Design method and preparation method of low-melting-point GaInSnBiZn liquid metal

Abstract

The invention discloses a design method and a preparation method of low-melting-point high-entropy liquid metal GaInSnBiZn, and belongs to the field of alloy research and development. The liquid metal alloy is formed by mixing five metal elements including Ga, In, Sn, Bi and Zn according to the equal atomic proportion, and aims at avoiding formation of intermetallic compounds and optimizing the microstructure through the high-entropy effect, and low melting point, high stability and good mechanical property of the alloy are achieved. The mixing enthalpy of the binary alloy and the formation enthalpy of the ternary alloy are calculated, thermodynamic analysis and phase diagram research are combined, the proportion of the five elements is determined, the high-entropy alloy is prepared through a vacuum arc melting method under the high vacuum condition, and the high purity and stability of the high-entropy alloy are ensured. The liquid alloy is low in melting point and high in stability, theoretical guidance and technical support are provided for design and preparation methods of novel liquid metal materials, some limitations in the prior art are overcome, and the liquid alloy has high practical application value.

Description

Technical Field

[0001] The present invention relates to the technical field of alloy research and development, and specifically to a design method and a preparation method for a low-melting-point GaInSnBiZn liquid metal. Background Art

[0002] As a new type of functional material, the unique physical and chemical behaviors of liquid metals are attracting increasing attention, with representative ones including gallium-based alloys, bismuth-based alloys, etc. Generally, liquid metals are defined as a class of metals or alloys with low melting points, whose melting points are below or close to room temperature, or even below 100 °C, and whose properties may change with the changes in alloy composition and ratio. In recent years, these metals have attracted extensive attention in the fields of basic science and engineering. Liquid metals have attracted much attention because they possess a variety of excellent inherent properties, including metallic properties, amorphous characteristics (such as excellent fluidity, morphological plasticity, excellent flexibility, low viscosity, and self-healing ability), and more superior properties (easy to transform from liquid to solid at room temperature, good biocompatibility, low toxicity, biodegradability, easy to carry out functional treatment, having catalytic effects, and responding to stimuli).

[0003] For liquid metals composed of single-phase metal elements and having eutectic structures, such as pure gallium, eutectic gallium-indium alloy E-GaIn (Ga75.5-In24.5), eutectic gallium-tin alloy E-GaSn (Ga86.3-Sn13.7), eutectic gallium-indium-tin alloy E-GaInSn (Ga67-In20.5-Sn12.5), etc., they can maintain uniform distribution, without separation regions, and melt synchronously at a single melting point, remaining in a liquid state. These materials can dissolve trace amounts of additional elements (such as transition metals, lanthanide elements, silicon, and phosphorus) in the molten state. However, the arrangement of atoms in the liquid state is still controversial and not yet clear. In the solid state, the additional atoms may replace or occupy interstitial positions, depending on the size of the added elements. Although the weight fractions of these trace elements often are lower than 1 wt.%, they may have a profound impact on the physical and chemical properties of liquid metals. For example, trace amounts of platinum dissolve naturally in liquid gallium (remaining liquid without atomic separation), which can activate the surrounding gallium atoms and play a catalytic role.

[0004] Biphasic liquid metal materials can be formed by changing the eutectic composition or adding metal elements beyond the solubility limit. When the internal solid-phase particles are small and do not precipitate, the biphasic liquid metal can remain stable in a homogeneous colloidal suspension. Compared with eutectic liquid metals, biphasic liquid metals require a higher temperature to form a single-phase state. During the gradual melting process, the compositions of the liquid phase and the solid phase may change with temperature, and the morphology may also change from solid to slurry and finally to liquid. The final melting point depends on the number of solid domains and the melting point temperature of possible intermetallic compounds. When cooling from the single-phase state, nucleation and phase separation occur, forming biphasic liquid metal materials. This unique phase separation behavior may lead to new properties and applications. For example, when the solute metal in a homogeneous liquid alloy cools with the gallium solvent, once the solubility is exceeded, the solute metal will precipitate from the liquid metal solvent in the form of crystals.

