EP2447381A1 - Platte aus magnesiumlegierung - Google Patents

Platte aus magnesiumlegierung Download PDF

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Publication number
EP2447381A1
EP2447381A1 EP10791969A EP10791969A EP2447381A1 EP 2447381 A1 EP2447381 A1 EP 2447381A1 EP 10791969 A EP10791969 A EP 10791969A EP 10791969 A EP10791969 A EP 10791969A EP 2447381 A1 EP2447381 A1 EP 2447381A1
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EP
European Patent Office
Prior art keywords
magnesium alloy
sheet
alloy sheet
crystallized phases
casting
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EP10791969A
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English (en)
French (fr)
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EP2447381A4 (de
Inventor
Yukihiro Oishi
Takahiko Kitamura
Nozomu Kawabe
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Sumitomo Electric Industries Ltd
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Sumitomo Electric Industries Ltd
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Publication of EP2447381A1 publication Critical patent/EP2447381A1/de
Publication of EP2447381A4 publication Critical patent/EP2447381A4/de
Withdrawn legal-status Critical Current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
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
    • B21B1/46—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling metal immediately subsequent to continuous casting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B3/00—Rolling materials of special alloys so far as the composition of the alloy requires or permits special rolling methods or sequences ; Rolling of aluminium, copper, zinc or other non-ferrous metals
    • 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
    • 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 housings and various parts, a magnesium alloy structural member using the alloy sheet, and a method for producing a magnesium alloy sheet.
  • a magnesium alloy sheet and a magnesium alloy structural member having high impact resistance at low temperature are examples of magnesium alloy sheet suitable as a material for housings and various parts.
  • Magnesium alloys containing magnesium and various additive elements are increasingly employed as materials for housings of mobile electronic devices such as cellular phones and laptop computers, and automobile parts.
  • magnesium alloy structural members such as the housings described above are mainly formed of cast materials by a die casting method or a thixomolding method. Recently, studies have been made to form the housing by press-forming a sheet composed of an AZ31 alloy according to American Society for Testing and Materials (ASTM) standard.
  • Patent literature 1 proposes a rolled sheet composed of an alloy equivalent to AZ91 alloy of the ASTM standard, the rolled sheet having good press formability.
  • magnesium alloys are light-weight and exhibit good specific strength and specific rigidity, they are desirably used in not only an ordinary temperature environment at about 0°C to 30°C but also below-zero cold districts and refrigeration rooms. However, the mechanical properties of magnesium alloys in such low-temperature environments have not been fully investigated.
  • Cast materials of magnesium alloys are inferior to rolled materials of magnesium alloys and press-formed structural members in terms of strength.
  • the inventors of the present invention have also found that the structural members formed by press-forming an AZ31 alloy also has insufficient strength and low impact resistance in a low-temperature environment.
  • rolled sheets composed of AZ91 alloys described in patent literature 1 and structural members formed by press-forming these rolled sheets have a higher strength than the sheet composed of AZ31 alloys and pressed structural members composed of AZ31 alloys.
  • the inventors have conducted studies and found that the rolled sheets composed of AZ91 alloys and structural members formed by plastic-forming, such as press-forming, the rolled sheets sometimes lack sufficient impact resistance in a low-temperature environment.
  • the inventors have produced magnesium alloy sheets under various conditions, subjected the resulting sheets to plastic-forming such as press-forming to prepare magnesium alloy structural members, and investigated the impact resistance (dent resistance) and mechanical properties of these magnesium alloy sheets and structural members in a low-temperature environment. As a result, they have found that a magnesium alloy sheet that has high dent resistance contains few crystallized phases having a particular composition that are small in size.
  • a magnesium alloy structural member obtained from the magnesium alloy sheet that contains few crystallized phases having a particular composition that are small in size also has high dent resistance, and as with the sheet of the material, the structural member also contains few crystallized phases having a particular composition that are small in size.
  • the magnesium alloy sheet of the present invention is composed of a magnesium alloy containing Al and Mn.
  • a region from a surface of the alloy sheet to 30% of the thickness of the alloy sheet in a thickness direction of the magnesium alloy sheet is defined as a surface region and when a 50 ⁇ m 2 sub-region is arbitrarily selected from this surface region, the number of grains that are crystallized phases containing both Al and Mn and having a maximum diameter of 0.1 to 1 ⁇ m is 15 or less.
  • the mass ratio Al/Mn of Al to Mn is 2 to 5.
  • the magnesium alloy sheet of the present invention having a particular structure can be produced by, for example, a production method of the invention below.
