An aging-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy and its preparation method

Abstract

The present invention provides an aged-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy and a preparation method thereof. The aged-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy uses high-purity Mg, high-purity Sn, high-purity Zn, high-purity Ag, Mg-Sc master alloy, and Mg-Ti master alloy as raw materials, and is prepared through melting, casting, cooling, solution treatment, aging treatment, extrusion, and stress relief. The alloy preparation process relies on multiple strengthening mechanisms such as precipitation strengthening, solid solution strengthening, and fine grain strengthening, breaks the fixed orientation relationship between the precipitated phase and the matrix, fully exerts the solid solution strengthening effect of various elements, promotes the precipitation of Mg2Sn and MgZn2 phases, and strengthens the fine grain effect, thereby obtaining a high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy.

Description

Technical Field

[0001] The present invention belongs to the technical field of non-ferrous metal design and forming, and particularly relates to an aging-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy system and a preparation method thereof. Background Art

[0002] Magnesium-tin alloys and magnesium-zinc alloys, as high-strength magnesium alloy systems with important development potential, have gradually attracted attention in recent years. Mainly relying on the strengthening effect of Mg 2 Sn precipitation phases and MgZn 2 , typical Mg-Sn-Al-Zn alloys (T.T. Sasaki et al, Strong and ductile heat-treatable Mg-Sn-Zn-Al wrought alloys, Acta Materialia. 99(2015)176-186) and Mg-Sn-Cu-Ag alloys (CN201310626666.3) have achieved significant improvements in mechanical properties.

[0003] Research shows that in aged Mg-Sn alloys and Mg-Zn alloys, the precipitated nano-scale Mg 2 Sn precipitation phases and MgZn 2 precipitation phases have a certain orientation relationship with the matrix. To further improve the alloy properties, it mainly relies on adding elements such as Ag and Zr to increase the number of precipitation phases, while reducing the size of the precipitation phases, or refining the grains through deformation treatment.

[0004] At present, the strength improvement of Mg-Sn alloys and Mg-Zn alloys has reached a bottleneck, and new ideas are needed in alloy design and preparation processes to further improve the performance. Summary of the Invention

[0005] Based on the above technical background, the inventor has made unremitting efforts and provided a high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy in the aged-extruded state and a preparation method thereof. The high-strength alloy uses high-purity Mg, high-purity Sn, high-purity Zn, high-purity Ag, Mg-Sc master alloy, and Mg-Ti master alloy as raw materials, and is prepared through melting, casting, cooling, solution treatment, aging treatment, extrusion, and stress relief. By adding a variety of solution elements, the invention promotes the precipitation of the second phase. At the same time, through the treatment process of aging treatment first and then extrusion, not only the fixed orientation relationship between the precipitate phase and the matrix is broken, but also the grain size and the precipitate phase size are reduced simultaneously through extrusion treatment, giving full play to the strengthening effect of the nano-scale precipitate phase. In addition, the extrusion treatment promotes the dynamic recrystallization process of the grains, further strengthening the fine-grain effect, giving full play to the solution strengthening effect of various elements, and relying on multiple strengthening mechanisms such as precipitation strengthening, solution strengthening, and fine-grain strengthening, a high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy is obtained, thus completing the present invention.

[0006] In the first aspect of the present invention, there is provided a high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy in the aged-extruded state. The high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy in the aged-extruded state uses high-purity Mg, high-purity Sn, high-purity Zn, high-purity Ag, Mg-Sc master alloy, and Mg-Ti master alloy as raw materials, and is prepared through melting, casting, cooling, solution treatment, aging treatment, extrusion, and stress relief.

[0007] In the second aspect of the present invention, there is provided a method for preparing the high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy in the aged-extruded state described in the first aspect of the present invention. The method includes the following steps:

[0008] Step 1: Weigh the metal raw materials high-purity Mg, high-purity Sn, high-purity Zn, high-purity Ag, Mg-Sc master alloy, and Mg-Ti master alloy according to the mass percentages of the respective elements in the alloy;

[0009] Step 2: Place the metal raw materials in a melting furnace for melting treatment to obtain an alloy solution;

[0010] Step 3: Pour the alloy solution into a mold and obtain a as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy through natural cooling;

[0011] Step 4: Raise the temperature and perform solution treatment on the as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy;

[0012] Step 5: Subject the as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy after solution treatment to aging treatment, then extrude it after water cooling, and finally remove stress to obtain an age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy system. Description of the Drawings

[0013] Figure 1 Showing the scanning electron microscope photograph of the high-strength alloy prepared in Example 6 of the present invention;

[0014] Figure 2 Showing the transmission electron microscope photograph of the alloy prepared in Example 6. Detailed Description of the Invention

[0015] The present invention will be described in detail below, and the features and advantages of the present invention will become clearer and more definite with these descriptions.

