CN1203200C - Al-Zn-Mg-Er rare earth aluminium alloy - Google Patents

Abstract

The present invention relates to Al-Zn-Mg-Er rare-earth aluminium alloy which belongs to the technical field of metal alloy. The present invention has the key point that a certain amount of rare-earth element Er is added to Al-Zn-Mg alloy; experiment determines that the adding quality of the rare-earth element Er is 0.1 to 0.7% (weight percentage). In the method for preparing the novel rare-earth aluminium alloy, Al-Er intermediate alloy by vacuum melting is added in an Al-Zn-Mg alloy melting process. By adding Er, the crystal grains of Al-Zn-Mg alloy can be obviously refined, the strength of the alloy is greatly improved, and recrystallization is inhibited. The price of Er is low, and thus, the production cost can not be greatly increased when Er elements are added to aluminium alloy. The Al-Zn-Mg alloy also is typical industrial aluminium alloy; thus, on the basis of the present invention, a series of novel rare-earth aluminium-lithium alloy containing Er can be developed, and is widely applied to the technical fields of aviation, aerospace, communication, transportation, etc.

Description

Al-Zn-Mg-Er rare earth aluminum alloy

1. Technical field

The invention belongs to the technical field of metal alloys.

2. Background technology

The results of the literature survey show that there are very few foreign studies on rare earth aluminum alloys, and the only reports are limited to the research on Sc-containing aluminum alloys. The domestic development and application of rare earth aluminum alloys started earlier, and large-scale research and development of rare earth aluminum alloys began in the late 1970s. At present, domestic research on the modification of various rare earth elements in Al-Si alloys has been carried out in depth. The research on the application of rare earths in electrical aluminum alloys and the application of rare earths in architectural aluminum profiles has also achieved good results, but the research on other aluminum alloys, especially deformed aluminum alloys, is mainly concentrated on La, Ce , Y and mixed rare earths. The research team found that the rare earth Er has a significant strengthening effect on pure aluminum, and the strengthening effect mainly comes from the refinement of the Al matrix by the Er element and the uniform distribution of fine Al ₃ Er phases formed in the grains. Al ₃ Er has the same structure as Al ₃ Sc and Al ₃ Zr, belongs to the Pm3m space group (simple cubic), and the lattice parameters are very close to the Al matrix. It can be seen that Er is a trace alloy that can effectively improve the properties of aluminum alloys after Sc Elements (Sc is the most effective trace element for aluminum alloy modification, but the price of Sc is very expensive, and the price of Er is only 1/40 of Sc). In the present invention, the rare earth Er is further added to the Al-Zn-Mg alloy, and it is found that the addition of Er can significantly refine the alloy grains, greatly improve the alloy strength, and inhibit recrystallization; although the addition of Sc elements to Al-Zn-Mg Alloys also have this effect, but Sc is expensive, adding Sc to aluminum alloys will greatly increase production costs; while Er is relatively cheap, adding Er elements to aluminum alloys will not greatly increase production costs, so it is very suitable Promote and apply in industrial production. Al-Zn-Mg alloy is a typical industrial aluminum alloy, research on it can develop a series of new rare earth aluminum alloys containing Er, which are widely used in aviation, aerospace, transportation and many other fields. There is no report about Al-Zn-Mg-Er alloy so far.

3. Contents of the invention

The purpose of the present invention is to find a suitable rare earth element, which can be added into Al-Zn-Mg alloy in a suitable amount, and can effectively micro-alloy with the alloy, thereby improving the strength performance of the alloy.

Al-Zn-Mg-Er alloy provided by the present invention is characterized in that adding Al-Zn-Mg (6.0% by weight of Zn in the Al-Zn-Mg alloy described here, the weight percentage of Mg 0.1-0.7% by weight of the Al-Zn-Mg-Er rare earth aluminum alloy is added to the Al-Zn-Mg-Er rare earth aluminum alloy.

The preferred content range of Er mentioned above is: 0.25-0.55%.

The Al-Zn-Mg-Er alloy is prepared by the traditional ingot metallurgy method, which is divided into two steps: firstly, the Al-Er master alloy is prepared by vacuum melting and casting with pure Al and pure Er as raw materials; then, pure Al, pure Mg, pure Zn and The Al-Er intermediate alloy is used as a raw material and melted in a crucible resistance furnace, and then poured into a steel mold to prepare an Al-Zn-Mg-Er alloy.

