Preparation method of high-hardness 1K gold composite material and application of high-hardness 1K gold composite material in ornaments

Abstract

The invention relates to the technical field of precious metal materials, and discloses a preparation method of a high-hardness 1K gold composite material and application of the high-hardness 1K gold composite material in ornaments.The method comprises the steps that trace rare earth elements are added into a gold-copper-based master alloy melt, then manganese and boron are added, and the manganese and the boron are subjected to an in-situ reaction at the high temperature to generate a manganese boride hard reinforced phase; the rare earth element regulates and controls the in-situ reaction process and inhibits coarse agglomeration of a reinforced phase, so that the reinforced phase is fine and uniformly dispersed and distributed in a metal matrix. The hardness and wear resistance of the prepared composite material are far higher than those of traditional 1K gold, and the composite material has excellent polishing performance, high glossiness and vulcanization discoloration resistance. The material disclosed by the invention solves the problem that the traditional 1K gold ornament is soft and easy to damage, and the base body formula can enable the gold content of 1K gold to reach an appearance visual effect close to that of 18K gold, so that the material is particularly suitable for manufacturing ornaments with high wear resistance requirements, such as rings and bracelets.

Description

Technical Field

[0001] This invention relates to the field of precious metal materials technology, and in particular to a method for preparing a high-hardness 1K gold composite material and its application in jewelry. Background Technology

[0002] 1K gold, also known as gold-plated copper or sub-gold, is a low-gold-content copper-based alloy. Due to its similar color and appearance to 18K gold and significantly lower cost, it has gained widespread use in the jewelry industry. However, existing commercially available 1K gold alloys generally have inherent defects. Its main matrix is ​​copper, resulting in low overall hardness and poor wear resistance. Jewelry made from this alloy is easily scratched or deformed by scratches and impacts during daily wear, severely affecting its aesthetics and durability. Furthermore, the high content of copper, silver, and other chemically reactive elements in the alloy makes it prone to oxidation or sulfidation reactions when exposed to air or contact with the human body, causing the surface of the jewelry to discolor, blacken, and lose its original metallic luster.

[0003] To address these performance deficiencies, existing technologies have attempted to improve hardness through solid solution strengthening or composite strengthening with the addition of hard particles. Solid solution strengthening has relatively limited effectiveness and fails to meet market demands for high wear resistance. Traditional composite strengthening methods with hard particles typically employ an external addition approach, directly adding pre-prepared hard particles such as ceramics to the molten metal. This method suffers from a significant technical bottleneck: the extremely poor wettability between the added particles and the molten metal leads to uneven dispersion and agglomeration, creating defect sources during subsequent casting and processing. These large, agglomerated particles not only fail to provide effective strengthening but also peel off from the matrix during polishing, causing pitting and dents on the surface of the jewelry, severely compromising the high-gloss surface quality essential for jewelry. Therefore, developing a novel 1K gold material and its preparation method that can significantly improve hardness and wear resistance while maintaining excellent surface gloss and chemical stability is a pressing technical challenge in this field. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a preparation method that can overcome the technical defects of existing 1K gold alloys, such as low hardness and poor wear resistance, while avoiding the sacrifice of the high gloss and chemical stability necessary for jewelry materials due to the introduction of hard phases for strengthening.

[0005] To address the above problems, the present invention provides the following technical solution:

[0006] In a first aspect, the present invention provides a method for preparing a high-hardness 1K gold composite material, which adopts the following technical solution:

[0007] A method for preparing a high-hardness 1K gold composite material includes the following steps:

[0008] (a) Provide a master alloy melt composed of gold, copper and at least one metallic element selected from silver, zinc and nickel;

[0009] (b) Add rare earth elements, manganese and boron to the master alloy melt;

[0010] (c) The manganese and boron are kept at a predetermined temperature and stirred so that the manganese and boron react in situ in the melt to generate manganese boride reinforcing phase, forming a composite material melt;

[0011] (d) The composite material melt is cast into shape.

[0012] By adopting the above technical solution, the core of the preparation method provided by this invention lies in generating a hard reinforcing phase in a metal matrix through in-situ liquid-phase chemical reaction, and effectively controlling the formation process of this reinforcing phase using rare earth elements, ultimately obtaining a composite material with excellent comprehensive performance. The specific technical principle is explained below:

[0013] 1. In-situ formation of hard reinforcing phase:

[0014] In a high-temperature molten environment, the added manganese and boron undergo a chemical reaction: Mn + 2B → MnB2, forming manganese diboride. Manganese diboride is a known stable compound with high hardness and a high melting point. This reaction occurs directly in the liquid phase of the master alloy, and the resulting product is the reinforcing phase. Compared to adding pre-formed powder from the outside, this in-situ formation method ensures a strong metallurgical bond between the reinforcing phase and the metal matrix.

[0015] 2. The role of rare earth elements in process regulation:

[0016] Another key aspect of this invention lies in the introduction of trace amounts of rare earth elements into the melt. The presence of rare earth elements significantly alters the final morphology and distribution of the manganese diboride reinforcing phase. Its effects are manifested in:

[0017] (i) Suppressing the formation of coarse particles: In systems without rare earth elements, in-situ generated manganese diboride particles tend to grow and aggregate, forming coarse agglomerates with uneven sizes. The addition of rare earth elements can effectively suppress this process, resulting in finer-sized reinforcing phase particles.

[0018] (ii) Promoting the uniform distribution of the reinforcing phase: Rare earth elements can improve the dispersion of the reinforcing phase in liquid metal and hinder the agglomeration between particles. Under the action of melt stirring, the fine reinforcing phase can be more uniformly suspended in the entire melt and captured by the matrix during the subsequent solidification process, forming a uniformly distributed structure.

[0019] In summary, the material prepared by the method of this invention has finely dispersed hard reinforcing phases that are firmly bonded to the matrix. This composite structure endows the material with excellent macroscopic properties: mechanically, the hard phase acts as a skeleton to effectively resist external scratches and wear, thereby significantly improving the material's hardness and wear resistance; optically, because the reinforcing phase is small in size and does not easily detach from the matrix during polishing, the material surface can be processed into a smooth mirror surface with very few defects, thus exhibiting high gloss; chemically, rare earth elements can also form a protective passivation film on the material surface, effectively blocking external corrosive media, thereby significantly improving the material's resistance to sulfide discoloration.

[0020] Preferably, the final chemical composition of the composite material comprises, by weight percentage: 4.10% to 4.60% gold, 0.50% to 2.00% manganese, 0.10% to 0.45% boron, 0.01% to 0.10% rare earth elements, with the balance being copper and at least one metallic element selected from silver, zinc, and nickel.

