WO2018159394A1 - Magnesium alloy and method for manufacturing magnesium alloy - Google Patents

Abstract

A magnesium alloy which is very versatile and can achieve both workability and strength in a temperature range including room temperature, and a method for manufacturing the magnesium alloy, wherein the obtained magnesium alloy contains 0.2 to 2 wt.% of Al, 0.2 to 1 wt.% of Mn, 0.2 to 2 wt.% of Zn, and at least 0.2 to 1 wt.% of Ca, the remainder comprises Mg and unavoidable impurities, and a precipitate comprising Mg, Ca, and Al is dispersed on the (0001) plane of a magnesium parent phase.

Description

Magnesium alloy and method for producing magnesium alloy

The present invention relates to a magnesium alloy and a method for producing the magnesium alloy.

Magnesium alloy is known as the lightest metal among practical metals, and its application to railways, aircraft, automobiles, etc. is being studied as a lightweight material to replace aluminum alloys. However, magnesium alloy wrought material is inferior in strength and workability compared to aluminum alloy. In order to overcome this point and expand the applications of magnesium alloys, various studies have been conducted including the development of new wrought materials.

A conventional wrought magnesium alloy has a strength exceeding 300 MPa by refining crystal grains by strong processing and adding rare earth metal elements and zinc as alloy elements (see, for example, Patent Document 1). However, there are many practical problems in the alloys developed by the prior art.

As in Patent Document 1, an alloy added with a rare earth metal as an alloy element has excellent strength. However, since the expensive rare earth metal is used, the raw material cost becomes high. In addition, since the primary processing such as hot processing and the secondary processing to the final shape cannot be easily performed, the manufacturing cost is high. Therefore, the possibility of developing a general-purpose material that can be applied to automobiles, railways, and the like is extremely low.

Further, a wrought material whose strength is improved by refining crystal grains by strong processing is known (see Non-Patent Document 1, for example). However, since a deformed structure is formed and already in a work-hardened state, secondary processing at room temperature is extremely difficult. In addition, it is difficult to produce a large member.

On the other hand, in addition to the development of high-strength alloys, many studies have been conducted so far on improving workability at room temperature (see Patent Documents 2 and 3). In these reported examples, workability at room temperature is evaluated by the Erichsen value (IE value).

In some reports, an example of developing an alloy having excellent workability at room temperature comparable to an aluminum alloy by adding an alloying element or improving a rolling process has been reported (see Patent Document 3). However, there was a tendency for the strength to decrease as the room temperature processability improved. In addition, the example which improved the intensity | strength using the aging treatment in the specific casting material and extrusion material is also reported (refer patent document 4, 5).

JP 2013-79436 A JP 2004-10959 A JP 2010-13725 A JP 2002-266044 A JP 2016-169427 A

By the way, for example, in the case of an automobile body panel, an alloy having a 0.2% proof stress of 160 MPa, which is required as a mechanical property, and an Erichsen value of about 8 mm is required, and in many applications, it is excellent in strength and room temperature. There is a strong demand for alloys that exhibit both secondary workability. However, conventional magnesium alloys and magnesium alloy production methods have not yielded highly versatile materials that have both strength and secondary workability at room temperature.

Therefore, an object of the present invention is to provide a highly versatile magnesium alloy and a magnesium alloy manufacturing method that can achieve both workability and strength in a temperature range including normal temperature.

The application of an aging treatment is a method for solving the above-mentioned problems. The heat treatment called T6 treatment is a kind of heat treatment process applied to the wrought material obtained by hot or warm working, and is a solution treatment (T4 treatment) in which an alloying element is supersaturated in the alloy. And an aging treatment in which precipitates are dispersed and strengthened to the maximum hardness.

When T6 treatment is applied to plastic processed products such as plates and bars, plastic processed products are softened after T4 treatment due to solid solution of precipitates in the parent phase, recovery of the parent phase, recrystallization, and a decrease in crystal orientation. Therefore, moldability can be improved, and strength can be imparted by dispersing fine precipitates at high density by subsequent aging treatment. Such heat treatment cannot be applied because Mg-3Al-1Zn alloy, which is known as a current commercial magnesium alloy plate material, does not age harden. However, as a result of intensive studies by the present inventors, if a specific magnesium alloy is used, a T6 treatment is possible. The present inventors have found that it is possible to achieve both workability and strength in a temperature range including normal temperature by utilizing the above, and have reached the present invention.

That is, the magnesium alloy of the present invention that achieves the above object is provided with 0.2-2% by mass of Al, 0.2-1% by mass of Mn, 0.2-2% by mass of Zn, and at least 0.1% by mass. 2 to 1% by mass of Ca, the balance being made of Mg and inevitable impurities, and precipitates made of Mg, Ca and Al are dispersed on the (0001) plane of the magnesium matrix.
The magnesium alloy of the present invention may further contain precipitates made of Al and Mn.

In this magnesium alloy, the precipitates made of Mg, Ca and Al have a plate shape, the long side of the plate has a range of 3 to 6 nm, and the number density of the precipitates is 10 ²⁰ to 10 ²⁴ / mm. ³ is preferred. The average crystal grain size of the magnesium matrix is preferably 20 μm or less.

In this magnesium alloy, it is preferable that the integration degree of the (0002) poles in the central portion of the plate thickness of the normalized RD-TD plane of the (0002) pole figure measured by X-ray diffraction is 5.0 or less.

In the magnesium alloy of the present invention, it is preferable that the Erichsen value at room temperature is 6.5 mm or more. Further, the 0.2% proof stress of the solution treated material is preferably 120 MPa or more, and the 0.2% proof stress of the magnesium alloy finally subjected to aging treatment after molding is preferably 160 MPa or more. In any stage, the breaking elongation is preferably 20% or more.

The method for producing a magnesium alloy of the present invention that achieves the above object comprises the steps 1 of obtaining Mg, Al, Mn, Zn, and Ca to obtain a cast solid, and the step of homogenizing the cast solid to obtain a homogenized solid. 2, a process 3 to obtain a tangible solid by processing the homogenized solid hot or warm, a process 4 to obtain a cooling solid by solution treatment of the tangible solid, an aging treatment of the cooling solid to obtain a magnesium alloy And obtaining a homogenized solid by performing a homogenization treatment at 400 ° C. or more and 500 ° C. or less for a predetermined time in Step 2, and aging at a temperature of 140 to 250 ° C. for a predetermined time in Step 5 The magnesium alloy is obtained by processing.