[0016] The first aspect of the present invention is to provide an age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy, and the age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy is made from high-purity Mg, high-purity Sn, high-purity Zn, high-purity Ag, Mg-Sc master alloy, and Mg-Ti master alloy as raw materials through melting, casting, cooling, solution treatment, aging treatment, extrusion, and stress removal.

[0017] The age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy mainly contains elements Mg, Sn, Zn, Sc, Ag, and Ti.

[0018] By adding a variety of solution elements in the present invention, such as Sc, Ag, Ti, etc., it effectively promotes the precipitation of the second phase and at the same time promotes the dynamic recrystallization process of grains during extrusion, and fully exerts the solution strengthening effect of various elements, thereby obtaining an alloy with relatively high strength.

[0019] Preferably, by mass percentage, the element composition of the age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy is: Sn: 5.0 - 15.0 wt%, Zn: 1.0 - 10.0 wt%, Sc: 0.1 - 3.0 wt%, Ag: 0.2 - 3.0 wt%, Ti: 0.05 - 1.0 wt%, and the rest is Mg and inevitable impurities.

[0020] More preferably, the element composition of the age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy is: Sn: 7.0 - 10.0 wt%, Zn: 2.0 - 6.0 wt%, Sc: 0.2 - 1.5 wt%, Ag: 0.5 - 1.5 wt%, Ti: 0.1 - 0.5 wt%, and the rest is Mg and inevitable impurities.

[0021] The aging-extrusion high-strength Mg-Sn-Zn-Sc-Ag-Ti series alloy of the present invention is processed by first aging treatment and then extrusion treatment, so that the Mg 2 Sn phase and MgZn 2 phase are completely precipitated at the same time, thereby obtaining a magnesium alloy with relatively high Sn and Zn contents. At the same time, the method of first aging treatment and then extrusion treatment can, on the one hand, break the fixed orientation relationship between the precipitated phase and the matrix, and on the other hand, through extrusion treatment, the grain size and the precipitated phase size can be reduced simultaneously, effectively improving the strength of the alloy.

[0022] The aging-extrusion high-strength Mg-Sn-Zn-Sc-Ag-Ti series alloy of the present invention has relatively high microhardness, and its microhardness is above 88 HV, and the highest can reach 101.4 HV.

[0023] The second aspect of the present invention lies in providing a method for preparing an aging-extrusion high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy described in the first aspect of the present invention. The method includes melting, casting, solution treatment, aging treatment, extrusion, and stress relief of high-purity Mg, high-purity Sn, high-purity Zn, high-purity Ag, Mg-Sc master alloy, and Mg-Ti master alloy in sequence.

[0024] In the present invention, the purity of the high-purity Mg is higher than 99.9%, the purity of the high-purity Sn is higher than 99%, the purity of the high-purity Zn is higher than 99.9%, and the purity of the high-purity Ag is higher than 99%.

[0025] According to a preferred embodiment of the present invention, the method includes the following steps:

[0026] Step 1: Weigh the metal raw materials of high-purity Mg, high-purity Sn, high-purity Zn, high-purity Ag, Mg-Sc master alloy, and Mg-Ti master alloy according to the mass percentages of the respective elements in the alloy;

[0027] Step 2: Place the metal raw materials in a melting furnace for melting treatment to obtain an alloy solution;

[0028] Step 3: Pour the alloy solution into a mold and cool it naturally to obtain a as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy;

[0029] Step 4: Raise the temperature and perform solution treatment on the as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy;

[0030] Step 5: Perform aging treatment on the solution-treated as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy, then extrude it after water cooling, and finally remove stress to obtain an aging-extrusion high-strength Mg-Sn-Zn-Sc-Ag-Ti series alloy.

[0031] In Step 2, according to the present invention, the smelting includes low-temperature smelting and high-temperature smelting that are carried out in sequence.

[0032] The temperature of the low-temperature smelting is 150 to 300 °C, preferably 200 to 250 °C.

[0033] The time of the low-temperature smelting is 10 to 60 min, preferably 15 to 30 min.