[0021] By adopting the above technical solution, the setting of the composition range ensures that the material meets the fineness standard of 1K gold, while providing sufficient reactants for in-situ reaction to generate an effective volume fraction of reinforcing phase, and controlling the content of rare earth elements within the optimal range that can be effectively regulated without damaging the matrix performance.

[0022] Preferably, the rare earth element is lanthanum or cerium.

[0023] By adopting the above technical solutions, lanthanum and cerium, as representatives of light rare earth elements, have active chemical properties, exhibit good process control effects in melts, and have relatively controllable costs, making them suitable for industrial applications.

[0024] Preferably, in step (b), the rare earth elements are first added and uniformly dispersed in the melt, and then the manganese and boron are added.

[0025] By adopting the above technical solution, the pre-addition of rare earth elements can achieve full dissolution and uniform distribution in the master alloy melt, thereby enabling them to exert their regulatory role on the formation process of the reinforcing phase when the subsequent in-situ reaction occurs.

[0026] Preferably, the predetermined temperature for the in-situ reaction is 1150℃~1300℃.

[0027] By adopting the above technical solution, this temperature range can ensure that the in-situ reaction has sufficient chemical driving force and reaction rate, so that the reaction can proceed relatively completely within a reasonable time, while avoiding problems such as violent volatilization of melt, severe element burn-off, and coarse grains in the final casting caused by excessively high temperature.

[0028] Secondly, this invention provides a high-hardness 1K gold composite material, which adopts the following technical solution:

[0029] A high-hardness 1K gold composite material, prepared by any of the methods described in the first aspect, comprises:

[0030] A metal matrix, comprising, by weight percentage, 4.10% to 4.60% gold, 0.01% to 0.10% rare earth elements, with the balance being copper and at least one metallic element selected from silver, zinc, and nickel; and

[0031] The manganese boride reinforcing phase is dispersed in the metal matrix and is generated by the in-situ reaction of manganese and boron in the matrix.

[0032] By adopting the above technical solution, the composite material provided by this invention consists of a continuous metal matrix and a hard reinforcing phase dispersed therein. The metal matrix mainly determines the inherent noble metal properties of the material, such as its base color and ductility. The manganese boride reinforcing phase, as a high-hardness compound, is the fundamental reason why the material achieves high hardness and high wear resistance.

[0033] The key innovation of this invention lies in the fact that the manganese boride reinforcing phase within the composite material possesses a fine-grained and uniformly distributed structural feature. This structural feature endows the material with a unique combination of properties:

[0034] First, the uniform dispersion of the hard phase makes the material appear as a homogeneous whole on a macroscopic scale, which can effectively suppress the plastic deformation of the matrix when subjected to stress, thereby achieving a hardness and wear resistance far exceeding that of traditional 1K gold alloys.

[0035] Secondly, the fine size of the reinforcing phase prevents the formation of microscopic pits on the surface during mirror polishing due to the peeling of hard particles. The material surface can be processed into a highly smooth mirror finish, achieving a gloss level comparable to homogeneous alloys, thus solving the technical challenge of polishing conventional composite materials due to the significant differences in hardness between phases.

[0036] In addition, the rare earth elements dissolved in the metal matrix can form a chemically stable passivation film on the material surface, thereby effectively improving the material's ability to resist corrosion from external sulfur-containing environments and giving it excellent anti-discoloration properties.

[0037] Thirdly, this invention provides an application of a high-hardness 1K gold composite material in jewelry manufacturing, employing the following technical solution:

[0038] The application of a high-hardness 1K gold composite material as described in the second aspect in jewelry manufacturing.

[0039] By adopting the above technical solution, the high-hardness 1K gold composite material prepared by this invention can be applied to jewelry manufacturing, effectively solving the inherent technical problems of traditional 1K gold jewelry. Although traditional 1K gold alloys have good color and processing performance, their low hardness makes the jewelry very prone to scratches, dents, and wear during daily wear, seriously affecting its appearance and service life.

[0040] The composite material of this invention exhibits significantly improved hardness and wear resistance due to the presence of dispersed, firmly bonded hard reinforcing phases within the matrix. Using this material in jewelry manufacturing significantly enhances the jewelry's resistance to external physical damage, maintains its surface smoothness and design integrity, and extends its effective lifespan. Simultaneously, this composite material possesses excellent polishing properties and resistance to sulfur discoloration, ensuring that the finished jewelry not only has a high-gloss aesthetic appearance upon initial manufacturing but also maintains color stability during long-term wear, resisting blackening and discoloration. Therefore, this application introduces the advantages of high-performance engineering materials into the traditional jewelry field, breaking through the performance bottlenecks of traditional materials.

[0041] Preferably, the jewelry is a ring, necklace, bracelet, earring, or pendant.

[0042] By adopting the above technical solution, the specific application scenarios of this composite material are pointed out. Rings, bracelets, and other jewelry, due to their placement, are among the items most susceptible to friction and impact during daily activities. Using this material can maximize its advantages of high hardness and high wear resistance. Necklaces, earrings, pendants, and other items require extremely high gloss and colorfastness; using this material can fully utilize its high gloss and anti-discoloration properties to ensure the long-term beauty of the jewelry.

[0043] In summary, the present invention has at least one of the following beneficial technical effects:

[0044] 1. This invention introduces manganese and boron into molten 1K gold for in-situ reaction, generating a high-hardness manganese boride reinforcing phase. This reinforcing phase forms a strong metallurgical bond with the metal matrix, acting as a load-bearing skeleton dispersed within the material. This significantly improves the hardness and wear resistance of the composite material, effectively solving the technical problem that traditional 1K gold alloys are prone to scratches and wear during wear due to their soft texture.

[0045] 2. This invention introduces trace amounts of rare earth elements into the in-situ reaction system, effectively controlling the formation process and final morphology of the manganese boride reinforcing phase, resulting in a fine-sized and uniformly distributed reinforcing phase. This structural feature allows the material to achieve a high-gloss mirror finish through standard processes while maintaining high hardness, overcoming the technical contradiction of traditional composite materials where the surface quality is reduced and polishing is difficult due to the coarse and uneven hard phase.

[0046] 3. The rare earth elements dissolved in the composite material of this invention can form a dense and chemically stable passivation film on the material surface. This passivation film effectively blocks the contact between external corrosive media such as sulfur and the internal active metal matrix, thereby significantly improving the material's resistance to sulfide discoloration and ensuring that the finished jewelry maintains its original bright color during long-term wear and storage. This allows the use of 1K gold to achieve an appearance close to that of 18K gold. Detailed Implementation

[0047] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments, comparative examples and test examples.

[0048] It should be noted that the following embodiments and comparative examples are merely specific illustrations of the present invention and are not intended to limit the scope of the present invention in any way. Any non-substantial modifications or substitutions made by those skilled in the art based on the content disclosed in this specification, without departing from the core idea of ​​the present invention, to process parameters, raw material ratios, etc., shall fall within the protection scope of the present invention. Unless specific process conditions are specified in the following embodiments and comparative examples, they are all carried out according to conventional techniques or conditions in the art.

