Mg-Zn-Ca alloy with amorphous phase and preparation method thereof

Abstract

The invention belongs to the technical field, and particularly relates to an Mg-Zn-Ca alloy with an amorphous phase and a preparation method of the Mg-Zn-Ca alloy. A preparation method of the Mg-Zn-Ca alloy with the amorphous phase comprises the following steps that the Mg-Zn-Ca alloy is prepared from the following elements in percentage by mass: 1%-3% of Zn, 0.5%-1% of Ca, 0.1%-0.5% of Sc and the balance of Mg and inevitable impurities, and the total percentage is 100%; the preparation method comprises the following steps: melting all elements according to the element composition of the Mg-Zn-Ca alloy, and casting into an alloy casting blank to obtain the Mg-Zn-Ca alloy; carrying out asymmetrical rolling on the Mg-Zn-Ca alloy; and carrying out post-rolling heat treatment on the Mg-Zn-Ca alloy subjected to the asymmetrical rolling for 10 to 15 minutes, so as to obtain the Mg-Zn-Ca alloy with an amorphous phase. The method is simple and practical to operate and can be applied to large-scale production.

Description

Technical Field

[0001] This invention belongs to the technical field, specifically relating to a Mg-Zn-Ca alloy with an amorphous phase and its preparation method. Background Technology

[0002] Magnesium alloys have broad application prospects in aerospace, automotive, and 3C products due to their advantages such as low density, high specific strength and specific stiffness, good damping and vibration reduction properties, strong electromagnetic shielding, and easy recycling. However, magnesium has a close-packed hexagonal crystal structure and few independent slip systems that can be activated at room temperature, resulting in poor plastic forming ability, which greatly limits its large-scale commercial application.

[0003] Existing technologies utilize the addition of rare earth or alkaline earth elements to alter the deformation mechanism or generate a second phase, thereby disrupting the formation of the basal texture and improving the overall plastic deformation capacity of magnesium alloys through microstructural control. For example, adding Ca to the Mg-Zn alloy system can form intermetallic compounds such as Ca2Mg6Zn3. However, while traditional alloying methods can weaken the texture to some extent, the effect is limited and often accompanied by coarsening of the second phase and a decrease in plasticity. Summary of the Invention

[0004] To address the technical problem that traditional alloying methods have limited effectiveness in weakening texture, this invention provides a Mg-Zn-Ca alloy with an amorphous phase and its preparation method.

[0005] The first objective of this invention is to provide a method for preparing a Mg-Zn-Ca alloy having an amorphous phase, comprising the following steps: The Mg-Zn-Ca alloy is composed of the following elements by mass percentage: Zn 1%–3%, Ca 0.5%–1%, Sc 0.1%–0.5%, with the balance being Mg and unavoidable impurities, totaling 100%. According to the elemental composition of the Mg-Zn-Ca alloy, each element is melted and cast into an alloy billet to obtain the Mg-Zn-Ca alloy. The Mg-Zn-Ca alloy is then subjected to asynchronous rolling. The asynchronously rolled Mg-Zn-Ca alloy is subjected to post-rolling heat treatment for 10–15 minutes. This utilizes the preferential formation of the ZnSc phase by Sc to reduce the supersaturation of residual Zn in the alloy. Simultaneously, the Ca2Mg6Zn3 phase undergoes vacancy defects and lattice distortion during crystallization, transforming into an amorphous structure, thus obtaining a Mg-Zn-Ca alloy with an amorphous phase.