In the method for producing a magnesium alloy of the present invention, a secondary processing step of secondary processing of the cooling solid can be included between Step 4 and Step 5. In that case, it is preferable to perform secondary processing of a cooled solid having a 0.2% proof stress of 120 MPa or more and to make the 0.2% proof stress 160 MPa or more in Step 5. Further, in step 3, it is preferable to perform processing by hot or warm processing. Furthermore, in step 5, it is preferable to perform an aging treatment for increasing the hardness of the magnesium alloy.

According to the present invention, it is possible to achieve both workability and strength in a temperature range including normal temperature, and since an expensive rare earth metal element is not used as an alloy element, it is possible to manufacture a highly versatile magnesium alloy and magnesium alloy. A method can be provided.

The optical microscope image of the solution treatment material which is the cooling solid of the process 4 in Example 1 of this invention is shown. The (0002) pole figure obtained from the X-ray diffraction of the solution treatment material which is the cooling solid of the process 4 in Example 1 is shown. The tensile stress-strain curve of the solution treatment material which is the cooling solid of the process 4 in Example 1, and the aging treatment material of the process 5 is shown. The aging treatment material of Example 1 was observed with a transmission electron microscope. (A) was obtained from a bright-field TEM image, and (b) was obtained from [011 (bar) 0] and [112 (bar) 0] orientations. Limited field diffraction image, (c) is a diagram showing a three-dimensional atom map. The aging treatment material of Example 1 was observed with a transmission electron microscope. (A) is a bright-field TEM image, (b) is a HAADF-STEM image (High-angle Annular Dark Field Scanning Transmission Electron Microscopy, high angle scattering annular darkness). (Scanning transmission electron microscope image), (c) is an enlarged view of the HAADF-STEM image of (b), and (d) is a diagram showing the results of elemental analysis along the arrow of (c). It is a figure which shows the optical microscope image of the solution treatment material which is a cooling solid of the process 4 in Example 5. FIG. The (0002) pole figure obtained from the X-ray diffraction of the solution treatment material which is the cooling solid of the process 4 in Example 5 is shown. The tensile stress-strain curve of the solution treatment material which is the cooling solid of the process 4 in Example 5, and the aging treatment material of the process 5 is shown. It is a figure which shows the optical microscope image of the solution treatment material which is a cooling solid of the process 4 in Example 7. FIG. The (0002) pole figure obtained from the X-ray diffraction of the solution treatment material which is the cooling solid of the process 4 in Example 7 is shown. The tensile stress-strain curve of the solution treatment material which is the cooling solid of the process 4 in Example 7, and the aging treatment material of the process 5 is shown. It is a figure which shows the optical microscope image of the solution treatment material which is a cooling solid of the process 4 in Example 9. FIG. The (0002) pole figure obtained from the X-ray diffraction of the solution treatment material which is the cooling solid of the process 4 in Example 9 is shown. The tensile stress-strain curve of the solution treatment material which is the cooling solid of the process 4 in Example 9, and the aging treatment material of the process 5 is shown. It is a figure which shows the optical microscope image of the solution treatment material which is the cooling solid of the process 4 in the comparative example 1. FIG. The (0002) pole figure obtained from the X-ray diffraction of the solution treatment material which is the cooling solid of the process 4 in the comparative example 1 is shown. The tensile stress-strain curve of the solution treatment material which is the cooling solid of the process 4 in the comparative example 1 and the aging treatment material of the process 5 is shown.

Hereinafter, embodiments of the present invention will be described in detail.
The magnesium alloy of the present invention comprises 0.2-2 mass% Al, 0.2-1 mass% Mn, 0.2-2 mass% Zn, and at least 0.2-1 mass% Ca. And the balance of Mg and inevitable impurities.

This magnesium alloy has a magnesium matrix composed of Mg in which Mg or Al, Mn, Zn and Ca are dissolved, and a precipitate containing one or more of Al, Mn, Zn and Ca. The form of the magnesium alloy is not particularly limited, and may be, for example, a form of various materials such as a plate material, or may be a form of an intermediate or a final product.

In the magnesium matrix phase in the magnesium alloy of the present invention, the degree of crystal orientation is reduced by the T4 treatment, and Al, Ca, Zn, and Mn, which are alloy elements that form precipitates, are in solid solution. The average crystal grain size of the magnesium matrix is preferably 20 μm or less. If the crystal grain size is excessively large, the formation of a deformation twin that becomes the starting point of a crack becomes easy, and the moldability at room temperature is remarkably lowered, which is not preferable.

The proportion of Al contained in the magnesium alloy of the present invention is preferably 0.2 to 2% by mass. When the Al content is small, it is difficult to obtain useful precipitates to be described later. On the other hand, when the Al content is excessive, the precipitated phase is preferably changed to coarse precipitates such as an Al ₂ Ca phase that is not effective for strengthening. Absent.

The proportion of Mn contained in the magnesium alloy of the present invention is preferably 0.2% by mass or more and 1% by mass or less. When the Mn content is small, an Al—Mn compound that plays a role in suppressing the coarsening of crystal grains is likely to be formed. On the other hand, when it is excessive, Al is used to form the Al—Mn compound. Therefore, it is not preferable because large age hardening is not exhibited.

The proportion of Zn contained in the magnesium alloy of the present invention is preferably 0.2% by mass or more and 2% by mass or less. If the Zn content is low, the degree of crystal orientation becomes high, so that excellent room temperature workability cannot be obtained. On the other hand, if the amount is excessive, the melting point of the alloy is lowered, and not only is there a possibility of cracking during cooling after the solution treatment, but also the age-hardening ability is remarkably lowered, which is not preferable.

The ratio of Ca contained in the magnesium alloy of the present invention is preferably 0.2% by mass or more and 1% by mass or less. When the Ca content is small, it is difficult to obtain useful precipitates described later. On the other hand, when the Ca content is excessive, precipitates composed of Al and Ca or Mg and Ca are formed, and formability and ductility are reduced. This is not preferable because it causes a decrease in the thickness.