[0049] To facilitate the uniform addition of active elements and reduce burn-off in subsequent embodiments, the following copper-based master alloy was prepared in advance.

[0050] Preparation Example 1: Preparation of Copper-Manganese Master Alloy (Cu-30wt%Mn)

[0051] Weigh 700g of 99.99% pure electrolytic copper and 300g of 99.7% pure electrolytic manganese flakes, place them in a high-purity graphite crucible, and then place the crucible into a high-frequency vacuum induction melting furnace. Evacuate the furnace to 1.0 × 10⁻⁶ ppm. -2 The pressure was increased to 0.05 MPa by introducing high-purity argon gas and maintaining the protective atmosphere. Induction heating was then activated, raising the furnace charge to 1300–1350 °C and holding it at this temperature for 30 minutes, during which electromagnetic stirring was performed to ensure uniform mixing of the components. After melting, the molten alloy was poured into a preheated graphite mold and cooled to room temperature under an argon atmosphere. A homogeneous copper-manganese master alloy ingot was obtained for later use.

[0052] Preparation Example 2: Preparation of Copper-Boron Master Alloy (Cu-2wt%B)

[0053] Weigh 980g of 99.99% pure electrolytic copper and 20g of 99% pure crystalline boron powder, place them in a high-purity graphite crucible, and then place the crucible into a high-frequency vacuum induction melting furnace. Evacuate the furnace to 1.0 × 10⁻⁶ ppm. -2The pressure was increased to 0.05 MPa by introducing high-purity argon gas and maintaining the protective atmosphere. Induction heating was then activated, raising the furnace charge to 1350–1400 °C and holding it at this temperature for 45 minutes, during which electromagnetic stirring was performed to ensure complete dissolution and uniform distribution of boron. After melting, the molten alloy was poured into a preheated graphite mold and cooled to room temperature under an argon atmosphere. A homogeneous copper-boron master alloy ingot was obtained for later use.

[0054] Preparation Example 3: Preparation of Copper-Lanternium Master Alloy (Cu-4wt%La)

[0055] Weigh 960g of 99.99% pure electrolytic copper and 40g of 99.5% pure metallic lanthanum, place them in a high-purity graphite crucible, and then place the crucible into a high-frequency vacuum induction melting furnace. Evacuate the furnace to 1.0 × 10⁻⁶ mm. -2 The pressure was increased to 0.05 MPa by introducing high-purity argon gas and maintaining the protective atmosphere. Induction heating was then activated, raising the furnace charge to 1200–1250 °C and holding it at this temperature for 30 minutes, during which electromagnetic stirring was performed to ensure uniform mixing of the components. After melting, the molten alloy was poured into a preheated graphite mold and cooled to room temperature under an argon atmosphere. A homogeneous copper-lanthanum master alloy ingot was obtained and set aside for later use.

[0056] Preparation Example 4: Preparation of Copper-Cerium Master Alloy (Cu-4wt%Ce)

[0057] 960g of electrolytic copper with a purity of 99.99% and 40g of metallic cerium with a purity of 99.5% were weighed and placed in a high-purity graphite crucible, which was then placed in a high-frequency vacuum induction melting furnace. The preparation process parameters were exactly the same as in Preparation Example 3. A homogeneous copper-cerium master alloy ingot was finally obtained and set aside for later use.

[0058] Example 1:

[0059] This embodiment provides a method for preparing a high-hardness 1K gold composite material, the final chemical composition of which is designed as follows: Au 4.20wt%, Cu 81.39wt%, Ag 9.60wt%, Zn 3.50wt%, Ni 0.10wt%, Mn 1.00wt%, B 0.20wt%, La 0.01wt%. The specific preparation steps are as follows:

[0060] (1) Based on a total feed amount of 1000g, weigh out: 42.0g gold, 96.0g silver, 35.0g zinc, 1.0g nickel, and 690.2g electrolytic copper; and according to the preparation methods of Examples 1, 2, and 3, weigh out 33.3g of Cu-30wt%Mn master alloy equivalent to 10.0g pure manganese, 100.0g of Cu-2wt%B master alloy equivalent to 2.0g pure boron, and 2.5g of Cu-4wt%La master alloy equivalent to 0.1g pure lanthanum.

[0061] (2) Place gold, electrolytic copper, silver, nickel, and zinc in a graphite crucible in a high-frequency vacuum induction melting furnace, and evacuate to a vacuum level of 1.0 × 10⁻⁶. -2 After Pa, argon gas is introduced to 0.05 MPa. Heating is started, and the furnace charge is heated to 1200℃ and held for 20 minutes. During this time, electromagnetic stirring is turned on to form a uniform master alloy melt.

[0062] (3) Maintain the melt temperature at 1200℃, add Cu-La master alloy through the feeder, and continue stirring for 5 minutes to make it evenly dispersed.

[0063] (4) Subsequently, Cu-Mn master alloy and Cu-B master alloy were added to the melt together. The temperature was raised to 1230℃ and held at this temperature for 20 minutes with stirring to carry out in-situ reaction and homogenization treatment.

[0064] (5) The prepared composite material melt is cooled to 1100℃ and poured into a plaster mold shell preheated to 650℃, and then cooled under an argon atmosphere. After cooling, the shell is broken and cleaned to obtain a 1K gold composite material casting for performance testing.

[0065] Example 2:

[0066] This embodiment provides a method for preparing a high-hardness 1K gold composite material, the final chemical composition of which is designed as follows: Au 4.60wt%, Cu 82.25wt%, Ag 4.00wt%, Zn 6.50wt%, Ni 0.15wt%, Mn 2.00wt%, B 0.45wt%, La 0.05wt%. The specific preparation steps are as follows:

[0067] (1) Based on a total feed amount of 1000g, weigh out: 46.0g gold, 40.0g silver, 65.0g zinc, 1.5g nickel, and 543.3g electrolytic copper; and according to the preparation methods of Examples 1, 2, and 3, weigh out 66.7g of Cu-30wt%Mn master alloy equivalent to 20.0g pure manganese, 225.0g of Cu-2wt%B master alloy equivalent to 4.5g pure boron, and 12.5g of Cu-4wt%La master alloy equivalent to 0.5g pure lanthanum.

[0068] (2) The smelting steps of the master alloy are the same as those in Example 1.

[0069] (3) The steps for introducing stabilizers and reactants are the same as in Example 1.

[0070] (4) In the in-situ reaction and homogenization steps, the melt is kept at 1250°C and stirred for 25 minutes.

[0071] (5) In the casting process, the casting temperature is 1120℃, the preheating temperature of the mold shell is 700℃, and the remaining steps are the same as in Example 1. Finally, a 1K gold composite material casting is obtained.

