.

[0014] Based on the above technical solutions, preferably, the impurity elements include O: ≤0.15%, Fe: ≤0.25%, C: ≤0.08%, N: ≤0.05%, and H: ≤0.015%.

[0015] Secondly, the present invention provides a titanium alloy with low cracking tendency suitable for additive manufacturing, obtained by the above-described method.

[0016] Based on the above technical solutions, preferably, the TC11 titanium alloy, by mass percentage (100%), comprises Al: 6.2%~6.5%, Mo: 3.0%~3.5%, Zr: 1.5%, Si: 0.25%; and specified impurity element contents: O: 0.08%-0.1%, Fe: ≤0.25%, C: ≤0.08%, N: ≤0.05%, H: ≤0.015%; with the balance being Ti.

[0017] Thirdly, the present invention provides a method for preparing a titanium alloy with low cracking tendency suitable for additive manufacturing, comprising the following steps: preparing the titanium alloy into a wire, and then forming the wire into a three-dimensional component using a laser additive manufacturing method.

[0018] The method for optimizing the composition of titanium alloys with low cracking tendency in additive manufacturing, as proposed in this invention, has the following advantages over existing technologies: (1) This invention applies the solidification cracking factor (SCI) criterion to the field of titanium alloy composition design. By combining thermodynamic calculation simulation, the SCI values ​​of different titanium alloy compositions are calculated, and the compositions are predicted and screened. This enables the scientific and efficient identification of low cracking tendency compositions before the experiment, thereby significantly reducing the research and development costs and cycle.

[0019] (2) The alloy designed according to this method exhibits excellent crack resistance with no cracks or extremely low crack density in additive manufacturing. The effectiveness of the design method and the reliability of the designed composition have been fully verified by the strong correlation between the SCI calculation values ​​and the actual printing results of multiple examples and comparative examples. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a graph showing the relationship between Al element and solidification cracking factor in Example 2; Figure 2 This is a graph showing the relationship between Zr and Mo elements and the solidification cracking factor in Example 2; Figure 3 This is a graph showing the relationship between O and Si elements and the solidification cracking factor in Example 2; Figure 4 These are photographs of different TC11 titanium alloy printed samples from Example 3; Figure 5A photograph of a 2-meter component printed using the TC11 titanium alloy composition of serial number 1 in Example 3; Figure 6 Print an image of the cracked 3D component from Comparative Example 1. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] Example 1

[0024] This embodiment provides a composition design method suitable for additive manufacturing of titanium alloys. The method includes applying a solidification cracking factor criterion to the composition screening of titanium alloys. The specific steps are as follows: a) Determine the basic composition system of the target titanium alloy, wherein the basic composition system is TC11 titanium alloy, and set the composition variation range of each alloying element and impurity element; The composition range of TC11 titanium alloy is selected in accordance with the range specified in GB / T 3620.1-2016.

[0025] Specifically, based on a 100% mass percentage, TC11 titanium alloy comprises Al: 5.8%~7.0%, Mo: 2.8%~3.8%, Zr: 0.8%~2.0%, Si: 0.2%~0.35%, and specified impurity element contents: O: ≤0.15%, Fe: ≤0.25%, C: ≤0.08%, N: ≤0.05%, H: ≤0.015%, with other elements not exceeding 0.1% individually and not exceeding 0.4% in total. The balance is Ti.

[0026] b) Iterative calculations were performed using materials thermodynamics software (JMatPro, Thermo-Calc) to obtain the solid fraction of each TC11 titanium alloy component during non-equilibrium solidification. f s With temperature T The relationship.

[0027] c) Based on the relationship obtained in step b), calculate the solid fraction of each titanium alloy component at the end of solidification. f s The solidification cracking factor (SCI) value (ranging from 0.85 to 0.99) is calculated using the following formula: ; in,T For temperature, f s The SCI value is the solid fraction; the calculation of the SCI value is based on the solidification and solid-state phase transformation path of the titanium alloy, and the solid fraction is calculated accordingly. f s With temperature T Change relationship f s (T).