[0005] The multi-component characteristics of liquid metal alloys exhibit a variety of attractive features, which are crucial for fully realizing their potential value. Multi-component alloy liquid metals have the characteristics of low melting point and high boiling point, so they can maintain fluidity within a very wide temperature range. Taking gallium as an example, it has both covalent and metallic bonding in the solid state, with a relatively low melting point (about 29.8 °C) and a high boiling point (about 2204.8 °C). The melting temperature is greatly affected by the crystal structure. A larger atomic spacing means weaker bonding, which is more conducive to breaking the crystal structure at a lower temperature, and the high boiling point may be due to the presence of unpaired p-shell electrons, which can form covalent dimers of gallium atoms that are difficult to break. For liquid metals based on binary, ternary or multi-metal elements, their melting points and boiling points can also be maintained within a wide range. For example, for typical binary, ternary or multi-metal element liquid metals (such as GaIn24.5, GaIn21.5Sn10 and GaIn25Sn13Zn1), their melting points and boiling points are approximately 15.5 °C, 10.0 °C, 7.6 °C; 2000 °C, 1300 °C and >900 °C respectively. Tsinghua University has statistically analyzed the physical properties of important multi-component liquid metals, providing guiding opinions for their design, as shown in Table 1.

[0006] Table 1 Physical properties of some important liquid metals

[0007]

[0008]

[0009] Through the above analysis, the problems and defects of the existing technologies are as follows: The current mainstream liquid metal materials are still mainly binary and ternary alloys (such as E-GaIn, E-GaSn, etc.). Although certain progress has been made in their composition design and property regulation, the systematic research on multi-component liquid metals (such as quaternary and above) is still relatively scarce, which limits the performance optimization of the materials in a wider temperature range and complex scenarios. In addition, although the melting points of existing liquid metals are already close to room temperature, further reducing the melting point and broadening the liquid temperature range still face challenges. Especially in multi-component systems, the element compatibility, phase separation behavior, and solid-liquid transformation mechanism have not been fully clarified. For example, although gallium-based alloys (such as GaInSnZn) can achieve an ultra-low melting point (such as 7.6 °C) through multi-element doping, the influence of their composition ratio, atomic arrangement, and the synergistic effect of trace elements on the performance lacks theoretical guidance, resulting in material design relying on empirical trial and error. In addition, multi-component liquid metals are prone to losing uniformity due to element segregation or the formation of intermetallic compounds during the preparation process, and their long-term stability at high temperatures still needs to be verified.

[0010] Therefore, there is an urgent need to develop a new type of liquid metal system with both ultra-low melting point, high stability, and functional customization through multi-component composition design and atomic-level structure regulation to meet the urgent needs of high-performance liquid metals in frontier fields such as flexible electronics and low-temperature soldering. Summary of the Invention

[0011] In view of this, the present invention provides a design method and a preparation method for a multi-component high-entropy low-melting-point GaInSnBiZn liquid alloy.

[0012] To achieve the above object, the present invention adopts the following technical solutions:

[0013] A design method for a low-melting-point GaInSnBiZn liquid metal, comprising the following steps:

[0014] (1) Determine the alloying elements and their thermodynamic parameters: Select five elements, namely Ga, In, Sn, Bi, and Zn, as alloy components, and then calculate the mixing enthalpy of any binary alloy and the formation enthalpy of ternary alloys based on the Miedema model;

[0015] (2) Analyze the binary phase diagram and intermetallic compounds: The calculated mixing enthalpies of the In-Sn and In-Bi systems are negative, while those of the other systems are positive; It is analyzed and determined that there is a solid solution in the In-Sn system without the formation of intermetallic compounds; In the In-Bi system, there is a phase change between BiIn 2 and the Bi-containing solid solution at 49 °C;

[0016] (3) Study the enthalpy of formation of ternary alloys and compound formation: Analyze the enthalpy of formation of ternary alloys. The calculation results show that there are no ternary compounds during the alloy formation process, proving the compatibility of multi-component alloys;