Precipitates in the magnesium alloy of the present invention include precipitates made of Mg, Ca and Al and precipitates made of Al and Mn. Precipitates composed of Mg, Ca, and Al are obtained from Guinier. Preston. It is a nano-sized precipitate called a Zone (GP Zone, GP zone). By forming precipitates made of Mg, Ca and Al during the aging treatment, the strength of the alloy can be improved.
Note that the precipitates are dispersed as long as a large number of fine nano-order precipitates are deposited. The precipitate (GP Zone) made of Mg, Ca, and Al observed in the aging treatment material of the magnesium alloy may be a plate-like precipitate. This nano-sized plate-like precipitate has, for example, a plate-like long side in the range of 3 to 6 nm, and the elemental composition formula is Mg ₂ (Ca, Al). That is, Mg is 67 at% and Ca + Al is 33 at%, but it is not limited to these dimensions and elemental composition formulas.

The precipitate composed of Al and Mn is a rod-like Al—Mn-based precipitate. The Al—Mn-based precipitates can be refined by forming precipitates during the homogenization or solution treatment with Al and Mn. Precipitates made of Al and Mn are observed in the solution treatment material and the aging treatment material of the magnesium alloy. The rod-like Al—Mn-based precipitate has a length of about 50 nm to 300 nm and a diameter of about 2 to 20 nm, but is not limited thereto.

The number density of precipitates (GP Zone) made of Mg, Ca and Al is preferably 10 ²⁰ to 10 ²⁴ / mm ³ . When the number density is excessively low, it is difficult to obtain the effect of improving the strength due to the nanoprecipitate, which is not preferable. On the other hand, the number density of precipitates made of Al and Mn is about 10 ²⁰ to 10 ²¹ / mm ³ . Compared to the number density of the precipitates composed of Al and Mn, which is 10 ²⁰ to 10 ²⁴ / mm ³ , which is the number density of GP Zone, the value is about 10 ³ to 10 ⁴ mm ^-3 . Does not significantly affect strength.

The degree of orientation of crystal grains is such that the degree of integration of the (0002) plane at the center of the thickness of the normalized RD-TD plane of the (0002) pole figure is less than 5.0. Thereby, the orientation degree of a crystal grain can be made low and the outstanding moldability can be obtained.

The magnesium alloy of the present invention preferably has an Erichsen value at room temperature of 6.5 mm or more. Thereby, the workability of the magnesium alloy such as pressing at room temperature can be improved, and the workability in the heated state can be further improved. This Erichsen value (IE value) is determined by the height of the depression until the material breaks by deforming the thin plate by pressing the ball head punch at a constant speed against the thin plate with the outer periphery fixed by the Eriksen test. This is to evaluate the workability of the material.

On the other hand, the magnesium alloy of the present invention should have a 0.2% proof stress of 120 MPa or more and a breaking elongation of 20% or more while improving the workability at room temperature. The 0.2% proof stress is also called yield stress. Furthermore, it is desirable that the Vickers hardness is 45HV or more. The 0.2% yield strength of the aging treatment material of the magnesium alloy of the present invention is preferably 160 MPa or more.

Next, the manufacturing method of a magnesium alloy is demonstrated.
This manufacturing method includes a step 1 for obtaining a cast solid by melting and casting Mg, Al, Mn, Zn and Ca, a step 2 for obtaining a homogenized solid by homogenizing the cast solid, and a homogenized solid. Step 3 for obtaining a tangible solid by hot working or warm processing, Step 4 for obtaining a cooling solid by solution treatment of the tangible solid, and Step 5 for obtaining a magnesium alloy by aging the cooling solid. It is out.

(Process 1: Casting)
In step 1, 0.2-2% by mass of Al, 0.2-1% by mass of Mn, 0.2-2% by mass of Zn, and at least 0.2-1% by mass of Ca. A cast solid is produced by melting and casting an alloy component containing Mg and inevitable impurities. The size of the melting furnace and cast solid used for melting is not particularly limited as long as a cast solid having a desired composition can be produced.

(Process 2: Homogenization treatment)
In step 2, the homogenized solid is produced by subjecting the cast solid to a homogenization treatment at a temperature of 400 ° C. to 500 ° C. for a predetermined time. In the homogenization treatment, the distribution of alloy elements present in the cast solid is homogenized, and precipitates formed during cooling of the molten metal are dissolved in the magnesium matrix.

In the region where Zn is macrosegregated at a high concentration, the alloy may melt when heat treatment is started at a temperature of 340 ° C. or higher. For this reason, first, heat treatment is performed at a temperature of less than 340 ° C., the initial melting of the Mg—Zn phase formed during casting is suppressed and Zn is dispersed, and then heat treatment is performed at 400 ° C. to 500 ° C. for a predetermined time. Then, the distribution of Zn is homogenized to obtain a homogenized solid.

The conditions for the homogenization treatment are not particularly limited and can be set according to the casting solid and the alloy element components. The alloy elements are dissolved in the magnesium matrix by heat treatment at a predetermined temperature and time. I can do it.

(Process 3: Hot or warm processing)
In step 3, the homogenized solid is processed into a plate material by hot rolling to produce a plate-shaped tangible solid. In rolling, the homogenized solid is processed into a plate material by setting rolling conditions such as sample temperature, roll temperature, rolling reduction, roll peripheral speed, number of passes, presence or absence of intermediate heat treatment of the sample, temperature and time of intermediate heat treatment.
The sample temperature and roll temperature may be lowered to such an extent that the sample does not break during rolling. The rolling reduction may be increased to such an extent that the sample does not break during rolling. The intermediate heat treatment of the sample is a heat treatment performed in the middle of rolling, and may be performed at a high temperature that does not cause cracks in the cooling process and does not cause local melting.
Note that the hot or warm working is not particularly limited to rolling, and any stretching method that can produce a fine structure may be used. For example, any method such as forging and extrusion, including twin-roll casting and rolling, may be used. .

(Step 4: Solution treatment)
In step 4, a plate-shaped tangible solid is subjected to a solution treatment, and this is cooled to produce a cooled solid. In the solution treatment, a tangible solid is heat-treated, so that fine precipitates formed during hot or warm processing are dissolved in a matrix and recrystallized to form a structure.

By applying a solution treatment after hot or warm processing, the orientation of crystal grains can be randomly oriented, and excellent formability can be imparted. The solution treatment is performed by holding the solution treatment time from 15 minutes to 24 hours at a solution treatment temperature of 350 to 500 ° C. according to the tangible solid. However, since the longer heat treatment time leads to an increase in manufacturing cost, it is not necessary to perform more time than necessary.

