JPS6157384B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a superplastic aluminum alloy, and more particularly, to a method for producing a high-strength Al-Zn-Mg-based superplastic aluminum alloy. Superplasticity is a phenomenon in which a material undergoes enormous elongation of several 100 to 1000% without necking under certain external conditions. It is broadly classified into fine-grained superplasticity (structural superplasticity). In order to cause this fine grain superplasticity, it is essential to finely control the crystal grain size of the material. Generally, high-strength aluminum alloys are produced by homogenizing the ingot after casting at a temperature of 400 to 550°C, then hot working and cold working at a temperature of 350 to 550°C, and then The desired material is obtained by solution heat treatment and aging treatment at a temperature of 550℃, but in such a normal process, the crystal grain size is 40~
It becomes as large as 100 μm, and superplastic elongation cannot be obtained even if deformation is performed at high temperatures. As explained above, the present invention has been described above.
The present invention provides a method for producing a superplastic aluminum alloy that can obtain a fine grain structure that is difficult to obtain with Al-Zn-Mg-based high-strength aluminum alloys. The method for producing a superplastic aluminum alloy according to the present invention includes (1) essential components of Zn3-8wt%, Mg0.5-3wt%, Cu3wt% or less, Mn0.05-2.0wt%, Cr0.05;
~2.0wt%, Zr0.05~0.5wt%, V0.05~0.5wt%,
Al containing one or more selected from Ti0.15wt% or less, with the balance consisting of Al and impurities.
-The Zn-Mg alloy ingot is subjected to homogenization heat treatment at a temperature of 400 to 550°C, and then at a temperature of 350 to 500°C.
After hot working at a temperature of Perform the second heating and holding for 0.5 to 50 Hr at
The first invention provides a method for producing a superplastic aluminum alloy, which is characterized by cooling at a cooling rate of 30°C/Hr or higher and then cold working by at least 30%, and (2) Zn3-8wt%. , Mg0.5~3wt% as essential components, Cu3wt% or less, Mn0.05~2.0wt%,
Cr0.05~0.5wt%, Zr0.05~0.5wt%, V0.05~
An Al-Zn-Mg alloy ingot containing one or more selected from 0.5wt% and 0.15wt% or less of Ti, with the balance consisting of Al and impurities is homogenized at a temperature of 400 to 550℃. Heat treatment is performed, and then
After hot working at a temperature of 350 to 500℃, the first
Heating and holding for 0.5 to 10 hours at a temperature of 450 to 550℃, then cooling to the second heating temperature and heating to 350℃
A second heating hold for 0.5-50 Hr at a temperature of ~450°C, followed by cooling at a cooling rate of 30°C/Hr or higher, followed by 20-60% cold working, followed by 300°C
The second invention is a method for producing a superplastic aluminum alloy, which is characterized by performing the following low-temperature annealing and cold working one or more times: (3) Zn3-8wt%, Mg0.5-3wt%
% is an essential component, Cu3wt% or less, Mn0.05~
2.0wt%, Cr0.05~2.0wt%, Zr0.05~0.5wt%,
An Al-Zn-Mg alloy ingot containing one or more selected from V0.05~0.5wt% and Ti0.15wt% or less, with the balance being Al and impurities,
Homogenization heat treatment at a temperature of ~550℃,
Next, after hot working at a temperature of 350 to 500°C, the first heating holding is performed at a temperature of 450 to 550°C for 0.5
〜10Hr, then cool down to the second heating temperature, hold the second heating for 0.5~50Hr at a temperature of 350~450℃, and then cool at a cooling rate of 30℃/Hr or more. , at least 30% or more cold working, or 20~60% cold working, followed by low temperature softening annealing and cold working at 300°C or less once or more, and then 100°C This invention consists of three inventions, the third invention being a method for producing a superplastic aluminum alloy, which is characterized by performing heat softening treatment at a temperature of 350 to 550° C. at a rate of at least /Hr. The method for producing a superplastic aluminum alloy according to the present invention will be described in detail below. First, the components and component ratios of the aluminum alloy will be explained. If the Zn content is less than 3 wt%, sufficient strength cannot be obtained, and if the content exceeds 8 wt%, ductility and corrosion resistance are impaired. Therefore, the Zn content is 3 to 8 wt.
%. If Mg is less than 0.5wt%, sufficient strength cannot be obtained.
Moreover, if the content exceeds 3 wt%, cold workability will be impaired. Therefore, the Mg content is set to 0.5 to 3 wt%. If Cu is contained in an amount exceeding 3wt%, ductility and toughness will be impaired. Therefore, the Cu content should be 3wt% or less. If Mn, Cr, Zr, and V are each less than 0.05wt%, fine crystal grains cannot be obtained as described later, and
Mn2.0wt%, Cr, Zr, V each 0.5wt% and
If Ti is contained in excess of 0.15 wt%, it will not be sufficiently solid-dissolved during casting, and giant intermetallic compounds will occur, making it impossible to obtain sufficient elongation. Therefore, the Mn content is 0.
05~2.0wt%, Cr content is 0.05~0.5wt%, Zr0.05
~0.5wt%, V0.05*0.5wt%, Ti 0.15wt% or less. In addition, it may be contained as an impurity.
