HIGH-STRENGTH AND HIGH-CORROSION-RESISTANT TERNARY MAGNESIUM ALLOY AND PREPARATION METHOD THEREOF

Abstract

The present invention relates to a high-strength, high-corrosion resistance ternary magnesium alloy and a preparation method therefor, the magnesium alloy comprising the following element components by mass percentage: 8-12 wt % of Y, 0.6-3 wt % of Al and the remainder being Mg. The method comprises: (1) under a protective atmosphere, preparing a Mg—Y intermediate alloy, an aluminum ingot and a magnesium ingot into a magnesium alloy melt; (2) under a protective atmosphere, allowing the magnesium alloy melt to stand after stirring, then carrying out refining, degassing, and slag removal, allowing the magnesium alloy melt to stand again, then thermally insulating to obtain a magnesium alloy liquid; and (3) casting and molding the magnesium alloy liquid under a protective atmosphere, and forming a cast ingot; the three steps above ultimately obtain a high-strength, high-corrosion resistance ternary magnesium alloy.

Claims

1. A high-strength and high-corrosion-resistant ternary magnesium alloy, the magnesium alloy including the following elements in percentage by weight: 8-12 wt % of Y, 0.6-3 wt % of Al, and the balance of Mg.

2. A preparation method of the high-strength and high-corrosion-resistant ternary magnesium alloy according to claim 1, the method comprising the following steps: (1) under a protective atmosphere, preparing a magnesium alloy melt from an Mg—Y master alloy, an aluminum ingot and a magnesium ingot; (2) under the protective atmosphere, stirring the magnesium alloy melt, holding, then performing refined degassing and deslagging, holding again, and performing heat preservation to obtain a magnesium alloy liquid; and (3) under the protective atmosphere, casting the magnesium alloy liquid into a mold to form an ingot, and finally obtaining the corrosion-resistant ternary magnesium alloy.

3. The preparation method of the high-strength and high-corrosion-resistant ternary magnesium alloy according to claim 2, wherein preparing the magnesium alloy melt comprises the following specific steps: under the protective atmosphere, after the magnesium ingot is melted, adding the Mg—Y master alloy and the aluminum ingot at a high temperature, and after the Mg—Y master alloy and the aluminum ingot are melted, obtaining the magnesium alloy melt.

4. The preparation method of the high-strength and high-corrosion-resistant ternary magnesium alloy according to claim 3, wherein a protective gas is a mixed gas of SF.sub.6 and CO.sub.2, and a temperature at which the Mg—Y master alloy and the aluminum ingot are added is 660-700° C.

5. The preparation method of the high-strength and high-corrosion-resistant ternary magnesium alloy according to claim 2, wherein a holding temperature after stirring is 720-740° C., and a holding time is 20-60 min; a temperature of the refined degassing and deslagging is 730-750° C.; and a temperature of the heat preservation is 720-740° C., and a time of the heat preservation is 20-60 min.

6. The preparation method of the high-strength and high-corrosion-resistant ternary magnesium alloy according to claim 2, wherein the ingot is solution-treated to obtain the corrosion-resistant ternary magnesium alloy.

7. The preparation method of the high-strength and high-corrosion-resistant ternary magnesium alloy according to claim 2, wherein the ingot is solution-treated, and then is extruded and water-quenched to obtain the corrosion-resistant ternary magnesium alloy.

8. The preparation method of the high-strength and high-corrosion-resistant ternary magnesium alloy according to claim 7, wherein a temperature of the solution treatment is 500-580° C., a time of the solution treatment is 8-24 h, a temperature of extrusion is 300-450° C., an extrusion ratio is (9-30):1, and an outflow speed of an extruded section is 3-10 m/min.

9. The preparation method of the high-strength and high-corrosion-resistant ternary magnesium alloy according to claim 2, wherein a protective gas is a mixed gas of SF.sub.6 and CO.sub.2.