  • the method for producing a magnesium alloy sheet according to the present invention includes a casting step and a rolling step below:
  • a magnesium alloy structural member of the present invention is produced by subjecting the magnesium alloy sheet of the present invention to plastic forming such as press forming.
  • This structural member also has the same structure as the magnesium alloy sheet of the present invention, i.e., when a 50 ⁇ m 2 sub-region is arbitrarily selected from the surface region, the number of grains that are crystallized phases of a particular size and a particular composition is 15 or less.
  • the amounts of oxides and segregates can be reduced, generation of coarse crystallized phases can be suppressed, and fine crystallized phases can be formed.
  • the cooling rate is sufficiently increased by adjusting the roll temperature and the thickness of the cast sheet in the above-described particular ranges, and thus the generation of the crystallized phases itself can be suppressed. Accordingly, the structure of a surface-side region of a sheet susceptible to impact can be turned into a structure containing few fine crystallized phases.
  • the size and the amount of the crystallized phases are small, the decrease in the amount of dissolved Al in the matrix caused by coarse crystallized phases or large amounts of crystallized phases is suppressed, and the degradation of solution hardening associated with the decrease in Al content is suppressed.
  • rapid solidification gives a cast sheet having a fine structure with a small average crystal grain diameter.
  • Such a cast sheet contains few coarse crystallized phases that serve as starting points of breaking and deformation and thus has high plastic formability such as rolling. When the cast sheet is rolled, strength and elongation can be improved.
  • the invention alloy sheet obtained by the production method described above has a reduced amount of coarse crystallized phases and few crystallized phases.
  • the structure contains a reduced amount of coarse crystallized phases in a surface-side region susceptible to impact and has a structure in which a minute amount of and more preferably substantially no fine crystallized phases are present, and thus breaking and cracking do not readily occur even when an impact is applied by, for example, dropping. Since the amount of the crystallized phases is small, the decrease in dissolved Al content can be suppressed, a high strength can be maintained due to presence of a sufficient amount of dissolved Al, and the strength can be further enhanced by rolling.
  • the invention alloy sheet is resistance to denting even when an impact is applied and exhibits high impact resistance not only at room temperature (about 20°C) but also in a low-temperature environment below 0°C.
  • the invention alloy sheet having the particular structure also has good plastic formability and can be easily subjected to press-forming, for example.
  • the invention alloy structural member obtained thereby also has a structure in which crystallized phases are small in size and in amount in a surface-side region particularly susceptible to impact as with the invention alloy sheet. Accordingly, the invention alloy structural member also has good mechanical properties such as strength and elongation in a low-temperature environment and exhibits high impact resistance.
  • Examples of the magnesium alloy constituting the invention magnesium alloy sheet and the invention magnesium alloy structural member include those having various compositions and containing at least Al and Mn as additive elements (balance being Mg and impurities).
  • An example of the additive element other than Al and Mn is at least one element selected from Zn, Si, Ca, Sr, Y, Cu, Ag, Ce, Zr, and rare earth elements (excluding Y and Ce).
  • 5% to 12% by mass of Al and 0.1% to 2.0% by mass of Mn are preferably contained.
  • Al and Mn are contained in these ranges, not only mechanical properties such as strength and elongation is improved but also corrosion resistance is improved. However, if the contents of these elements are excessively large, a decrease in plastic formability results.
  • the contents of the additive elements other than Al and Mn are, for example, Zn: 0.2 to 7.0% by mass, Si: 0.2 to 1.0% by mass, Ca: 0.2 to 6.0% by mass, Sr: 0.2 to 7.0% by mass, Y: 1.0 to 6.0% by mass, Cu: 0.2 to 3.0% by mass, Ag: 0.5 to 3.0% by mass, Ce: 0.05 to 1.0% by mass, Zr: 0.1 to 1.0% by mass, and RE (rare earth element (excluding Y and Ce)): 1.0 to 3.5% by mass.
  • Zn 0.2 to 7.0% by mass
  • Si 0.2 to 1.0% by mass
  • Ca 0.2 to 6.0% by mass
  • Sr 0.2 to 7.0% by mass
  • Y 1.0 to 6.0% by mass
  • Cu 0.2 to 3.0% by mass
  • Ag 0.5 to 3.0% by mass
  • Ce 0.05 to 1.0% by mass
  • Zr 0.1 to 1.0% by mass
  • RE rare earth element (excluding Y and Ce)): 1.0 to 3.5% by mass.
  • compositions of the alloy containing Al, Mn, and at least one of these elements in amounts in the above-described ranges include AZ series alloys (Mg-Al-Zn series alloys, Zn: 0.2 to 1.5% by mass) and AM series alloys (Mg-Al-Mn series alloys, Mn: 0.15 to 0.5% by mass) of the ASTM standard.