[0017] (4) Design the composition ratio of high-entropy alloys: Based on the thermodynamic analysis and phase diagram study in steps (1)-(3), determine to mix five elements, Ga, In, Sn, Bi, and Zn, in equal atomic ratios to meet the thermodynamic conditions for the formation of high-entropy alloys;

[0018] (5) Prepare the GaInSnBiZn high-entropy alloy: Select the corresponding pure metal sheets of the GaInSnBiZn high-entropy alloy in an atomic ratio of 1:1:1:1:1. Cut them into pieces and place them in a corundum crucible. Heat them to 425 °C under vacuum conditions and keep them warm for 30 min, and then rapidly cool to obtain the GaInSnBiZn high-entropy alloy.

[0019] Furthermore, in the binary alloys of step (2): The mixing enthalpy of the Ga-In system is 10.177 kJ / mol; the mixing enthalpy of the Ga-Sn system is 3.239 kJ / mol; the mixing enthalpy of the Ga-Bi system is 14.342 kJ / mol; the mixing enthalpy of the Ga-Zn system is 0.064 kJ / mol; the mixing enthalpy of the In-Zn system is 14.193 kJ / mol; the mixing enthalpy of the In-Sn system is -1.415 kJ / mol; the mixing enthalpy of the In-Bi system is -4.738 kJ / mol; the mixing enthalpy of the Sn-Bi system is 4.808 kJ / mol; the mixing enthalpy of the Sn-Zn system is 5.272 kJ / mol; the mixing enthalpy of the Bi-Zn system is 22.764 kJ / mol.

[0020] Furthermore, in the In-Bi system, BiIn, Bi 3 In 5 and BiIn 2 three intermetallic compounds can be formed, and their melting points are 110 °C, 88.9 °C, and 89.5 °C respectively.

[0021] Furthermore, in the ternary alloy of step (3): the enthalpy of formation of the Ga-In-Sn system is 2.077 kJ / mol; the enthalpy of formation of the Ga-In-Bi system is 3.484 kJ / mol; the enthalpy of formation of the Ga-In-Zn system is 3.944 kJ / mol; the enthalpy of formation of the Ga-Sn-Bi system is 4.169 kJ / mol; the enthalpy of formation of the Ga-Sn-Zn system is 4.169 kJ / mol; the enthalpy of formation of the Ga-Bi-Zn system is 5.980 kJ / mol; the enthalpy of formation of the In-Sn-Bi system is 0.229 kJ / mol; the enthalpy of formation of the In-Sn-Zn system is 2.198 kJ / mol; the enthalpy of formation of the In-Bi-Zn system is 3.444 kJ / mol; the enthalpy of formation of the Sn-Bi-Zn system is 4.238 kJ / mol.

[0022] Furthermore, in step (4), through the thermodynamic analysis and phase diagram study of steps (1)-(3) of the present invention, first assume an equiatomic ratio mixture of the five elements, and then calculate the mixing entropy. The obtained result conforms to a high-entropy alloy. Combining the previous thermodynamics and phase diagram, it is determined that the alloy with an equal ratio designed by the present invention meets the conditions of a high-entropy alloy.

[0023] Furthermore, in the present invention, during the design of the high-entropy alloy, the mixing entropy needs to be between 11 J / mol*K and 17.5 J / mol*K. The mixing entropy is related to the ratio of each element in the alloy, and the alloy with an equal ratio has the highest mixing entropy. According to the calculation formula of the mixing entropy:

[0024]

[0025] where R is the gas constant, c i is the atomic fraction of the i-th element, and n is the number of elements (n = 5 in the present invention). Through calculation, the mixing entropy of the designed low-melting-point GaInSnBiZn alloy is 13.38 J / mol*K, belonging to a high-entropy alloy.

[0026] Furthermore, in step (5), the vacuum condition is 10 -3 Pa.

[0027] The design of the low-melting-point high-entropy liquid metal GaInSnBiZn in the present invention follows the following principles:

[0028] (1) High mixing entropy effect: The high mixing entropy effect is the key to the design of low-melting-point liquid metals. It refers to an alloy composed of multiple elements, in which the atomic ratio of each element is relatively uniform, which helps to increase the entropy value and lower the melting point. Although the mixing of multiple elements will increase the complexity of the alloy, it will also enhance the mixing entropy effect.

