EP2351863A1 - Produit travaillé en alliage de magnésium et feuille d'alliage de magnésium - Google Patents

Produit travaillé en alliage de magnésium et feuille d'alliage de magnésium Download PDF

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Publication number
EP2351863A1
EP2351863A1 EP09821745A EP09821745A EP2351863A1 EP 2351863 A1 EP2351863 A1 EP 2351863A1 EP 09821745 A EP09821745 A EP 09821745A EP 09821745 A EP09821745 A EP 09821745A EP 2351863 A1 EP2351863 A1 EP 2351863A1
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Prior art keywords
magnesium alloy
sheet
formed product
dent
specimen
Prior art date
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EP09821745A
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German (de)
English (en)
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EP2351863A4 (fr
Inventor
Yukihiro Oishi
Nozomu Kawabe
Nobuyuki Okuda
Nobuyuki Mori
Masatada Numano
Koji Mori
Takahiko Kitamura
Ryuichi Inoue
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Sumitomo Electric Industries Ltd
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Sumitomo Electric Industries Ltd
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Publication of EP2351863A1 publication Critical patent/EP2351863A1/fr
Publication of EP2351863A4 publication Critical patent/EP2351863A4/fr
Withdrawn legal-status Critical Current

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C23/00—Alloys based on magnesium
    • C22C23/02—Alloys based on magnesium with aluminium as the next major constituent
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/06—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of magnesium or alloys based thereon

Definitions

  • the present invention relates to a magnesium alloy sheet suitable as a material for, for example, housings of mobile electronic devices and relates to a formed product of an magnesium alloy, the formed product being produced by press forming.
  • the present invention relates to a formed product of a magnesium alloy having excellent impact resistance.
  • Resins such as acrylonitrile butadiene styrene (ABS) copolymer resins and polycarbonate (PC) resins, and metals, such as aluminium alloys and stainless steel (SUS), have been used as housing materials for mobile electronic devices, such as cellular phones and notebook personal computers.
  • ABS acrylonitrile butadiene styrene
  • PC polycarbonate
  • SUS stainless steel
  • Magnesium alloys which are lightweight and excellent in specific strength and specific rigidity, have recently been studied as housing materials described above. Housings of magnesium alloys are mainly formed of cast materials produced by die casting and thixomolding. Press formed sheets of wrought magnesium alloys typified by the AZ31 alloy according to American Society for Testing and Materials (ASTM) standards are being used. In Patent Literature 1, the press forming of an AZ91 alloy according to ASTM standards is studied.
  • Metals generally have higher impact resistance than resins and are less likely to be broken. It is easy to reduce the thickness of metals. Aluminium alloys, however, have poor plastic deformation resistance and deform quite readily by an impact, such as falling. Stainless steel is not easily broken or deformed but is heavy.
  • Magnesium alloys has excellent plastic deformation resistance compared with aluminium alloys, and are very light compared with stainless steel.
  • cast materials of magnesium alloys have a strength inferior to those of press-formed bodies of magnesium alloys.
  • Press-formed bodies of the AZ31 alloy also have an insufficient strength.
  • the inventors have produced material sheets of a magnesium alloys each having an Al content of 7% by mass or more by various production methods. Press-formed bodies of the resulting sheets were produced and examined for the impact resistance (dent resistance). It was found that a press-formed body with good dent resistance has small particles composed of an intermetallic compound (precipitations), such as Mg 17 Al 12 , and a small number of coarse particles. So, a production method for controlling the maximum particle size and the number of the particles having the maximum particle size, i.e., a production method for reducing coarse precipitations, was studied. The total time that a sheet is held in a specific temperature range mainly in a rolling step is reduced compared with that in the related art. This resulted in a magnesium alloy sheet having a small number of coarse precipitations. Furthermore, a press-formed body produced by press-forming the magnesium alloy sheet has excellent impact resistance.
  • a formed product of a magnesium alloy is produced by press-forming a sheet composed of a magnesium alloy having an Al content of 7% by mass to 12% by mass.
  • the formed product has a flat portion that is not subjected to drawing deformation.
  • the number of coarse particles of an intermetallic compound present in each of the fields of observation is five or less.