[0034] The temperature of the high-temperature smelting is 700 to 800 °C, preferably 720 to 750 °C.

[0035] The time of the high-temperature smelting is 10 to 45 min, preferably 15 to 30 min.

[0036] Stirring is carried out after smelting for 10 to 30 min to make the alloy solution in the smelting furnace mix evenly.

[0037] The smelting is preferably carried out in a protective atmosphere, and the protective atmosphere is preferably a mixed gas of SF 6 and CO 2 The mixed gas of SF 6 has a volume fraction higher than 95%.

[0038] This protective atmosphere is introduced before alloy smelting. Preferably, the alloy is added for smelting 2 to 10 min after introducing the protective atmosphere. More preferably, the protective atmosphere is introduced after the temperature rises to 150 to 300 °C.

[0039] According to a preferred embodiment of the present invention, after smelting, the temperature is lowered to 600 to 700 °C, preferably lowered to 650 to 690 °C. Cooling after smelting can remove the residue on the melt surface at one time, which is beneficial to improving the hardness of the alloy.

[0040] In Step 3, before pouring, it is preferable to preheat the mold. After preheating, the melt is poured into the metal mold. The preheating temperature is 80 to 120 °C, and the preheating time is 10 to 30 min. The as-cast alloy is obtained after cooling.

[0041] In Step 4, the solution treatment is preferably carried out under the protection of an inert gas, preferably in an Ar gas atmosphere.

[0042] The solution treatment of the present invention is carried out according to the following heating regime: 350 to 440 °C / 10 to 30 h + 440 to 470 °C / 2 to 10 h + 470 to 550 °C / 1 to 5 h. That is, after holding at 350 to 440 °C for 10 to 30 h, the temperature is raised to 440 to 470 °C and held for 2 to 10 h, and finally the temperature is raised to 470 to 550 °C and held for 1 to 5 h.

[0043] Preferably, the heating regime is 390 - 420 °C / 15 - 20 h + 450 - 460 °C / 5 - 7 h + 480 - 520 °C / 2 - 4 h. That is, keep the temperature at 390 - 420 °C for 15 - 20 h, then raise the temperature to 450 - 460 °C and keep it for 5 - 7 h, and finally raise the temperature to 480 - 520 °C and keep it for 2 - 4 h.

[0044] In step 5, after solution treatment, the present invention breaks the orientation relationship between the precipitate phase and the matrix by first performing aging treatment and then extrusion treatment, and at the same time can effectively refine the size of the precipitate phase, fully exert the strength of the nanoscale precipitate phase, and effectively improve the microhardness of the alloy.

[0045] The aging treatment temperature is 150 - 250 °C, preferably 180 - 220 °C. The aging treatment time is 100 - 300 h, preferably 120 - 220 h.

[0046] In the present invention, the extrusion temperature is 150 - 300 °C, preferably 200 - 250 °C.

[0047] The extrusion ratio is 2 - 15, preferably 3 - 10.

[0048] The extrusion rate is 50 - 150 mm / min, preferably 70 - 100 mm / min.

[0049] Under the action of the above extrusion temperature and extrusion time, the grain size can be further refined, so that the grain size and the precipitate phase size are reduced simultaneously, and the microhardness of the alloy is improved by relying on the nanoscale precipitate phase and the smaller grain structure. The alloy can reach a higher strength under the condition of a lower extrusion ratio, and the extrusion cost is reduced.

[0050] The stress relief temperature is 100 - 200 °C, preferably 120 - 170 °C.

[0051] The stress relief time is 1 - 5 h, preferably 2 - 3 h.

[0052] The beneficial effects of the present invention:

[0053] (1) The aging - extrusion - state high - strength Mg - Sn - Zn - Sc - Ag - Ti - based alloy of the present invention gives the alloy higher strength by adding a variety of solution elements and fully exerting the solution strengthening effect of various elements.

[0054] (2) The preparation process of the aging - extrusion - state high - strength Mg - Sn - Zn - Sc - Ag - Ti - based alloy of the present invention can fully complete Mg 2 Sn and MgZn 2The precipitation behavior, through the process of pre-aging and then deformation, breaks the orientation relationship between the precipitate phase and the matrix, refines the size of the precipitate phase, and fully exerts the strength of the nano-scale precipitate phase. At the same time, through the solid solution strengthening effect of multiple elements such as Ag, Sc, and Ti, and the fine grain strengthening effect of extrusion treatment, the combined action of multiple effects makes the microhardness of the alloy reach above 100.00 HV at most.