[0072] Example 3:

[0073] This embodiment provides a method for preparing a high-hardness 1K gold composite material, the final chemical composition of which is designed as follows: Au 4.10wt%, Cu 72.91wt%, Ag 9.80wt%, Zn 12.00wt%, Ni 0.08wt%, Mn 0.80wt%, B 0.21wt%, La 0.10wt%. The specific preparation steps are as follows:

[0074] (1) Based on a total feed amount of 1000g, weigh out: 41.0g gold, 98.0g silver, 120.0g zinc, 0.8g nickel, and 583.5g electrolytic copper; and according to the preparation methods of Examples 1, 2, and 3, weigh out 26.7g of Cu-30wt%Mn master alloy equivalent to 8.0g pure manganese, 105.0g of Cu-2wt%B master alloy equivalent to 2.1g pure boron, and 25.0g of Cu-4wt%La master alloy equivalent to 1.0g pure lanthanum.

[0075] (2) The smelting steps of the master alloy are the same as those in Example 1.

[0076] (3) The steps for introducing stabilizers and reactants are the same as in Example 1.

[0077] (4) In the in-situ reaction and homogenization steps, the melt is kept at 1280℃ and stirred for 30 minutes.

[0078] (5) The casting process is the same as in Example 1. The final product is a 1K gold composite casting.

[0079] Example 4:

[0080] This embodiment provides a method for preparing a high-hardness 1K gold composite material, the final chemical composition of which is designed as follows: Au 4.20wt%, Cu 81.39wt%, Ag 9.60wt%, Zn 3.50wt%, Ni 0.10wt%, Mn 1.00wt%, B 0.20wt%, Ce 0.01wt%. The specific preparation steps are as follows:

[0081] (1) Based on a total feed amount of 1000g, weigh out: 42.0g gold, 96.0g silver, 35.0g zinc, 1.0g nickel, and 690.2g electrolytic copper; and according to the preparation methods of Examples 1, 2, and 4, weigh out 33.3g of Cu-30wt%Mn master alloy equivalent to 10.0g pure manganese, 100.0g of Cu-2wt%B master alloy equivalent to 2.0g pure boron, and 2.5g of Cu-4wt%Ce master alloy equivalent to 0.1g pure cerium.

[0082] (2) All parameters of the overall preparation process, including melting temperature, reaction temperature, reaction time, and casting parameters, are exactly the same as in Example 1. Finally, a 1K gold composite material casting is obtained.

[0083] Example 5:

[0084] This embodiment provides a method for preparing a high-hardness 1K gold composite material, the final chemical composition of which is designed as follows: Au 4.50wt%, Cu 45.80wt%, Ag 45.09wt%, Zn 3.80wt%, Ni 0.20wt%, Mn 0.50wt%, B 0.10wt%, La 0.01wt%. The specific preparation steps are as follows:

[0085] (1) Based on a total feed amount of 1000g, weigh out: 45.0g gold, 450.9g silver, 38.0g zinc, 2.0g nickel, and 394.9g electrolytic copper; and according to the preparation methods of Examples 1, 2, and 3, weigh out 16.7g of Cu-30wt%Mn master alloy equivalent to 5.0g pure manganese, 50.0g of Cu-2wt%B master alloy equivalent to 1.0g pure boron, and 2.5g of Cu-4wt%La master alloy equivalent to 0.1g pure lanthanum.

[0086] (2) In the melting step of the master alloy, the temperature is raised to 1150℃ and held for 20 minutes.

[0087] (3) The steps for introducing stabilizers and reactants are the same as in Example 1.

[0088] (4) In the in-situ reaction and homogenization steps, the melt is kept at 1180℃ and stirred for 15 minutes.

[0089] (5) In the casting process, the casting temperature is 1050℃, the preheating temperature of the mold shell is 600℃, and the remaining steps are the same as in Example 1. Finally, a 1K gold composite material casting is obtained.

[0090] Comparative Example 1:

[0091] Compared to Example 1, this comparative example prepares a conventional 1K gold alloy of the prior art, the difference being that its final chemical composition does not contain manganese (Mn), boron (B), and rare earth elements (La). The increased weight percentage is made up by copper (Cu), that is, the final chemical composition is: Au 4.20wt%, Cu 82.60wt%, Ag 9.60wt%, Zn 3.50wt%, Ni 0.10wt%. The preparation process does not involve the addition of in-situ reactants or related process steps; only the basic alloy components are conventionally smelted and cast, and everything else is the same.

[0092] Comparative Example 2:

[0093] Compared to Example 1, the difference lies in that its final chemical composition does not contain manganese (Mn) and boron (B). The increased weight percentage is made up by copper (Cu), that is, the final chemical composition is: Au 4.20wt%, Cu 82.59wt%, Ag 9.60wt%, Zn 3.50wt%, Ni 0.10wt%, La 0.01wt%. In the preparation process, after the master alloy is melted, only the Cu-La master alloy is added and stirred evenly before casting. No in-situ reaction step is performed. Everything else is the same.

[0094] Comparative Example 3:

[0095] Compared to Example 1, the difference lies in that its final chemical composition does not contain rare earth element (La), and the increased weight percentage is made up by copper (Cu), that is, the final chemical composition is: Au 4.20wt%, Cu 81.40wt%, Ag 9.60wt%, Zn 3.50wt%, Ni 0.10wt%, Mn 1.00wt%, B 0.20wt%. In the preparation process, after the master alloy is melted, no Cu-La master alloy is added, and Cu-Mn and Cu-B master alloys are directly added for in-situ reaction, and the rest are the same.

[0096] Comparative Example 4:

[0097] The difference between this comparative example and Example 1 is that the final chemical composition ratio is exactly the same, but the preparation method is different. This comparative example does not use an in-situ reaction, but rather an external addition method. Commercially available manganese diboride (MnB2) micron-sized powder, with a total mass equivalent to the theoretical amount produced in Example 1, is mechanically stirred into the master alloy melt at the same reaction temperature (1230°C) as in Example 1, and then stirred for the same time before casting. All other aspects are the same.

[0098] Test Example 1:

[0099] This test aims to indirectly verify the feasibility of the present invention's scheme for in-situ generation of solid particles in a liquid state by characterizing the fluidity of the alloy melt.

[0100] Experimental equipment and materials:

[0101] (1) Experimental equipment: high frequency vacuum induction melting furnace, preheated graphite Archimedes spiral flow test mold (spiral channel cross-section size is 5mm×5mm), high precision infrared thermometer.

[0102] (2) Experimental samples: Alloy ingots prepared in Example 1 and Comparative Example 1 were used.

[0103] Experimental steps:

[0104] (1) Sample preparation: 200g ± 0.5g samples were cut from the ingots of Example 1 and Comparative Example 1, respectively.

