Method for improving phase transition temperature of 4D printing high-temperature high-entropy shape memory alloy

Abstract

A method for improving phase transition temperature of 4D printing high-temperature high-entropy shape memory alloy, comprising the following steps: firstly, forming Ti 25 Zr 12 Hf 13 Ni 25 Cu 18 Co7 high-temperature high-entropy shape memory alloy by using 4D printing technology T S and then heating the printed alloy sample to semi-solid temperature between solidus temperature and liquidus temperature of the alloy T L , keeping warm for 5-15 min, and then rapidly water quenching to obtain semi-solid isothermal heat treatment sample. The preparation method can reduce residual stress of 4D printing forming sample, and prepare high-temperature high-entropy shape memory alloy with high density, few defects and high phase transition temperature.

Description

Technical Field

[0001] This invention relates to the field of alloy preparation technology, and in particular to a technology for improving the phase transformation temperature of high-temperature, high-entropy shape memory alloys for 4D printing. Background Technology

[0002] 4D printing technology, or additive manufacturing of smart components, allows the shape, performance, or function of 4D-printed components to be autonomously controlled by changes in time and space under the stimulation and induction of external factors such as light, electricity, magnetism, heat, and pre-deformation. However, the limited phase transformation temperature of traditional binary Ni-Ti shape memory alloys severely restricts their application in high-temperature service environments. High-entropy high-temperature shape memory alloys, on the other hand, possess significantly improved martensitic phase transformation temperature, high yield strength, excellent high-temperature phase stability, superelasticity over a wide temperature range, and high damping properties compared to conventional high-temperature shape memory alloys. They can be used as solid-state energy conversion devices, actuators, and sensors under high-temperature conditions, showing great application potential in defense, aerospace, biomedicine, automotive, and energy exploration industries. However, during the 4D printing process, the rapid movement of the high-energy-density laser leads to rapid melting and cooling of the metal. Furthermore, each metal layer and each micro-melt pool undergoes periodic thermal cycling, which significantly impacts the microstructure and defect formation of the metal part. It is now possible to increase the content of high-temperature martensite phase with high phase transformation temperature in the room temperature microstructure of high-entropy high-temperature shape memory alloys through semi-solid isothermal heat treatment, thereby increasing the phase transformation temperature of the alloy; and the solidification shrinkage rate after solidification treatment is small, which can reduce the residual stress of the molded sample, improve the alloy microstructure and increase the density of the alloy. Summary of the Invention

[0003] The main objective of this invention is to propose a method for increasing the phase transformation temperature of high-temperature, high-entropy shape memory alloys in 4D printing. The aim is to improve the internal structural defects of 4D-printed high-temperature, high-entropy shape memory alloys and increase their phase transformation temperature through a semi-solid isothermal heat treatment method.

[0004] This invention relates to a method for increasing the phase transformation temperature of high-temperature, high-entropy shape memory alloys in 4D printing, comprising the following steps:

[0005] (1) 4D printing: The Ti25Zr12Hf13Ni25Cu18Co7 pre-alloy powder prepared by the rotating electrode method was formed by laser selective melting additive manufacturing;

[0006] (2) Semi-solid isothermal heat treatment: The printed alloy sample is heated to the semi-solid temperature between the solidus temperature TS and the liquidus temperature TL of the alloy, held for 5~15 minutes and then quickly water-quenched to obtain the semi-solid isothermal heat-treated sample.

[0007] A further technical solution of the present invention is:

[0008] In step (1), the Ti25Zr12Hf13Ni25Cu18Co7 pre-alloy powder used for laser selective melting additive manufacturing is prepared by the rotating electrode method.

[0009] A further technical solution of the present invention is:

[0010] In step (1), the size of the Ti25Zr12Hf13Ni25Cu18Co7 pre-formed alloy powder used for laser selective melting additive manufacturing is 15~53μm.

[0011] A further technical solution of the present invention is:

[0012] In step (1), the process conditions for laser selective melting additive manufacturing are: laser power of 160W, laser scanning speed of 800mm / s, laser scanning spacing of 80μm, and powder layer thickness of 30μm.

