CN106676355B - High-plastic heat-resisting AZ systems magnesium alloy extrusion of one kind and preparation method thereof - Google Patents

Abstract

The invention belongs to the field of metal material technology and metallurgy technology, and specifically relates to a high-plasticity heat-resistant AZ series magnesium alloy extruded material and a preparation method thereof. The technical scheme of the present invention is as follows: a high-plastic heat-resistant AZ series magnesium alloy extruded material, the mass percentage of the alloy components is: the Al content is 3-4.5%, the Zn content is 0.8-1.2%, and the Mn content is 0.15% ~0.25%, the total content of Sm and La is 0.15-0.5%, the total content of impurity elements is less than 0.05%, and the rest is Mg, of which Sm content is 0.1-0.45%, and La content is 0.05-0.3%. The high-plastic heat-resistant AZ series magnesium alloy extruded material and its preparation method provided by the present invention increase the Al content on the basis of the AZ31 magnesium alloy and add rare earth elements Sm and La in a small amount of combination, and through the adjustment of extrusion process parameters, reduce The yield ratio of magnesium alloys improves the elongation and heat resistance of magnesium alloys.

Description

A high-plastic heat-resistant AZ series magnesium alloy extrusion material and its preparation method

technical field

The invention belongs to the field of metal material technology and metallurgy technology, and specifically relates to a high-plasticity heat-resistant AZ series magnesium alloy extruded material and a preparation method thereof.

Background technique

Magnesium alloy is an ideal material for lightweight structure. It has the advantages of low density, high specific strength, easy recycling, and excellent vibration damping, electromagnetic shielding and machining performance. It is widely used in automotive, aerospace, 3C, national defense and other fields. The application has broad application prospects. At present, industrial general-purpose magnesium alloys are mainly divided into two categories: cast magnesium alloys and deformed magnesium alloys. Deformed magnesium alloys can be obtained by forging, extrusion, rolling and other processes. Compared with cast magnesium alloys, they have higher strength and better performance. Extensibility and more diverse sizes, the application is also more extensive. However, the AZ series magnesium alloys widely used in industry currently have problems such as low absolute strength (especially low high-temperature mechanical properties), poor plastic forming ability (especially poor secondary forming ability), and poor corrosion resistance, which seriously restricts the development of magnesium alloys. The field of application of the material. Among them, the secondary forming ability and heat resistance of AZ31 wrought magnesium alloy need to be improved urgently. For example, the tensile properties of the extruded AZ31 magnesium alloy (ASM handbook: Magnesium and Magnesium Alloys) at room temperature are: yield strength 205MPa, tensile strength 275MPa, elongation 12%, yield ratio (Rp0.2/Rm) 0.745; at high temperature (150°C): 105MPa, 170MPa, 39%, and 0.618 respectively. It can be seen that its yield strength is relatively high, its elongation is low, and its yield and tensile strength at high temperature are both reduced by 100MPa, which are only about 1/2 and 2/3 of room temperature, and its strength cannot be improved by heat treatment. Therefore, it will be of great significance to improve the formability and heat resistance of AZ31 magnesium alloy through the adjustment of the alloy composition and the improvement of the preparation process.

The poor heat resistance of AZ series magnesium alloys is related to the existence of low melting point Mg ₁₇ Al ₁₂ phase and no high temperature stable precipitation phase in the alloy. In magnesium alloys, rare earth elements RE can preferentially form alloy phases with high thermal stability with Al elements, and at the same time reduce the precipitation of low melting point Mg ₁₇ Al ₁₂ phases, limit dislocation movement and improve the state of grain boundary structure, thereby increasing the room temperature of magnesium alloys. And high temperature mechanical properties, however, a large amount of expensive Nd, Y, Gd and other rare earth elements will also bring a significant increase in the cost of magnesium alloy materials, which also restricts the application of magnesium alloy materials. Therefore, choosing light rare earth elements such as La, Ce, Pr, and Sm with lower cost as additives is an important direction for the development of heat-resistant magnesium-rare earth alloys. In the patent application No. 201410309982.2, a method of adding 2.5% to 3.5% of La and 1.5% to 3.0% of Sm to a magnesium alloy with an aluminum content of 3.5% to 4.5% is disclosed to improve its heat resistance, although The tensile strength can reach about 150MPa at 150°C, but the elongation at room temperature is low, and the maximum does not exceed 10%. In general, reducing the yield ratio (R _p0.2 /Rm) and increasing the elongation can improve the plastic deformation capacity of metal materials.