[0028] d) Based on the SCI value described in step c), select titanium alloy compositions with low cracking tendency (SCI value < 30) from the candidate titanium alloys.

[0029] Titanium alloy compositions with low SCI values ​​are preferentially selected for additive manufacturing; and those compositions that show no cracking during the printing process are identified as candidate alloy compositions with low cracking tendency.

[0030] Example 2

[0031] Following the method of Example 1, this example calculated the SCI values ​​for five different elemental gradients of TC11 titanium alloys, with the specific compositions shown below: Group 1: Ti-(5.8-7.0, Al increases in a gradient of 0.2 wt.%)Al-2.8Mo-0.8Zr-0.2Si-0.15O; Group 2: Ti-5.8Al-(2.8-3.8, Mo increases in a gradient of 0.2 wt.%)Mo-0.8Zr-0.2Si-0.15O; Group 3: Ti-5.8Al-2.8Mo-(0.8-2.0, Zr increases in a gradient of 0.2wt.%)Zr-0.2Si-0.15O; Group 4: Ti-5.8Al-2.8Mo-0.8Zr-(0.2-7.0, Si increases in a gradient of 0.5wt.%)Si-0.15O; Group 5: Ti-5.8Al-2.8Mo-0.8Zr-0.2Si-(0.05-0.15, O increases in a gradient of 0.5wt.%)O.

[0032] The SCI values ​​of the above-mentioned different alloy compositions are as follows: Figure 1-3 As shown, O and Si elements have the greatest impact on alloy cracking. Adding only a small amount significantly increases their SCI value. Al, Mo, and Zr have relatively small effects on alloy cracking, but adding too much of them also significantly increases their SCI value.

[0033] Example 3

[0034] Based on the composition range of Example 2, this example screened out three different compositions of TC11 titanium alloy, the specific compositions of which are shown in Table 1.

[0035] Table 1 Comparison of TC11 titanium alloy composition and properties

[0036] The three-dimensional components were prepared according to the components in Table 1, and the preparation method is as follows: (1) Prepare titanium alloy components into wires First, using a Φ640mm ingot as raw material, homogenization annealing at 1200℃ for 36 hours was performed to improve composition distribution. Two-stage forging and repeated upsetting and drawing were then carried out at 1150℃ and 1100℃. The first stage included two upsetting and drawing stages with a deformation of 45% and a final forging temperature of 950℃. The second stage resulted in deformations of 40% and 45% respectively, with a final forging temperature of 920℃. After forging, the billet was air-cooled and ground to obtain a forged billet. Next, octagonal drawing was performed at 980℃, followed by recrystallization annealing at 880℃ for 120 minutes and water cooling to obtain a 180mm diameter billet. Finally, radial forging at 960℃ with a forging ratio of 3.3 yielded a 54mm diameter billet. The 0.5mm round bar is then rolled at 920℃ at a speed of 0.8m / s to produce a Φ7.2mm coiled wire. After that, it is vacuum recrystallized and annealed at 840℃ for 25 minutes, furnace cooled to 90℃ and then air cooled. Subsequently, it is cold drawn through a roller die at a drawing speed of 25m / min, and after the diameter is reduced to Φ2.4mm and after the final drawing, it is continuously annealed online at 780℃ at a travel speed of 30m / min. Finally, after surface grinding and polishing, a finished wire with a diameter of 1.0mm and a straightness of 2.2‰ is obtained.

[0037] (2) Using laser additive manufacturing process to form filament into three-dimensional components Laser additive manufacturing process parameters: laser power 3600W, wire feed speed 1.8m / min, scanning speed 10m / min, overlap spacing 2.4mm, z-axis lift 2.2mm.

[0038] Figure 4 The dimensions of the three-dimensional component are 120mm × 40mm × 90mm. Figure 5 The dimensions of the three-dimensional component are 2736mm × 411mm × 736mm.

[0039] The three-dimensional components prepared above were tested for cracks. The testing methods were as follows: the surface was visually inspected and no cracks were found; the interior was tested using ultrasound. The results are shown in Table 2. Figure 4-5 .