(Secondary processing process)
When manufacturing the magnesium alloy of the shape different from the shape of the cooling solid obtained after the solution treatment after the step 4, secondary processing can be performed on the cooling solid. The secondary processing is not particularly limited, and sheet metal processing such as press processing and drawing processing, machining, and the like can be appropriately performed according to a desired shape. Moreover, when manufacturing a magnesium alloy with the form of the cooling solid obtained by solution treatment, it is possible to perform the next process, without implementing secondary processing.

(Process 5: Aging treatment)
In step 5, the cooling solid is age-hardened by heat treatment to disperse the precipitate deposited on the solution-treated cooling solid, thereby imparting strength to produce the magnesium alloy of the present invention. Here, a significant strengthening of the magnesium alloy can be achieved by using an aging treatment that was not conventionally used in commercial magnesium alloys.
In the aging treatment, an aging treatment is performed at a temperature of 140 to 250 ° C. for a predetermined time. The time for performing the aging treatment is a time for increasing the hardness of the magnesium alloy, preferably a time for maximizing the hardness of the magnesium alloy.

The magnesium alloy of the present invention thus produced has a content of 0.2-2% by mass of Al, 0.2-1% by mass of Mn, 0.2-2% by mass of Zn, and at least 0.1% by mass. 2 to 1% by mass of Ca, with the balance being Mg and inevitable impurities, and a precipitate comprising Mg, Ca and Al dispersed on the (0001) plane of the magnesium matrix, preferably further Al and It is an alloy containing precipitates made of Mn.
According to the above magnesium alloy and its manufacturing method, the orientation of crystal grains can be randomly oriented by performing a solution treatment after rolling, thereby imparting excellent formability. In addition, the crystallinity of crystal grains is randomly oriented, so that the strength is drastically reduced. However, it is possible to achieve both formability, strength, and ductility by forming nano-sized precipitates by aging treatment.

Furthermore, according to these magnesium alloys and the manufacturing method thereof, a highly versatile magnesium alloy capable of achieving both workability and strength in a temperature range including normal temperature can be obtained. For example, the strength and room temperature workability required as applicable mechanical properties can be realized as an automobile material such as a body panel of an automobile.
A conventional commercial magnesium alloy made of a relatively inexpensive alloy element without using expensive and resource-free heavy rare earth metal elements, and with a combination of simple rolling and heat treatment using existing equipment. Excellent moldability and room temperature strength that greatly exceed the plate material can be exhibited. Thereby, for example, it is possible to satisfy the characteristics required for automobile applications.

In addition, the said embodiment can be suitably changed within the scope of the present invention. For example, in the above magnesium alloy production method, a magnesium alloy that has been subjected to a solution treatment after hot or warm processing is subjected to various processes such as drawing and bending to produce a molded body, and then subjected to an aging treatment. The example of strengthening was explained, but it is also possible to produce a magnesium alloy by solution treatment and aging treatment after hot or warm working, and then make various forms such as drawing and bending to produce a molded body It is. In that case, as a manufacturing method of the magnesium alloy, it can be completed in a state where the solution treatment is performed after hot or warm processing and the aging treatment is not performed, and the present invention can be applied as a manufacturing method of the processed material. It is.

Next, examples of the present invention will be described. In addition, all alloy compositions are described in mass%.
[Example 1]
(Process 1: Casting)
An alloy having a composition of Mg-1.2Al-0.3Ca-0.4Mn-0.3Zn as shown in A-1 of Table 1 using a high-frequency induction melting furnace (manufactured by ULVAC, FMI-I-20F) Was melted and cast using a mold to produce a cast solid. The numbers described before Al, Ca, Mn, and Zn, which are elements other than Mg, indicate mass% of each element. The thickness of the cast solid was approximately 10 mm.

(Process 2: Homogenization treatment)
The cast solid is held at 300 ° C. for 4 hours, then heated to 500 ° C. at a heating rate of 10 ° C./h, then held for 6 hours, and then water-cooled to room temperature to produce a homogenized solid. did. In this homogenization treatment, in order to suppress the initial melting of the Mg—Zn phase formed during casting, heat treatment was first performed at 300 ° C., and then heat treatment was performed at 500 ° C. to homogenize the Zn distribution.

(Process 3: Hot or warm processing)
By passing the homogenized solid through a rolling path that can be pressurized with a roll using a rolling device (manufactured by Unotex Co., Ltd., H9132), the rolling process is performed separately in the rough rolling process and the final rolling process, and a tangible solid Was made. In the rough rolling process, as shown in Table 1, using a rolling device with a roll peripheral speed of 2 m / min, the sample temperature and the roll temperature were set to 300 ° C., and the rolling passage was passed four times at a reduction rate of 15%. A homogenized solid having a thickness of 10 mm was rolled to a thickness of 5 mm.

Subsequent to the rough rolling step, the final rolling step was carried out while performing intermediate heat treatment using a rolling device having a roll peripheral speed of 2 m / min as shown in Table 1. In the final rolling step, the sample temperature and the roll temperature were set to 100 ° C., and the rolling passage was passed six times at a rolling reduction of 23%. Each time the rolling passage is passed, the final rolling is performed while performing an intermediate heat treatment in which the sample is reheated at 500 ° C. for 5 minutes and air-cooled, whereby the thickness is rolled to 1 mm to produce a tangible solid.

(Step 4: Solution treatment)
A cooling solid was produced by solution treatment of a plate-shaped tangible solid. The solution treatment temperature was 450 ° C., and the solution treatment time was 1 hour.
When the mechanical strength of the obtained cooling solid was measured, as shown in Table 2, the Erichsen value, which is the formability (index Erichsen value) evaluated by the Erichsen test (Tester: Model 111, manufactured by Eriksen), was 7 mm. The Vickers hardness was 47 VHN, the 0.2% proof stress was 127 MPa, the tensile strength was 223 MPa, and the elongation at break was 30%.

FIG. 1 shows an optical microscope image (Nikon Corporation, Eclipse LV-100) of a solution treatment material that is a cooling solid. The crystal grain size calculated by the intercept method was 12.0 μm. The crystal grain size was calculated in accordance with the American Society for Testing and Materials (ASTM) linear intercept method (E112-13). FIG. 2 shows a (0002) pole figure obtained by X-ray diffraction of the solution-treated material. The density of the (0002) pole (also called maximum random distribution, mrd, or texture strength) was 3.6. Here, the texture strength is a scale indicating the relative strength of the (0002) plane texture (1 when randomly oriented).