Contents of the invention

The invention provides a high-plastic heat-resistant AZ series magnesium alloy extruded material and its preparation method. On the basis of the AZ31 magnesium alloy, the Al content is increased and the rare earth elements Sm and La are added in combination in a small amount, and through the adjustment of the extrusion process parameters, Reduce the yield ratio of magnesium alloys, improve the elongation and heat resistance of magnesium alloys.

Technical scheme of the present invention is as follows:

A high-plastic heat-resistant AZ series magnesium alloy extruded material, the mass percent of the alloy components is: Al content is 3-4.5%, Zn content is 0.8-1.2%, Mn content is 0.15-0.25%, Sm and La The total content is 0.15-0.5%, the total content of impurity elements is less than 0.05%, and the rest is Mg, wherein the content of Sm is 0.1-0.45%, and the content of La is 0.05-0.3%.

The preferred version of the high-plastic heat-resistant AZ series magnesium alloy extruded material is that the Al content is 3.5-4.5%, the Zn content is 0.9-1.2%, the Mn content is 0.15-0.2%, and the total content of Sm and La is 0.35-0.5%, wherein the Sm content is 0.2-0.45%, and the La content is 0.05-0.3%.

A method for preparing the above-mentioned high-plasticity heat-resistant AZ series magnesium alloy extrusion material, comprising the following steps:

(1) Melting ingots: under the action of protective gas, place the magnesium ingots, aluminum ingots, zinc ingots, and anhydrous MnCl ₂ weighed according to the mass percentages in the furnace, and heat them to 710-715°C to melt them , remove slag to remove impurities floating on the surface of the melt, evenly sprinkle RJ-5 flux on the surface of the melt as a covering agent, add Sm master alloy and La master alloy weighed according to the mass percentage, and heat up to 730-750 ℃, after the Sm master alloy and La master alloy are melted, continue to add RJ-5 flux for stirring and refining, and then stand still for 8 to 10 minutes. In a low-carbon steel mold heated to 150-250°C, magnesium alloy ingots are obtained;

(2) Homogenization: Place the magnesium alloy ingot obtained in step (1) in a muffle furnace, heat it at 400-420°C for 10-12 hours for homogenization treatment, then air-cool to room temperature, and turn it into Φ46mm×100mm Magnesium alloy bars;

(3) Hot extrusion: After the magnesium alloy bar obtained in step (2) was kept at 350° C. for 2 hours, the reverse extrusion device was used to carry out hot extrusion on a 300-ton hydraulic press, and the extrusion temperature was 350° C. The speed of the extrusion outlet is 1.8-1.9m/min, the extrusion ratio is 16:1-18:1, and then air-cooled to room temperature to obtain the extruded material.

The preferred method for the preparation of the high-plastic heat-resistant AZ series magnesium alloy extruded material is that the purity of the magnesium ingot is ≥99.9wt.%, the purity of the aluminum ingot is ≥99.7wt.%, and the purity of the zinc ingot is ≥99.99wt. .%, the compositions of Sm master alloy and La master alloy are Mg-30wt.%Sm and Mg-25wt.%La respectively.

The preferred solution for the preparation method of the high-plasticity heat-resistant AZ series magnesium alloy extruded material is that the protective gas is a mixed gas of CO ₂ and SF ₆ , and the volume ratio is CO ₂ :SF ₆ =100:1.

The beneficial effects of the present invention are:

(1) The present invention is based on the AZ31 magnesium alloy, by increasing the aluminum content and adding rare earth elements Sm and La in a small amount of combination, the Al ₂ Sm and Al ₁₁ La ₃ alloy phases with high thermal stability are preferentially formed in the magnesium alloy, and the Al 11 La 3 alloy phase is suppressed The formation of the low-melting point Mg ₁₇ Al ₁₂ phase was improved, and the state of the grain boundary structure was improved. After homogenization and adjustment of extrusion process parameters, the microstructure of the magnesium alloy was significantly refined, the room temperature yield ratio was significantly reduced, and the room temperature elongation was increased. The elongation rate improves the high temperature (150°C) yield and tensile strength, and finally obtains a high-plasticity and heat-resistant AZ series magnesium alloy extrusion material;

(2) The high-plastic heat-resistant AZ series magnesium alloy extruded material of the present invention has the characteristics of high plasticity and heat resistance. 165MPa, the elongation is 22-28%, and the yield ratio is 0.55-0.65; at high temperature (150°C), the tensile strength of the magnesium alloy is 180-200MPa, the yield strength is 120-135MPa, and the elongation is 35 ~45%, the yield ratio is 0.6~0.7;

(3) The high-plasticity heat-resistant AZ series magnesium alloy extruded material of the present invention can be obtained by extrusion deformation at a low extrusion ratio, wherein the extrusion temperature is 350° C., and the extrusion ratio is 16:1 to 18:1, The extrusion process is simple and easy to implement.