[0006] It should be noted that in conventional Mg-Zn-Ca alloys, the Zn and Ca content is sufficient to form a complete Ca2Mg6Zn3 phase. However, this invention, by adding Sc, utilizes the high bonding energy between Sc and Zn, allowing Sc atoms to preferentially combine with Zn atoms in the alloy during post-rolling heat treatment, forming a stable ZnSc phase. This process consumes a large number of free Zn atoms in the melt, resulting in insufficient Zn atoms available for forming the stoichiometric Ca2Mg6Zn3 phase, significantly reducing the supersaturation of Zn components for Ca2Mg6Zn3 phase formation. During subsequent post-rolling heat treatment, the brief heat treatment time provides energy and atomic migration conditions for the precipitation of the second phase, but the time is insufficient; with a relatively insufficient Zn content, the Ca2Mg6Zn3 phase begins to nucleate and grow. However, due to the shortage of Zn atoms, this phase cannot form a complete long-range ordered lattice structure during crystallization; this leads to a large number of vacancy defects in the crystal structure. To compensate for these defects, the surrounding atomic matrix undergoes severe lattice distortion, causing a sharp increase in the system's free energy. When this distortion reaches a certain level, the long-range ordered crystal structure can no longer be maintained and collapses, transforming the atomic arrangement into an amorphous structure that is relatively more energy-stable with short-range order and long-range disorder. Therefore, the final Ca2Mg6Zn3 phase is amorphous.

[0007] Preferably, the post-rolling heat treatment time is 10 min to 15 min. Post-rolling heat treatment allows the second phase, mainly Ca2Mg6Zn3, which was suppressed during rolling, to nucleate. Simultaneously, by controlling the post-rolling heat treatment time, the grain growth and long-range ordering process of the Ca2Mg6Zn3 phase are significantly limited. Furthermore, since Sc consumes some Zn, the number of Zn atoms available for forming Ca2Mg6Zn3 is insufficient, leading to a large number of vacancies and defects during crystallization, resulting in severe lattice distortion, increased energy barriers, and ultimately inhibiting the complete formation of the crystal structure.

[0008] Preferably, the temperature of the post-rolling heat treatment is 573K to 623K.

[0009] Preferably, controlling the amount of Sc added ensures the formation of a sufficient Zn-Sc phase, effectively reducing the supersaturation of the Zn component. If the added Sc content is too low, the Zn consumption effect is insufficient, failing to effectively reduce Zn supersaturation; if the added Sc content is too high, excessive coarse Sc-containing phases will form, impairing mechanical properties and drastically increasing costs. Furthermore, Ca and Sc are extremely reactive; if added in pure metallic form, the burn-off rate is extremely high and difficult to control, and it also introduces a large number of oxide inclusions. Adding them in the form of Mg-30Ca and Mg-20Sc master alloys can significantly reduce their melting temperature, decrease burn-off, and ensure the precise addition of the target elements.

[0010] Preferably, the preparation method of the Mg-Zn-Ca alloy is as follows: Based on the elemental composition of the Mg-Zn-Ca alloy, Mg, Mg-30Ca master alloy, Zn block and Mg-20Sc master alloy are prepared; under a protective atmosphere, Mg is melted, and then preheated Mg-30Ca master alloy, Zn block and Mg-20Sc master alloy are added for smelting to make Ca, Zn, Sc and Mg uniformly distributed in the melt to obtain an alloy melt; the alloy melt is formed into an alloy billet to obtain the Mg-Zn-Ca alloy.

[0011] Preferably, the melting temperature of Mg is 933K to 963K.

[0012] Preferably, before adding the Mg-30Ca master alloy, Zn block, and Mg-20Sc master alloy to the Mg melt for smelting, they are preheated under vacuum at 473K-523K for 1 hour to obtain preheated Mg-30Ca master alloy, Zn block, and Mg-20Sc master alloy. This is because if adsorbed water and gas on the surface of the raw materials enter the melt, they will form pores and inclusions, which will seriously affect the quality of the subsequent rolled plate and the formation of amorphous phase; vacuum preheating is used to remove adsorbed water and gas on the surface of the raw materials.

[0013] Preferably, the casting temperature is 933K to 943K.

[0014] The preferred parameters for asynchronous rolling are as follows: The roll temperature is 50℃~100℃, and the roll speed is 15rpm~18rpm; the upper roll diameter is 150mm, and the lower roll diameter is 120mm; rolling is performed in multiple passes, with the rolled sample held at 573K~623K between passes for 3min~5min. This invention uses asynchronous rolling to break up the as-cast structure and refine the grains, providing a deformation basis for the formation of amorphous phases. The difference in linear velocity caused by the different diameters of the upper and lower rolls generates strong shear strain. This shear force helps promote element diffusion, increases crystal defect density, and provides energy conditions and nucleation sites for the amorphization transformation in subsequent heat treatment.