(Process 5: Aging treatment)
As shown in Table 3, the cooling solid was subjected to an aging treatment with an aging temperature of 200 ° C. and an aging time of 0.5 h (hours). When the mechanical strength of the obtained cooling solid was measured, as shown in Table 3, the Vickers hardness was 57 VHN, the 0.2% proof stress was 187 MPa, the tensile strength was 248 MPa, and the elongation at break was 28%.

FIG. 3 shows tensile stress-strain curves of the solution-treated material (T4), which is the cooling solid in Step 4, and the aging material (T6) in Step 5. With the aging treatment, the yield strength increased significantly to 187 MPa.

FIG. 4 shows an image obtained by observing the aging treatment material of Example 1 with a transmission electron microscope. (A) is a bright field TEM image, (b) is [011 (bar) 0], [112 (bar) 0. ] A limited field diffraction image obtained from the orientation, (c) is a diagram showing a three-dimensional atom map. As the transmission electron microscope, a scanning transmission electron microscope (Titan, G2 80-200) manufactured by FEI was used.
Due to the linear strain contrast in the bright field TEM image of FIG. P. The presence of Zone was confirmed.
A three-dimensional atom probe (also called 3DAP) applies a high voltage to a sample, detects ions evaporating from the surface of the sample with a mass spectrometer, and then detects each detected ion in depth. This is a method of measuring a three-dimensional atomic distribution by continuously detecting in the vertical direction and arranging ions in the detected order. The inventor of the National Institute for Materials Science (Kazuhiro Takano) made the three-dimensional atom probe, and a mass spectrometer (ADLD detector) manufactured by Kameka Corporation was used for ion analysis.
From the three-dimensional atom map of FIG. P. It was confirmed that the zone was composed of Mg, Ca, and Al. G. P. A typical element composition formula of Zone is Mg ₂ (Ca, Al), and there is a theoretical analysis that Mg is 67 at% and Ca + Al is 33 at%, but it was found that this is in agreement with this theory.

FIG. 5 shows the aging treatment material of Example 1 observed with a transmission electron microscope. (A) is a bright field TEM image, (b) is a HAADF-STEM image (High-angle Annular Dark Field Scanning Transmission Electron Microscopy (High-angle scattering annular dark field scanning transmission electron microscope image), (c) is an enlarged view of the HAADF-STEM image of (b), and (d) is a diagram showing the results of elemental analysis along the arrow of (c). The elemental analysis was performed using an EDS (EDI elemental analyzer (Super X) manufactured by FEI) attached to a scanning transmission electron microscope manufactured by FEI.
As shown in FIGS. 5A to 5C, in the magnesium matrix, G. P. Precipitates other than Zone were observed. As a result of elemental analysis, this precipitate was confirmed to be composed of Al and Mn as shown in FIG. As shown in FIG. 5 (d), Mg: 80 to 90 at%, Al: 5 to 10 at%, Mn: 5 to 10 at%, and Zn and Ca can be read as 0.5 at% to 1.0 at%. However, this is because, in the TEM-EDS elemental analysis, since the size of the precipitate is smaller than the film thickness of the sample, the signal generated from the magnesium matrix around the precipitate is included. That is, the magnesium matrix influences noise as an elemental analysis signal of the precipitate alone.
As is clear from the above, a magnesium alloy capable of achieving both workability and strength in a temperature range near room temperature could be obtained.

[Example 2]
When producing a cooling solid by solution treatment of a tangible solid in step 4, a magnesium alloy is produced in the same manner as in Example 1 except that the solution treatment time is 2 hours as shown in Table 2. did.
Tables 2 and 3 show the production conditions and mechanical characteristics of the obtained solid and the characteristics of the microstructure. As is clear from Tables 2 and 3, as in Example 1, a magnesium alloy capable of ensuring workability in the temperature range near room temperature and achieving both workability and strength was obtained.
With respect to the sample subjected to the solution treatment of Example 2, the number density of the precipitate composed of Al and Mn (see FIG. 5) observed in Example 1 was measured. The number density was 10 ²⁰ to 10 ²¹ mm ^−3. It was about. The number density of precipitates made of Al and Mn was found to be about 10 ³ to 10 ⁴ mm ⁻³ lower than the number density of GP Zone, which is 10 ²⁰ to 10 ²⁴ / mm ³ . As a result, it has been found that precipitates made of Al and Mn do not significantly affect the strength of the magnesium alloy as compared with GP Zone.

[Example 3]
When producing a cooling solid by solution treatment of a tangible solid in Step 4, as shown in Table 2, a magnesium alloy was produced in the same manner as in Example 1 except that the solution treatment time was 4 hours. did.
Tables 2 and 3 show the production conditions and mechanical characteristics of the obtained solid and the characteristics of the microstructure. As is clear from Tables 2 and 3, as in Example 1, a magnesium alloy capable of ensuring workability in the temperature range near room temperature and achieving both workability and strength was obtained.

[Example 4]
In step 1, as shown in A-2 of Table 1, an alloy having a composition of Mg-1.2Al-0.3Ca-0.4Mn-0.3Zn is melted and cast with a mold to produce a cast solid, The roll temperature in the final rolling process was 200 ° C. In step 5, as shown in Table 3, the aging temperature was 450 ° C. and the aging time was 2 hours. Otherwise, a magnesium alloy was produced in the same manner as in Example 1.
Tables 2 and 3 show the production conditions and mechanical characteristics of the obtained solid and the characteristics of the microstructure. As is apparent from Tables 2 and 3, a magnesium alloy capable of achieving both workability and strength was obtained even when the rolling treatment conditions and the aging treatment conditions were changed.

[Example 5]
When a tangible solid is produced by rolling the homogenized solid in step 3, the sample temperature and roll temperature in the final rolling step are set to 200 ° C. as shown in Table 2 and as shown in Table 2. A magnesium alloy was produced in the same manner as in Example 1 except that when the cooling solid was produced by solution treatment of the tangible solid in Step 4, the solution treatment time was changed to 2 hours.
Tables 2 and 3 show the production conditions and mechanical characteristics of the obtained solid and the characteristics of the microstructure. As is apparent from Tables 2 and 3, a magnesium alloy capable of achieving both workability and strength was obtained even when the rolling treatment conditions and the solution treatment conditions were changed.