10. The preparation method of the high-strength and high-corrosion-resistant ternary magnesium alloy according to claim 6, wherein a temperature of the solution treatment is 500-580° C., a time of the solution treatment is 8-24 h.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] FIG. 1 is a picture of a metallographic structure of a high-strength and high-corrosion-resistant ternary magnesium alloy prepared by the present disclosure; and

[0031] FIG. 2 is a typical tensile curve diagram of the high-strength and high-corrosion-resistant ternary magnesium alloy prepared by the present disclosure.

DESCRIPTION OF THE EMBODIMENTS

[0032] The present disclosure is described in detail below with reference to the accompanying drawings and specific examples.

Example 1

[0033] A method for preparing a ternary magnesium alloy in this embodiment, under a protective atmosphere (a protective gas is a mixed gas of SF.sub.6 and CO.sub.2), includes the following steps:

[0034] (1) Under the protective atmosphere (the protective gas is the mixed gas of SF.sub.6 and CO.sub.2), after a magnesium ingot with the purity of not less than 99.9 wt % was melted, an Mg—Y master alloy and an aluminum ingot were added at 660-700° C., and after the Mg—Y master alloy and the aluminum ingot were melted, a magnesium alloy melt was obtained.

[0035] (2) Under the protective atmosphere (the protective gas is the mixed gas of SF.sub.6 and CO.sub.2), the magnesium alloy melt was stirred at 730-740° C. and then was held for 20 min, then was subjected to refined degassing and deslagging at 740-750° C., was subjected to holding again, and was subjected to heat preservation at 730-740° C. for 30 min to obtain a magnesium alloy liquid.

[0036] (3) Under the protective atmosphere (the protective gas is the mixed gas of SF.sub.6 and CO.sub.2), the magnesium alloy liquid was subjected to cast molding to obtain an ingot.

[0037] (4) The ingot was put into an air furnace to be solution-treated at 550° C. for 16 h, then a heat preserving furnace was heated to 350° C., the solution-treated material was put into the heat preserving furnace to be preheated for 45 min, an extrusion mold was heated to 350° C. and subjected to heat preservation for 1 h, then hot extrusion was performed according to an extrusion ratio of about 16:1, an outflow speed of a section was controlled to be 8 m/min, and finally the high-strength and high-corrosion-resistant ternary magnesium alloy was obtained, as shown in FIG. 1(a).

[0038] After testing, the chemical components and percentages of the magnesium alloy obtained in this embodiment are as follows: Y: 10.4 wt %, Al: 0.82 wt %, impurity element Fe: 0.018 wt %, impurity element Cu: 0.01 wt %, impurity element Ni: 0.002 wt %, and the balance of magnesium. Its mechanical properties and hydrogen evolution performance are shown in Table 1.

Example 2

[0039] A method for preparing a novel corrosion-resistant ternary magnesium alloy in this embodiment includes the following steps:

[0040] (1) Under a protective atmosphere (a protective gas is a mixed gas of SF.sub.6 and CO.sub.2), after a magnesium ingot with the purity of not less than 99.9 wt % was melted, an Mg—Y master alloy and an aluminum ingot were added at 660-700° C., and after the Mg—Y master alloy and the aluminum ingot were melted, a magnesium alloy melt was obtained.

[0041] (2) Under the protective atmosphere (the protective gas is the mixed gas of SF.sub.6 and CO.sub.2), the magnesium alloy melt was stirred at 730-740° C. and then was held for 20 min, then was subjected to refined degassing and deslagging at 740-750° C., was subjected to holding again, and was subjected to heat preservation at 730-740° C. for 30 min to obtain a magnesium alloy liquid.

[0042] (3) Under the protective atmosphere (the protective gas is the mixed gas of SF.sub.6 and CO.sub.2), the magnesium alloy liquid was subjected to cast molding to obtain an ingot.

[0043] (4) The ingot was put into an air furnace to be solution-treated at 520° C. for 8 h, then a heat preserving furnace was heated to 375° C., the solution-treated material was put into the heat preserving furnace to be preheated for 45 min, an extrusion mold was heated to 375° C. and subjected to heat preservation for 1 h, then hot extrusion was performed according to an extrusion ratio of about 16:1, an outflow speed of a section was controlled to be 8 m/min, and finally the high-strength and high-corrosion-resistant ternary magnesium alloy was obtained, as shown in FIG. 1(b).