Description of drawings

Fig. 1 is the XRD spectrogram of the high-plastic heat-resistant AZ series magnesium alloy extruded material obtained in Example 1 of the present invention;

Fig. 2 is the typical metallographic structure diagram of the high-plastic heat-resistant AZ series magnesium alloy extruded material obtained in Example 1 of the present invention;

Fig. 3 is the tensile sample size diagram of the high plastic heat-resistant AZ series magnesium alloy extruded material of the present invention;

The XRD spectrogram of the high-plastic heat-resistant AZ series magnesium alloy extruded material obtained in Fig. 4 embodiment 2 of the present invention;

Fig. 5 is a typical metallographic structure diagram of the high-plasticity heat-resistant AZ series magnesium alloy extruded material in Example 2 of the present invention.

Detailed ways

In combination with the content of the solution of the present invention, the following four embodiments are provided, but the protection scope of the present invention is not limited to the following four embodiments.

Example 1

The extruded material of high plastic and heat-resistant AZ series magnesium alloy in this embodiment is composed of the following alloy components in mass percentage: 3.5% Al, 1.2% Zn, 0.2% Mn, 0.45% Sm+0.05% La, and the balance is magnesium and Unavoidable impurity elements.

The preparation method is as follows:

Using a resistance melting furnace, under the protective atmosphere of a mixed gas with a volume ratio of SF ₆ and CO ₂ of 1:100, heat Mg to 715°C to melt, add Al, Zn and Mn according to the mass percentage of the components, and use RJ-5 flux Purify and cover the magnesium alloy melt, add Mg-30%Sm and Mg-25%La master alloy according to the mass percentage of Sm and La, raise the temperature to 730°C, and continue to add RJ-5 flux for refining after the alloy is melted Stir, then stand still for 10 minutes, remove the slag when the melt temperature drops to 710°C, and cast it into a low-carbon steel mold preheated to 200°C under the action of protective gas to obtain AZ series with high plasticity and heat resistance Magnesium alloy ingot. The magnesium alloy ingot was kept at 420° C. for 10 h, air-cooled to room temperature, and turned into a magnesium alloy rod of Φ46 mm×100 mm to remove the oxidized part on the surface. After heat preservation treatment at 350°C×2h, the magnesium alloy bar was extruded on a 300-ton hydraulic press at an outlet speed of 1.9mm/min using a reverse extrusion device to obtain a Φ12mm magnesium alloy extruded material. The ratio is 17.4:1.

The XRD spectrum of the extruded material is shown in Figure 1, and the typical metallographic structure is shown in Figure 2. Process it into a tensile sample as shown in accompanying drawing 3, carry out room temperature and 150 ℃ high temperature stretching on the Instron8032 stretching machine, the stretching speed is 1mm/min, its tensile properties are as shown in Table 1, the average The values are: at room temperature, tensile strength = 260MPa, yield strength = 146MPa, elongation = 27.5%, yield ratio = 0.562; at 150°C high temperature, tensile strength = 195MPa, yield strength = 127MPa, elongation = 39%, yield ratio = 0.651.

Example 2

The extruded high-plasticity and heat-resistant AZ series magnesium alloy in this embodiment consists of the following alloy components in mass percentage: 3.5% Al, 0.9% Zn, 0.2% Mn, 0.2% Sm+0.3% La, and the balance is magnesium and Unavoidable impurity elements.

The preparation method is the same as in Example 1.

The XRD spectrum of the extruded material is shown in Figure 4, and the typical metallographic structure is shown in Figure 5. Process it into a tensile sample as shown in accompanying drawing 3, carry out room temperature and 150 ℃ high temperature stretching on the Instron8032 stretching machine, the stretching speed is 1mm/min, its tensile properties are as shown in Table 1, the average The values are: at room temperature, tensile strength = 265MPa, yield strength = 163MPa, elongation = 24%, yield ratio = 0.615; at a high temperature of 150°C, tensile strength = 189MPa, yield strength = 133MPa, elongation =39.5%, yield ratio=0.703.

Example 3

The extruded high-plasticity and heat-resistant AZ series magnesium alloy in this embodiment consists of the following alloy components in mass percentage: 4.5% Al, 0.9% Zn, 0.15% Mn, 0.2% Sm+0.15% La, and the balance is magnesium and Unavoidable impurity elements.