[0015] Compared with the prior art, the present invention has the following technical effects: This invention adds 0.1%–0.5% Sc element, which preferentially reacts with Zn in the alloy to form the ZnSc phase, consuming some Zn and reducing the supersaturation of remaining Zn in the alloy. This reduces the number of Zn atoms participating in the formation of the Ca2Mg6Zn3 phase. Simultaneously, a brief rolling heat treatment of 10–15 minutes ensures insufficient crystallization of the second phase in the alloy. During the crystallization process, the Ca2Mg6Zn3 phase forms numerous vacancy defects, leading to significant lattice distortion. Ultimately, this achieves in-situ induced amorphization of the Ca2Mg6Zn3 phase in the Mg-Zn-Ca alloy. By utilizing the isotropic properties of the amorphous phase to completely break the continuity of the crystalline texture, this invention solves the technical problem of limited textural weakening effects in traditional alloying methods.

[0016] This invention combines microalloying composition design with asynchronous controlled rolling technology to prepare Mg-Zn-Ca-Sc alloys. After room temperature pre-deformation, the basal surface texture is significantly weakened, breaking through the key bottleneck of "difficulty in eliminating basal surface texture" after room temperature deformation of traditional magnesium alloys.

[0017] This invention promotes the dynamic recrystallization ability of Mg-Zn-Ca alloy by forming an in-situ endogenous Ca2Mg6Zn3 phase, thereby improving the overall mechanical properties and processing capability of the alloy. Attached Figure Description

[0018] Figure 1 This is a photograph of the Mg-1Zn-0.5Ca-0.5Sc alloy.

[0019] Figure 2 Transmission electron microscopy (TEM) images of the rolled heat-treated Mg-1Zn-0.5Ca alloy prepared in Comparative Example 1 and the Mg-1Zn-0.5Ca-0.5Sc alloy prepared in Example 1. In the images, (a) is a bright-field image of the Ca2Mg6Zn3 phase in the Mg-1Zn-0.5Ca alloy, and the inset in (a) is a Ca2Mg6Zn3 diffraction spot; (b) is a bright-field image of the Ca2Mg6Zn3 phase in the Mg-1Zn-0.5Ca-0.5Sc alloy, and the inset in (b) is a Ca2Mg6Zn3 diffraction spot.

[0020] Figure 3 Texture diagrams of Mg-1Zn-0.5Ca-0.5Sc alloy under different conditions. Among them, (a) is the texture diagram of Mg-1Zn-0.5Ca-0.5Sc alloy in the rolled and annealed state; (b) is the texture diagram of Mg-1Zn-0.5Ca-0.5Sc alloy in the pre-deformed state; (c) is the recrystallization state diagram of (a); and (d) is the recrystallization state diagram of (b).

[0021] Figure 4The tensile properties of Mg-1Zn-0.5Ca-0.5Sc alloy under different conditions are shown in the figure. Detailed Implementation

[0022] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings.

[0023] Unless otherwise specified, all reagents used in this invention are commercially available, and all methods used are conventional techniques in the art.

[0024] Example 1 A method for preparing a Mg-1Zn-0.5Ca-0.5Sc alloy includes the following steps: Step 1, Ingredients: The mixture is prepared by mass percentage with 1 wt.% Zn, 0.5 wt.% Ca and 0.5 wt.% Sc, and the remainder is Mg; the amount of Mg added is the theoretical calculation value plus 10% loss due to burn-off; wherein, Zn is 99.99% pure Zn block, Ca is Mg-30Ca master alloy, and Sc is Mg-20Sc master alloy.

[0025] Step 2, Melting: Pure Mg with a purity of 99.85% was placed in a clay crucible and heated to melt in a pit furnace at 943 K. A mixture of SF6 and CO2 was introduced as a protective gas to obtain Mg melt.

[0026] The Mg-30Ca master alloy, 99.99% pure Zn block and Mg-20Sc master alloy were held in a vacuum furnace at 473K for 1 hour; then added to Mg melt at 943K, and a mixture of SF6 and CO2 was introduced as a protective gas. After standing for 10 minutes, the mixture was stirred for 2 minutes to ensure that the elements and Mg were evenly distributed in the melt, thus obtaining the alloy melt.