[0013] A further technical solution of the present invention is:

[0014] In step (2), the semi-solid isothermal treatment temperature is between the solidus temperature TS and the liquidus temperature TL of the alloy.

[0015] A further technical solution of the present invention is:

[0016] In step (2), magnesium oxide powder is used to cover and protect the alloy during the semi-solid isothermal treatment process.

[0017] A further technical solution of the present invention is:

[0018] In step (2), under semi-solid isothermal treatment, the semi-solid isothermal treatment is performed for 5~15 minutes to obtain an alloy with higher density and higher phase transformation temperature.

[0019] The advantages of this invention are as follows: High-temperature, high-entropy shape memory alloys formed by 4D printing undergo semi-solid isothermal treatment. During the holding process, liquid and solid phases coexist. The liquid phase is an austenitic phase enriched with lower melting point components, while the solid phase is an austenitic phase enriched with higher melting point components. After water quenching, the content of high-temperature martensite phase with a high phase transformation temperature increases in the room temperature microstructure, thereby increasing the alloy's phase transformation temperature. Furthermore, the semi-solid isothermal treatment results in a smaller shrinkage rate during solidification, which can improve the alloy microstructure, reduce defects, and increase the alloy's density. 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 the structures shown in these drawings without creative effort. Figure 1 The microstructure of the 4D-printed Ti25Zr12Hf13Ni25Cu18Co7 high-temperature, high-entropy shape memory alloy provided in Comparative Example 1 of this invention; Figure 2 The microstructure of the 4D-printed Ti25Zr12Hf13Ni25Cu18Co7 high-temperature and high-entropy shape memory alloy provided in Embodiment 1 of the present invention after being subjected to a semi-solid isothermal treatment for 5 minutes. Figure 3 The microstructure of the 4D-printed Ti25Zr12Hf13Ni25Cu18Co7 high-temperature and high-entropy shape memory alloy provided in Embodiment 1 of the present invention after being subjected to a semi-solid isothermal treatment for 10 minutes. Figure 4 The microstructure of the 4D-printed Ti25Zr12Hf13Ni25Cu18Co7 high-temperature, high-entropy shape memory alloy provided in Embodiment 1 of the present invention after semi-solid isothermal treatment for 15 minutes is shown below. The realization of the purpose, functional characteristics, and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0021] In its specific implementation, this invention proposes a method for increasing the phase transformation temperature of high-temperature, high-entropy shape memory alloys in 4D printing, comprising the following steps:

[0022] (1) 4D printing: The Ti25Zr12Hf13Ni25Cu18Co7 pre-alloy powder prepared by the rotating electrode method was formed by laser selective melting additive manufacturing;

[0023] (2) Semi-solid isothermal heat treatment: The printed alloy sample is heated to the semi-solid temperature between the solidus temperature TS and the liquidus temperature TL of the alloy, held for 5~15 minutes and then quickly water-quenched to obtain the semi-solid isothermal heat-treated sample.

[0024] To make the objectives and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially. Furthermore, the meaning of "and / or" throughout the text includes three parallel solutions; for example, "A and / or B" includes solution A, solution B, or a solution that simultaneously satisfies A and B. In addition, the technical solutions of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0025] This implementation provides a method for increasing the phase transformation temperature of high-temperature, high-entropy shape memory alloys in 4D printing, including the following steps:

[0026] (1) 4D printing: The Ti25Zr12Hf13Ni25Cu18Co7 pre-alloy powder prepared by the rotating electrode method was formed by laser selective melting additive manufacturing;

[0027] (2) Semi-solid isothermal heat treatment: The printed alloy sample is heated to the semi-solid temperature between the solidus temperature TS and the liquidus temperature TL of the alloy, held for 5 minutes and then quickly water-quenched to obtain a semi-solid isothermal heat-treated sample. Example 2

[0028] This implementation provides a method for increasing the phase transformation temperature of high-temperature, high-entropy shape memory alloys in 4D printing, including the following steps:

[0029] (1) 4D printing: The Ti25Zr12Hf13Ni25Cu18Co7 pre-alloy powder prepared by the rotating electrode method was formed by laser selective melting additive manufacturing;