[0029] (2) Avoid the formation of intermetallic compounds: Intermetallic compounds usually have a higher melting point and will affect the overall melting point of the alloy. Therefore, in the alloy design process, it is necessary to avoid or reduce the formation of intermetallic compounds to ensure that the melting point of the alloy is as low as possible.

[0030] (3) Thermodynamic stability: It is crucial to ensure that the alloy maintains thermodynamic stability within a specific temperature range and avoid phase changes or chemical reactions that increase the melting point. To achieve this, a deep understanding of the interactions and thermodynamic properties of the elements is required.

[0031] (4) Microstructure optimization: The microstructure of an alloy has a significant impact on its performance and melting point. By regulating the grain size, grain boundaries and other microstructural parameters of the alloy, the melting point and other physical and chemical properties of the alloy can be optimized.

[0032] The present invention also provides a method for preparing the low-melting-point GaInSnBiZn liquid metal, comprising the following steps:

[0033] 1) Ingredients: Select pure metal sheets corresponding to the five elements of Ga, In, Sn, Bi and Zn, cut them into pieces and place them in corundum crucibles respectively;

[0034] 2) Cleaning: The cut pure metal sheets are subjected to ultrasonic treatment to remove impurities, and then the surface is blown dry;

[0035] 3) Mixing: Mix the cleaned metal sheets evenly in an equal molar ratio and set aside;

[0036] 4) Vacuum melting: The mixed metal sheets are placed in a vacuum arc furnace for vacuum melting to obtain GaInSnBiZn alloy beads.

[0037] Furthermore, in step 2), acetone or alcohol is used for ultrasonic cleaning.

[0038] Further, the vacuum melting method in step 4) comprises: placing the mixed metal sheets in a water-cooled copper crucible of a vacuum arc melting furnace, and evacuating the arc melting furnace to 10 -3 Below Pa, pure argon was filled in, and the tungsten rocker arm was swung to start melting; the temperature was kept at 425°C for 30 minutes, and the heating was stopped after the raw materials were completely melted, and then the furnace was cooled to obtain GaInSnBiZn alloy beads.

[0039] The beneficial effects of the present invention are:

[0040] (1) The GaInSnBiZn alloy of the present invention has simple composition and reasonable design. On the basis of the traditional ternary liquid metal GaInSn, by introducing Bi and Zn elements into the GaInSn alloy system, multiple properties of the alloy are comprehensively improved, which may include the following points:

[0041] ①The addition of Bi and Zn works together to help lower the melting point of the alloy, enabling welding or other heat treatments to be carried out at lower temperatures.

[0042] ②Zn refines the grain size and increases the hardness of the alloy, while Bi improves the structural uniformity and corrosion resistance of the alloy. The synergistic effect of the two makes the alloy more stable during use and has excellent mechanical properties.

[0043] ③The addition of Zn improves the thermal stability of the alloy, and the addition of Bi helps enhance the stability of the alloy in a corrosive environment, enabling it to maintain good performance under various working conditions.

[0044] (2) The present invention ensures that intermetallic compounds in the alloy do not form or are limited to a relatively stable solid solution structure, thus avoiding the high melting point problem caused by intermetallic compounds in traditional alloys. This feature greatly improves the operability of the alloy in the manufacturing process, enabling brazing and other processing operations to be carried out at lower temperatures. During the rapid cooling process, the alloy exists in a liquid phase, which can effectively relieve the interfacial stress to adapt to a faster cooling rate without cracking.

[0045] (3) Compared with the prior art, the preparation method of the present invention adopts the vacuum arc melting technology under high vacuum conditions, and has high requirements for the purity of raw materials. The preparation process is relatively simple and easy to scale up production. This not only reduces the cost of alloy production, but also ensures the purity and stability of the alloy.