When the content of Fe and Si exceeds 0.15 wt%, insoluble crystallized substances are generated, resulting in a significant decrease in elongation. Therefore, the contents of Fe and Si are each 0.15 wt% or less. Next, the heat treatment method will be explained. In order to homogenize the main elements that are heterogeneously distributed inside the ingot and improve hot workability, we cast an ingot obtained by casting an aluminum alloy with the above-mentioned components and ratios. A homogenization heat treatment is carried out at a temperature of °C for a sufficient time. Next, hot working is carried out at a temperature of 350 to 500°C to reach the specified thickness, and the rough cast structure becomes a hot fiber structure, and at the same time, Zn, Mg, Cu, etc. Some transition elements such as Mn, Cr, Zr, V, and Ti are partially analyzed. Furthermore, after hot working, 30
If cold working is carried out by % or more, finer grains will be obtained and the superplastic elongation will also increase. This hot-processed material can be heated at temperatures between 450 and 550℃.
Perform the first heating and holding for 0.5 to 10 Hr, then cool to the second heating and holding temperature, and perform the second heating and holding for 0.5 to 50 Hr at a temperature of 350 to 450°C,
Cool at a cooling rate of 30℃/Hr or higher. The higher the temperature for this heating and holding, the shorter the time. During the two heating and holding cycles, most of the solute elements precipitated by the first heating and holding are dissolved in solid solution, and the second heating and holding process converts the transition elements Mn, Mn,
Intermetallic compound of Cr, Zr, etc. and Al MnAl ₆ ,
Cr ₂ Mg ₃ Al ₁₈ , ZrAl _{3 ,} etc. are precipitated, and the fine grain structure generated in the material is maintained by heating in the superplastic temperature range after the next cold working, resulting in superplasticity. In addition, compared to the case where heating and holding is performed once, the precipitation form of transition elements is finer, and some high-temperature aging precipitates of Zn, Mg, Cu, etc. and Al are present. In order to form Fine crystal grains are generated and a product with large superplastic elongation can be obtained. By this heating and holding, the dislocation underlying structure that had formed the hot fiber structure recovers and recrystallizes, reducing the strain energy, making it easier for dislocations to be introduced in the subsequent cold working. If the cooling rate after this heating and holding is less than 30°C/Hr, it becomes difficult to obtain superplastic elongation. After cooling, cold working is performed to a rate of at least 30%, but if the working rate is less than 30%, sufficiently fine grains cannot be obtained. Also, 20-60% cold working followed by 300℃
The following low-temperature softening annealing can be performed one or more times, and by introducing this low-temperature annealing, the crystal grains are further refined. In the material that has been cold-worked in this manner, a dense dislocation substructure with high strain energy is formed. When this material is heated to the superplastic temperature range (usually 400°C or higher for aluminum alloys) above 0.5Tm {Tm is the melting point (absolute temperature) of the material}, new crystal grains are formed starting from the high-density dislocation structure, and Therefore, the higher the density of the dislocation structure, the finer the grain structure and the greater the superplastic elongation. Once recrystallization is completed, dislocations move to reduce the energy at grain boundaries, and the grains tend to become coarser, and these coarsened grains inhibit superplastic deformation. . Therefore, in the method for producing a superplastic aluminum alloy according to the present invention, the size distribution of precipitates such as MnAl ₆ , Cr ₂ Mg ₃ Al ₁₆ , and ZrAl ₃ formed during heating and holding after hot rolling is determined. By controlling this, the movement of dislocations is prevented and the fine grain structure is maintained. That is, if the size of the precipitates is too small or the particle spacing is too large, the effect of inhibiting dislocation movement cannot be obtained. In addition, in the method for producing a superplastic aluminum alloy according to the present invention, the material as it is cold-worked may be subjected to superplastic working, but the material is heated at a heating rate of 100°C/Hr or more, and the material is heated at 350 to 550°C. Superplastic working can also be performed after heat softening treatment at a high temperature. The fine-grained superplastic material produced by the method for producing a superplastic aluminum alloy according to the present invention exhibits superplastic elongation of 500% or more without necking (local elongation) at an appropriate temperature (usually 400°C or higher). is obtained. An example of the method for manufacturing a superplastic aluminum alloy according to the present invention will be described. Example 1 Zn5.7wt% cast by normal DC casting method,
Mg2.3wt%, Cu1.5wt%, Cr0.20wt%, Fe0.10wt
%, Si0.05wt% balance Al ingot (thickness 400
mm) after 12Hr homogenization heat treatment at a temperature of 465℃, 400
A plate with a thickness of 4 to 6 mm was obtained by cold rolling at a temperature of 510°C, and a material with a final thickness of 2.5 mm was produced through the steps shown in Table 1. After heating to a temperature of 510°C, the strain rate was 2×.
It deformed at 10 ^-4 /sec. As is clear from Table 1, the superplastic elongation of the material produced by the method for producing a superplastic aluminum alloy according to the present invention is more than twice that of the comparative material, about 6
Some even double.