  • a magnesium alloy sheet is used for press forming and is composed of a magnesium alloy having an Al content of 7% by mass to 12% by mass, in which the number of coarse particles of an intermetallic compound present in each of fields of observation specified below is five or less.
  • any two 100 ⁇ m ⁇ 100 ⁇ m areas in the surface area region are set to the fields of observation.
  • the term "coarse particles” indicates particles composed of an intermetallic compound containing Al and Mg and each having a particle size of 5 ⁇ m or more.
  • the term "particle size” indicates the diameter of a circle having an area equivalent to the area of the cross section of the particle. Note that the intermetallic compound present in the cross section may be identified by measuring the composition and the structure of the particles using an energy dispersive x-ray spectrometer (EDS), X-ray diffraction, and so forth.
  • EDS energy dispersive x-ray spectrometer
  • the alloy sheet having the specific texture according to the present invention may be produced by, for example, a production method including steps described below.
  • a preparation step A cast sheet composed of a magnesium alloy having an Al content of 7% to 12% by mass and produced by a continuous casting process is prepared.
  • a solution heat treatment step The cast sheet is subjected to solution heat treatment at 350°C or higher.
  • a rolling step The resulting sheet material that has been subjected to the solution heat treatment is subjected to rolling.
  • the cooling rate is 0.1 °C/sec or more in a temperature range of 350°C to 250°C.
  • the total time that the sheet material, which is a workpiece, is held in a temperature range of 250°C to 350°C is within 60 minutes.
  • the minimization of the length of the time that the sheet is held at a specific temperature range (250°C to 350°C) in which precipitations are precipitated and liable to grow to form coarse particles reduces the number of coarse particles, thereby yielding a texture in which fine precipitations d 0 are dispersed as illustrated in part (1) of Fig. 1 .
  • the total time that a workpiece is held in the temperature range of 250°C to 350°C immediately before and during a rolling step has not been well studied.
  • the inventors have studied on the total time and have found as follows: For a magnesium alloy having an Al content of 7% to 12% by mass, in the case where the total holding time in the foregoing temperature range exceeds 1 hour in at least the rolling step, a texture containing coarse precipitations d 1 each having a particle size of 5 ⁇ m or more is formed, as illustrated in part (2) of Fig. 1 . In contrast, in the case where the total holding time in the foregoing temperature range is within 1 hour in the rolling step, it is possible to reduce the coarse precipitations.
  • the sum of the total holding time in the foregoing temperature range in the rolling step and the holding time in the foregoing temperature range in the cooling process in the solution heat treatment step is preferably within 1 hour.
  • the alloy sheet of the present invention has a small number of coarse precipitations in the surface area region and has a texture in which very fine precipitations are dispersed (part (1) of Fig. 1 ). Since the alloy sheet of the present invention has a small number of coarse precipitations, it is believed that a reduction in the amount of Al that forms a solid solution in a matrix (Mg) due to the presence of a large number of coarse precipitations is small and that a reduction in solid-solution strengthening due to the reduction in the Al content is small.
  • the alloy sheet of the present invention is less likely to be dented even when impacted and has excellent impact resistance because of improvement in the rigidity of the sheet itself as a result of dispersion strengthening owing to the dispersion of precipitations and because of maintaining the strength owing to the prevention of the reduction in the amount of Al that forms a solid solution. Furthermore, the alloy sheet of the present invention having a small number of coarse precipitations also has excellent plastic formability and can be easily subjected to press forming.
  • the alloy sheet of the present invention obtained by the control of the holding time in the specific temperature range mainly in the rolling step as described above is subjected to press forming to produce a formed product of the present invention.
  • the texture constituting the alloy sheet of the present invention and having a small number of coarse precipitations is generally maintained in a portion (flat portion) of the formed product of the present invention where the degree of deformation due to press forming is low.
  • the formed product of the present invention also has a texture which has a small number of coarse precipitations in a surface area region and in which very fine precipitations are dispersed.
  • the formed product of the present invention has excellent impact resistance and is less likely to be dented because of dispersion strengthening owing to the dispersion of fine precipitations and because of solid-solution strengthening owing to Al that sufficiently forms a solid solution, as described above.
  • Magnesium alloys include ones having various compositions and each containing Mg and an additive element (remainder: Mg and impurities).
