JPS62225B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a superplastic aluminum alloy, and more particularly, to a method for producing an Al--Mg-based superplastic aluminum alloy. In the method for producing a superplastic aluminum alloy according to the present invention, superplasticity refers to a phenomenon in which a material undergoes enormous elongation of several hundred to 1,000% without necking under certain external conditions. It is broadly divided into transformation superplasticity, which utilizes isothermal transformation, and fine-grained superplasticity (structural superplasticity), which is observed in fine-grained materials. In particular, the present invention is a method for producing a fine-grained superplastic aluminum alloy. [Prior Art] Generally, in order to cause fine grain superplasticity, it is essential to finely control the grain size of the material. In addition, generally Al-Mg aluminum alloys are
After casting, the ingot is subjected to homogenization heat treatment at a temperature of 400 to 550°C, and then hot worked and cold worked at a temperature of 300 to 550°C to produce the desired material. In normal processes such as
The aluminum alloy becomes as large as 30 to 100 μm, and even if it is deformed at high temperatures, the desired superplasticity (elongation) cannot be imparted to the aluminum alloy. [Problems to be solved by the invention] As explained above, the present invention solves the problems hitherto;
The present invention provides a method for producing a superplastic aluminum alloy that can obtain a fine crystal structure, which is difficult to achieve with Al--Mg-based aluminum alloys. [Means for Solving the Problems] The method for producing a superplastic aluminum alloy according to the present invention includes: (1) containing 2 to 7 wt% Mg, and further containing 0.05 to 1.5 wt% Mn, and 0.05 to 0.5 wt% Cr; %, Zr0.05~0.5wt%, V0.05~0.5wt%, Ti0.15wt% or less, and the balance is Al and impurities Al-Mg alloy ingot. , homogenization heat treatment at a temperature of 400 to 550°C, then hot working at a temperature of 300 to 550°C, and then a first heating holding at a temperature of 450 to 550°C for 0.5 to 10 hours. , then cooled to the second heating temperature, and heated from 0.5 to 350 to 450℃.
Perform the second heating hold for 50 hours, and then heat to 30℃/hour.
After cooling at a cooling rate of at least 30%
The first invention is a method for manufacturing a superplastic aluminum alloy characterized by performing the above cold working, and (2) containing Mg2 to 7wt%, further comprising Mn0.05 to 1.5wt%, Cr0.05 Al containing one or more selected from ~0.5wt%, Zr0.05~0.5wt%, V0.05~0.5wt%, Ti0.15wt% or less, with the balance consisting of Al and impurities.
The Mg-based alloy ingot is homogenized at a temperature of 400 to 550°C, then hot worked at a temperature of 300 to 550°C, and then heated and held for the first time at a temperature of 450°C.
0.5-10Hr at a temperature of ~550℃, then the second
Cool to the heating temperature of 350-450℃
Perform the second heating and holding for 0.5 to 50Hr, and
After cooling at a cooling rate of ℃/Hr or higher, 20 to 60
% cold working, followed by low temperature softening annealing at 300°C or less and cold working one or more times, (3) Mg2 ~7wt% and further selected from Mn0.05~1.5wt%, Cr0.05~0.5wt%, Zr0.05~0.5wt%, V0.05~0.5wt%, Ti0.15wt% or less. Al-
The Mg alloy ingot is subjected to homogenization heat treatment at a temperature of 400 to 550°C, then hot worked at a temperature of 300 to 550°C, and then subjected to the first heating and holding process.
Carry out for 0.5-10Hr at a temperature of 450-550℃, then
Cool to the second heating temperature, perform a second heating hold at a temperature of 350 to 450 ° C for 0.5 to 50 Hr,
After cooling at a cooling rate of 30°C/Hr or more, cold working is performed by at least 30%, or cold working is performed by 20 to 60%, and then,