[Table] Example 2 The same ingot (thickness: 400 mm) as in Example 1, which was cast by the normal DC method, was homogenized at a temperature of 465°C for 12 hours, and then hot rolled at a temperature of 400°C.
After making a 12.5mm thick plate, it was heated and held at a temperature of 510℃ for 3 hours and at a temperature of 400℃ for 10 hours.
After cooling at a cooling rate of approximately 100°C/Hr, a material with a thickness of 2.5 mm was produced by cold rolling and low-temperature annealing as shown in Table 2, and after heating to a temperature of 510°C, the strain rate was 2×.
Deformed at 10 ^-4 /sec. As is clear from Table 2, it can be seen that the material produced by the method for producing a superplastic aluminum alloy according to the present invention has a superplastic elongation equal to or greater than that of a material that is not subjected to low-temperature softening annealing.

[Table] Example 3 The same ingot (thickness: 400 mm) as in Example 1, which was cast by the normal DC method, was subjected to homogenization heat treatment at a temperature of 465°C for 12 hours, and then hot rolled at a temperature of 400°C.
6.3mm thick plate, 3Hr and 400 at a temperature of 510℃
After heating and holding for 10 hours at a temperature of ℃, approximately 100
Cooled at a cooling rate of ℃/Hr and cold rolled to 2.5
A plate with a thickness of mm was heat-softened at a temperature of 480℃ at the heating rate shown in Table 3, and the strain rate was 2 at a temperature of 510℃.
Deformed at ×10 ^-4 /sec. As is clear from Table 3, the temperature at 100°C/
It can be seen that the superplastic elongation of the material softened by heating at a heating rate of 40° C./Hr or more is much better than that when the heating rate is 40° C./Hr.

[Table] As explained above, since the method for producing a superplastic aluminum alloy according to the present invention has the above configuration, the material produced by this method has constriction (local elongation). without any
It has the effect of obtaining superplastic elongation of 500% or more.

Claims (1)

[Claims] 1 Zn3-8wt%, Mg0.5-3wt%, are essential components, Cu3wt% or less, Mn0.05-2.0wt%, Cr0.05-2.0wt%, Zr0.05-0.5wt %, V0.05 to 0.5wt%, Ti 0.15wt% or less, and the balance is Al and impurities. After performing homogenization heat treatment at a temperature of 350 to 500 °C, and then hot working at a temperature of 350 to 500 °C, the first heating holding was performed at a temperature of 450 to 550 °C for 0.5 to 10 hours, and then, Cool to the second heating temperature, perform a second heating hold for 0.5 to 50 Hr at a temperature of 350 to 450°C, cool at a cooling rate of 30°C/Hr or more, and then cool at least 30% or more. A method for manufacturing a superplastic aluminum alloy, which is characterized by performing preliminary working. 2 Zn3~8wt%, Mg0.5~3wt%, are essential components, Cu3wt% or less, Mn0.05~2.0wt%, Cr0.05~0.5wt%, Zr0.05~0.5wt%, V0.05~ An Al-Zn-Mg alloy ingot containing one or more selected from 0.5wt% and 0.15wt% or less of Ti, with the balance consisting of Al and impurities is homogenized at a temperature of 400 to 550℃. After heat treatment and then hot working at a temperature of 350 to 500°C, the first heating holding is performed at a temperature of 450 to 550°C for 0.5 to 10 hours, and then the second heating temperature is A second heating hold is performed for 0.5 to 50 hours at a temperature of 350 to 450℃, followed by cooling at a cooling rate of 30℃/Hr or higher, followed by cold working of 20 to 60%. 1. Low temperature annealing and cold working below 300℃
A method for producing a superplastic aluminum alloy, characterized by carrying out the process more than once. 3 Zn3~8wt%, Mg0.5~3wt%, are essential components, Cu3wt% or less, Mn0.05~2.0wt%, Cr0.05~2.0wt%, Zr0.05~0.5wt%, V0.05~ An Al-Zn-Mg alloy ingot containing one or more selected from 0.5wt% and 0.15wt% or less of Ti, with the balance consisting of Al and impurities is homogenized at a temperature of 400 to 550℃. After heat treatment and then hot working at a temperature of 350 to 500°C, the first heating holding is performed at a temperature of 450 to 550°C for 0.5 to 10 hours, and then the second heating temperature is After cooling to a temperature of 350 to 450℃ and a second heating hold for 0.5 to 50Hr, cooling at a cooling rate of 30℃/Hr or more, cold working by at least 30% or more, or Alternatively, perform 20-60% cold working, then perform low-temperature softening annealing and cold working at 300°C or less, and then heat at a temperature of 350-550°C at a rate of 100°C/Hr or more. A method for producing a superplastic aluminum alloy, which comprises performing a softening treatment.