Zn-Ag-Ca alloy and preparation method thereof

Abstract

The invention belongs to the technical field of metal materials, and particularly relates to a Zn-Ag-Ca alloy and a preparation method. The alloy comprises 1.0 wt%-4.5 wt% of Ag, 0.5 wt%-2.0 wt% of Ca and the balance Zn. By adding a limited amount of Ca into the Zn-Ag alloy and cooperating with equal-channel angular pressing, the strength of the alloy is improved, and meanwhile high ductility is guaranteed. Ca is added to form a CaZn13 precipitated phase in a Zn alloy matrix, a dislocated motion is hindered, under the influence of a PSN mechanism, non-uniform nucleation is formed, the strength of the Zn-based alloy is enhanced, the size of the CaZn13 phase is large, the edge of the CaZn13 phase is in a corner angle shape, the crystal morphology is regulated and controlled by controlling the calcium adding time and carrying out equal-channel angular pressing at a certain temperature, and the strength of the Zn-based alloy is improved. And the alloy material with high strength and ductility is obtained. The strength and ductility of the material are further improved through the remelting process.

Description

Technical Field

[0001] The invention belongs to the technical field of metal materials, in particular to a Zn-Ag-Ca alloy and a preparation method thereof. Background Art

[0002] Traditional medical implant materials need to be removed in a second operation after the damaged tissue heals, which increases the risk and cost for patients. The new generation of biodegradable implant materials can not only meet their use requirements, but also be completely degraded in the human body, and the degradation products are harmless to the human body. At present, the main biodegradable metal materials are iron-based alloys, magnesium-based alloys and zinc-based alloys. Zinc-based alloys have become a research hotspot in the field of medical implant materials due to their excellent biosafety and moderate degradation rate. However, the current Zn-based alloys have an alloy elongation of mostly below 10% when the strength meets the standard, and it is difficult to obtain alloy materials with both high strength and high ductility.

[0003] The patent with publication number CN108220683A discloses a low-alloyed Zn-Mn-Ag or Zn-Mn-Ca alloy and a preparation method thereof. The zinc alloy provided by the invention is composed of the following components by mass percentage: (1) 0.1-5% Mn, 0.05-5% Ag, and the balance is Zn; (2) 0.1-5% Mn, 0.02-2% Ca, and the balance is Zn; the alloy structure is optimized by rolling or extruding the cast alloy obtained by vacuum melting, so that the alloy has good comprehensive mechanical properties. However, when the strength performance of the alloy prepared by this method reaches more than 300 MPa, the elongation is less than 10%. Summary of the invention

[0004] In view of the above problems existing in the prior art, the present invention provides a Zn-Ag-Ca alloy and a preparation method thereof, which can obtain an alloy material having both excellent strength performance and elongation.

[0005] To achieve the above object, the technical solution provided by the present invention is as follows:

[0006] In a first aspect, the present application provides a Zn-Ag-Ca alloy, in which, by mass percentage, Ag accounts for 1.0-4.5%, Ca accounts for 0.5-2.0%, and the rest is Zn.

[0007] Optionally, the Zn-Ag-Ca alloy has a strength of 300-340 MPa and an elongation of 19%-59%.

[0008] On the other hand, the present application also provides a method for preparing the above-mentioned Zn-Ag-Ca alloy, comprising the following steps:

[0009] S1: Weigh the metal raw material according to the mass percentage of the metal element;

[0010] S2: Mixing and melting the metal raw materials and then pouring them to obtain a cast alloy;

[0011] S3: homogenizing the as-cast alloy;

[0012] S4: the alloy after homogenization treatment is kept at 150-180° C. for 1-2 hours; then, equal channel angular extrusion is performed for not less than 10 times, and cooling is performed to obtain the Zn—Ag—Ca alloy.

[0013] Optionally, the specific steps of S2 are: add high-purity zinc and high-purity silver into the crucible and heat it to 450-480°C, then keep it warm for 1-1.5 hours, then add high-purity calcium, and introduce protective gas argon, heat the crucible to 720-800°C and keep it warm for 1-1.5 hours, and then cast it into a mold under argon protection.

[0014] Optionally, the equal channel angular extrusion conditions shown in S4 are: the extrusion speed is 2.5 mm / s, and after each extrusion, the mold is turned 90° and kept at a temperature of 150-160° C. for 15 minutes.

[0015] Optionally, the cast alloy obtained in S2 is remelted and then subjected to homogenization treatment.

[0016] Optionally, the homogenization treatment conditions in S3 are: 320-360° C. for 3-4 h.

[0017] Optionally, the extrusion passes are 12 times.

[0018] Optionally, Ag accounts for 3.5-4.5 wt % in the Zn-Ag-Ca alloy.