In the present invention, due to the addition of rare earth Er, the Al-Zn-Mg alloy grains are significantly refined, and the strength is greatly improved. Under the premise that the elongation (δ) is basically unchanged, the tensile strength (σ _b ) of the alloy is reduced to and yield strength (σ _0.2 ) increased by about 100MPa; at the same time, the rare earth Er can significantly inhibit the recrystallization of Al-Zn-Mg alloy, increase the initial recrystallization temperature of the alloy by 50°C, and increase the final recrystallization temperature by 80°C.

4. Description of drawings

Figure 1: The as-cast metallographic structure of the alloy, wherein Figure 1 (a) is an Al-Zn-Mg alloy, and Figure 1 (b) is an Al-Zn-Mg-0.4Er alloy;

Figure 2: The relationship between the tensile properties of the Al-Zn-Mg-Er alloy in the cold-rolled state and the Er content;

Figure 3: Al-Zn-Mg-Er alloy (470°C/0.5h quenching + 120°C/30h aging) relationship curve between tensile properties and Er content;

Figure 4: The relationship between hardness and annealing temperature of Al-Zn-Mg and Al-Zn-Mg-0.4Er alloys;

Figure 5 is the metallographic microstructure of Al-Zn-Mg and Al-Zn-Mg-0.4Er annealed at different temperatures,

Among them, Figure 5(a) is the annealed structure of Al-Zn-Mg alloy at 325°C/1h, Figure 5(b) is the annealed structure of Al-Zn-Mg-0.4Er alloy at 325°C/1h, and Figure 5(c) is Al-Zn-Mg alloy 450℃/1h annealed microstructure, Figure 5(d) is the Al-Zn-Mg-0.4Er alloy 450℃/1h annealed microstructure.

5. Specific implementation

Comparative example: adopt ingot metallurgy method to prepare Al-Zn-Mg alloy (0# alloy in table 1), used raw material is high-purity Al (purity is 99.99%), industrial pure Mg (purity is 99.9%), industrial pure Zn (99.9% pure). First, 1612.4 grams of high-purity aluminum is added to the graphite clay crucible, and melted in a crucible resistance furnace at a melting temperature of 780°C. After the high-purity aluminum is completely melted, 113.3 grams of pure Zn is added to the melt, and after fully stirring, Then add 38.6 grams of pure Mg, stir evenly, add 3 grams of hexachloroethane (C ₂ Cl ₆ ) for degassing, remove slag, and finally pour the melt into a rectangular iron mold, and demould after cooling for 3 minutes .

Example 1: Al-Zn-Mg-Er alloy is prepared by ingot metallurgy method. First, high-purity Al (purity up to 99.99%) and pure Er (purity up to 99.9%) are used as raw materials, and the mixing method (mixed melting method) is adopted. Melting and casting in a vacuum induction furnace to prepare Al-6.2Er master alloy. Then 1584.9 grams of high-purity aluminum and 27.4 grams of Al-6.2Er master alloy were added to the graphite clay crucible, and melted in a crucible resistance furnace at a melting temperature of 780 ° C. After the high-purity aluminum and Al-6.2Er master alloy were completely melted, Add 113.3 grams of pure Zn to the melt, stir well, then add 38.6 grams of pure Mg, stir evenly, add 3 grams of hexachloroethane (C ₂ Cl ₆ ) for degassing, slag removal, and finally The melt was poured into a rectangular iron mold, cooled for 3 minutes and released from the mold. The size of each ingot was 120×90×32 (mm ³ ).

Example 2: Al-Zn-Mg-Er alloy is prepared by ingot metallurgy. First, high-purity Al (purity up to 99.99%) and pure Er (purity up to 99.9%) are used as raw materials, and the mixing method (mixed melting method) is adopted. Melting and casting in a vacuum induction furnace to prepare Al-6.2Er master alloy. Then add 1543.7 grams of high-purity aluminum and 68.5 grams of Al-6.2Er master alloy into a graphite clay crucible, and melt in a crucible resistance furnace at a melting temperature of 780 ° C. After the high-purity aluminum and Al-6.2Er master alloy are completely melted, Add 113.3 grams of pure Zn to the melt, stir well, then add 38.6 grams of pure Mg, stir evenly, add 3 grams of hexachloroethane (C ₂ Cl ₆ ) for degassing, slag removal, and finally The melt was poured into a rectangular iron mold, cooled for 3 minutes and released from the mold. The size of each ingot was 120×90×32 (mm ³ ).