[0105] (2) Mold preparation: The spiral flow test mold is heated as a whole and kept at a constant temperature of 250℃±5℃.

[0106] (3) Melting and temperature measurement: A sample is placed in a graphite crucible in an induction furnace and remelted under an argon atmosphere. The temperature of the melt is precisely monitored using an infrared thermometer and heated to a uniform casting temperature of 1150℃±5℃.

[0107] (4) Casting: When the temperature of the melt reaches and stabilizes at the set casting temperature, the melt is quickly poured into the preheated spiral mold from a height of 100mm above the mold gate in one go.

[0108] (5) Measurement: After the casting has completely solidified in the mold and cooled to room temperature, remove it. Use a tape measure to measure the length from the root of the gate along the center of the spiral to the end of the metal flow. This length is the melt flow length.

[0109] (6) For the samples of Example 1 and Comparative Example 1, the above steps were repeated 5 times independently. The flow length was recorded each time, and the average value and standard deviation were calculated. The test results are shown in Table 1.

[0110] Table 1 Melt flowability test data for Example 1 and Comparative Example 1:

[0111]

[0112] The test data in Table 1 show that, under the same casting process parameters, the average flow length (211.6 mm) of the material melt prepared in Example 1 is significantly lower than that of the conventional alloy melt prepared in Comparative Example 1 (351.8 mm).

[0113] The melt in Comparative Example 1 is a homogeneous single-phase liquid metal system, and its fluidity depends on the inherent physical properties of the alloy, such as viscosity and surface tension. The relatively long flow length obtained from the test is typical of this type of alloy.

[0114] The melt in Example 1 is a liquid-solid two-phase composite slurry system. According to the technical mechanism of the present invention, before casting, in-situ chemical reactions of manganese and boron generate dispersed solid manganese diboride (MnB2) particles with melting points much higher than the base alloy. These tiny solid particles suspended in the liquid matrix constitute an obstacle to liquid flow, effectively increasing the overall apparent viscosity of the melt. When the melt flows in the spiral channel, the presence of solid particles disrupts the laminar flow state of the liquid and exacerbates energy dissipation within the melt, leading to faster loss of kinetic and thermal energy at its flow front, thus solidifying over a shorter distance.

[0115] This result confirms that the technical concept of the present invention can be realized in the actual preparation process. That is, before the final solidification and molding, the homogeneous liquid alloy has been successfully transformed into a liquid-based metal composite material system containing dispersed solid phase reinforcement, laying the foundation for obtaining high-hardness solid materials with dispersion reinforcement.

[0116] Test Example 2:

[0117] This test aims to verify, from a macroscopic physical performance perspective, whether manganese (Mn) and boron (B) elements in the present invention have reacted in situ to form manganese diboride (MnB2) ceramic phase by comparing the actual measured density of the sample with the theoretically calculated density of the two different phase compositions.

[0118] Experimental equipment and materials:

[0119] (1) Experimental equipment: analytical balance (accuracy 0.1mg), specific gravity measuring device, constant temperature water bath (maintaining deionized water temperature at 20℃), ultrasonic cleaner.

[0120] (2) Experimental sample: Take the alloy casting prepared in Example 1.

[0121] Experimental steps:

[0122] (1) Theoretical density calculation:

[0123] Theoretical density 1 (ρ 理论1 (Unreacted model): Based on the chemical composition of Example 1, it is assumed that Mn and B elements are both dissolved or uniformly mixed in the Au-Cu-Ag-Zn-Ni matrix in the form of elemental atoms. The theoretical density of the alloy is calculated using the mixing rule based on the standard density and mass fraction of each component.

[0124] Theoretical density 2(ρ) 理论2(Complete Reaction Model): Based on the chemical composition of Example 1, it is assumed that Mn and B elements have completely reacted to form the MnB2 phase. The material system is considered to consist of two parts: an Au-Cu-Ag-Zn-Ni matrix alloy and a dispersed MnB2 phase. The theoretical density of the composite material is calculated using the mixing rule based on the standard densities of the matrix alloy and MnB2 and their respective mass fractions in the final material.

[0125] (2) Sample preparation: Five block samples with a size of approximately 10mm×10mm×5mm were cut from the ingot of Example 1. The surface oxide layer and defects were removed by grinding, and the samples were ultrasonically cleaned in acetone and then dried for later use.

[0126] (3) Actual density measurement: The Archimedes immersion method was used for measurement.

[0127] The mass (m) of the dried sample in air was accurately weighed using an analytical balance. a ).

[0128] The sample was suspended by a thin thread and completely immersed in deionized water at 20°C. Its suspended mass in the water was then measured (m). s ).

[0129] According to the formula ρ 实际 =(m a / (m a -m s ))×ρ 水 Calculate the actual density of the sample, where ρ 水 This is the density of deionized water at 20℃.

[0130] (4) Data recording: The actual density values ​​of the five samples were measured and recorded, and the average value was calculated. The results are shown in Table 2.

[0131] Table 2 Comparison of theoretical and actual densities of the sample from Example 1:

[0132]

[0133] The test results in Table 2 show that the actual measured average density of the sample in Example 1 was 9.68 g·cm³. -3 This value is consistent with the theoretical density calculated based on the complete reaction model: 2 (9.68 g·cm³). -3 It closely matches the theoretical density (9.85 g·cm³) calculated based on the unreacted model. -3 There is a significant bias.

[0134] The macroscopic density of a material is an external manifestation of its microscopic atomic packing and phase composition. Theoretical density 1 is based on the assumption that Mn and B atoms exist in the crystal lattice of a metal matrix in the form of substitutional or interstitial solid solutions, representing the atomic arrangement of a conventional alloy. Theoretical density 2, on the other hand, assumes that Mn and B atoms are chemically bonded to form a manganese diboride compound with an independent crystal structure (hexagonal C32 type). The atomic packing efficiency and specific gravity of this compound differ from those of its constituent elements; therefore, the overall density of composite material systems containing this compound will inevitably change.

[0135] The consistency between the experimentally measured actual density and the theoretical density 2 provides strong evidence from a physical performance perspective, proving that during the preparation process of Example 1, the Mn and B elements in the melt did not simply undergo physical mixing, but rather a complete chemical reaction occurred, forming a new phase, namely MnB2. This result directly confirms the core mechanism of the technical solution of this invention, namely, the successful synthesis of a ceramic reinforcing phase in a liquid metal matrix through in-situ self-generated reaction. This test verifies that the material prepared by this invention is essentially a metal matrix composite material, rather than a homogeneous alloy in the traditional sense, thus providing a fundamental phase structure basis for the excellent properties such as high hardness and high wear resistance exhibited by this material.

[0136] Test Example 3:

[0137] This test aims to quantitatively characterize the hardness of the materials obtained in each embodiment and comparative example.