[0046] (4) Through hardness testing, the GaInSnBiZn high-entropy alloy of the present invention significantly increases the hardness value. Compared with traditional quinary alloys, its grain size is smaller, which hinders the enrichment of Bi, Sn, and In, thus increasing the hardness of the alloy. Through resistivity testing, the results show that the resistivity of the alloy is 45.32 μΩ·cm, meeting the performance requirements of most high-entropy alloys, and the surface oxidation is properly controlled to ensure the reliability of the alloy in high-temperature and harsh environments.

[0047] (5) The technical solution of the present invention overcomes some technical prejudices:

[0048] Traditionally, low-melting-point solders (such as tin-based alloys) have often been considered inferior to high-melting-point solders (such as silver solders or copper solders) in terms of strength and thermal stability. The main reason for this prejudice is that low-melting-point solders are thought to be unable to withstand the mechanical stress and temperature changes that may occur during the long-term use of 3C products. Secondly, low-melting-point solders have poor corrosion resistance and environmental stability, especially in complex environments such as humidity and thermal cycling during the long-term use of electronic products. Moreover, traditional low-melting-point solders are generally considered to have poor electrical conductivity, especially in applications where high-frequency and high-density currents pass through, which may affect the electrical performance of 3C products. Finally, low-melting-point solders often face the problem of poor surface wetting during the soldering process, especially when soldering metals come into contact with different materials such as ceramics and glass, and it is often difficult to form a stable soldering interface. The GaInSnBiZn alloy designed in the present invention has a lower melting point (lower than common SnPb or SnAg alloys) through precise design of its composition. However, after adding Bi and Zn elements, the hardness and strength of the alloy are improved. The addition of Bi element can improve its corrosion resistance. The addition of Zn not only improves the thermal stability of the GaInSnBiZn alloy but also increases its electrical conductivity. Both elements have the advantage of improving the wetting property of the alloy. Therefore, the GaInSnBiZn alloy designed in the present invention has a wide range of uses in the connection of dissimilar materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 It is a flow chart of the design method of the liquid metal GaInSnBiZn provided by the present invention;

[0050] Figure 2 It is a flow chart of the preparation method of the liquid metal GaInSnBiZn provided by the present invention;

[0051] Figure 3 It is the microscopic morphology (a) and local enlarged image (b) of the GaInSnBiZn alloy prepared in the embodiment of the present invention observed under SEM;

[0052] Figure 4 It is the XRD pattern of the GaInSnBiZn alloy prepared in the embodiment of the present invention after XRD testing;

[0053] Figure 5 It is the DSC curve of the GaInSnBiZn alloy prepared in the embodiment of the present invention after DSC testing. DETAILED DESCRIPTION OF THE INVENTION

[0054] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0055] Embodiment 1

[0056] A design method for a low-melting-point GaInSnBiZn liquid metal, comprising the following steps:

[0057] (1) Determine alloy elements and their thermodynamic parameters: Select five elements, namely Ga, In, Sn, Bi, and Zn, as alloy components, and then calculate the mixing enthalpy of any binary alloy and the formation enthalpy of a ternary alloy based on the Miedema model;

[0058] (2) Analyze binary phase diagrams and intermetallic compounds: The calculated results show that the mixing enthalpy of the Ga-In system is 10.177 kJ / mol; the mixing enthalpy of the Ga-Sn system is 3.239 kJ / mol; the mixing enthalpy of the Ga-Bi system is 14.342 kJ / mol; the mixing enthalpy of the Ga-Zn system is 0.064 kJ / mol; the mixing enthalpy of the In-Zn system is 14.193 kJ / mol; the mixing enthalpy of the In-Sn system is -1.415 kJ / mol; the mixing enthalpy of the In-Bi system is -4.738 kJ / mol; the mixing enthalpy of the Sn-Bi system is 4.808 kJ / mol; the mixing enthalpy of the Sn-Zn system is 5.272 kJ / mol; the mixing enthalpy of the Bi-Zn system is 22.764 kJ / mol.