Example 3: Al-Zn-Mg-Er alloy is prepared by ingot metallurgy method. First, high-purity Al (purity up to 99.99%) and pure Er (purity up to 99.9%) are used as raw materials, and the mixing method (mixed melting method) is adopted. Melting and casting in a vacuum induction furnace to prepare Al-6.2Er master alloy. Then add 1502.5 grams of high-purity aluminum and 109.7 grams of Al-6.2Er master alloy into a graphite clay crucible, and melt in a crucible resistance furnace at a melting temperature of 780 ° C. After the high-purity aluminum and Al-6.2Er master alloy are completely melted, Add 113.3 grams of pure Zn to the melt, stir well, then add 38.6 grams of pure Mg, stir evenly, add 3 grams of hexachloroethane (C ₂ Cl ₆ ) for degassing, slag removal, and finally The melt was poured into a rectangular iron mold, cooled for 3 minutes and released from the mold. The size of each ingot was 120×90×32 (mm ³ ).

Example 4: Al-Zn-Mg-Er alloy is prepared by ingot metallurgy. First, high-purity Al (purity up to 99.99%) and pure Er (purity up to 99.9%) are used as raw materials, and the method of mixing (melting method) is adopted. Melting and casting in a vacuum induction furnace to prepare Al-6.2Er master alloy. Then high-purity aluminum 1461.2 and 150.8 grams of Al-6.2Er master alloy are added to the graphite clay crucible and melted in the crucible resistance furnace at a melting temperature of 780°C. After the high-purity aluminum and Al-6.2Er master alloy are completely melted, the Add 13.3 grams of pure Zn to the melt, stir well, then add 38.6 grams of pure Mg, stir evenly, add 3 grams of hexachloroethane (C ₂ Cl ₆ ) for degassing, slag removal, and finally melt The ingot was poured into a rectangular iron mold and demolded after cooling for 3 minutes. The size of each ingot was 120×90×32 (mm ³ ).

Example 5: Al-Zn-Mg-Er alloy is prepared by ingot metallurgy. First, high-purity Al (purity up to 99.99%) and pure Er (purity up to 99.9%) are used as raw materials, and the method of mixing (melting method) is adopted. Melting and casting in a vacuum induction furnace to prepare Al-6.2Er master alloy. Then add 1420.1 grams of high-purity aluminum and 191.9 grams of Al-6.2Er master alloy into a graphite clay crucible, and melt in a crucible resistance furnace at a melting temperature of 780 ° C. After the high-purity aluminum and Al-6.2Er master alloy are completely melted, Add 113.3 grams of pure Zn to the melt, stir well, then add 38.6 grams of pure Mg, stir evenly, add 3 grams of hexachloroethane (C ₂ Cl ₆ ) for degassing, slag removal, and finally The melt was poured into a rectangular iron mold, cooled for 3 minutes and released from the mold. The size of each ingot was 120×90×32 (mm ³ ). Embodiment 1: adopt ingot metallurgical method to prepare Al-Zn-Mg-Er alloy, at first with high-purity Al (purity reaches 99.99%) and pure Er (purity reaches 99.9%) as raw material, adopts to blending method (blending method ) Melting and casting in a vacuum induction furnace to prepare Al-6.2Er master alloy. Then 1584.9 grams of high-purity aluminum and 27.4 grams of Al-6.2Er master alloy were added to the graphite clay crucible, and melted in a crucible resistance furnace at a melting temperature of 780 ° C. After the high-purity aluminum and Al-6.2Er master alloy were completely melted, Add 113.3 grams of pure Zn to the melt, stir well, then add 38.6 grams of pure Mg, stir evenly, add 3 grams of hexachloroethane (C ₂ Cl ₆ ) for degassing, slag removal, and finally The melt was poured into a rectangular iron mold, cooled for 3 minutes and released from the mold. The size of each ingot was 120×90×32 (mm ³ ).

The specific ingredients and ingredients of each element of the alloy are shown in Table 1.

After the ingot was prepared, the chemical composition of the ingot was tested by the ICP-AES method, that is, the inductively coupled plasma atomic emission spectrometry (the instrument used was the LEEMAN SPEC-E inductively coupled plasma atomic emission spectrometer), and the test results are shown in Table 2 , it can be seen that the actual composition is within the allowable range of the nominal composition.

The as-cast alloy sample was taken, and the microstructure was observed with polarized light under a NEOPHOT-21 metallographic microscope made in Germany. Figure 1(a) and Figure 1(b) are the as-cast microstructures of Al-Zn-Mg alloy and Al-Zn-Mg-0.4Er alloy, respectively. It can be seen from the figure that the as-cast structure of the Al-Zn-Mg alloy is a coarse dendrite network cell, while the dendrites of the Al-Zn-Mg-0.4Er alloy have been basically eliminated and the grains have been significantly refined. It can be seen that the addition of rare earth Er can indeed significantly refine the as-cast grains of Al-Zn-Mg alloys.