[0019] Optionally, the cooling in S4 is performed at room temperature.

[0020] Optionally, the purity of the metal raw materials is greater than or equal to 99.99%.

[0021] Compared with the prior art, this application has at least the following beneficial effects:

[0022] The present invention improves the strength of the alloy while ensuring high elongation by adding a limited amount of Ca to the Zn-Ag alloy and combining homogenization and equal channel angular extrusion. The addition of Ca will form CaZn in the Zn alloy matrix. 13 The precipitated phase hinders the dislocation movement and forms heterogeneous nucleation under the influence of PSN mechanism, which enhances the strength of Zn-based alloy. However, CaZn 13The size of the phase is large and the edges are angular. By controlling the addition time of calcium and performing equal channel angular extrusion at a certain temperature after homogenization treatment to regulate the crystal morphology, an alloy material with both high strength and ductility is obtained. At the same time, the added elements are beneficial to the human body and expand the field of biodegradable materials. The strength and ductility of the material are further improved through the remelting process. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the SEM structure of the alloy obtained in Example 1;

[0024] Figure 2 The SEM structure of the alloy obtained in Comparative Example 1;

[0025] Figure 3 EBSD structure of the alloy obtained in Example 1;

[0026] Figure 4 EBSD structure of the alloy obtained in Example 5;

[0027] Figure 5 This is the EBSD structure of the alloy obtained by extrusion 8 times in Example 6. DETAILED DESCRIPTION

[0028] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0029] The experimental methods used in the embodiments of the present invention are conventional methods unless otherwise specified.

[0030] The reagents and materials used in this example can all be purchased conventionally. The quantitative experiments involved in the examples were repeated at least three times, and the results were averaged.

[0031] Example 1

[0032] A Zn-Ag-Ca alloy comprises the following components in percentages: 3.5wt% Ag, 1.0wt% Ca, and the remainder being Zn and inevitable impurities.

[0033] A method for preparing a high-strength and high-ductility Zn-based alloy comprises the following steps:

[0034] S1: weighing metal raw materials according to the mass percentage of metal elements, the metal raw materials include high-purity Zn with a purity greater than 99%, high-purity Ag with a purity greater than 99%, and high-purity Ca with a purity greater than 99%;

[0035] S2: Add high-purity zinc and high-purity silver into the crucible and heat it to 450°C. Then keep it at 450°C for 1 hour, skim off the slag and add high-purity calcium. Then introduce protective argon gas. Heat the crucible to 720°C and keep it at that temperature for 1 hour. Stir once every 20 minutes. Then cast it into a mold under the protection of argon gas and cool it at room temperature to obtain a cast alloy.

[0036] S3: The cast alloy obtained by casting was cut into 19.5 mm × 19.5 mm × 45 mm, and homogenized in a cassette furnace at 350 ° C for 4 h;

[0037] S4: The homogenized alloy was kept at 150°C for 1 hour, and then subjected to equal channel angular extrusion (ECAP) for 12 passes on a machine tool (JBK3-250) equipped with a rotary die and a slider, with an extrusion speed of 2.5 mm / s. Between each pass, the die was flipped 90° and kept at 150°C for 15 minutes. After the extrusion, the alloy was air-cooled at room temperature to obtain the Zn-Ag-Ca alloy.

[0038] Example 2

[0039] A Zn-Ag-Ca alloy comprises the following components in percentages: 4.0 wt% Ag, 1.2 wt% Ca, and the remainder being Zn and inevitable impurities.

[0040] A method for preparing a high-strength and high-ductility Zn-based alloy comprises the following steps:

[0041] S1: weighing metal raw materials according to the mass percentage of metal elements, the metal raw materials include high-purity Zn with a purity greater than 99%, high-purity Ag with a purity greater than 99%, and high-purity Ca with a purity greater than 99%;

[0042] S2: Add high-purity zinc and high-purity silver into the crucible and heat it to 450°C. Then keep it at 450°C for 1 hour, skim off the slag and add high-purity calcium. Then introduce protective argon gas. Heat the crucible to 720°C and keep it at that temperature for 1 hour. Stir once every 20 minutes. Then cast it into a mold under the protection of argon gas and cool it at room temperature to obtain a cast alloy.

[0043] S3: The cast alloy obtained by casting was cut into 19.5 mm × 19.5 mm × 45 mm, and homogenized in a cassette furnace at 350 ° C for 4 h;

[0044] S4: The homogenized alloy was kept at 150°C for 1 hour, and then subjected to equal channel angular extrusion (ECAP) for 12 passes on a machine tool (JBK3-250) equipped with a rotary die and a slider, with an extrusion speed of 2.5 mm / s. Between each pass, the die was flipped 90° and kept at 150°C for 15 minutes. After the extrusion, the alloy was air-cooled at room temperature to obtain the Zn-Ag-Ca alloy.