[0138] Experimental equipment and materials:

[0139] (1) Experimental equipment: HV-1000 micro Vickers hardness tester.

[0140] (2) Experimental samples: Alloy castings prepared in Examples 1-5 and Comparative Examples 1-4 were used.

[0141] Experimental steps:

[0142] (1) Sample preparation: Samples were cut from each casting, inlaid with epoxy resin, and then successively ground with 400-mesh, 800-mesh, 1200-mesh, 2000-mesh, and 3000-mesh silicon carbide wet sandpaper until the surface scratches were uniform and fine. Subsequently, a final mirror polish was performed on a polishing machine using diamond polishing paste with a particle size of 1.0 μm. The polished samples were ultrasonically cleaned with acetone and dried.

[0143] (2) Hardness measurement: Place the prepared sample on the stage of the Vickers hardness tester, level it and focus it. Select a test load of 1.96 N (HV0.2) and set the holding time to 15 seconds.

[0144] (3) Data acquisition: Ten areas without obvious casting defects were randomly selected on the surface of each sample for indentation testing, ensuring that the distance between each indentation was greater than three times the length of the diagonal of the indentation. The lengths of the two diagonals (d1 and d2) of each indentation were measured, and the corresponding Vickers hardness values ​​were automatically calculated and recorded by the built-in program of the hardness tester.

[0145] (4) Data processing: After removing the highest and lowest values, the arithmetic mean of the remaining 8 effective hardness values ​​is calculated as the final Vickers hardness of the sample. The test results are shown in Table 3.

[0146] Table 3 Vickers hardness test results for each embodiment and comparative example:

[0147] Sample number Average Vickers hardness / HV 0.2 Example 1 226.8 Example 2 241.2 Example 3 229.5 Example 4 223.1 Example 5 207.3 Comparative Example 1 136.4 Comparative Example 2 146.9 Comparative Example 3 187.5 Comparative Example 4 172.8

[0148] The hardness test results in Table 3 clearly show that the Vickers hardness values ​​(207.3 to 241.2 HV0.2) of all the example samples are significantly higher than the hardness values ​​(136.4 to 187.5 HV0.2) of all the comparative sample samples.

[0149] Comparative Example 1, serving as the baseline alloy without any strengthening components, exhibits a hardness value of 136.4 HV0.2, reflecting the intrinsic hardness level of this Au-Cu-Ag-Zn-Ni solid solution alloy. Comparative Example 2, with the addition of only trace amounts of rare earth elements, shows a slight increase in hardness to 146.9 HV0.2. This may be due to limited solid solution strengthening or grain refinement effects, but the improvement is quite limited.

[0150] The significant increase in hardness achieved in Examples 1-5 of this invention is fundamentally due to the successful construction of a dispersion-strengthened composite structure within the material. Through the in-situ reaction of Mn and B, a high-hardness MnB2 ceramic phase is generated within the metal matrix. These dispersed hard particles act as barriers, effectively pinning dislocations and hindering their slip movement within the crystal, thereby greatly enhancing the matrix's resistance to plastic deformation, macroscopically manifested as a sharp increase in hardness. This is a typical dispersion-strengthening mechanism.

[0151] The comparison between Comparative Example 3 and Example 1 reveals the crucial role of the synergistic stabilizer. Comparative Example 3, which underwent an in-situ reaction without rare earth elements, showed a significantly improved hardness (187.5 HV0.2) compared to Comparative Example 1, but still considerably lower than Example 1 (226.8 HV0.2). This is because, in the absence of rare earth elements, the newly grown MnB2 particles lack effective interfacial regulation, making them prone to spontaneous growth and aggregation. This results in an unevenly sized and poorly distributed reinforcing phase, weakening its dislocation-resistance efficiency. In contrast, the trace rare earth element La added in Example 1, acting as a surface-active element, preferentially adsorbs at the MnB2 / melt interface, reducing the interfacial energy and inhibiting Oldswald ripening and aggregation of the particles, thus obtaining a finer, more uniformly distributed dispersed phase. This optimized microstructure leads to more frequent and effective hindrance of dislocation slip, resulting in superior strengthening effects.

[0152] Comparative Example 4, which introduced MnB2 powder using an additive method, exhibited a hardness (172.8 HV0.2) that was not only lower than that of the embodiments of the present invention but also lower than that of Comparative Example 3 without stabilizer. This demonstrates the superiority of the in-situ self-generating method of the present invention. Added ceramic particles typically exhibit poor interfacial wettability with the metal matrix and are easily contaminated, resulting in low interfacial bonding strength and ineffective load transfer. Furthermore, added powders are prone to agglomeration in the melt, making uniform dispersion difficult. In contrast, the in-situ generated reinforcing phase possesses a clean, typically semi-coherent or coherent, interface, exhibits good bonding with the matrix, and its nucleation and growth processes are more easily uniformly distributed, thus resulting in a significantly higher strengthening efficiency than the additive method.

[0153] In summary, the test data proves that the technical solution of the present invention generates a hard phase through in-situ reaction and is further stabilized by rare earth elements, which is an effective and necessary technical combination to achieve a breakthrough improvement in material hardness.

[0154] Test Example 4:

[0155] This test aims to evaluate the wear resistance of materials under specific sliding friction conditions.

[0156] Experimental equipment and materials:

[0157] (1) Experimental equipment: MMG-200 pin-disc friction and wear tester, analytical balance (accuracy 0.1mg), ultrasonic cleaner.

[0158] (2) Experimental Samples: The as-cast materials of Examples 1-5 and Comparative Examples 1-4 were prepared by machining. Cylindrical pin specimen.

[0159] (3) Grinding disc: GCr15 bearing steel disc, the hardness after heat treatment is HRC 60~62, and the working surface is polished to roughness Ra≤0.2μm.

[0160] Experimental steps:

[0161] (1) Sample preparation: The friction end face of the pin sample was smoothed with 1200-grit silicon carbide wet sandpaper to ensure the stability of the initial contact state. Then, the sample was ultrasonically cleaned in acetone solvent for 5 minutes to remove surface oil and impurities, and then dried with cold air.

[0162] (2) Initial mass measurement: Weigh the cleaned and dried pin sample using an analytical balance and accurately record its initial mass m1.

[0163] (3) Friction test: The pin specimen is vertically mounted on the fixture of the testing machine, with its end face in contact with the horizontally placed GCr15 steel disc. A constant normal load of 10N is applied, and the rotational speed of the grinding disc is set so that the linear velocity of the pin specimen contact point is 0.1m / s. Under room temperature and atmospheric dry friction conditions, the equipment is started to conduct a total of 1000 meters of sliding friction test.