[0027] Step 3, Casting: After the alloy melt is allowed to stand for 8 minutes, the temperature is adjusted to 933K±5K and poured into a steel mold with a cavity thickness of 20mm~25mm to obtain a Mg-Zn-Ca alloy billet.

[0028] Step 4, Rolling: After cutting the Mg-Zn-Ca alloy billet into rolling samples of 50mm×25mm×5mm, the samples were held at 573K for 10min in a heat treatment furnace and then asynchronously rolled. The asynchronous rolling conditions were: roll temperature 50℃, rotation speed 15rpm, upper roll diameter 150mm, and lower roll diameter 120mm. The rolling was performed in 4 passes, with a reduction of 20% in each pass. The samples were held at 583K±10K for 3min between passes to obtain rolling samples with a thickness of 1mm.

[0029] Step 5, Heat Treatment: A rolled sample with a thickness of 1 mm was held in a heat treatment furnace at 583 K ± 10 K for 10 min to obtain a Mg-1Zn-0.5Ca-0.5Sc alloy.

[0030] Example 2 A method for preparing a Mg-1.5Zn-1Ca-1Sc alloy includes the following steps: Step 1, Ingredients: The mixture is formulated with 1.5 wt.% Zn, 1 wt.% Ca and 1 wt.% Sc by mass percentage, with the remainder being Mg; the amount of Mg added is the theoretical calculation value plus 10% loss due to burn-off; wherein, Zn is 99.99% pure Zn block, Ca is Mg-30Ca master alloy, and Sc is Mg-20Sc master alloy.

[0031] Step 2, Melting: Pure Mg with a purity of 99.85% was placed in a clay crucible and heated to melt in a pit furnace at 953 K. A mixture of SF6 and CO2 was introduced as a protective gas to obtain Mg melt.

[0032] The Mg-30Ca master alloy, 99.99% pure Zn block and Mg-20Sc master alloy were held in a vacuum furnace at 473K for 1 hour; then added to Mg melt at 953K, and a mixture of SF6 and CO2 was introduced as a protective gas. After standing for 10 minutes, the mixture was stirred for 2 minutes to ensure that the elements and Mg were evenly distributed in the melt, thus obtaining the alloy melt.

[0033] Step 3, Casting: After the alloy melt is allowed to stand for 8 minutes, the temperature is adjusted to 933K±5K and poured into a steel mold with a cavity thickness of 20mm~25mm to obtain a Mg-Zn-Ca alloy billet.

[0034] Step 4, Rolling: After cutting the Mg-Zn-Ca alloy billet into rolling samples of 50mm×25mm×5mm, the samples were held at 573K for 10min in a heat treatment furnace and then asynchronously rolled. The asynchronous rolling conditions were: roll temperature 100℃, rotation speed 18rpm, upper roll diameter 150mm, and lower roll diameter 120mm. The rolling was performed in 4 passes, with a reduction of 20% in each pass. The samples were held at 583K±10K for 3min between passes to obtain rolling samples with a thickness of 1mm.

[0035] Step 5, Heat Treatment: A rolled sample with a thickness of 1 mm was held in a heat treatment furnace at 583 K ± 10 K for 10 min to obtain a Mg-1.5Zn-1Ca-1Sc alloy.

[0036] Comparative Example 1 A method for preparing a Mg-1Zn-0.5Ca alloy includes the following steps: Step 1, Ingredients: The ingredients are prepared by mass percentage, with 1 wt.% Zn, 0.5 wt.% Ca, and the remainder Mg; the amount of Mg added is the theoretical calculation value plus 10% loss due to burn-off; Zn is 99.99% pure Zn block and Ca is Mg-30Ca master alloy.

[0037] Step 2, Melting: Pure Mg with a purity of 99.85% was placed in a clay crucible and heated to melt in a pit furnace at 953 K. A mixture of SF6 and CO2 was introduced as a protective gas to obtain Mg melt.

