Manufacturing process for enhancing strength and plasticity synergy of CoNiV multi-component alloy

Abstract

The invention discloses a manufacturing process for enhancing CoNiV multi-component alloy strength and plasticity synergy, which is characterized in that according to the method, a traditional laser powder bed melting method is used for additive manufacturing of equal-atom CoNiV multi-component alloy, and the excellent strength and plasticity synergy of the alloy is realized through simple aging treatment. By regulating and controlling the high-entropy alloy CoNiV, the CoNiV alloy has excellent mechanical properties at the room temperature of 298K, fluctuation of elements in an alloy matrix is intensified under an aging sample deformed at the low temperature of 77K, and the offset distance of vanadium on the intracrystalline cellular structure wall is intensified, so that the cellular structures can generate strong interaction with dislocation; and the alloy is effectively enhanced and toughened, and the yield strength of kilopascals and the uniform elongation of more than 40% are obtained.

Description

Technical Field

[0001] The present invention relates to a manufacturing process for enhancing the strength-ductility synergy of CoNiV multi-element alloys, belonging to the field of new material processing and preparation. Background Art

[0002] Multi-element alloys containing three or more main elements are abbreviated as MCA. As a new type of metallic material, in the past decade or so, due to their excellent properties such as high strength, good corrosion resistance, and excellent magnetic properties, which exceed those of many traditional alloys containing only one or two main elements, many MCA systems have been reported to exhibit excellent strength-ductility synergy mechanical properties over a wide temperature range. Laser additive manufacturing is a newly emerging method for manufacturing metallic parts used in aerospace and vehicle engineering in recent years. By means of a layer-by-layer construction method that precisely controls the use of micron-sized pre-alloyed powder with a laser, geometric design of metallic parts with complex configurations can be achieved, as well as low-cost but efficient processing. Among all additive manufacturing technologies, laser powder bed fusion additive manufacturing technology shows overwhelming advantages over traditional manufacturing processes when producing metallic parts. This technology has great potential in manufacturing complex-shaped parts with ultra-fine grain sizes, which is beneficial to improving the strength under extreme service conditions. Summary of the Invention

[0003] The present invention provides a manufacturing process for enhancing the strength-ductility synergy of CoNiV multi-element alloys, characterized in that: this method uses the traditional laser powder bed fusion printing method to prepare equiatomic ratio CoNiV multi-element alloy castings:

[0004] 1), Use Ar atomized CoNiV pre-alloyed powder;

[0005] 2), Preheat to 100 °C, use an FS271 laser melting device, under the protection of an inert high-purity argon atmosphere, use a 5000W Gaussian beam fiber laser to prepare an alloy block of 90mm×40mm×15mm;

[0006] 3), Use a laser spot diameter of 80 - 120 μm, and perform laser melting at a scanning speed of 140 - 180W and 700 - 900mm / s.

[0007] 4), Cut a piece of alloy sample from the printed MCA block, then seal it in a quartz tube in a vacuum state, and then heat the alloy plate sealed in the quartz tube to 500 °C in an oven and age for 24h, and then water quench.

[0008] Preferably, the laser spot diameter is 100 μm, and laser melting is performed at a scanning speed of 160W and 800mm / s.

[0009] Preferably, the powder layer thickness is controlled at 20 μm and the hatch distance is 1 mm;

[0010] Preferably, the laser scanning direction is rotated counterclockwise by 67° between each printing layer;

[0011] In summary, the beneficial effects of the present invention are as follows:

[0012] 1. In the present invention, through simple post-aging treatment, the strength and ductility of the alloy are significantly improved, and the mechanical properties of the alloy are enhanced.

[0013] 2. In the present invention, the aged specimens of the alloy deformed at 77K reached a yield strength of gigapascals and a uniform elongation of more than 40%, improving the compressive properties of the alloy.

[0014] 3. In the present invention, the generation of local chemical order in the alloy strengthens the fluctuations of elements in the alloy matrix and enhances the offset of vanadium on the cell wall of the intragranular cellular structure.

[0015] 4. In the present invention, the deformed microstructure in which the plane slip array with a very high density of dislocations dominates in the aged specimens strengthens and toughens the alloy.

[0016] 5. The present invention provides an alternative method for producing high-performance structural materials for use under extreme conditions.

[0017] The improvement of the alloy properties is of great significance for development. The comparison of the corresponding alloys is illustrated by the following figures:

[0018] Figure 1 a is the 3D inverse pole figure of the printed sample, b is the surface inverse pole figure, c is the side inverse pole figure, and d is the cross-section inverse pole figure;

[0019] Figure 2 a is a typical backscattered electron image, and b is a backscattered electron image at the grain boundary;

[0020] Figure 3 is the high-resolution and EDS image of the printed sample;

[0021] Figure 4 is the engineering stress-strain diagram of the printed sample. Specific implementation

[0022] In this study, a multi-component alloy of equiatomic CoNiV was used in the present invention, and a traditional laser powder bed fusion (LPBF) printing method was used to produce

[0023] In the present invention, argon atomized CoNiV pre-alloyed powder was used, and a commercial 45# steel plate was used as the building substrate. Before printing, the substrate was sandblasted, then thoroughly cleaned with acetone, and then preheated to a temperature of 100°C.

[0024] In the present invention, a FS271 laser melting equipment was adopted. Under the protection of inert high-purity argon gas, a 5000W Gaussian beam fiber laser was used, and the oxygen content was controlled below 0.04% during the LPBF process to prepare an alloy block with dimensions of approximately 90mm×40mm×15mm.