[0164] (4) Final mass measurement: After the test, remove the pin sample. Use the same cleaning and drying process as in step (1) to thoroughly remove the abrasive debris adhering to the surface. Weigh its final mass m2 using the same analytical balance.

[0165] (5) Data Calculation and Processing: Calculate the mass loss of a single sample, Δm = m1 - m2. Mass wear rate (W) r W is defined as the mass loss per unit sliding distance. r =Δm / L, where L is the total sliding distance (1km). Three independent pin samples of each material were tested, and the average value was taken. The test results are shown in Table 4:

[0166] Table 4. Mass wear rate of each embodiment and comparative example:

[0167] Sample number Mass wear rate (mg / km) Example 1 2.24 Example 2 1.89 Example 3 2.16 Example 4 2.31 Example 5 3.05 Comparative Example 1 9.21 Comparative Example 2 8.15 Comparative Example 3 5.17 Comparative Example 4 7.08

[0168] The wear rate data in Table 4 show that the wear resistance of all embodiments of the present invention is significantly better than that of all comparative examples.

[0169] Comparative Example 1, as a pure metal matrix alloy, experienced severe ploughing and adhesive tearing due to its softer surface directly contacting the hard GCr15 steel disc during friction, resulting in the highest mass wear rate.

[0170] The excellent wear resistance of the samples in this invention embodiment is directly attributed to the high-hardness MnB2 dispersed particles generated in situ within them. During the friction process, these hard phases play two key roles:

[0171] Load-bearing function: The hardness of MnB2 particles is much higher than that of the metal matrix and GCr15 steel disc, so they can serve as the main load-bearing points, bearing and dispersing the normal load from the grinding disc. This prevents the soft metal matrix from being directly exposed to the friction interface over a large area, thus effectively suppressing the plastic deformation and plowing of the matrix.

[0172] "Pinning" protection: The diffusely distributed hard particles are anchored in the matrix like nails, and under the action of tangential friction, they can prevent large pieces of matrix material from peeling off and extending.

[0173] The comparison between Comparative Example 3 and Example 1 further verifies the decisive influence of the synergistic stabilizer (rare earth element) on optimizing the microstructure and improving macroscopic performance. Although MnB2 was also generated in Comparative Example 3, the particles were large and unevenly distributed. During friction, the interface between the large particles and the matrix was prone to stress concentration and preferentially peeled off, forming wear debris. In contrast, in Example 1, the fine and uniform MnB2 particles optimized by rare earth elements bonded more firmly with the matrix, forming a denser and more stable protective framework. Therefore, its wear rate was much lower than that of Comparative Example 3.

[0174] Comparative Example 4, which introduced MnB2 using an external method, exhibited a wear rate even higher than Comparative Example 3, revealing the inherent advantages of the in-situ self-generated method. The physical interface bonding between the externally added particles and the matrix is ​​weak, making them prone to detachment under frictional shear stress. These detached hard particles enter the friction interface, transforming into free abrasive grains, causing severe "three-body abrasive wear" on both sides of the friction pair, thus accelerating material loss. In contrast, the particles generated in-situ in this invention have a metallurgical bonding interface with the matrix, exhibiting high bonding strength, are not easily detached, and can stably exert their wear-resistant effect.

[0175] In summary, the results of the wear resistance test are highly consistent with the results of the hardness test, and further confirm the technical mechanism of the present invention from the perspective of dynamic friction and wear.

[0176] Test Example 5:

[0177] This test aims to evaluate the surface quality that materials can achieve after undergoing a standardized finishing process.

[0178] Experimental equipment and materials:

[0179] (1) Experimental equipment: jewelry polishing machine (equipped with cloth wheels of different hardness), a series of polishing pastes, LS192 portable gloss meter (60° geometric angle), and ultrasonic cleaner.

[0180] (2) Experimental samples: Take the cast materials of Examples 1-5 and Comparative Examples 1-4.

[0181] Experimental steps:

[0182] (1) Sample preparation: Cut sheet-shaped samples of uniform size from each casting.

[0183] (2) Standardized Polishing: All samples underwent a completely consistent polishing process. First, the sample surface was progressively ground using 400- to 3000-grit silicon carbide wet sandpaper to obtain a smooth base. Subsequently, a three-stage cloth wheel polishing was performed on a polishing machine: the first stage used a hard cloth wheel with brown polishing paste for coarse polishing to eliminate grinding scratches; the second stage used a medium-hardness cloth wheel with white polishing paste for medium polishing to improve smoothness; and the third stage used a soft flannel cloth wheel with red polishing paste for fine polishing to obtain a final mirror finish.

[0184] (3) Cleaning and preparation: After polishing, the sample is placed in alcohol for ultrasonic cleaning to thoroughly remove the polishing paste residue on the surface, and then dried with compressed air.

[0185] (4) Gloss measurement: Use a gloss meter calibrated with a standard plate. Place the instrument's measuring port firmly against the surface of the sample to be tested, ensuring good contact. Randomly select 10 different locations on the mirror-polished surface of each sample for measurement.

[0186] (5) Data processing: Record each measurement reading (unit: GU) and calculate the arithmetic mean of 10 measurements as the final gloss value of the sample. The test results are shown in Table 5.

[0187] Table 5. Surface gloss after polishing for each embodiment and comparative example:

[0188] Sample number Average gloss level / GU Example 1 896.2 Example 2 884.7 Example 3 891.5 Example 4 899.1 Example 5 876.3 Comparative Example 1 911.8 Comparative Example 2 904.6 Comparative Example 3 657.4 Comparative Example 4 621.9

[0189] The test results in Table 5 show that all embodiments of the present invention (876.3-899.1 GU) achieved extremely high surface gloss, with values ​​very close to those of Comparative Example 1 (911.8 GU) and Comparative Example 2 (904.6 GU), which do not contain a hard phase. In stark contrast, the gloss of Comparative Example 3 (657.4 GU) and Comparative Example 4 (621.9 GU) showed a precipitous decrease.

[0190] The physical prerequisite for a material to achieve high gloss is that its surface has extremely high flatness at the microscale, enabling effective specular reflection of incident light. Comparative Examples 1 and 2, as homogeneous single-phase or near-single-phase metallic solid solutions, can be uniformly cut and ground during the polishing process, thus forming high-quality mirror surfaces. Their gloss values ​​represent the ideal upper limit achievable by this alloy system.

[0191] The high gloss of the samples in this invention's embodiments is primarily due to the two key characteristics of the internal MnB2 reinforcing phase: its fine size and uniform distribution. During multi-stage polishing, these micron- or even submicron-sized, well-bonded hard particles can be synergistically ground and polished with the softer metal matrix, rather than being pulled out or torn in chunks. This allows the material surface to form a continuous and smooth composite surface on an optical scale, thus ensuring high specular reflectivity.