[0055] (3) The age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy of the present invention can achieve the effect of high strength of the alloy under the condition of relatively low extrusion ratio, which is convenient for preparing large-sized extruded parts, reduces the extrusion cost, and has good application prospects.

[0056] Examples

[0057] The present invention will be further described below through specific examples. These examples are only for illustrating the present invention and are not used to limit the scope of the present invention.

[0058] In the following examples, each raw material is high-purity Mg (99.95%), high-purity Sn (99.9%), high-purity Zn (99.99%), high-purity Ag (99.9%), Mg-6Sc master alloy (Sc accounts for 6 wt% of the mass of the Mg-6Sc master alloy, and the rest is Mg), Mg-10Ti (Ti accounts for 10 wt% of the mass of the Mg-10Ti master alloy, and the rest is Mg) master alloy. All of the above raw materials are commercially available products.

[0059] Example 1

[0060] By weight percentage: Sn: 7.0 wt%, Zn: 3.0 wt%, Sc: 0.4 wt%, Ag: 0.6 wt%, Ti: 0.2 wt%, Mg: the balance, weigh the metal raw materials high-purity Mg (99.95%), high-purity Sn (99.9%), high-purity Zn (99.99%), high-purity Ag (99.9%), Mg-Sc master alloy, Mg-Ti master alloy.

[0061] After raising the temperature of the melting furnace to 200 °C, introduce a protective gas into the melting furnace for 5 min. The protective gas is 99% SF 6 and 1% CO 2 mixed gas. Place the weighed high-purity Mg (99.95%), high-purity Sn (99.9%), high-purity Zn (99.99%), high-purity Ag (99.9%), Mg-Sc master alloy, and Mg-Ti master alloy in the melting furnace, keep it at 200 °C for 20 min, and then raise the temperature of the melting furnace to 730 °C and keep it for 20 min. Then stir to make the alloy solution mix evenly. Subsequently, lower the temperature of the melting furnace to 690 °C and remove the slag on the surface of the melt at one time.

[0062] Preheat the metal mold at 100 °C for 20 min, pour the above melt into the metal mold, and cool it naturally to obtain as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy.

[0063] Under the condition of Ar gas protection, hold the as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy at 400 °C for 16 h for homogenization treatment, then raise the temperature to 460 °C and hold for 6 h, and continue to raise the temperature to 480 °C and hold for 2 h to complete the solution treatment.

[0064] Perform aging treatment on the solution-treated as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy. The aging temperature is 200 °C, and the holding time is 160 h. After aging, water-cool it to room temperature. The Mg-Sn-Zn-Sc-Ag-Ti alloy after aging treatment is extruded at 220 °C, the extrusion ratio is 4, the size after extrusion is 5 mm, and the extrusion rate is 80 mm / min. After extrusion, hold it at 150 °C for 2 h for stress relief treatment to obtain the age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy.

[0065] Perform microhardness test on the obtained age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy. The test load is 200 g, the loading time is 15 s, and the microhardness of the alloy is measured to be 88.7 HV.

[0066] Example 2

[0067] According to the weight percentage: Sn: 8.0 wt%, Zn: 2.0 wt%, Sc: 0.6 wt%, Ag: 0.6 wt%, Ti: 0.2 wt%, and Mg: the balance, weigh the metal raw materials high-purity Mg (99.95%), high-purity Sn (99.9%), high-purity Zn (99.99%), high-purity Ag (99.9%), Mg-6Sc master alloy, and Mg-10Ti master alloy.

[0068] After raising the temperature of the melting furnace to 200 °C, pass the protective gas into the melting furnace for 5 min. The protective gas is 99% SF 6 and 1% CO 2 mixed gas. Place the weighed metal raw materials high-purity Mg (99.95%), high-purity Sn (99.9%), high-purity Zn (99.99%), high-purity Ag (99.9%), Mg-Sc master alloy, and Mg-Ti master alloy in the melting furnace, hold at 200 °C for 20 min, then raise the temperature of the melting furnace to 730 °C and hold for 20 min. Then stir to make the alloy solution mixed evenly. Subsequently, lower the temperature of the melting furnace to 690 °C and remove the slag on the surface of the melt at one time.

[0069] Preheat the metal mold at 100 °C for 20 min, pour the above melt into the metal mold, and cool it naturally to obtain as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy.