[Example 6]
In step 1, as shown in B-1 of Table 1, an alloy having a composition of Mg-1.2Al-0.5Ca-0.4Mn-0.3Zn is melted and cast with a mold to produce a cast solid. In step 2, the cast solid was held at 300 ° C for 4 hours, heated to 450 ° C at a heating rate of 7.5 ° C /, then held for 6 hours, and then water-cooled to room temperature for homogenization. A solid was made.
In step 3, the sample reheating temperature in the final rolling step was 450 ° C., and in step 5, the aging temperature was 350 ° C. and the aging time was 4 hours as shown in Table 3. Otherwise, a magnesium alloy was produced in the same manner as in Example 1.
Tables 2 and 3 show the production conditions, mechanical properties, and microstructure characteristics of the obtained solid. As is clear from Tables 2 and 3, a magnesium alloy capable of achieving both workability and strength was obtained even when the composition, homogenization conditions, rolling treatment conditions, and aging treatment conditions were changed.

[Example 7]
In step 1, as shown in B-1 of Table 1, an alloy having a composition of Mg-1.2Al-0.5Ca-0.4Mn-0.3Zn is melted and cast with a mold to produce a cast solid. In No. 2, the cast solid was held at 300 ° C. for 4 hours, heated to 450 ° C. at a heating rate of 7.5 ° C./h, then held for 6 hours, and then water-cooled to room temperature for homogenization. Solidified solids were prepared.
In step 3, the sample reheating temperature in the final rolling step was 450 ° C., and in step 5, the aging time was 0.25 as shown in Table 3. Otherwise, a magnesium alloy was produced in the same manner as in Example 1.

The production conditions and mechanical properties of the obtained solid, and the characteristics of the microstructure are shown in Tables 2 and 3 and FIGS.
FIG. 6 shows an optical microscope image of the solution treatment material that is a cooling solid. The crystal grain size calculated by the intercept method was 9.7 μm. FIG. 7 shows a (0002) pole figure obtained by X-ray diffraction of the solution-treated material. The degree of integration of the (0002) pole was 3.7 and inclined in the rolling direction.
FIG. 8 shows the tensile stress-strain curves of the solution treated material (T4), which is the cooling solid in Step 4, and the aging treated material (T6) in Step 5. Table 3 shows the 0.2% proof stress, tensile strength and elongation (E _f ) obtained from the stress-strain curve.
The yield strength of the solution-treated material was 142 MPa, and it had excellent room temperature formability with an Erichsen value of 7.5 mm. With subsequent aging, the yield strength increased significantly to 201 MPa.
As is clear from the above, a magnesium alloy capable of achieving both workability and strength in a temperature range near room temperature could be obtained.

[Example 8]
In step 1, as shown in B-2 of Table 1, a magnesium alloy was produced in the same manner as in Example 7, except that the sample temperature and roll temperature in the final rolling step were set to 200 ° C.
Tables 2 and 3 show the production conditions and mechanical characteristics of the obtained solid and the characteristics of the microstructure. As is clear from Tables 2 and 3, as in Example 7, a magnesium alloy capable of ensuring workability in the temperature range near room temperature and achieving both workability and strength was obtained.

[Example 9]
In step 1, an alloy having a composition of Mg-1.2Al-0.5Ca-0.4Mn-0.8Zn is melted and cast with a mold as shown in C-1 of Table 1, and a cast solid is produced. In No. 2, the cast solid was held at 300 ° C. for 4 hours, heated to 450 ° C. at a heating rate of 7.5 ° C./h, then held for 6 hours, and then water-cooled to room temperature for homogenization. Solidified solids were prepared.
In step 3, the sample reheating temperature is set to 450 ° C., and as shown in Table 2, when forming a cooling solid by solution treatment of the tangible solid in step 4, the solution treatment temperature is set to 350 ° C. Was set to 4 hours, and in step 5, as shown in Table 3, the aging temperature was 200 ° C. and the aging time was 2 hours.
Otherwise, a magnesium alloy was produced in the same manner as in Example 1.
Tables 2 and 3 show the production conditions and mechanical characteristics of the obtained solid and the characteristics of the microstructure. As is clear from Tables 2 and 3, a magnesium alloy capable of achieving both workability and strength was obtained even when the composition, homogenization conditions, rolling treatment conditions, and aging treatment conditions were changed.

[Example 10]
In step 1, an alloy having a composition of Mg-1.2Al-0.5Ca-0.4Mn-0.8Zn is melted and cast with a mold as shown in C-1 of Table 1, and a cast solid is produced. In Step 2, the cast solid was held at 300 ° C. for 4 hours, heated to 450 ° C. at a heating rate of 7.5 ° C./h (hours), then held for 6 hours, and then water-cooled to room temperature. To produce a homogenized solid. In step 3, the sample reheating temperature in the final rolling step was 450 ° C., and in step 5, the aging time was 1 h (hours) as shown in Table 3. Otherwise, a magnesium alloy was produced in the same manner as in Example 1.

The production conditions and mechanical properties of the obtained solid and the characteristics of the microstructure are shown in Tables 2 and 3 and FIGS.
FIG. 9 shows an optical microscope image of the solution treatment material that is a cooling solid. The crystal grain size calculated by the intercept method was 10.7 μm. FIG. 10 shows a (0002) pole figure obtained by X-ray diffraction of the solution treatment material. The integration degree of the (0002) pole was 3.5.
FIG. 11 shows tensile stress-strain curves of the solution treated material (T4), which is the cooling solid in Step 4, and the aging treated material (T6) in Step 5. Table 3 shows the 0.2% yield strength, tensile strength, elongation, and Erichsen value obtained from the stress-strain curve. The yield strength of the solution-treated material was 144 MPa, and it had excellent room temperature formability with an Erichsen value of 7.7 mm. Subsequent aging treatment significantly increased the yield strength to 204 MPa.
As is clear from the above, a magnesium alloy capable of achieving both workability and strength in a temperature range near room temperature could be obtained.

[Example 11]
In step 1, as shown in C-2 of Table 1, a magnesium alloy was produced in the same manner as in Example 10 except that the sample temperature and the roll temperature in the final rolling step were set to 200 ° C.
Tables 2 and 3 show the production conditions and mechanical characteristics of the obtained solid and the characteristics of the microstructure. As is clear from Tables 2 and 3, as in Example 10, a workability in a temperature range near room temperature can be secured, and a magnesium alloy capable of achieving both workability and strength was obtained.