The preparation method is the same as in Example 1.

Process it into a tensile sample as shown in accompanying drawing 3, carry out room temperature and 150 ℃ high temperature stretching on the Instron8032 stretching machine, the stretching speed is 1mm/min, its tensile properties are as shown in Table 1, the average The values are: at room temperature, tensile strength = 265MPa, yield strength = 150MPa, elongation = 23%, yield ratio is 0.566; at 150°C high temperature, tensile strength = 185MPa, yield strength = 125MPa, elongation =42%, yield ratio is 0.676.

Example 4

In this embodiment, the high-plastic heat-resistant AZ series magnesium alloy extruded material is composed of the following alloy components in mass percentage: 4.5% Al, 0.9% Zn, 0.15% Mn, 0.2% Sm+0.2% La, and the balance is magnesium and Unavoidable impurity elements.

The preparation method is the same as in Example 1.

Process it into a tensile sample as shown in accompanying drawing 3, and carry out room temperature and 150 ℃ high-temperature stretching respectively on the Instron8032 stretching machine, and the stretching speed is 1mm/min, and its tensile properties are shown in Table 1, The average values are: at room temperature, tensile strength = 268MPa, yield strength = 155MPa, elongation = 22.5%, yield ratio = 0.578; Ratio = 45%, the yield ratio is 0.656.

The tensile mechanical property test result of the magnesium alloy that table 1 embodiment gains

( ^* Note: The mechanical properties data of AZ31 extrusions are from ASM handbook:Magnesium and MagnesiumAlloys)

Claims (4)

1. A method for preparing a high-plasticity heat-resistant AZ series magnesium alloy extruded material, the mass percent of the high plasticity heat-resistant AZ series magnesium alloy component is: the Al content is 3-4.5%, the Zn content is 0.8-1.2%, The content of Mn is 0.15~0.25%, the total content of Sm and La is 0.15~0.5%, the total content of impurity elements is less than 0.05%, and the rest is Mg, of which the content of Sm is 0.1~0.45%, and the content of La is 0.05~0.3%. It consists of the following steps: (1) Melting ingots: under the action of protective gas, place magnesium ingots, aluminum ingots, zinc ingots, and anhydrous MnCl ₂ weighed according to the stated mass percentages in a melting furnace, and heat them to 710~715°C to melt them , remove slag to remove impurities floating on the surface of the melt, evenly sprinkle RJ-5 flux on the surface of the melt as a covering agent, add Sm master alloy and La master alloy weighed according to the mass percentage, and heat up to 730~750 ℃, after the melting of Sm master alloy and La master alloy, continue to add RJ-5 flux for stirring and refining, and then let it stand for 8~10min. In a low-carbon steel mold heated to 150~250°C, magnesium alloy ingots are obtained; (2) Homogenization: Place the magnesium alloy ingot obtained in step (1) in a muffle furnace, heat it at 400-420°C for 10-12 hours for homogenization treatment, then air-cool to room temperature, and turn it into Φ46mm×100mm Magnesium alloy bars; (3) Hot extrusion: heat the magnesium alloy rod obtained in step (2) at 350°C for 2 hours, then use a reverse extrusion device to carry out hot extrusion on a 300-ton hydraulic press at an extrusion temperature of 350°C. The speed of the extrusion outlet is 1.8~1.9m/min, the extrusion ratio is 16:1~18:1, and then air-cooled to room temperature to obtain the extruded material. 2. The method for preparing high-plasticity and heat-resistant AZ-series magnesium alloy extruded material according to claim 1, characterized in that the mass percentage of the high-plasticity and heat-resistant AZ-series magnesium alloy component is: the Al content is 3.5-4.5% , Zn content is 0.9~1.2%, Mn content is 0.15~0.2%, Sm and La total content is 0.35~0.5%, wherein Sm content is 0.2~0.45%, La content is 0.05~0.3%. 3. The method for preparing high plastic heat-resistant AZ series magnesium alloy extruded material according to claim 1, characterized in that, the purity of magnesium ingot is ≥99.9wt.%, the purity of aluminum ingot is ≥99.7wt.%, and the purity of zinc ingot is ≥99.7wt.%. The purity of ≥99.99wt.%, the composition of Sm master alloy and La master alloy are Mg-30wt.%Sm and Mg-25wt.%La respectively. 4. the preparation method of high-plastic heat-resistant AZ series magnesium alloy extruded material according to claim 1, is characterized in that, described shielding gas is the mixed gas of CO ₂ and SF ₆ , and volume ratio is CO ₂ :SF ₆ = 100:1.