[0038] The Mg-30Ca master alloy and 99.99% pure Zn block were held in a vacuum furnace at 473K for 1 hour. Then, Mg melt at 953K was added and a mixture of SF6 and CO2 was introduced as a protective gas. After standing for 10 minutes, the mixture was stirred for 2 minutes to ensure that the elements and Mg were evenly distributed in the melt, thus obtaining the alloy melt.

[0039] Step 3, Casting: After the alloy melt is allowed to stand for 8 minutes, the temperature is adjusted to 943K±5K and poured into a steel mold with a cavity thickness of 20mm~25mm to obtain a Mg-Zn-Ca alloy billet.

[0040] Step 4, Rolling: After cutting the Mg-Zn-Ca alloy billet into rolling samples of 50mm×25mm×5mm, the samples were held in a 573K heat treatment furnace for 10min and then asynchronously rolled. The asynchronous rolling conditions were: roll temperature 80℃, rotation speed 16rpm, upper roll diameter 150mm, and lower roll diameter 120mm. The rolling was performed in 4 passes, with a reduction of 20% in each pass. The samples were held at 583K±10K for 3min between passes to obtain rolling samples with a thickness of 1mm.

[0041] Step 5, Heat Treatment: A 1 mm thick rolled sample was held in a heat treatment furnace at 583 K ± 10 K for 10 min to obtain a Mg-1Zn-0.5Ca alloy.

[0042] like Figure 1 As shown, the combination of microalloying composition design and asynchronous controlled rolling technology results in a better rolling effect of the prepared alloy.

[0043] Experimental test: 1. Surface morphology test.

[0044] from Figure 2 As can be seen from the Ca2Mg6Zn3 diffraction pattern in (a), the Ca2Mg6Zn3 phase in the Mg-1Zn-0.5Ca alloy has a single-crystal structure. Figure 2 As shown in (b) of the figure, the diffraction spots of the Ca2Mg6Zn3 phase in the Mg-1Zn-0.5Ca-0.5Sc alloy prepared in Example 1 are ring-shaped, indicating that its crystal structure is amorphous. This shows that by adding Sc to the Mg-1Zn-0.5Ca alloy, Sc preferentially forms the ZnSc phase with Zn in the alloy, consuming some Zn and reducing the supersaturation of the remaining Zn in the alloy, thus reducing the number of Zn atoms participating in the formation of the Ca2Mg6Zn3 phase. At the same time, through a brief heat treatment after rolling, the crystallization of the second phase in the alloy is ensured to be insufficient. The Ca2Mg6Zn3 phase forms a large number of vacancy defects during the crystallization process, resulting in a large lattice distortion, and finally achieving in-situ induced amorphization of the Ca2Mg6Zn3 phase in the Mg-Zn-Ca alloy.

[0045] By comparing the texture patterns of Mg-1Zn-0.5Ca-0.5Sc alloy under different conditions, and comparing the pre-deformed Mg-1Zn-0.5Ca-0.5Sc alloy obtained by rolling deformation with a 2% reduction at room temperature, the pre-deformed Mg-1Zn-0.5Ca-0.5Sc alloy can be obtained. like Figure 3 As shown, Figure 3 (a) The texture of the rolled and annealed Mg-1Zn-0.5Ca-0.5Sc alloy, from Figure 3 As shown in (a), the Mg-1Zn-0.5Ca-0.5Sc alloy exhibits a fully recrystallized structure after rolling heat treatment. A pre-deformed Mg-1Zn-0.5Ca-0.5Sc alloy was obtained by rolling and annealing the Mg-1Zn-0.5Ca-0.5Sc alloy at room temperature with a 2% reduction. The microstructure of the pre-deformed Mg-1Zn-0.5Ca-0.5Sc alloy remained fully recrystallized, and its basal texture was significantly weakened, with grain refinement. This indicates that the amorphous Ca2Mg6Zn3 phase can promote dynamic recrystallization of the alloy.

[0046] 2. Mechanical property testing.