[Example 12]
In step 1, as shown in D-1 of Table 1, an alloy having a composition of Mg-1.2Al-0.5Ca-0.4Mn-1.6Zn is melted and cast with a mold to produce a cast solid. In Step 2, the cast solid was held at 300 ° C. for 4 hours, heated to 450 ° C. at a heating rate of 7.5 ° C./h (hours), then held for 6 hours, and then water-cooled to room temperature. To produce a homogenized solid. Further, in the third step, the sample reheating temperature in the final rolling step is set to 450 ° C., and when the cooling solid is produced by solution treatment of the tangible solid in step 4, the solution treatment temperature is as shown in Table 2. Was 350 ° C., the solution treatment time was 4 hours, and in Step 5, the aging time was 1 h (hours) as shown in Table 3. Otherwise, a magnesium alloy was produced in the same manner as in Example 1.

Tables 2 and 3 and FIGS. 12 to 14 show the manufacturing conditions, mechanical properties, and microstructure of the obtained solid physical properties. FIG. 12 shows an optical microscope image of the solution treatment material that is a cooling solid. The crystal grain size calculated by the intercept method was 8.5 μm. FIG. 13 shows a (0002) pole figure obtained by X-ray diffraction of the solution-treated material. The integration degree of the (0002) pole was 3.7.
FIG. 14 shows the tensile stress-strain curves of the solution treated material (T4), which is the cooling solid in Step 4, and the aging treated material (T6) in Step 5. Table 3 shows the 0.2% yield strength, tensile strength, elongation, and Erichsen value obtained from the stress-strain curve.
The yield strength of the solution treatment material was 160 MPa, and the Erichsen value had excellent room temperature moldability with a value of 8.3 mm. Yield strength did not increase much even after aging treatment.
As is clear from the above, a magnesium alloy capable of achieving both workability and strength in a temperature range near room temperature could be obtained.

[Example 13]
When the cooling solid is produced by solution treatment of the tangible solid in step 4, the solution treatment temperature is set to 450 ° C. as shown in Table 2, and the aging time is set to 0. 5 as shown in Table 3 in step 5. A magnesium alloy was produced in the same manner as in Example 12 except that the duration was 5 hours (30 minutes).
Tables 2 and 3 show the production conditions and mechanical characteristics of the obtained solid and the characteristics of the microstructure. As is clear from Table 2 and Table 3, as in Example 12, a workability in the temperature range near room temperature can be secured, and a magnesium alloy capable of achieving both workability and strength was obtained.

[Example 14]
In Example 1, the sample temperature and the roll temperature in the final rolling process were set to 200 ° C. as shown in D-2 of Table 1, and the solution treatment time was set to 1 hour as shown in Table 2. In the same manner as in No. 12, a magnesium alloy was produced.
Tables 2 and 3 show the production conditions and mechanical characteristics of the obtained solid and the characteristics of the microstructure. As is clear from Table 2 and Table 3, as in Example 12, a workability in the temperature range near room temperature can be secured, and a magnesium alloy capable of achieving both workability and strength was obtained.

[Example 15]
When the cooling solid is produced by solution treatment of the tangible solid in step 4, the solution treatment temperature is set to 450 ° C. as shown in Table 2, and the aging time is set to 0. 5 as shown in Table 3 in step 5. A magnesium alloy was produced in the same manner as in Example 12 except that the duration was 25 hours (15 minutes).
Tables 2 and 3 show the production conditions and mechanical characteristics of the obtained solid and the characteristics of the microstructure. As is clear from Table 2 and Table 3, as in Example 12, a workability in the temperature range near room temperature can be secured, and a magnesium alloy capable of achieving both workability and strength was obtained.

[Comparative Example 1]
When a cooling solid is prepared by solution treatment of a tangible solid in step 4, the solution treatment temperature is set to 350 ° C. and the solution treatment time is set to 4 h (hours) as shown in Table 2, and the aging is performed in step 5. A magnesium alloy was produced in the same manner as in Example 1 except that the treatment was not performed.

Tables 1 to 3 and FIGS. 15 to 17 show the production conditions, mechanical properties, and microstructure characteristics of the obtained solid. FIG. 15 shows an optical microscope image of the solution treatment material that is a cooling solid. The crystal grain size calculated by the intercept method was 9.9 μm. FIG. 16 shows a (0002) pole figure obtained by X-ray diffraction of the solution-treated material. The integration degree of the (0002) pole was 4.0.
FIG. 17 shows the tensile stress-strain curves of the solution treated material (T4), which is the cooling solid in Step 4, and the aging treated material (T6) in Step 5. Table 3 shows the 0.2% yield strength, tensile strength, elongation, and Erichsen value obtained from the stress-strain curve. The yield strength of the solution treatment material was 149 MPa, and the Erichsen value was 6.4 mm. Therefore, as apparent from Table 2, the workability was insufficient.

[Comparative Example 2]
When preparing a cooling solid by solution treatment of a tangible solid in step 4, as shown in Table 2, the solution treatment temperature is set to 450 ° C. and the solution treatment time is set to 0.17 h (hours). In the same manner as in Comparative Example 1, a magnesium alloy was produced.
Table 2 shows the production conditions, mechanical properties, and microstructure characteristics of the obtained solid. As shown in Table 2, the Erichsen value of the solution-treated material of Comparative Example 2 was 6.2 mm, and the workability was clearly insufficient.

[Comparative Example 3]
When preparing a cooling solid by solution treatment of a tangible solid in Step 4, as shown in Table 2, the solution treatment temperature was set to 500 ° C. and the solution treatment time was set to 1 h (hours). A magnesium alloy was produced in the same manner as in Example 1.
Table 2 shows the production conditions, mechanical properties, and microstructure characteristics of the obtained solid. As shown in Table 2, the Erichsen value of the solution-treated material of Comparative Example 3 was 5.6 mm, and the workability was clearly insufficient.

[Comparative Example 4]
When producing a cooling solid by solution treatment of a tangible solid in Step 4, as shown in Table 2, the solution treatment temperature was set to 500 ° C. and the solution treatment time was set to 24 h (hours). A magnesium alloy was produced in the same manner as in Example 1.
Table 2 shows the production conditions, mechanical properties, and microstructure characteristics of the obtained solid. As apparent from Table 2, the crystal grain size was excessively large and the 0.2% proof stress was insufficient.