[0030] (2) Semi-solid isothermal heat treatment: The printed alloy sample is heated to the semi-solid temperature between the solidus temperature TS and the liquidus temperature TL of the alloy, held for 10 min and then quickly water-quenched to obtain a semi-solid isothermal heat-treated sample. Example 3

[0031] This implementation provides a method for increasing the phase transformation temperature of high-temperature, high-entropy shape memory alloys in 4D printing, including the following steps:

[0032] (1) 4D printing: The Ti25Zr12Hf13Ni25Cu18Co7 pre-alloy powder prepared by the rotating electrode method was formed by laser selective melting additive manufacturing;

[0033] (2) Semi-solid isothermal heat treatment: The printed alloy sample is heated to the semi-solid temperature between the solidus temperature TS and the liquidus temperature TL of the alloy, held for 15 minutes and then quickly water-quenched to obtain a semi-solid isothermal heat-treated sample.

[0034] Comparative Example 1

[0035] This embodiment provides a method to increase the phase transformation temperature of high-temperature, high-entropy shape memory alloys in 4D printing. The pre-made alloy powder of Ti25Zr12Hf13Ni25Cu18Co7 prepared by the rotating electrode method is formed by selective laser melting additive manufacturing.

[0036] 1.1 Microstructure

[0037] Compared to Figure 1 Comparative Example 1 provides a 4D-printed Ti25Zr12Hf13Ni25Cu18Co7 high-temperature, high-entropy shape memory alloy. Figure 2 Example 1 Figure 3 Example 2 Figure 4 The 4D-printed high-temperature, high-entropy shape memory alloy Ti25Zr12Hf13Ni25Cu18Co7, provided in Example 3, exhibits reduced microstructure defects and increased density after semi-solid isothermal heat treatment.

[0038] 1.2 Phase transition temperature

[0039] High-temperature, high-entropy shape memory alloys exhibit thermoelastic martensitic phase transformation behavior. The phase transformation temperature was measured using differential scanning calorimetry (DSC). The test results are shown in Table 1, where Ms, Mf, As, and Af represent the start and end temperatures of the martensitic phase transformation, and the start and end temperatures of the reverse martensitic phase transformation, respectively. Table 1 clearly shows that, compared to Comparative Example 1, the Ti25Zr12Hf13Ni25Cu18Co7 high-temperature, high-entropy shape memory alloys obtained in Examples 1, 2, and 3 have higher phase transformation temperatures in Examples 1, 2, and 3.

[0040] Table 1:

[0041] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for improving the phase transition temperature of a 4D printed high-temperature high-entropy shape memory alloy, characterized in that, Comprising the following steps: (1) 4D printing forming: Ti 25 Zr 12 Hf 13 Ni 25 Cu 18 Co7 pre-alloyed powder is formed by laser selective melting additive manufacturing; (2) Semi-solid isothermal heat treatment: the printed alloy sample is heated to semi-solid temperature between solidus temperature and liquidus temperature of the alloy, and held for 5-15 min, and then rapidly water quenched to obtain semi-solid isothermal heat treatment sample. T S and liquidus temperature T L between solidus temperature and liquidus temperature of the alloy, and held for 5-15 min, and then rapidly water quenched to obtain semi-solid isothermal heat treatment sample. 2.The method of claim 1, wherein the high-temperature high-entropy shape memory alloy is a 4D printing high-temperature high-entropy shape memory alloy. Ti for laser selective melting additive manufacturing as described in step (1) 25 Zr 12 Hf 13 Ni 25 Cu 18 The pre-alloyed powder size of Co7 is 15-53 pm. 3.The method of claim 1, wherein the high-temperature high-entropy shape memory alloy is a 4D printing high-temperature high-entropy shape memory alloy. The process conditions for selective laser melting additive manufacturing in step (1) are as follows: laser power is 160 W, laser scanning speed is 800 mm / s, laser scanning interval is 80 μm, and powder layer thickness is 30 μm. 4.The method of claim 1, wherein the high-temperature high-entropy shape memory alloy is a 4D printing high-temperature high-entropy shape memory alloy. In step (2), magnesium oxide powder is used to cover and protect the alloy during semi-solid isothermal heat treatment.

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