[0025] In the present invention, the laser spot diameter used was approximately 100μm, and laser melting was carried out at a scanning speed of 160W and 800mm / s. During the printing process, the powder layer thickness was controlled at 20μm, the hatch distance was set at 0.1mm, and the laser scanning direction was rotated counterclockwise by 67° between each adjacent printing layer.

[0026] In the invention, the printed sample under an argon atmosphere was naturally cooled to room temperature indoors, then an alloy sample was cut from the printed MCA block, and then sealed in a quartz tube under vacuum. After that, the alloy plate sealed in the quartz tube was heated to 500°C in an oven and aged for 24h, followed by water quenching.

[0027] In the present invention, the initial microstructural characteristics of the printed MCA samples were studied by means of electron scanning microscope characterization. Figure 1 The 3D inverse pole figures of the printed samples obtained from three planes are shown. It can be seen that the microstructure of the LPBF printed samples is essentially inhomogeneous and has microstructural characteristics along three different directions, which is caused by the extremely inhomogeneous temperature field during the printing process. On the top view plane perpendicular to the building direction, the alloy matrix is found to be surrounded by equiaxed grains with larger sizes, and there are fine grains with random orientations around. For the two side planes parallel and perpendicular to the building direction, epitaxial grain bundles are generated along the direction of the melt boundary, rather than the equiaxed grains generated on the top view plane. This is due to the nature of the temperature gradient during layer-by-layer LPBF printing, and the cooling rate is the fastest along the direction perpendicular to the melt boundary.

[0028] In the present invention, BSE characterization was carried out on the samples, and the microstructure is as Figure 2 shown. It was found that a large number of cellular structures were generated in the alloy matrix. The contour of this cellular structure shows a strong dependence on the grain orientation, that is, many cellular structures show columnar morphologies with different orientations in adjacent grains. The cellular structures in the LPBF printed alloy usually consist of dislocation bundle walls and dislocation-free inner domains, and are usually generated by cellular solidification induced by constitutional supercooling and cellular dislocation structures caused by thermal cycling during the printing process. These cellular structures can effectively act as obstacles to mobile dislocations, thus resulting in profound strength and facilitating work-hardening behavior.

[0029] In the present invention, high-resolution images were framed for the samples, as Figure 3The left side is a high-resolution image, and the right side is the corresponding EDS image. In the image on the left, the local fluctuation of the distribution of major elements in the aged alloy is significantly intensified, and the peak value of the V atomic ratio is close to 0.5. In the EDS image on the right, it is found that the intensity of V in the cell wall rich in V but poor in Co and Ni is much higher than that of the cell wall before printing.

[0030] In the present invention, the mechanical properties of printed and aged MCAs were studied by uniaxial tensile tests at room temperature (298K) and low temperature (77K). Figure 4 The engineering stress-strain curves show that under 298K, the yield strength of the printed and aged MCA samples is between about 780MPa and 930MPa, respectively. Compared with the original sample, its uniform elongation at break is slightly higher, about 41%, while the sample after aging treatment is slightly lower, 33%. However, its ultimate tensile strength is slightly lower than the original sample (about 1070MPa) and stronger after aging treatment (about 1170MPa). These results show that aging treatment has a significant effect on improving the yield strength of the alloy manufactured by the LBPF of the present invention, and does not significantly weaken its plasticity. All this is due to the effect of the change in its microstructural characteristics. Although there is still a traditional trade-off between strength and ductility in metal materials, in the tensile test at 77K, the yield strength and maximum tensile strength of MCA have been significantly improved, reaching 950MPa and 1250MPa, respectively. This result is consistent with previously published studies, and many MCAs with FCC structures show significantly enhanced strength characteristics when deformed at low temperatures.

[0031] The above is only a specific implementation of the invention, but the protection scope of the invention is not limited to it. Any changes or substitutions that are not conceived through creative work should be included in the protection scope of the invention. Therefore, the protection scope of the invention should be based on the protection scope defined in the claims.

Claims

1. A manufacturing process for enhancing the strength and plasticity synergy of CoNiV multi-element alloy, characterized by: The process for manufacturing CoNiV uses the conventional laser powder bed fusion printing method to prepare CoNiV multi-element alloy castings with equal atomic ratios; 1) Using Ar atomized CoNiV pre-alloyed powder; 2) Preheat to 100°C, use FS271 laser melting equipment, and use 5000W Gaussian beam fiber laser to prepare 90mm×40mm×15mm alloy blocks under the protection of inert high-purity argon atmosphere; 3) Use a laser spot diameter of 80-120 μm, laser melting at 140-180 W and a scanning speed of 700-900 mm / s.

2. A manufacturing process for enhancing the strength and plasticity synergy of CoNiV multi-element alloy as claimed in claim 1, characterized in that The laser spot diameter was 100 μm, and laser melting was performed at 160 W and a scanning speed of 800 mm / s.

3. The manufacturing process for enhancing the strength and plasticity synergy of CoNiV multi-element alloy according to claim 1 is characterized in that The thickness of the printed powder layer was controlled at 20 μm, and the opening spacing was set to 0.1 mm.

4. The manufacturing process for enhancing the strength and plasticity synergy of CoNiV multi-element alloy according to claim 1 is characterized in that The laser scanning direction is rotated 67° counterclockwise between each adjacent printed layer to reduce internal stress.

5. The manufacturing process for enhancing the strength and plasticity synergy of CoNiV multi-element alloy as claimed in claim 1 is characterized in that An alloy sample was cut from the printed MCA block, sealed in a quartz tube in a vacuum state, sealed in an oven, heated to 500°C and aged for 24 hours, and then water quenched.

Images