[Comparative Example 5]
When a tangible solid is produced by rolling the homogenized solid in step 3, the sample temperature and roll temperature in the final rolling step are set to 200 ° C. as shown in Table 2 and as shown in Table 2. A magnesium alloy was produced in the same manner as in Comparative Example 1 except that the solution treatment temperature was 450 ° C. and the solution treatment time was 4 h (hours) in Step 4.
Table 2 shows the production conditions, mechanical properties, and microstructure characteristics of the obtained solid. As shown in Table 2, the Erichsen value of the solution-treated material of Comparative Example 4 was 4 mm, and the workability was clearly insufficient.

[Comparative Example 6, Comparative Example 7, Comparative Example 8]
When producing a tangible solid by rolling the homogenized solid in step 3, the sample temperature and roll temperature in the final rolling step are set to 300 ° C. as shown in A-3 of Table 1, and as shown in Table 2. In the same manner as in Comparative Example 1, except that the solution treatment temperature in Step 4 is 450 ° C. and the solution treatment time is 1 h (Comparative Example 6), 2 h (Comparative Example 7), and 4 h (Comparative Example 8). A magnesium alloy was produced.
Table 2 shows the production conditions, mechanical properties, and microstructure characteristics of the obtained solid. As is clear from Table 2, in Comparative Example 6, Comparative Example 7, and Comparative Example 8, the Erichsen values were small as 6.3 mm, 5.4 mm, and 5.3 mm, respectively, and the crystal grain size was large. Sex was lacking.

[Comparative Example 9, Comparative Example 10, Comparative Example 11]
When producing a tangible solid by rolling the homogenized solid in step 3, the sample temperature and roll temperature in the final rolling step are set to 300 ° C. and the sample is reheated as shown in A-4 of Table 1. As shown in Table 2, the solution treatment temperature is set to 450 ° C., and the solution treatment time is set to 1 h (Comparative Example 9), 2 h (Comparative Example 10), and 4 h. A magnesium alloy was produced in the same manner as in Comparative Example 1 except that (Comparative Example 11) was used.
Table 2 shows the production conditions, mechanical properties, and microstructure characteristics of the obtained solid. As is clear from Table 2, in Comparative Example 9, Comparative Example 10, and Comparative Example 11, the Erichsen values were small, such as 5.3 mm, 6.2 mm, and 5.9 mm, respectively, and the crystal grain size was large. Sex was lacking.

[Comparative Example 12]
In step 1, as shown in B-2 of Table 1, an alloy having a composition of Mg-1.2Al-0.5Ca-0.4Mn-0.3Zn is melted and cast with a mold to produce a cast solid. In No. 2, the cast solid was held at 300 ° C. for 4 hours, heated to 450 ° C. at a heating rate of 7.5 ° C./h, then held for 6 hours, and then water-cooled to room temperature for homogenization. Solidified solids were prepared. In step 3, the sample temperature and the roll temperature in the final rolling step are set to 200 ° C., and as shown in Table 2, the solution treatment temperature is set to 350 when the tangible solid is solution treated in step 4 to form a cooling solid. A magnesium alloy was produced in the same manner as in Comparative Example 1 except that the solution treatment time was 1 hour at 0 ° C.
Table 2 shows the production conditions, mechanical properties, and microstructure characteristics of the obtained solid. As shown in Table 2, the Erichsen value of the solution-treated material of Comparative Example 12 was 5.8 mm, and the workability was clearly insufficient.

From the above Examples 1 to 15 and Comparative Examples 1 to 12, it was found that Examples 1 to 15 had high room temperature workability, that is, high strength together with a large Erichsen value.

The present invention is not limited to the above embodiment, and various modifications are possible within the scope of the invention described in the claims, and it goes without saying that these are also included in the scope of the present invention. Nor.

Claims (13)

1. 0.2-2 mass% Al or less,
   0.2 to 1% by mass or less of Mn,
   0.2-2 mass% Zn,
   Containing at least 0.2 to 1% by mass of Ca,
   The balance consists of Mg and inevitable impurities,
   A magnesium alloy in which precipitates made of Mg, Ca and Al are dispersed on the (0001) plane of a magnesium matrix.
2. Furthermore, the magnesium alloy of Claim 1 containing the precipitate which consists of Al and Mn.
3. The precipitate made of Mg, Ca and Al is plate-shaped, the long side of the plate is in the range of 3 to 6 nm, and the number density of the precipitate is 10 ²⁰ to 10 ²⁴ / mm ³ . The magnesium alloy according to claim 1.
4. The magnesium alloy according to claim 1, wherein an average crystal grain size of the magnesium matrix is 20 µm or less.
5. 2. The magnesium alloy according to claim 1, wherein the degree of integration of the (0002) plane at the center of the thickness of the normalized RD-TD plane of the (0002) pole figure measured by X-ray diffraction is 5.0 or less.
6. The magnesium alloy according to claim 1, wherein the Erichsen value at room temperature is 6.5 mm or more.
7. The magnesium alloy according to claim 1, wherein the 0.2% proof stress of the solution treatment material is 120 MPa or more.
8. The magnesium alloy according to claim 1, wherein the aging treatment material has a 0.2% proof stress of 160 MPa or more.
9. The magnesium alloy according to claim 1, wherein the elongation at break is 20% or more.
10. Step 1 of dissolving Mg, Al, Mn, Zn and Ca to obtain a cast solid;
    Step 2 of homogenizing the cast solid to obtain a homogenized solid;
    Processing the homogenized solid hot or warm to obtain a tangible solid; and
    Step 4 of solution treatment of the tangible solid to obtain a cooled solid;
    Aging the cooled solid to obtain a magnesium alloy 5;
    Including
    In the step 2, a homogenization treatment is performed for a predetermined time at 400 ° C. or more and 500 ° C. or less to obtain the homogenized solid,
    A method for producing a magnesium alloy, wherein in the step 5, a magnesium alloy is obtained by performing an aging treatment at a temperature of 140 to 250 ° C. for a predetermined time.
11. The method for producing a magnesium alloy according to claim 10, further comprising a secondary processing step of secondary processing the cooling solid between the step 4 and the step 5.
12. The method for producing a magnesium alloy according to claim 10, wherein the cooling solid having a 0.2% proof stress of 120 MPa or more is secondarily processed, and the 0.2% proof stress is made 160 MPa or more in the step 5.
13. The manufacturing method of the magnesium alloy of Claim 10 which performs the time aging process in which the hardness of the said magnesium alloy increases in the said process 5.
    
    

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