[0044] After testing, the chemical components and percentages of the magnesium alloy obtained in this embodiment are as follows: Y: 10.4 wt %, Al: 0.82 wt %, impurity element Fe: 0.018 wt %, impurity element Cu: 0.01 wt %, impurity element Ni: 0.002 wt %, and the balance of magnesium. Its mechanical properties and hydrogen evolution performance are shown in Table 1.

Example 3

[0045] A method for preparing a novel corrosion-resistant ternary magnesium alloy in this embodiment includes the following steps:

[0046] (1) Under a protective atmosphere (a protective gas is a mixed gas of SF.sub.6 and CO.sub.2), after a magnesium ingot with the purity of not less than 99.9 wt % was melted, an Mg—Y master alloy and an aluminum ingot were added at 660-700° C., and after the Mg—Y master alloy and the aluminum ingot were melted, a magnesium alloy melt was obtained.

[0047] (2) Under the protective atmosphere (the protective gas is the mixed gas of SF.sub.6 and CO.sub.2), the magnesium alloy melt was stirred at 730-740° C. and then was held for 20 min, then was subjected to refined degassing and deslagging at 720-730° C., was subjected to holding again, and was subjected to heat preservation at 720-730° C. for 30 min to obtain a magnesium alloy liquid.

[0048] (3) Under the protective atmosphere (the protective gas is the mixed gas of SF.sub.6 and CO.sub.2), the magnesium alloy liquid was subjected to cast molding to obtain an ingot.

[0049] (4) The ingot was put into an air furnace to be solution-treated at 550° C. for 16 h, then a heat preserving furnace was heated to 375° C., the solution-treated material was put into the heat preserving furnace to be preheated for 45 min, an extrusion mold was heated to 375° C. and subjected to heat preservation for 1 h, then hot extrusion was performed according to an extrusion ratio of about 25:1, an outflow speed of a section was controlled to be 8 m/min, and finally the high-strength and high-corrosion-resistant ternary magnesium alloy was obtained, as shown in FIG. 1(c).

[0050] After testing, the chemical components and percentages of the magnesium alloy obtained in this embodiment are as follows: Y: 10.4 wt %, Al: 0.82 wt %, impurity element Fe: 0.04 wt %, impurity element Cu: 0.01 wt %, impurity element Ni: 0.002 wt %, and the balance of magnesium. Its mechanical properties and hydrogen evolution performance are shown in Table 1.

[0051] Performance Testing:

[0052] 1. Hydrogen Evolution and Weight Loss Testing:

[0053] The high-strength and high-corrosion-resistant ternary magnesium alloy obtained in Examples 1-3 was soaked in 3.5 wt % of an NaCl solution for 336 h, and hydrogen evolution and weight loss testing was performed. Results are shown in Table 1.

TABLE-US-00001 TABLE 1 Hydrogen Yield Elongation evolution rate strength rate Alloy (ml/cm.sup.−2 .Math. day.sup.−1) (MPa) (%) Example 1 0.05 350 8 Example 2 0.08 273 15 Example 3 0.07 300 13.5

[0054] Table 1 shows the hydrogen evolution rate, yield strength and elongation rate of the high-strength and high-corrosion-resistant ternary magnesium alloy prepared by the present disclosure soaked in 3.5 wt % of the NaCl aqueous solution for 336 h at room temperature. It reveals that the hydrogen evolution rate is not more than 0.1 ml/cm.sup.−2.Math.day.sup.−1, the yield strength is greater than 250 MPa, and the elongation rate is greater than 8%.

[0055] It may be seen from Table 1 that the high-strength and high-corrosion-resistant ternary magnesium alloy in Example 1 has the best performance, with the hydrogen evolution rate of 0.05 ml/cm.sup.−2.Math.day.sup.−1, the yield strength of 350 MPa, and the elongation rate of not less than 8%.