[0070] Under the protection of Ar gas, keep the as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy at 400 °C for 16 h for homogenization treatment, then raise the temperature to 460 °C and keep it for 6 h, and continue to raise the temperature to 480 °C and keep it for 2.5 h to complete the solution treatment.

[0071] Perform aging treatment on the solution-treated as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy. The aging temperature is 200 °C and the holding time is 140 h. After aging, water-cool it to room temperature. The Mg-Sn-Zn-Sc-Ag-Ti alloy after aging treatment is extruded at 230 °C, the extrusion ratio is 4, the size after extrusion is 5 mm, and the extrusion rate is 80 mm / min. After extrusion, keep it at 150 °C for 2 h for stress relief treatment to obtain the age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy.

[0072] Perform microhardness test on the obtained age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy. The test load is 200 g and the loading time is 15 s. The microhardness of the alloy is measured to be 89.3 HV.

[0073] Example 3

[0074] According to the weight percentage: Sn: 8.0 wt%; Zn: 4.0 wt%; Sc: 1.0 wt%; Ag: 0.8 wt%; Ti: 0.4 wt%; Mg: the balance, weigh the metal raw materials high-purity Mg (99.95%), high-purity Sn (99.9%), high-purity Zn (99.99%), high-purity Ag (99.9%), Mg-6Sc master alloy, Mg-10Ti master alloy.

[0075] After raising the temperature of the melting furnace to 200 °C, pass the protective gas into the melting furnace for 5 min. The protective gas is 99% SF 6 and 1% CO 2 mixed gas. Place the weighed high-purity Mg (99.95%), high-purity Sn (99.9%), high-purity Zn (99.99%), high-purity Ag (99.9%), Mg-Sc master alloy, and Mg-Ti master alloy in the melting furnace, keep it at 200 °C for 20 min, then raise the temperature of the melting furnace to 730 °C and keep it for 20 min. Then stir to make the alloy solution mix evenly. Subsequently, lower the temperature of the melting furnace to 690 °C and remove the slag on the melt surface at one time.

[0076] Preheat the metal mold at 100 °C for 20 min, pour the above melt into the metal mold, and cool it naturally to obtain as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy.

[0077] Under the condition of Ar gas protection, hold the as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy at 400 °C for 16 h for homogenization treatment, then raise the temperature to 460 °C and hold for 6 h, and continue to raise the temperature to 490 °C and hold for 2.5 h to complete the solution treatment.

[0078] Perform aging treatment on the solution-treated as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy. The aging temperature is 200 °C and the holding time is 180 h. After aging, water-cool to room temperature. The Mg-Sn-Zn-Sc-Ag-Ti alloy after aging treatment is extruded at 220 °C, the extrusion ratio is 9, the size after extrusion is 5 mm, and the extrusion rate is 80 mm / min. After extrusion, hold at 150 °C for 2 h for stress relief treatment to obtain age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy.

[0079] Perform microhardness test on the obtained age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy. The test load is 200 g and the loading time is 15 s. The microhardness of the alloy is measured to be 97.1 HV.

[0080] Example 4

[0081] According to the weight percentage: Sn: 9.0 wt%; Zn: 4.5 wt%; Sc: 0.6 wt%; Ag: 0.8 wt%; Ti: 0.2 wt%; Mg: the balance, weigh the metal raw materials high-purity Mg (99.95%), high-purity Sn (99.9%), high-purity Zn (99.99%), high-purity Ag (99.9%), Mg-6Sc master alloy, Mg-10Ti master alloy.

[0082] After raising the temperature of the melting furnace to 200 °C, pass the protective gas into the melting furnace for 5 min. The protective gas is 99% SF 6 and 1% CO 2 mixed gas. Place the weighed high-purity Mg (99.95%), high-purity Sn (99.9%), high-purity Zn (99.99%), high-purity Ag (99.9%), Mg-Sc master alloy, and Mg-Ti master alloy in the melting furnace, hold at 200 °C for 20 min, then raise the temperature of the melting furnace to 750 °C and hold for 20 min. Then stir to make the alloy solution mix evenly. Subsequently, lower the temperature of the melting furnace to 690 °C and remove the slag on the melt surface at one time.

[0083] Preheat the metal mold at 100 °C for 20 min, pour the above melt into the metal mold, and cool it naturally to obtain as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy.