[0192] The drastic deterioration of gloss in Comparative Examples 3 and 4 exposes the fatal flaws of inhomogeneous composite materials in finishing. In Comparative Example 3, due to the lack of stabilizing rare earth elements, the in-situ generated MnB2 particles are large and agglomerated. Under the high-speed shearing force of the polishing wheel, the interface between these large, hard agglomerates and the matrix becomes a stress concentration point, easily peeled off from the matrix, leaving numerous micro-pits on the surface. The situation in Comparative Example 4 is even more severe; the added particles have only a weak physical interface with the metal matrix, and are almost indiscriminately pulled out during polishing, causing more serious surface damage. The presence of these micro-pits and scratches makes the sample surface a scatterer of light rather than a reflector, macroscopically manifested as a dull gloss.

[0193] Test Example 6:

[0194] This test aims to evaluate the material's ability to resist surface discoloration (sulfidation) in a simulated sulfur-containing environment.

[0195] Experimental equipment and materials:

[0196] (1) Experimental equipment: Ci7600 benchtop spectrophotometer, constant temperature water bath, beaker, analytical grade sodium sulfide (Na2S), deionized water.

[0197] (2) Experimental samples: Take sheet-like samples of Examples 1-5 and Comparative Examples 1-4 after standardization and polishing by Test Example 5.

[0198] Experimental steps:

[0199] (1) Initial colorimetric measurement: Place the clean, dry, polished sample in the measuring port of the colorimeter, and measure the initial colorimetric coordinates L1, a1 of its surface in the CIE Lab color space. * b1 * Three different points were measured for each sample, and the average value was taken.

[0200] (2) Sulfurization treatment: Prepare a 0.1 wt% sodium sulfide aqueous solution. Hang the sample vertically so that about half of its area is immersed in the solution. Place the beaker in a constant temperature water bath and keep it at 25℃±1℃ for 2 hours.

[0201] (3) Post-treatment: Remove the sample from the solution and immediately rinse it with plenty of deionized water to remove the reactants remaining on the surface, and then dry it with compressed air.

[0202] (4) Final colorimetric measurement: Using the same colorimeter, measure the final colorimetric coordinates L2 of the sample in the area where it has been vulcanized, using the same method as in step (1). * a2 * b2 * .

[0203] (5) Color difference calculation: According to the formula Calculate the total color difference ΔE for each sample. * ΔE * The higher the value, the more significant the color change and the worse the resistance to sulfurization. The test results are shown in Table 6:

[0204] Table 6. Total color difference ΔE between the examples and comparative examples in terms of sulfur resistance * :

[0205] Sample number Total color difference ΔE* Example 1 2.58 Example 2 2.11 Example 3 2.65 Example 4 2.49 Example 5 3.12 Comparative Example 1 18.54 Comparative Example 2 7.63 Comparative Example 3 15.88 Comparative Example 4 16.51

[0206] The test data in Table 6 clearly indicate that the anti-sulfurization discoloration performance of all embodiments of the present invention is far superior to that of the comparative examples.

[0207] Comparative Example 1, as the reference alloy, has a total color difference ΔE * The highest value indicates that a severe chemical reaction occurred on its surface in the sodium sulfide solution. This is because the active copper and silver elements in its matrix are directly exposed to the sulfur-containing environment, rapidly forming dark-colored sulfides (such as Cu2S, Ag2S), resulting in a dramatic color change.

[0208] The comparison between Comparative Example 2 and Comparative Example 1 reveals the crucial role of rare earth elements. Adding only trace amounts of rare earth elements to the benchmark alloy significantly increases ΔE. * The value then decreases significantly. This is because rare earth elements (such as La) have extremely high chemical reactivity and can preferentially and selectively oxidize the alloy surface, forming an extremely thin, dense, and chemically inert passivation film (mainly La2O3). This passivation film, as an effective physical barrier layer, significantly slows down the rate of diffusion of external sulfur ions inward and migration of internal metal ions outward, thereby protecting the underlying copper and silver substrate and inhibiting the sulfidation reaction.

[0209] The results of Comparative Examples 3 and 4 demonstrate that relying solely on the hard phase is insufficient to effectively improve the material's resistance to sulfidation. Although these two comparative examples contain a hard MnB2 phase, their ΔE... *The value remains high. This is because sulfidation corrosion primarily occurs on the chemically active metal matrix phase. While MnB2 particles themselves possess high chemical stability, they cannot provide protection for the surrounding large area of ​​the metal matrix. Therefore, without the formation of a continuous protective passivation film by rare earth elements, large-scale sulfidation will still occur in the matrix.

[0210] The superior anti-discoloration performance of this invention is a manifestation of the synergistic effect brought about by its unique composition design. First, trace amounts of rare earth elements form a continuous, self-healing passivation film on the material surface, which is crucial for providing basic anti-sulfurization protection. Second, the in-situ generated, well-bonded fine MnB2 particles, as chemically inert phases, are dispersed on the surface and do not participate in the sulfidation reaction, objectively reducing the proportion of reactive metals available for reaction per unit area. The coexistence of the passivation film and inert particles constructs a composite surface with higher chemical stability, thus enabling the material as a whole to exhibit extremely strong resistance to sulfidation discoloration.

[0211] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for producing a high-hardness 1K gold composite material, characterized by, Includes the following steps: (a) Provide a master alloy melt composed of gold, copper and at least one metallic element selected from silver, zinc and nickel; (b) Add rare earth elements, manganese and boron to the master alloy melt; (c) The manganese and boron are kept at a predetermined temperature and stirred so that the manganese and boron react in situ in the melt to generate manganese boride reinforcing phase, forming a composite material melt; (d) The composite material melt is cast into shape.

2. The method for preparing the high-hardness 1K gold composite material according to claim 1, characterized in that, The final chemical composition of the composite material, by weight percentage, includes: 4.10% to 4.60% gold, 0.50% to 2.00% manganese, 0.10% to 0.45% boron, 0.01% to 0.10% rare earth elements, with the balance being copper and at least one metallic element selected from silver, zinc, and nickel.

3. The method for preparing the high-hardness 1K gold composite material according to claim 1, characterized in that, The rare earth element is lanthanum or cerium.

4. The method for preparing the high-hardness 1K gold composite material according to claim 1, characterized in that, In step (b), the rare earth elements are first added and uniformly dispersed in the melt, and then the manganese and boron are added.

5. The method for preparing the high-hardness 1K gold composite material according to claim 1, characterized in that, The predetermined temperature for the in-situ reaction is 1150℃~1300℃.

6. A high-hardness 1K gold composite material prepared by the preparation method according to any one of claims 1-5.

7. The application of the high-hardness 1K gold composite material as described in claim 6 in jewelry manufacturing.

8. The application according to claim 7, characterized in that, The jewelry refers to rings, necklaces, bracelets, earrings, or pendants.

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