  • the sheet and the formed product of the present invention are composed of a Mg-Al-based alloy containing at least 7% by mass to 12% by mass Al serving as an additive element.
  • the additive element other than Al is at least one element selected from Zn, Mn, Si, Ca, Sr, Y, Cu, Ag, and rare-earth elements (except Y). In the case where the element is contained, the proportion thereof is in the range of 0.01 % by mass to 10% by mass and preferably 0.1% by mass to 5% by mass.
  • Mg-Al-based alloys More specific examples of the Mg-Al-based alloy include AZ-based alloys (Mg-Al-Zn-based alloys, Zn: 0.2% to 1.5% by mass), AM-based alloys (Mg-Al-Mn-based alloys, Mn: 0.15% to 0.5% by mass), and Mg-Al-RE (rare-earth element)-based alloys according to ASTM standards.
  • Mg-Al-based alloys containing 8.3% to 9.5% by mass Al and 0.5% to 1.5% by mass Zn, typically, an AZ91 alloy have excellent mechanical properties, such as corrosion resistance, strength, and plastic deformation resistance, compared with other Mg-Al-based alloys, such as the AZ31 alloy.
  • the alloy sheet of the present invention is subjected to press forming, such as bending and drawing, and is used as a material for a thin, lightweight component, such as a housing.
  • a housing produced by press forming in order to achieve a small thickness of a portion of the housing where the thickness is not changed substantially by deformation during plastic forming (a flat portion of the formed product of the present invention), the alloy sheet of the present invention preferably has a thickness of 2.0 mm or less, particularly preferably 1.5 mm or less, more preferably 1 mm or less.
  • the magnesium alloy sheet having a larger thickness has higher strength, and the magnesium alloy sheet having a smaller thickness is more suitable for a thin, lightweight housing.
  • the thickness may be selected, depending on an intended use.
  • the alloy sheet of the present invention is less likely to be dented when subjected to an impact, such as falling. Specifically, in the case where a dent test of a 30 mm x 30 mm specimen with a thickness of t b cut from the alloy sheet of the present invention is performed as described below, the depth x b of the dent of the specimen meets the expression x b ⁇ 0.47 ⁇ t b -1.25 . Furthermore, in the formed product of the present invention, a flat portion that is not subj ected to drawing deformation has a small number of coarse precipitations as described above. The properties of the alloy sheet of the present invention are substantially maintained as described above.
  • the dent test described below is performed.
  • the depth x p of the dent of the specimen meets the expression x p ⁇ 0.47 ⁇ t p -1.25 .
  • a specimen is arranged on a support having an opening with a diameter of 20 mm so as to close the hole.
  • a cylindrical bar having a weight of 100 g and a tip radius r of 5 mm is allowed to free fall from a position 200 mm above the specimen.
  • the depth x b of the dent or the depth x p of the dent are each defined as a distance between a straight line that connects both sides of the specimen and the most dented point after the dent test.
  • the formed product of the present invention typically has a shape including a top plate (bottom face) and side walls each extending upright from the outer edge of the top plate. More specific examples thereof include a bracket shape consisting of a rectangular plate-like top plate and a pair of opposite side walls; a box shape including two pairs of opposite side walls and having a bracket-shaped cross section; and a closed-end cylinder including a disk-like top plate and a cylindrical side wall.
  • each of the top plate and the side walls is typically a flat plane.
  • the shape and size thereof are not limited.
  • Each of the top plate and the side walls may include a boss and so forth integrally formed or joined, a through hole and a recess formed in the thickness direction, a groove formed in the thickness direction, a bump, and a portion having a locally varying thickness formed by plastic forming, surface cutting, or the like.
  • the flat portion that is not subjected to drawing is defined as follows: When a piece cut from a region excluding a portion that includes the boss and so forth is placed on a horizontal plane, a portion of the piece where the degree of warpage is low is referred to as the flat portion.
  • a portion where a distance between the horizontal plane and a point of the surface most remote from the horizontal plane is within 1 mm in the vertical direction is defined as the flat portion.
  • a dent is commonly likely to be made in a flat portion. So, for the alloy sheet of the present invention and the formed product of the present invention, dent resistance is evaluated in the flat portion described above.