[0084] Under the protection of Ar gas, hold the as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy at 400 °C for 16 h for homogenization treatment, then raise the temperature to 460 °C and hold for 6 h, and continue to raise the temperature to 480 °C and hold for 3 h to complete the solution treatment.

[0085] Perform aging treatment on the solution-treated as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy. The aging temperature is 200 °C and the holding time is 160 h. After aging, water-cool to room temperature. The Mg-Sn-Zn-Sc-Ag-Ti alloy after aging treatment is extruded at 240 °C, the extrusion ratio is 4, the size after extrusion is 5 mm, and the extrusion rate is 80 mm / min. After extrusion, hold at 150 °C for 2 h for stress relief treatment to obtain the age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy.

[0086] Perform microhardness test on the obtained age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy. The test load is 200 g and the loading time is 15 s. The microhardness of the alloy is measured to be 93.8 HV.

[0087] Example 5

[0088] According to the weight percentage: Sn: 9.0 wt%; Zn: 5.5 wt%; Sc: 0.7 wt%; Ag: 1.0 wt%; Ti: 0.4 wt%; Mg: the balance, weigh the metal raw materials high-purity Mg (99.95%), high-purity Sn (99.9%), high-purity Zn (99.99%), high-purity Ag (99.9%), Mg-6Sc master alloy, Mg-10Ti master alloy.

[0089] After raising the temperature of the melting furnace to 200 °C, introduce the protective gas into the melting furnace for 5 min. The protective gas is 99% SF 6 and 1% CO 2 mixed gas. Place the weighed high-purity Mg (99.95%), high-purity Sn (99.9%), high-purity Zn (99.99%), high-purity Ag (99.9%), Mg-Sc master alloy, and Mg-Ti master alloy in the melting furnace, hold at 200 °C for 20 min, and then raise the temperature of the melting furnace to 740 °C and hold for 20 min. Then stir to make the alloy solution mix evenly. Subsequently, lower the temperature of the melting furnace to 690 °C and remove the slag on the surface of the melt at one time.

[0090] Preheat the metal mold at 100 °C for 20 min, pour the above melt into the metal mold, and cool it naturally to obtain as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy.

[0091] Under the condition of Ar gas protection, hold the as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy at 400 °C for 16 h for homogenization treatment, then raise the temperature to 460 °C and hold for 6 h, and continue to raise the temperature to 500 °C and hold for 2.0 h to complete the solution treatment.

[0092] Perform aging treatment on the solution-treated as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy. The aging temperature is 200 °C and the holding time is 180 h. After aging, water-cool to room temperature. The Mg-Sn-Zn-Sc-Ag-Ti alloy after aging treatment is extruded at 230 °C, the extrusion ratio is 9, the size after extrusion is 5 mm, and the extrusion rate is 80 mm / min. After extrusion, hold at 150 °C for 2 h for stress relief treatment to obtain age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy.

[0093] Perform microhardness test on the obtained age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy. The test load is 200 g and the loading time is 15 s. The microhardness of the alloy is measured to be 98.6 HV.

[0094] Example 6

[0095] According to the weight percentage: Sn: 10.0 wt%; Zn: 5.0 wt%; Sc: 0.9 wt%; Ag: 1.0 wt%; Ti: 0.4 wt%; Mg: the balance, weigh the metal raw materials high-purity Mg (99.95%), high-purity Sn (99.9%), high-purity Zn (99.99%), high-purity Ag (99.9%), Mg-6Sc master alloy, Mg-10Ti master alloy.

[0096] After raising the temperature of the melting furnace to 200 °C, introduce the protective gas into the melting furnace for 5 min. The protective gas is 99% SF 6 and 1% CO 2 mixed gas. Place the weighed metal raw materials high-purity Mg (99.95%), high-purity Sn (99.9%), high-purity Zn (99.99%), high-purity Ag (99.9%), Mg-Sc master alloy, Mg-Ti master alloy in the melting furnace, hold at 200 °C for 20 min, and then raise the temperature of the melting furnace to 740 °C and hold for 20 min. Then stir to make the alloy solution mix evenly. Subsequently, lower the temperature of the melting furnace to 690 °C and remove the slag on the surface of the melt at one time.

[0097] Preheat the metal mold at 100 °C for 20 min, pour the above melt into the metal mold, and cool it naturally to obtain as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy.

[0098] Under the condition of Ar gas protection, hold the as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy at 400 °C for 16 h for homogenization treatment, then raise the temperature to 460 °C and hold for 6 h, and continue to raise the temperature to 500 °C and hold for 2.0 h to complete the solution treatment.