[0040] Table 2 Comparison of 3D Component Performance

[0041] Table 2 and Figure 4-5 As shown, the alloy designed according to the method of the present invention exhibits excellent crack resistance without cracking during additive manufacturing. This is fully verified by the strong correlation between the SCI calculation values ​​and the actual printing results in the above embodiments.

[0042] Comparative Example 1 The main components (wt.%) of the three-dimensional component in Comparative Example 1 are shown in Table 3. The preparation method of the three-dimensional component is the same as that in Example 3. The dimensions of the three-dimensional component are 120mm × 40mm × 90mm. The results are shown in Table 3 and... Figure 6 .

[0043] Table 3 Comparison of 3D Component Performance

[0044] Table 3 and Figure 6 As shown, the SCI value of the 3D component in Comparative Example 1 is >30, and cracking occurred during printing.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for optimizing the composition of titanium alloys with low cracking tendency suitable for additive manufacturing, characterized in that, Includes the following steps: S1: Offers a variety of titanium alloys with different composition systems; S2: Obtain the solid fraction of each titanium alloy component during non-equilibrium solidification using materials thermodynamics calculation software. f s With temperature T Relationship; S3. Based on the relationship obtained in step S2, calculate the solidification cracking factor (SCI) value of each titanium alloy component at the end of solidification. S4. Based on the SCI value described in step S3, select titanium alloy components with low cracking tendency.

2. The method for optimizing the composition of titanium alloys with low cracking tendency in additive manufacturing as described in claim 1, characterized in that, The formula for calculating the SCI value in step S3 is as follows: ； in, T For temperature, f s This represents the solid fraction.

3. The method for optimizing the composition of titanium alloys with low cracking tendency in additive manufacturing as described in claim 1, characterized in that, In step S3, the SCI value at the end of solidification is the solid fraction. f s The SCI value corresponding to a value of 0.85-0.

99.

4. The method for optimizing the composition of titanium alloys with low cracking tendency in additive manufacturing as described in claim 1, characterized in that, In step S4, it is specified that an SCI value < 30 indicates a low tendency to crack.

5. The method for optimizing the composition of titanium alloys with low cracking tendency in additive manufacturing as described in claim 1, characterized in that, The material thermodynamics calculation software mentioned in step S2 includes JMatPro and Thermo-Calc.

6. The method for optimizing the composition of titanium alloys with low cracking tendency in additive manufacturing as described in claim 1, characterized in that, The titanium alloy mentioned in step S1 is TC11 titanium alloy.

7. The method for optimizing the composition of titanium alloys with low cracking tendency in additive manufacturing as described in claim 6, characterized in that, Based on a mass percentage of 100%, the TC11 titanium alloy comprises Al: 5.8%~7.0%, Mo: 2.8%~3.8%, Zr: 0.8%~2.0%, Si: 0.2%~0.35%; and specified impurity element contents: O: ≤0.15%, Fe: ≤0.25%, C: ≤0.08%, N: ≤0.05%, H: ≤0.015%; with the balance being Ti.

8. A titanium alloy with low cracking tendency suitable for additive manufacturing, characterized in that, It is obtained by screening using the method described in any one of claims 1 to 7.

9. A titanium alloy with low cracking tendency suitable for additive manufacturing as described in claim 8, characterized in that, Based on a mass percentage of 100%, the TC11 titanium alloy comprises Al: 6.2%~6.5%, Mo: 3.0%~3.5%, Zr: 1.5%, Si: 0.25%; and specified impurity element contents: O: 0.08%~0.1%, Fe: ≤0.25%, C: ≤0.08%, N: ≤0.05%, H: ≤0.015%; with the balance being Ti.

10. A method for preparing a low-cracking titanium alloy suitable for additive manufacturing, as described in any one of claims 8 to 9, characterized in that, Includes the following steps: Titanium alloys are prepared into wires or powders, and then components are formed using laser additive manufacturing methods.

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