  • the formed product of the present invention may include a covering layer for corrosion prevention, protection, an ornament, or the like on a surface of the magnesium alloy sheet.
  • the magnesium alloy mainly contained in the formed product of the present invention has an Al content of 7% by mass or more and thus has excellent corrosion resistance compared with alloys having a low Al content, for example, the AZ31 alloy.
  • the magnesium alloy sheet is subjected to anticorrosion treatment, e.g., chemical-conversion treatment or anodic-oxidation treatment, to form a corrosion prevention layer, thereby further enhancing the corrosion resistance of the formed product of the present invention.
  • anticorrosion treatment e.g., chemical-conversion treatment or anodic-oxidation treatment
  • the number of the coarse particles is five or less. Furthermore, in the case where the dent test is performed, x p ⁇ 0.47 ⁇ t p -1.25 is met.
  • a cast sheet produced by a continuous casting process such as a twin-roll casting process, in particular, a casting process described in WO/2006/003899 is preferably used.
  • a continuous casting process rapid solidification can be performed, thereby reducing oxide and segregation and providing a cast sheet having excellent rollability.
  • the size of the cast sheet is not particularly limited. An excessively thick cast sheet is liable to cause segregation. So, the thickness is preferably 10 mm or less and particularly preferably 5 mm or less.
  • the cast sheet is subjected to solution heat treatment to homogenize the composition.
  • the holding temperature is set to 350°C or higher.
  • the holding temperature is in the range of 380°C to 420°C for a holding time of 60 to 2400 minutes.
  • the holding time is preferably increased.
  • the holding time in the temperature range of 350°C to 250°C is controlled. Specifically, to reduce the holding time in the foregoing temperature range as illustrated in part (1) of Fig.
  • the cooling rate in this temperature range is set to 0.1 °C/sec or more (holding time: about 16.6 minutes or less) and preferably 0.5 °C/sec or more (holding time: 3.3 minutes or less).
  • a cooling rate can be achieved by forced cooling, e.g., water cooling or an air blast.
  • a sheet material heated to 200°C or higher and, in particular, 250°C or higher is preferably subjected to rolling, as described above.
  • a higher heating temperature enhances the plastic formability of the sheet material.
  • a heating temperature exceeding 350°C causes problems of the occurrence of seizure and the coarsening of crystal grains to reduce the mechanical properties of the sheet material after rolling.
  • the heating temperature is preferably 350°C or lower and more preferably 270°C to 330°C. Rolling is performed multiple times (multipass), thereby achieving an intended thickness, reducing the average crystal grain size of the magnesium alloy, and enhancing the press formability.
  • Rolling may be performed under known conditions. For example, rollers may be heated in addition to the sheet material. Controlled rolling disclosed in Patent Literature 1 may be combined. Furthermore, in the final pass and passes near the final pass, in order to increase dimensional accuracy and so forth, the heating temperature of the sheet material may be set to a low temperature (for example, room temperature).
  • a low temperature for example, room temperature
  • the holding time in the temperature range of 250°C to 350°C is controlled. Specifically, as illustrated in part (1) of Fig. 2 , in order to reduce the holding time in the foregoing temperature range in each pass in the rolling step, for example, the heating time to heat a workpiece is reduced, the rolling speed (circumferential speed of the roll) is increased, or the cooling rate is increased.
  • the rolling conditions are controlled in such a manner that the total holding time in the temperature range of 250°C to 350°C in the rolling step is within 60 minutes or less.
  • a higher Al content facilitates the deposition of precipitations. So, the total holding time is preferably adjusted, depending on the Al content. Furthermore, the total holding time is preferably minimized.
  • the total holding time is preferably 45 minutes or less and particularly preferably 30 minutes.
  • Intermediate heat treatment is performed between the passes of the rolling to eliminate or reduce strain, residual stress, texture, and so forth, which are introduced into the sheet material, which is a workpiece, by processing before the intermediate heat treatment, thereby preventing inadvertent cracking, strain, and deformation in the subsequent rolling and achieving smoother rolling.
  • the intermediate heat treatment is preferably performed at a holding temperature of 250°C to 350°C. This temperature range is liable to cause the growth of precipitations to form coarse particles as described above.
  • the total holding time includes the treatment time of the intermediate heat treatment and is controlled.