[0059] The mixing enthalpies of the In-Sn and In-Bi systems are negative, and the mixing enthalpies of the remaining systems are positive; it is analyzed and determined that there is a solid solution in the In-Sn system, and no intermetallic compound is formed; the In-Bi system can form three intermetallic compounds, namely BiIn, Bi 3 In 5 and BiIn 2 The melting points of the three intermetallic compounds are 110 °C, 88.9 °C, and 89.5 °C respectively, and there is a phase change between BiIn 2 and the Bi-containing solid solution at 49 °C;

[0060] (3) Study on the formation enthalpy of ternary alloys and compound formation: The formation enthalpy of ternary alloys was analyzed. The results showed that the formation enthalpy of Ga-In-Sn system was 2.077 kJ / mol; the formation enthalpy of Ga-In-Bi system was 3.484 kJ / mol; the formation enthalpy of Ga-In-Zn system was 3.944 kJ / mol; the formation enthalpy of Ga-Sn-Bi system was 4.169 kJ / mol; the formation enthalpy of Ga-Sn-Zn system was 4.169 kJ / mol. The formation enthalpy of Ga-Bi-Zn system is 5.980 kJ / mol; the formation enthalpy of In-Sn-Bi system is 0.229 kJ / mol; the formation enthalpy of In-Sn-Zn system is 2.198 kJ / mol; the formation enthalpy of In-Bi-Zn system is 3.444 kJ / mol; the formation enthalpy of Sn-Bi-Zn system is 4.238 kJ / mol. The calculation results show that there is no ternary compound in the alloy formation process, proving the compatibility of multi-component alloys.

[0061] (4) Designing the composition ratio of the high entropy alloy: Based on the thermodynamic analysis and phase diagram study of steps (1) to (3), it is determined that the five elements Ga, In, Sn, Bi, and Zn are mixed in an equiatomic ratio to meet the thermodynamic conditions for the formation of a high entropy alloy;

[0062] (5) Preparation of GaInSnBiZn high entropy alloy: The corresponding pure metal sheets were selected with an atomic ratio of 1:1:1:1:1 for GaInSnBiZn high entropy alloy, cut into pieces and placed in a corundum crucible. -3 The alloy was heated to 425℃ and kept for 30min under vacuum conditions and then rapidly cooled to obtain GaInSnBiZn high entropy alloy.

[0063] Example 2 A method for preparing a low melting point GaInSnBiZn liquid metal:

[0064] 1) Ingredients: Select pure metal sheets corresponding to the five elements of Ga, In, Sn, Bi and Zn, cut them into pieces and place them in corundum crucibles respectively;

[0065] 2) Cleaning: Use acetone to ultrasonically clean the cut pure metal sheets to remove impurities, and then blow dry the surface;

[0066] 3) Mixing: Mix the cleaned metal sheets evenly in an equal molar ratio and set aside;

[0067] 4) Vacuum melting: Place the mixed metal pieces in a water-cooled copper crucible in a vacuum arc melting furnace and use a mechanical pump to evacuate the arc melting furnace to 10 -3Below Pa, pure argon gas was filled in, and the tungsten electrode swing arm started melting; it was kept at 425 °C for 30 min, heating was stopped after the raw materials were completely melted, and then it was cooled in the furnace to obtain GaInSnBiZn alloy beads (0.2 g).

[0068] Test Example 1

[0069] The GaInSnBiZn alloy was tested by SEM, EDS, XRD, DSC, hardness, and resistivity.

[0070] 1.1 Surface morphology: The surface microstructure was characterized by combining SEM and EDS, as Figure 3 shown. According to Figure 3 (a) The elemental distribution map shows that the five elements in the alloy are evenly distributed, showing an irregular and well-mixed pattern. This uniformity is one of the characteristics pursued by high-entropy alloys, demonstrating the well-mixed nature of its multi-element composition and high material homogeneity, indicating that the GaInSnBiZn prepared with an equiatomic ratio is a high-entropy alloy. Further observing its local enlarged image ( Figure 3 (b)), it can be clearly found that there are three regions: a small amount of black irregular regions rich in Ga and Zn elements; dark gray regions rich in Sn elements; light gray regions rich in In and Bi elements;

[0071] 1.2 XRD test: When designing a low-melting-point high-entropy alloy, the formation of intermetallic compounds should be minimized or avoided as much as possible to maintain a uniform solid-solution structure. This uniform structure may help improve the toughness, ductility, and corrosion resistance of the material. The XRD pattern of the alloy after solidification is as Figure 4 shown. The alloy shows a relatively uniform structure at the microscopic level, without obvious phase separation or compound formation, meeting the expectations. This structural feature may help improve the overall performance of the alloy and make it more promising for engineering applications.