Production of a superplastic aluminum alloy characterized by performing low-temperature softening annealing at 300°C or less and cold working one or more times, and further heat-softening treatment at a temperature of 350 to 550°C at a heating rate of 100°C/Hr or more. This invention consists of three inventions, with the third invention being a method. 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 used in the method for producing a superplastic aluminum alloy according to the present invention will be explained. If Mg is less than 2wt%, sufficient strength cannot be obtained.
Moreover, if the content exceeds 7wt%, hot workability will be significantly reduced. Therefore, the Mg content is 2 to 7 wt%.
shall be. If the content of Mn, Cr, Zr, and V is less than 0.05wt%, fine crystal grains cannot be obtained as described later, and
Mn1.5wt%, Cr, Zr, V0.5wt% and Ti0.15wt
If the content exceeds %, sufficient solid solution cannot be obtained during casting, resulting in the formation of giant compounds, and sufficient elongation cannot be obtained. Therefore, the Mn content is 0.05-1.5wt%,
Cr content is 0.05~0.5wt%, Zr0.05~0.5wt%,
V0.05~0.5wt%, Ti content is 0.15wt% or less. In addition, if the content of Fe and Si contained as impurities exceeds 0.25wt%, undissolved crystallized substances will be formed and the elongation will decrease significantly, so it is necessary to suppress the content of Fe and Si as much as possible. There is. Next, a heat treatment method in the method for producing a superplastic aluminum alloy according to the present invention 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. Homogenization heat treatment is carried out at a temperature of 300 to 550 degrees Celsius for a sufficient period of time, followed by hot working at a temperature of 300 to 550 degrees Celsius to reach a predetermined thickness. Precipitates such as Mg and some transition elements such as Mn, Cr, Zr, V, and Ti are partially separated. Furthermore, if cold working is performed by 30% or more after hot working, finer grains will be obtained and superplastic elongation will also increase. This hot-processed material is produced at temperatures of 450-550℃
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 during the first heating and holding process are solid-solubilized, and the subsequent two heating and holding processes convert the transition elements Mn, Mn,
Intermetallic compound of Cr, Zr, etc. and Al MnAl ₆ ,
Cr ₂ Al 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 carried out only once, these two heating and holding processes result in finer precipitation of transition elements and the formation of some high-temperature aging precipitates of Mg, etc. and Al. In order to achieve this, the cooling rate after heating and holding may be as slow as 30°C/Hr or more, making manufacturing easier, and increasing the density of dislocations generated during cold working, resulting in finer Crystal grains are formed and a product with large superplastic elongation is 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 and distribution of precipitates such as MnAl ₆ , Cr ₂ Mg ₃ Al ₁₆ , and ZrAl ₃ formed during heating and holding after hot rolling are 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 a temperature of 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. [Example] An example of the method for producing a superplastic aluminum alloy according to the present invention will be described. Example 1 Mg2.5wt%, Cr0.15wt%, Zr0.15wt%,
Ti0.02wt%, balance Al (alloy 1), Mg5.6wt%,
Cr0.1wt%, Mn0.1wt%, Ti0.02wt%, balance Al
(Alloy 2) and Mg4.5wt%, Zr0.2wt%,
Mn0.1wt%, V0.05wt%, Ti0.02wt%, balance Al
After casting a 400 mm thick ingot of (alloy 3) using the normal DC casting method, after homogenizing heat treatment at a temperature of 510 °C for 12 hours, hot rolling at a temperature of 450 to 300 °C.
Rolled into 40mm plate, 3Hr at 540℃ and 10Hr at 420℃
After heating and holding for several hours, cooling at a cooling rate of approximately 100°C/Hr, a plate with a thickness of 1.5 mm was produced by cold rolling (cold working rate: 63%), and the strain rate was 2 × 10 ^- at 550°C. ^Four /
Transformed in sec. As shown in Table 1, the superplastic elongation of the method of the present invention for producing a superplastic aluminum alloy is more than twice that of the conventional method of the comparative example.