  • the resulting rolled sheet may be subjected to final heat treatment at, for example, 300°C or higher, thereby eliminating processing strain and performing complete recrystallization.
  • precipitations are liable to grow in the temperature range of 250°C to 350°C.
  • the total holding time includes the treatment time of the final heat treatment and is controlled. The time of the final heat treatment is controlled as described above, so that the magnesium alloy sheet of the present invention has a small number of coarse precipitations.
  • the final heat treatment is not performed after rolling, and warm flattening treatment may be performed in which strain is imparted to the resulting rolled sheet using a roller leveler or the like with the rolled sheet heated to 100°C to 250°C.
  • warm flattening treatment may be performed in which strain is imparted to the resulting rolled sheet using a roller leveler or the like with the rolled sheet heated to 100°C to 250°C.
  • the sheet is recrystallized during the press forming, thereby resulting in a formed product having a fine crystal texture. Fine crystal grains are likely to be formed, and a texture in which fine precipitations are more evenly dispersed is likely to be formed, as compared with the case where the final heat treatment is performed.
  • the magnesium alloy sheet of the present invention has higher impact resistance because of a small number of coarse precipitations and the foregoing fine texture.
  • the heating temperature of the rolled sheet is set to at most 250°C, so that precipitations may be less likely to coarsen.
  • the formed product of the present invention may be produced by press-forming a rolled sheet obtained by the foregoing rolling step or press-forming a treated sheet obtained by subjecting the rolled sheet to the final heat treatment or the warm flattening treatment described above.
  • the press forming is preferably performed in the temperature range of 200°C to 300°C in order to increase the plastic formability of the rolled sheet or the treated sheet, which is a workpiece. It is believed that even if the press forming is performed at a temperature in the temperature range of 250°C to 350°C, the problems, such as the coarsening of precipitations as described above are less likely to occur because the holding time in the temperature range of 250°C to 350°C in the press forming is very short.
  • heat treatment may be performed to eliminate strain and residual stress introduced by press forming and to improve the mechanical properties.
  • the heating temperature is in the range of 100°C to 400°C
  • the heating time is in the range of about 5 minutes to about 60 minutes.
  • the holding time in the temperature range of 250°C to 350°C is not long.
  • a formed product obtained by pressing may not be treated.
  • treatment to form the covering layer for corrosion prevention, protection, an ornament, or the like is performed, the corrosion resistance, the commodity value, and so forth are further enhanced.
  • a formed product of an magnesium alloy of the present invention and a magnesium alloy sheet of the present invention have excellent impact resistance.
  • a plurality of sheets composed of a magnesium alloy and press-formed bodies obtained by press-forming these magnesium alloy sheets were produced and examined for metal textures and impact resistance.
  • a plurality of cast sheets composed of a magnesium alloy having a composition equivalent to that of the AZ91 alloy (Mg-9.0% Al-1.0% Zn (all units are percent by mass)) were prepared by a twin-roll casting process.
  • Each of the resulting cast sheets were subjected to solution heat treatment at 400°C for 24 hours. Cooling in the solution heat treatment was performed by an air blast in such a manner that the cooling rate in the temperature range of 350°C to 250°C was 0.1 °C/sec or more.
  • the sheet material that had been subjected to the solution heat treatment was rolled multiple times under rolling conditions described below so as to have a thickness of 0.6 mm.
  • the resulting rolled sheets were subjected to final heat treatment at 300°C for 10 minutes, thereby resulting in magnesium alloy sheets.
  • the heating temperature of the sheets and the rolling speed were adjusted to change the total holding time that the sheet materials, which were workpieces subjected to rolling, were held in the temperature range of 250°C to 350°C, thereby preparing four types of samples in which the total holding times were 20 minutes (sample a), 35 minutes (sample b), 50 minutes (sample c), and 80 minutes (sample d).
  • the magnesium alloy sheets that had been subjected to the final heat treatment were subjected to square cup deep-drawing processing at a heating temperature of 250°C, thereby providing press-formed bodies.
  • Each of the press-formed bodies had a box shape including a rectangular top plate having dimensions of 48 mm x 98 mm and side walls each extending upright from the top plate.