[0099] Perform aging treatment on the solution-treated as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy. The aging temperature is 200 °C and the holding time is 200 h. After aging, water-cool to room temperature. The Mg-Sn-Zn-Sc-Ag-Ti alloy after aging treatment is extruded at 240 °C, the extrusion ratio is 9, the size after extrusion is 5 mm, and the extrusion rate is 80 mm / min. After extrusion, hold at 150 °C for 2 h for stress relief treatment to obtain the age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy.

[0100] Perform microhardness test on the obtained age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy. The test load is 200 g and the loading time is 15 s. The microhardness of this alloy is measured to be 101.4 HV.

[0101] The scanning electron micrograph of the high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy prepared in this example is as Figure 1 shown, and the white part therein is Mg 2 Sn phase, which is uniform, fine and evenly distributed, indicating that the preparation process described in the present invention can obtain uniform and fine precipitation phases, which is beneficial to the improvement of the alloy strength. The transmission electron microscope is as Figure 2 shown, and the black part is Mg 2 Sn phase. It can be seen that the size of the Mg 2 Sn phase is small, at the nanometer level.

[0102] The present invention has been described in detail above in combination with specific embodiments and exemplary examples, but these descriptions should not be construed as limiting the present invention. Those skilled in the art understand that without departing from the spirit and scope of the present invention, various equivalent substitutions, modifications or improvements can be made to the technical solutions and their implementation manners of the present invention, and these all fall within the scope of the present invention. The protection scope of the present invention is subject to the appended claims.

Claims

1. A method for preparing an age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy, characterized in that, the age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy uses high-purity Mg, high-purity Sn, high-purity Zn, high-purity Ag, Mg-Sc master alloy, and Mg-Ti master alloy as raw materials, and is prepared by melting, casting, cooling, solution treatment, aging treatment, extrusion, and stress relief; the method comprises the following steps: Step 1: Weigh the metal raw materials high-purity Mg, high-purity Sn, high-purity Zn, high-purity Ag, Mg-Sc master alloy, and Mg-Ti master alloy according to the mass percentages of the respective elements in the alloy; Step 2: Place the metal raw materials in a melting furnace for melting treatment to obtain an alloy melt; Step 3: Pour the alloy melt into a mold and obtain as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy through natural cooling; Step 4: Raise the temperature and perform solution treatment on the as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy; The solution treatment is carried out according to the following heating regime: 350 - 440 °C / 10 - 30 h + 440 - 470 °C / 2 - 10 h + 470 - 550 °C / 1 - 5 h; Step 5: Perform aging treatment on the solution-treated as-cast Mg-Sn-Zn-Sc-Ag-Ti alloy, then carry out extrusion after water cooling, and finally relieve stress to obtain an age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy system; the aging treatment temperature is 150 - 250 °C, and the aging treatment time is 100 - 300 h; the extrusion temperature is 150 - 300 °C, the extrusion ratio is 2 - 15, and the extrusion speed is 50 - 150 mm / min.

2. The method according to claim 1, characterized in that, by mass percentage, the element composition of the age-extruded high-strength Mg-Sn-Zn-Sc-Ag-Ti alloy is: Sn: 5.0 - 15.0 wt%, Zn: 1.0 - 10.0 wt%, Sc: 0.1 - 3.0 wt%, Ag: 0.2 - 3.0 wt%, Ti: 0.05 - 1.0 wt%, and the balance is Mg and unavoidable impurities.

3. The method according to claim 1, characterized in that, in step 2, the melting includes low-temperature melting and high-temperature melting carried out in sequence; the low-temperature melting temperature is 150 - 300 °C, and the low-temperature melting time is 10 - 60 min; the high-temperature melting temperature is 700 - 800 °C, and the high-temperature melting time is 10 - 45 min.

4. The method according to claim 1, characterized in that, in step 2, The smelting is carried out in a protective atmosphere, the protective atmosphere is SF 6 and CO 2 The mixed gas is cooled to 600-700℃ after melting.

5. The method according to claim 1, characterized in that, in step 3, before pouring, preheat the mold, the preheating temperature is 80 - 120 °C, and the preheating time is 10 - 30 min.

6. The method according to claim 1, characterized in that, in step 5, the stress relief temperature is 100 - 200 °C, and the stress relief time is 1 - 5 h.

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