[0045] Example 3

[0046] The difference between this embodiment and embodiment 1 is that: S2: high-purity zinc, high-purity silver and high-purity calcium are added into the crucible and the temperature is raised to 720°C and kept warm for 1 hour, during which time the mixture is stirred every 20 minutes, and then cast into a mold under argon protection, and cooled at room temperature to obtain a cast alloy.

[0047] Example 4

[0048] The difference between this embodiment and embodiment 1 is that: S4: the homogenized alloy is kept at 150°C for 1 hour, and then equal channel angular extrusion (ECAP) is performed on a machine tool (JBK3-250) equipped with a rotary die and a slider for 12 passes, the die is turned 90° between each pass, and after extrusion, it is air-cooled at room temperature to obtain the Zn-Ag-Ca alloy.

[0049] Example 5

[0050] A Zn-Ag-Ca alloy comprises the following components in percentages: 1.5wt% Ag, 1.0wt% Ca, and the remainder being Zn and inevitable impurities.

[0051] A method for preparing a high-strength and high-ductility Zn-based alloy comprises the following steps:

[0052] S1: weighing metal raw materials according to the mass percentage of metal elements, the metal raw materials include high-purity Zn with a purity greater than 99%, high-purity Ag with a purity greater than 99%, and high-purity Ca with a purity greater than 99%;

[0053] S2: Add high-purity zinc and high-purity silver into the crucible and heat it to 450°C. Then keep it at 450°C for 1 hour, skim off the slag and add high-purity calcium. Then introduce protective argon gas. Heat the crucible to 720°C and keep it at that temperature for 1 hour. Stir once every 20 minutes. Then cast it into a mold under the protection of argon gas and cool it at room temperature to obtain a cast alloy.

[0054] S3: The cast alloy obtained by casting was cut into 19.5 mm × 19.5 mm × 45 mm, and homogenized in a cassette furnace at 350 ° C for 4 h;

[0055] S4: The homogenized alloy was kept at 150°C for 1 hour, and then subjected to equal channel angular extrusion (ECAP) for 12 passes on a machine tool (JBK3-250) equipped with a rotary die and a slider, with an extrusion speed of 2.5 mm / s. Between each pass, the die was flipped 90° and kept at 150°C for 15 minutes. After the extrusion, the alloy was air-cooled at room temperature to obtain the Zn-Ag-Ca alloy.

[0056] Example 6

[0057] The difference between this embodiment and embodiment 1 is that the number of equal channel angular pressing (ECAP) passes is 8.

[0058] Example 7

[0059] A Zn-Ag-Ca alloy comprises the following components in percentages: 3.5wt% Ag, 1.0wt% Ca, and the remainder being Zn and inevitable impurities.

[0060] A method for preparing a high-strength and high-ductility Zn-based alloy comprises the following steps:

[0061] S1: weighing metal raw materials according to the mass percentage of metal elements, the metal raw materials include high-purity Zn with a purity greater than 99%, high-purity Ag with a purity greater than 99%, and high-purity Ca with a purity greater than 99%;

[0062] S2: Add high-purity zinc and high-purity silver into the crucible and heat it to 450°C. Then, keep it at 450°C for 1 hour, skim off the slag and add high-purity calcium, and introduce protective gas argon. Heat the crucible to 720°C and keep it at this temperature for 1 hour. Stir once every 20 minutes during this period. Then, cast it into a mold under the protection of argon gas, and cool it at room temperature to obtain a cast alloy. Put the cooled cast alloy into the crucible again and introduce argon gas. Heat the crucible to 720°C and keep it at this temperature for 2 hours. Stir once every 20 minutes during this period. Then, cast it into a mold under the protection of argon gas to obtain a new cast alloy.

[0063] S3: The cast alloy obtained by casting was cut into 19.5 mm × 19.5 mm × 45 mm, and homogenized in a cassette furnace at 350 ° C for 4 h;

[0064] S4: The homogenized alloy was kept at 150°C for 1 hour, and then subjected to equal channel angular extrusion (ECAP) for 12 passes on a machine tool (JBK3-250) equipped with a rotary die and a slider. The extrusion process controlled the temperature at 150-160°C and the extrusion speed at 2.5 mm / s. Between each pass, the die was flipped 90° and kept warm for 15 minutes. After the extrusion was completed, the alloy was air-cooled at room temperature to obtain the Zn-Ag-Ca alloy.

[0065] Example 8

[0066] The difference between this embodiment and embodiment 1 is that:

[0067] A Zn-Ag alloy comprises the following components in percentages: 3.5wt% Ag, and the remainder being Zn and inevitable impurities.