[0072] 1.3 DSC test: The synchronous thermal analysis pattern of the GaInSnBiZn alloy shows its thermal behavior during heating from 5 °C / min to 180 °C, as specifically Figure 5 shown. In the curve, two significant endothermic peaks were observed. First, an endothermic peak appeared at 49.6 °C, corresponding to the temperature point of the phase change between BiIn 2 and the Bi-containing solid solution in In in the phase diagram. Second, a more significant endothermic peak appeared around 62.4 °C, corresponding to the melting point of the alloy. The observation of these endothermic peaks provides important information about the thermodynamic behavior of the alloy. In particular, the phase change temperature point of 49.6 °C indicates a specific change in the internal structure of the alloy, which may affect its properties and applications.

[0073] 1.4 Hardness test: The polished alloy was subjected to microhardness test, and the constant load was set to 147.09N, and the holding time was 10s. During the test, the hardness values ​​of 15 different positions were taken, and the average value was calculated after excluding the maximum and minimum test values. The microhardness value of GaInSnBiZn alloy is 0.7383GPa, which is significantly higher than that of Ga 4.6 In 22.6 Sn 28.5 Bi 39.3 Zn 5 alloy. Further analysis showed that the formation of Zn at the grain boundary hindered the growth of Bi, Sn and In-rich grains. This resulted in a relatively small grain size in the alloy. Compared with other quinary alloys with larger grains, the presence of such smaller grains may be one of the reasons for the increased hardness of the alloy. 4.6 In 22.6 Sn 28.5 Bi 39.3 Zn 5 In comparison, the GaInSnBiZn alloy with an equiatomic ratio contains more Zn element, which is one of the reasons why the alloy has better hardness.

[0074] 1.5 Resistivity test: The GaInSnBiZn alloy was prepared into a circular sheet with a diameter of 1 cm and a thickness of 0.5 mm, and the resistivity of the alloy was tested using a four-probe resistivity tester. Four probe electrodes were installed on the sample to be tested, two external probe electrodes (transmitting electrodes) applied a current of 0.416A, and two internal probes (receiving electrodes) were used to measure the voltage. Multiple tests were performed to ensure accuracy and stability: Where ρ is the resistivity, V is the measured voltage, I is the applied current, and A is the distance between the probe electrodes. The measurement results show that the resistivity of the GaInSnBiZn alloy is 45.32μΩ·cm.

[0075] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A design method for low melting point GaInSnBiZn liquid metal, characterized in that: The following steps are involved: (1) Determine the alloying elements and their thermodynamic parameters: Select five elements, Ga, In, Sn, Bi, and Zn, as alloying components, and then calculate the mixing enthalpy of any binary alloy and the formation enthalpy of the ternary alloy based on the Miedema model; (2) Analysis of binary phase diagrams and intermetallic compounds: The calculated mixing enthalpy of the In-Sn and In-Bi systems is negative, while the mixing enthalpy of the other systems is positive; the analysis confirms that there is a solid solution in the In-Sn system, but no intermetallic compound is formed; in the In-Bi system, there is a phase transition between BiIn2 and the Bi-containing solid solution at 49°C; (3) Study on the formation enthalpy of ternary alloys and compound formation: The formation enthalpy of ternary alloys was analyzed and the calculation results showed that there were no ternary compounds in the alloy formation process, proving the compatibility of multi-component alloys; (4) Designing the composition ratio of the high entropy alloy: Based on the thermodynamic analysis and phase diagram study of steps (1) to (3), it is determined that the five elements Ga, In, Sn, Bi, and Zn are mixed in an equiatomic ratio to meet the thermodynamic conditions for the formation of a high entropy alloy; (5) Preparation of GaInSnBiZn high entropy alloy: Pure metal sheets corresponding to the GaInSnBiZn high entropy alloy were selected in an atomic ratio of 1:1:1:1:1, cut into pieces and placed in a corundum crucible, heated to 425°C under vacuum conditions for 30 min, and then rapidly cooled to obtain the GaInSnBiZn high entropy alloy.