[0056] 2. Potentiodynamic Polarization Curve Testing:

[0057] The magnesium alloy obtained in Examples 1-3 was subjected to potentiodynamic polarization curve testing in 3.5 wt % of an NaCl solution by adopting a PARSTAT 2273 electrochemical workstation. The polarization curve testing starts from being lower than an open circuit potential of 300 mV, and a scanning speed is 1 mV/s. The corrosion current density I.sub.corr of the magnesium alloy obtained in each example is as shown in Table 2

TABLE-US-00002 TABLE 2 Example 1 Example 2 Example 3 I.sub.corr(μA/cm.sup.2) 4.9 6.2 6.0

[0058] It may be seen from Table 2 that the corrosion-resistant ternary magnesium alloy prepared by the present disclosure has the same order of magnitude of i.sub.corr in 3.5 wt % of the NaCl aqueous solution at room temperature, which is less than 10 μA/cm.sup.2.

[0059] At the same time, it may be seen that the corrosion-resistant ternary magnesium alloy Mg-10Y-0.8Al prepared in Example 1 has the best corrosion resistance, and i.sub.corr is 4.9 μA/cm.sup.2.

[0060] The corrosion resistance comparison between the magnesium alloy prepared by the present disclosure and a magnesium alloy in the prior art is as shown in Table 3.

TABLE-US-00003 TABLE 3 Corrosion current density Tensile strength Elongation rate Sample (μA/cm.sup.2) (MPa) (%) Example 1 4.9 350 8 Example 2 6.2 273 15 AZ31.sup.[1] 11.5 195 12.5 ZK60AF.sup.[2] 14 260 11.5

[0061] The detailed description of the properties of an AZ31 alloy comes from the reference: [1] Vrátná, J., Hadzima, B., Bukovina, M. & Janec̆ek, M. Room temperature corrosion properties of AZ31 magnesium alloy processed by extrusion and equal channel angular pressing. Journal of Materials Science 48 (2013), 4510-4516.

[0062] The detailed description of the properties of a ZK60AF alloy comes from references: [2] Orlov, D., Ralston, K. D., Birbilis, N. & Estrin, Y. Enhanced corrosion resistance of Mg alloy ZK60 after processing by integrated extrusion and equal channel angular pressing, Acta Mater. 59 (2011) 6176-6186.

[0063] It may be concluded from Table 3 that the magnesium alloy obtained by the present disclosure has excellent mechanical properties and belongs to high-strength magnesium alloys. However, alloys with the better mechanical properties than this alloy have poor corrosion resistance. Meanwhile, the high-strength and high-corrosion-resistant ternary magnesium alloy obtained by the present disclosure, compared with other alloys, also has the better corrosion resistance than most other magnesium alloys. The magnesium alloy obtained by the present disclosure is an ideal magnesium alloy with high strength and high corrosion resistance.

[0064] It should be noted that the components of the magnesium alloy provided by the present disclosure is not limited to the range disclosed in the above examples, and as long as the components of alloys satisfy the conditions that the weight percentage content of Y is 8-12 wt %, the weight percentage content of Al is 0.6-3 wt % (preferably the weight percentage content of Y is 8-11 wt %, and the weight percentage content of Y is 0.6-1.5 wt %), the content of inevitable impurity element Fe does not exceed 0.1 wt %, the content of impurity element Cu does not exceed 0.02 wt %, and the content of impurity element Ni does not exceed 0.003 wt % (preferably the content of Fe does not exceed 0.02 wt %, the content of Cu does not exceed 0.01 wt %, and the content of Ni does not exceed 0.0005 wt %), the alloys all have good corrosion resistance; and sections obtained after solution treatment at 500-580° C. for 8-24 h, extrusion at 300-450° C. according to the extrusion ratio of (9-25):1, and operation of controlling the outflow speed of the section to be 5-10 m/min all have the better mechanical properties and maintain the better corrosion resistance.

[0065] Finally, it should be noted that the above preferred examples are merely used to illustrate the technical solution of the present disclosure and not to limit it. Although the present disclosure has been described in detail through the above preferred examples, those skilled in the art should understand that various changes in form and detail may be made to it without departing from the scope defined by the claims of the present disclosure.