  • AZ31 alloy material thickness: 0.6 mm
  • aluminium alloy material thickness: 0.6 mm
  • the AZ31 alloy material was subjected to square cup deep-drawing processing under conditions the same as those of the rolled sheets composed of the AZ91 alloy described above.
  • the A5052 material was subjected to square cup deep-drawing processing at room temperature.
  • the metal texture of each of the resulting magnesium alloy sheets and the press-formed bodies was observed as described below, and precipitations were studied. Furthermore, a dent test of each of the resulting magnesium alloy sheets and the resulting press-formed bodies was performed, and impact resistance was evaluated.
  • Each of the resulting magnesium alloy sheets composed of the AZ91 alloy was cut in the thickness direction.
  • the resulting cross section was observed with an optical microscope (1000 ⁇ ).
  • any two 100 ⁇ m ⁇ 100 ⁇ m areas in the surface area region were selected from a surface area region extending from a surface of the sheet to a position one-third of the thickness from the surface. These areas were defined as the fields of observation.
  • the particle size of particles composed of an observed intermetallic compound containing Al and Mg was measured. The number of particles having a particle size of 5 ⁇ m or more was counted.
  • the resulting magnesium alloy sheets composed of the AZ91 alloy and the prepared AZ31 alloy material and A5052 material (aluminium alloy material) were cut into 30 mm x 30 mm specimens.
  • a support 20 having a horizontal surface with a round hole 21 having a diameter d of 20 mm was prepared.
  • the depth of the round hole 21 was set in such a manner that a cylindrical bar 10 described below was able to be sufficiently inserted therein.
  • a specimen 1 was placed so as to close the round hole 21.
  • the cylindrical ceramic bar 10 having a weight of 100 g and a tip radius r of 5 mm was arranged at a position 200 mm above the specimen 1 in such a manner that the central axis of the bar was arranged coaxially with the central axis of the round hole 21.
  • the cylindrical bar 10 was allowed to free fall from the position toward the specimen 1, the depth of the dent of the specimen 1 was measured. With respect to the depth (mm) of the dent, a distance between a straight line that connected both opposite sides of the specimen 1 and the most dented point was measured with a point micrometer.
  • the thickness was measured at any four points in the 30 mm x 30 mm specimen cut from the top plate. The results demonstrated that the thickness at any point was equal to the thickness of the magnesium alloy sheet described above (thickness of the specimen: 0.6 mm).
  • the sheets and the press-formed bodies composed of the magnesium alloy having an Al content of 7% by mass or more has excellent impact resistance compared with the sheet and the press-formed body composed of the AZ31 alloy having a low Al content and the sheet and the press-formed body composed of the aluminum alloy.
  • Magnesium alloy sheets having different thicknesses and press-formed bodies obtained by press-forming these magnesium alloy sheets were produced and examined for metal textures and impact resistance.
  • a plurality of cast sheets (each having a composition equivalent to that of the AZ91 alloy and a thickness of 4 mm) similar to those in Test Example 1 were prepared. Under the same conditions as those in Test Example 1, the solution heat treatment (400°C for 24 hours, the cooling rate from 350°C to 250°C: 0.1 °C/sec or more) and multipass rolling (rolling reduction: 5 % per pass to 40% per pass, heating temperature of the sheets: 200°C to 400°C, and roll temperature: 100°C to 250°C) were performed to provide rolled sheets. As with Test Example 1, also in this test, the total holding time that the sheet materials were held in the temperature range of 250°C to 350°C in the rolling step, was changed.
  • the rolled sheets having different thicknesses were produced by adjusting the rolling reduction.
  • the total time was set to 35 minutes or 80 minutes by adjusting the heating time of the sheets and the rolling speed.
  • samples in which the total holding times, including the time of the final heat treatment after the rolling, in the foregoing temperature range were 45 minutes (sample ⁇ ) and 90 minutes (sample ⁇ ) were prepared.
  • the resulting rolled sheets were subjected to the final heat treatment at 300°C for 10 minutes and then were subjected to square cup deep-drawing processing at a heating temperature of 250°C, thereby providing box-shaped press-formed bodies similar to those in Test Example 1.