[0047] The rolled annealed Mg-1Zn-0.5Ca-0.5Sc alloy prepared in Example 1 was subjected to rolling deformation with a 2% reduction at room temperature to obtain a pre-deformed Mg-1Zn-0.5Ca-0.5Sc alloy. Mechanical properties were tested on both the rolled annealed Mg-1Zn-0.5Ca-0.5Sc alloy and the pre-deformed Mg-1Zn-0.5Ca-0.5Sc alloy. The tensile speed was 1 mm / min, the gauge length was 10 mm, and at least three samples were tested. The average value was calculated, and the results are as follows: Figure 4 As shown.

[0048] from Figure 4 As can be seen, the alloy strength is significantly improved after 2% room temperature rolling pre-deformation, and its fracture elongation is also relatively high. This indicates that the formation of the amorphous Ca2Mg6Zn3 phase promotes dynamic recrystallization, thereby refining the grains and ultimately improving the mechanical properties of the alloy.

[0049] It should be noted that when numerical ranges are involved in this invention, it should be understood that the two endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described in this invention to avoid redundancy. Although preferred embodiments of this invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments, and all such changes and modifications fall within the scope of this invention.

[0050] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. If these modifications and variations fall within the scope of equivalents of this invention, then this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a Mg-Zn-Ca alloy with an amorphous phase, characterized in that, Includes the following steps: By mass percentage, the Mg-Zn-Ca alloy is composed of the following elements: Zn 1%~3%, Ca 0.5%~1%, Sc 0.1%~0.5%, with the balance being Mg and unavoidable impurities, totaling 100%; according to the elemental composition of the Mg-Zn-Ca alloy, the elements are melted and cast into an alloy billet to obtain the Mg-Zn-Ca alloy. The Mg-Zn-Ca alloy is subjected to asynchronous rolling; The asynchronously rolled Mg-Zn-Ca alloy is subjected to post-rolling heat treatment for 10 to 15 minutes. The Sc element preferentially forms the ZnSc phase, reducing the supersaturation of the remaining Zn in the alloy. At the same time, the Ca2Mg6Zn3 phase generates vacancy defects and lattice distortion during the crystallization process, transforming into an amorphous structure, thus obtaining a Mg-Zn-Ca alloy with an amorphous phase.

2. The method for preparing the Mg-Zn-Ca alloy with an amorphous phase according to claim 1, characterized in that, The temperature of the post-rolling heat treatment is 573K to 623K.

3. The method for preparing the Mg-Zn-Ca alloy with an amorphous phase according to claim 1, characterized in that, The preparation method of the Mg-Zn-Ca alloy is as follows: Based on the elemental composition of the Mg-Zn-Ca alloy, prepare Mg, Mg-30Ca master alloy, Zn block and Mg-20Sc master alloy; Under a protective atmosphere, Mg is melted, and then preheated Mg-30Ca master alloy, Zn block and Mg-20Sc master alloy are added for smelting to make Ca, Zn, Sc and Mg uniformly distributed in the melt to obtain an alloy melt. The alloy melt is cast into an alloy billet to obtain a Mg-Zn-Ca alloy.

4. The method for preparing the Mg-Zn-Ca alloy with an amorphous phase according to claim 3, characterized in that, The melting temperature of Mg is 933K to 963K.

5. The method for preparing the Mg-Zn-Ca alloy with an amorphous phase according to claim 3, characterized in that, The preheating temperature for Mg-30Ca master alloy, Zn block and Mg-20Sc master alloy is 473K to 523K.

6. The method for preparing the Mg-Zn-Ca alloy with an amorphous phase according to claim 3, characterized in that, The casting temperature is 933K~943K.

7. The method for preparing the Mg-Zn-Ca alloy with an amorphous phase according to claim 1, characterized in that, The parameter conditions for asynchronous rolling are as follows: The roll temperature is 50℃~100℃, and the roll speed is 15rpm~18rpm; The upper roll has a diameter of 150mm, and the lower roll has a diameter of 120mm; The rolling process is carried out in multiple passes, and the rolled sample is held at 573K to 623K between passes for 3 to 5 minutes.

8. A Mg-Zn-Ca alloy having an amorphous phase, characterized in that, The Mg-Zn-Ca alloy having an amorphous phase is prepared by the method for preparing the Mg-Zn-Ca alloy having an amorphous phase according to any one of claims 1 to 7.

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