2. The design method of a low melting point GaInSnBiZn liquid metal according to claim 1, characterized in that: In the binary alloy of step (2): the mixing enthalpy of the Ga-In system is 10.177 kJ / mol; the mixing enthalpy of the Ga-Sn system is 3.239 kJ / mol; the mixing enthalpy of the Ga-Bi system is 14.342 kJ / mol; the mixing enthalpy of the Ga-Zn system is 0.064 kJ / mol; the mixing enthalpy of the In-Zn system is 14.193 kJ / mol; the mixing enthalpy of the In-Sn system is -1.415 kJ / mol; the mixing enthalpy of the In-Bi system is -4.738 kJ / mol; the mixing enthalpy of the Sn-Bi system is 4.808 kJ / mol; the mixing enthalpy of the Sn-Zn system is 5.272 kJ / mol; and the mixing enthalpy of the Bi-Zn system is 22.764 kJ / mol.

3. The design method of a low melting point GaInSnBiZn liquid metal according to claim 2, characterized in that: The In-Bi system can generate three intermetallic compounds, BiIn, Bi3In5 and BiIn2, whose melting points are 110℃, 88.9℃ and 89.5℃ respectively.

4. The design method of a low melting point GaInSnBiZn liquid metal according to claim 1, characterized in that: In the ternary alloy of step (3): the formation enthalpy of the Ga-In-Sn system is 2.077 kJ / mol; the formation enthalpy of the Ga-In-Bi system is 3.484 kJ / mol; the formation enthalpy of the Ga-In-Zn system is 3.944 kJ / mol; the formation enthalpy of the Ga-Sn-Bi system is 4.169 kJ / mol; the formation enthalpy of the Ga-Sn-Zn system is 4.169 kJ / mol; The formation enthalpy of Ga-Bi-Zn system is 5.980 kJ / mol; the formation enthalpy of In-Sn-Bi system is 0.229 kJ / mol; the formation enthalpy of In-Sn-Zn system is 2.198 kJ / mol; the formation enthalpy of In-Bi-Zn system is 3.444 kJ / mol; the formation enthalpy of Sn-Bi-Zn system is 4.238 kJ / mol.

5. The design method of a low melting point GaInSnBiZn liquid metal according to claim 1, characterized in that: The vacuum condition in step (5) is 10 -3 Pa.

6. A method for preparing the low melting point GaInSnBiZn liquid metal according to any one of claims 1 to 5, characterized in that: The following steps are involved: 1) Ingredients: Select pure metal sheets corresponding to the five elements of Ga, In, Sn, Bi, and Zn, cut them into pieces, and place them in a corundum crucible respectively; 2) Cleaning: The cut pure metal sheets are subjected to ultrasonic treatment to remove impurities, and then the surface is blown dry; 3) Mixing: Mix the cleaned metal sheets evenly in an equal molar ratio and set aside; 4) Vacuum melting: The mixed metal sheets are placed in a vacuum arc furnace for vacuum melting to obtain GaInSnBiZn alloy beads.

7. A method for preparing a low melting point GaInSnBiZn liquid metal according to claim 6, characterized in that: In step 2), acetone or alcohol is used for ultrasonic cleaning.

8. The method for preparing a low melting point GaInSnBiZn liquid metal according to claim 6, characterized in that: The vacuum melting method in step 4) comprises: placing the mixed metal sheets in a water-cooled copper crucible of a vacuum arc melting furnace, and evacuating the arc melting furnace to 10 -3 Below Pa, pure argon was filled in, and the tungsten rocker arm was swung to start melting; the temperature was kept at 425℃ for 30min, and the heating was stopped after the raw materials were completely melted, and then the furnace was cooled to obtain GaInSnBiZn alloy beads.

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