After the ingot is homogenized and annealed, it is then subjected to hot rolling-intermediate annealing-cold rolling (cold rolling deformation is 60%) to obtain a 2mm thin plate. The cold-rolled sheet is made into a standard tensile sample according to the national standard GB6397-86, and the cold-rolled state and quenched aging state of the sample are measured on an 810MTS (Material Test System) material testing machine (470°C/0.5h quenching+120°C/30h aging ) mechanical properties, the test results are shown in Figure 2 and Figure 3. Figure 2 and Figure 3 show that the rare earth Er can greatly increase the tensile strength σ _b and yield strength σ _0.2 of the Al-Zn-Mg alloy. When the nominal content of Er is 0.7%, the strength reaches the maximum (Al-Zn-Mg-0.7Er alloy cold-rolled state tensile strength σ _b is 450MPa, aged state tensile strength σ _b reaches 513Mpa, and the alloy without Er Al-Zn-Mg alloy cold-rolled tensile strength σ _b is 350Mpa, aged tensile strength σ _b is 420MPa), but the elongation drops significantly (Al-Zn-Mg alloy cold-rolled elongation δ is 9% , while the cold-rolled elongation δ of the Al-Zn-Mg-0.7Er alloy is 7%); when the Er addition amount is 0.4%, both the strength and plasticity remain at a high level (Al-Zn-Mg-0.4Er alloy The aging state tensile strength σ _b is 490MPa, and the elongation δ is 10%). Therefore, the addition of Er is 0.25-0.55Wt%, and the effect is better. The strengthening effect of rare earth Er on Al-Zn-Mg alloy mainly comes from the significant refinement effect of Er on the grain and the rich substructure formed by the addition of Er. In addition, rare earth Er can promote the strengthening phase of Al-Zn-Mg alloy. The aging precipitation can greatly improve the aging strength of the alloy (as shown in Figure 3).

The recrystallization temperature of the alloy was determined by hardness-metallographic method. Fig. 4 is the relationship between hardness and annealing temperature of Al-Zn-Mg and Al-Zn-Mg-0.4Er alloys. From Figure 4, the recrystallization temperature T _s and final recrystallization temperature T _f of Al-Zn-Mg and Al-Zn-Mg-0.4Er alloys can be preliminarily determined (as indicated by the arrows in the figure). It can be seen that the addition of 0.4% Er can increase the initial recrystallization temperature of Al-Zn-Mg alloy by about 50°C, and the final recrystallization temperature by about 80°C. Metallographic observation and analysis show that the recrystallization of Al-Zn-Mg alloy after annealing at 325 °C for 1 hour has been completed (Fig. 5.a), while the Al-Zn-Mg-0.4Er alloy only shows signs of recrystallization (Fig. 5. b): After the Al-Zn-Mg alloy was annealed at 450°C for 1 hour, the grains were obviously coarsened (Fig. 5.c), while the structure of the Al-Zn-Mg-0.4Er alloy was still fine and equiaxed grains (Fig. 5 .d). It can be seen that the addition of Er can obviously inhibit the recrystallization of Al-Zn-Mg alloy.

Table 1 Nominal composition and batching amount of alloy (unit: g) serial number Alloy type Pure Al Pure Zn Pure Mg Al-6.2Er 0# Al-6.0Zn-2.0Mg 1612.4 113.3 38.6 0 1# Al-6.0Zn-2.0Mg-0.1Er 1584.9 113.3 38.6 27.4 2# Al-6.0Zn-2.0Mg-0.25Er 1543.7 113.3 38.6 68.5 3# Al-6.0Zn-2.0Mg-0.4Er 1502.5 113.3 38.6 109.7 4# Al-6.0Zn-2.0Mg-0.55Er 1461.2 113.3 38.6 150.8 5# Al-6.0Zn-2.0Mg-0.7Er 1420.1 113.3 38.6 191.9

Note: (1) The total weight of ingredients for each spindle is 1700g. (2) Burning loss rate: Al-3%, Mg-12%, Zn-10%, master alloy Al-6.2Er does not consider burning loss.

                                                                                          

Claims (2)

1, a kind of Al-Zn-Mg-Er rare earth aluminium alloy, it is characterized in that: added in the Al-Zn-Mg alloy that to account for this Al-Zn-Mg-Er rare earth aluminium alloy weight percent be 0.1～0.7% Er, the weight percentage of Zn is 6.0% in the described Al-Zn-Mg alloy, the weight percentage of Mg is 2.0%, and Al is a surplus.

2, Al-Zn-Mg-Er rare earth aluminium alloy according to claim 1 is characterized in that: the addition of described Er is for accounting for this Al-Zn-Mg-Er rare earth aluminium alloy weight percent 0.25～0.55%.

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