[0068] The alloys obtained in Examples 1-5 and Comparative Examples were subjected to SEM and EBSD test analysis, and the results are as follows: Figure 1-5 shown.

[0069] The mechanical properties of the alloys prepared in Examples 1-5 and Comparative Examples 1-3 were tested. The test results are shown in Table 1.

[0070] Table 1 Mechanical properties test results

[0071] Tensile strength (Mpa) Yield strength (Mpa) Elongation (%) Example 1 311.6 275.4 58.6 Example 2 315.7 278.1 63.7 Example 3 308.8 263.2 40.6 Example 4 300.2 253.4 29.1 Example 5 323.4 249 20.7 Example 6 338.3 298.5 19.3 Example 7 331.7 309.4 55.3 Example 8 91.9 64.4 158.5

[0072] As can be seen from Table 1, the method of the present invention gradually obtains good mechanical properties, with a yield strength of more than 250MPa, a tensile strength of more than 300MPa, and an elongation of up to 60%. Adding remelting treatment helps to improve the tensile strength and elongation. When calcium is not added or all metals are mixed at one time during the smelting stage, the tensile strength or elongation of the alloy obtained is lower than that of the alloy obtained by the method of the present invention. The temperature control of the equal channel angular extrusion process also has an important influence on the properties of the alloy.

[0073] Depend on Figure 1 It can be observed that the homogenized CaZn 13 The phase tends to be rounded and passivated after ECAP extrusion, and the size of the phase becomes much smaller. At the same time, the distribution of the phase also becomes dispersed as the ECAP proceeds. The fine grain strengthening caused by the reduction of grain size is the main reason for the increase in the strength of the zinc alloy.

[0074] Figure 2 The white dots in the figure are AgZn3 phase, which is a nanoscale phase and helps to improve the elongation of the alloy. This phase will only appear after the Ag content is increased to 3.5wt%. Therefore, when the Ca content is the same, the elongation of the Zn-Ag-Ca alloy is better when the Ag content is increased to 3.5wt%.

[0075] pass Figure 3 and Figure 5 It can be seen that when the extrusion pass is too low, the ductility is poor. Increasing the extrusion pass will promote dynamic recrystallization (DRX), thereby refining the grains and reducing defects while reducing the dislocation density. The alloy obtained under the appropriate extrusion pass can have both excellent tensile strength and elongation.

Claims

1. A Zn-Ag-Ca alloy, characterized in that: In terms of mass percentage, Ag accounts for 1.0~4.5%, Ca accounts for 0.5~2.0%, and the rest is Zn.

2. The Zn-Ag-Ca alloy according to claim 1, characterized in that: The Zn-Ag-Ca alloy has a strength of 300-340 MPa and an elongation of 19%-59%.

3. The method for preparing the Zn-Ag-Ca alloy according to any one of claims 1 to 2, characterized in that: The following steps are involved: S1: Weigh the metal raw material according to the mass percentage of the metal element; S2: Mixing and melting the metal raw materials and then pouring them to obtain a cast alloy; S3: homogenizing the as-cast alloy; S4: the alloy after homogenization treatment is kept at 150-180° C. for 1-2 hours; then, equal channel angular extrusion is performed for not less than 10 times, and cooling is performed to obtain the Zn—Ag—Ca alloy.

4. The method for preparing the Zn-Ag-Ca alloy according to claim 3, characterized in that: The specific steps of S2 are: add high-purity zinc and high-purity silver into the crucible and heat it to 450-480°C, then keep it warm for 1-1.5 hours, then add high-purity calcium, and introduce protective gas argon, heat the crucible to 720-800°C and keep it warm for 1-1.5 hours, then cast it into a mold under argon protection to obtain a cast alloy.

5. The method for preparing the Zn-Ag-Ca alloy according to claim 3, characterized in that: The equal channel angular extrusion conditions shown in S4 are: the extrusion speed is 2.5 mm / s, and after each extrusion, the mold is turned 90° and kept at a temperature of 150-160°C for 15 minutes.

6. The method for preparing the Zn-Ag-Ca alloy according to claim 3, characterized in that: The cast alloy obtained in S2 is remelted and then homogenized.

7. The method for preparing the Zn-Ag-Ca alloy according to claim 3, characterized in that: The homogenization treatment conditions in S3 are: 320-360° C. for 3-4 h.

8. The method for preparing the Zn-Ag-Ca alloy according to claim 3, characterized in that: The number of extrusion passes is 12.

9. The method for preparing the Zn-Ag-Ca alloy according to claim 3, characterized in that: In the Zn-Ag-Ca alloy, Ag accounts for 3.5-4.5 wt %.

10. A Zn-Ag-Ca alloy prepared according to the method according to any one of claims 1 to 8, characterized in that: The purity of the metal raw materials is greater than or equal to 99.99%.

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