  • sample ⁇ in which the total holding time in the temperature range of 250°C to 350°C is within 60 minutes in the rolling step does not have a coarse intermetallic compound having a particle size of 5 ⁇ m or more in the surface area region (the number of the coarse intermetallic compound is zero), regardless of the thickness, and has a smaller depth of the dent than that of sample ⁇ having the same thickness.
  • k is preferably 0.5 and the neighborhood thereof.
  • x 0.47 ⁇ t -1.25 .
  • x ⁇ 0.47 ⁇ t p -1.25 is used as an index of the formed product of the present invention.
  • a magnesium alloy sheet was similarly examined.
  • x ⁇ 0.47 ⁇ t b -1.25 (where t b : thickness) was also applicable.
  • x ⁇ 0.47 ⁇ t b -1.25 is used as an index of the magnesium alloy sheet of the present invention.
  • Magnesium alloy sheets produced by performing another treatment after the rolling were prepared.
  • the magnesium alloy sheets were subjected to press forming to produce press-formed bodies. They were examined for metal textures and impact resistance.
  • the resulting rolled sheets were subjected to warm flattening treatment.
  • the warm flattening treatment is performed with a roller leveler including a furnace capable of heating a rolled sheet and a roller section that includes a plurality of rollers configured to continuously impart a bend (strain) to a heated rolled sheet.
  • the roller section includes the plural rollers which face each other and which are located above and below in a staggered configuration.
  • each of the rolled sheets is transferred to the roller section while being heated in the furnace.
  • these rollers impart a series of bends to the sheet.
  • the warm flattening was performed in the temperature range of 220°C to 250°C.
  • the transfer speed and so forth during the flattening was adjusted in such a manner that the total time that the rolled sheet was held in the temperature range of 250°C to 350°C was within 60 minutes.
  • the magnesium alloy sheets that had been subjected to the warm flattening treatment were subjected to square cup deep-drawing processing at a heating temperature of 250°C, thereby providing box-shaped press-formed bodies similar to those in Test Example 1.
  • Table III shows that any sample has a small depth of the dent and excellent impact resistance.
  • sample 3-1 in which the magnesium alloy sheet that had been subjected to the warm flattening treatment after the rolling was used, has a small depth of the dent and excellent impact resistance, compared with sample 2-1 (0.6 mmt- ⁇ in Test Example 2), in which the final heat treatment was performed after the rolling.
  • the foregoing embodiments may be appropriately changed without departing from the scope of the present invention.
  • the present invention is not restricted to the foregoing configurations.
  • the composition of the magnesium alloy, the thickness of the magnesium alloy sheet, the shape of the press-formed body, and so forth may be appropriately changed.
  • a formed product of a magnesium alloy of the present invention can be suitably used for components of various electronic devices, in particular, housings for mobile electronic devices.
  • a magnesium alloy sheet of the present invention can be suitably used as a material for the formed product of the magnesium alloy of the present invention.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Shaping Metal By Deep-Drawing, Or The Like (AREA)
  • Other Surface Treatments For Metallic Materials (AREA)
  • Laminated Bodies (AREA)
  • Powder Metallurgy (AREA)
  • Continuous Casting (AREA)
EP09821745.8A 2008-10-22 2009-09-29 Produit travaillé en alliage de magnésium et feuille d'alliage de magnésium Withdrawn EP2351863A4 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2008272241 2008-10-22
PCT/JP2009/005004 WO2010047045A1 (fr) 2008-10-22 2009-09-29 Produit travaillé en alliage de magnésium et feuille d'alliage de magnésium

Publications (2)

Publication Number Publication Date
EP2351863A1 true EP2351863A1 (fr) 2011-08-03
EP2351863A4 EP2351863A4 (fr) 2015-08-26

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AU2009305830A1 (en) 2010-04-29
RU2011120482A (ru) 2012-11-27
CN102197152A (zh) 2011-09-21
BRPI0919653A2 (pt) 2015-12-08
JP2015034350A (ja) 2015-02-19
CA2741210A1 (fr) 2010-04-29
WO2010047045A1 (fr) 2010-04-29
JPWO2010047045A1 (ja) 2012-03-15
EP2351863A4 (fr) 2015-08-26
CN102197152B (zh) 2013-11-13
US20110203706A1 (en) 2011-08-25
JP6065346B2 (ja) 2017-01-25
KR20110070884A (ko) 2011-06-24

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