[Table] Example 2 Alloy 3 of Example 1 cast by normal DC casting method
(thickness 400mm) was homogenized at a temperature of 510℃ for 12 hours, then hot rolled at 450~300℃ to a thickness of 7.5mm.
It was processed into a plate of Fabricate a material with a thickness of 1.5 mm,
After heating to 550°C, it was deformed at a strain rate of 2×10 ^-4 /sec. It can be seen that the superplastic elongation of the material manufactured by the method for manufacturing a superplastic aluminum alloy according to the present invention is significantly superior to that of a material that is not subjected to low-temperature softening annealing.

[Table] Example 3 Alloy 3 of Example 1 (thickness: 400 mm), which was cast by a normal DC casting method, was homogenized at a temperature of 510°C for 12 hours, and then heated and rolled at a temperature of 450 to 300°C. Processed into a 4.0mm thick plate and heated at 540℃ for 3 hours and
After heating and holding for 10 hours at a temperature of 450℃, approx.
1.5 by cold rolling after cooling at a cooling rate of 100℃/Hr
mm thick (cold working ratio 63%), heat softened at a temperature of 530°C at the heating rate shown in Table 3, and heated at a temperature of 550°C with a strain rate of 2×10 ^-4 /sec. Deformed.

〔Effect of the invention〕

As explained above, since the method for producing a superplastic aluminum alloy according to the present invention has the above configuration, there is no local elongation of necking at an appropriate temperature. This has the effect of providing a material with excellent superplastic elongation.

Claims (1)

[Claims] 1 Contains Mg2-7wt%, and further includes Mn0.05-1.5wt%, Cr0.05-0.5wt%, Zr0.05-0.5wt%, V0.05-0.5wt%, Ti0 Al-Mg containing one or more selected from .15wt% or less, with the balance consisting of Al and impurities.
The alloy ingot is subjected to homogenization heat treatment at a temperature of 400 to 550°C, then hot worked at a temperature of 300 to 550°C, and then the first heating holding is carried out at a temperature of 450 to 550°C. Then, it was cooled to the second heating temperature, and the second heating was held at a temperature of 350 to 450°C for 0.5 to 50 hours, and then cooled at a cooling rate of 30°C/Hr or more. 1. A method for producing a superplastic aluminum alloy, which is then subjected to cold working of at least 30% or more. 2 Contains Mg2~7wt%, and further contains Mn0.05~1.5wt%, Cr0.05~0.5wt%, Zr0.05~0.5wt%, V0.05~0.5wt%, and Ti0.15wt% or less. Al-Mg containing one or more selected from the following, with the balance consisting of Al and impurities
The alloy ingot is subjected to homogenization heat treatment at a temperature of 400 to 550°C, then hot worked at a temperature of 300 to 550°C, and then the first heating holding is carried out at a temperature of 450 to 550°C. Then, it was cooled to the second heating temperature, and the second heating was held at a temperature of 350 to 450°C for 0.5 to 50 hours, and then cooled at a cooling rate of 30°C/Hr or more. A method for producing a superplastic aluminum alloy, which comprises performing cold working of 20 to 60%, followed by low-temperature softening annealing at 300°C or less and cold working one or more times. 3 Contains Mg2~7wt%, and further contains Mn0.05~1.5wt%, Cr0.05~0.5wt%, Zr0.05~0.5wt%, V0.05~0.5wt%, and Ti0.15wt% or less. Al-Mg containing one or more selected from the following, with the balance consisting of Al and impurities
The alloy ingot is subjected to homogenization heat treatment at a temperature of 400 to 550°C, then hot worked at a temperature of 300 to 550°C, and then the first heating holding is carried out at a temperature of 450 to 550°C. Then, it was cooled to the second heating temperature, and the second heating was held at a temperature of 350 to 450°C for 0.5 to 50 hours, and then cooled at a cooling rate of 30°C/Hr or more. After that, cold working is performed by at least 30%, or cold working is performed by 20 to 60%, followed by low temperature softening annealing and cold working at 300°C or less, and then 100% cold working is performed. A method for producing a superplastic aluminum alloy, comprising heating and softening the alloy to a temperature of 350 to 550°C at a heating rate of ℃/Hr or more.