  • the amount of Al contained (hereinafter referred to as the "Al content”) is preferably large since the mechanical properties and corrosion resistance improve with the increase in Al content, and the Al content is more preferably 5.8% by mass or more and 10% by mass or less.
  • the magnesium alloys having an Al content of 5.8% to 10% by mass include Mg-Al-Zn series alloys such as AZ61 alloys, AZ80 alloys, AZ81 alloys, and AZ91 alloys, and Mg-Al-Mn series alloys such as AM60 alloys and AM100 alloys.
  • Mg-Al-Zn series alloys such as AZ61 alloys, AZ80 alloys, AZ81 alloys, and AZ91 alloys
  • Mg-Al-Mn series alloys such as AM60 alloys and AM100 alloys.
  • AZ91 alloys having an Al content of 8.3 to 9.5% by mass have superior corrosion resistance and mechanical properties such as strength and plastic deformation resistance compared to other Mg-Al series alloys.
  • the invention alloy sheet has a first surface and a second surface that are a pair of surfaces opposing each other. These two surfaces are typically in parallel with each other and usually serve as a front surface and a back surface during the use.
  • the first and second surfaces may be flat or curved.
  • the distance between the first and second surfaces is the thickness of the magnesium alloy sheet.
  • the invention alloy sheet is obtained by rolling a cast sheet having a thickness of 5 mm or less as described above; thus, the thickness of the invention alloy sheet is less than 5 mm.
  • the thickness of the alloy sheet is about 0.3 mm to 3 mm and preferably 0.5 mm to 2.0 mm.
  • the alloy sheet exhibits a high strength when the thickness is large within this range, and becomes suitable for use in thin, light-weight housings etc., when the thickness is small.
  • the thickness of the magnesium alloy sheet obtained as a final product may be selected by controlling the casting conditions and rolling conditions in accordance with the desired usage.
  • the shape of the invention alloy structural member include various shapes formed by subjecting the magnesium alloy sheet to plastic forming such as press-forming, e.g., a square-bracket-shaped or box-shaped member having a bottom portion and a side wall portion extending upward from the bottom portion.
  • the thickness of the magnesium alloy structural member in a flat portion not substantially subjected to deformation caused by plastic forming such as press-forming is substantially the same as that of the magnesium alloy sheet used as the material, and the structure thereof is also about the same.
  • the surface region satisfies that the number of Al-Mn crystallized phases having a maximum diameter of 0.1 to 1 ⁇ m is 15 or less per 50 ⁇ m 2 .
  • Examples of the invention alloy sheet include a rolled sheet prepared by rolling a cast material and a treated sheet prepared by subjecting the rolled sheet to a heat treatment, a leveling process, a polishing process, or the like.
  • the invention alloy structural member may be a structural member prepared by subjecting the alloy sheet to plastic forming such as press-forming and those subjected to a heat treatment or a polishing process after the plastic forming.
  • the rolled sheet, the treated sheet, and the alloy structural member may be further provided with an anticorrosion layer of a coating layer.
  • the invention alloys sheet and the invention alloy structural member have good mechanical properties such as strength and elongation even in a low-temperature environment and are resistant to dent upon impact such as dropping.
  • the invention alloy sheet and the invention alloy structure member in a flat portion (a portion substantially the same as the sheet of the material) not substantially subjected to deformation (e.g., deformation by drawing) caused by plastic forming such as press-forming exhibit a tensile strength of 350 MPa or more, a 0.2% proof stress of 280 MPa or more, and an elongation of 2% or more.
  • the structure includes substantially no coarse crystallized phases but includes minute amounts of fine crystallized phases.
  • a region from the surface of the alloy sheet to 30% of the thickness of the alloy sheet is defined as a surface region, a 50 ⁇ m 2 sub-region is arbitrarily selected from this surface region, and the grain diameters of all the crystallized phases found in one sub-region are measured.
  • the maximum diameter is measured from each crystallized phases, the number of fine crystallized phases having a maximum diameter of 0.1 ⁇ m to 1 ⁇ m in the sub-region is 15 or less.
  • the crystallized phases having a maximum diameter of 0.5 ⁇ m or less are present.
  • the coarse crystallized phases can serve as starting points for breaking upon impact such as dropping.
  • breaking and cracking easily occur and the impact resistance is low.
  • the crystallized phases have a maximum diameter of 1 ⁇ m or less, when more than 15 such impurities are present in 50 ⁇ m 2 , the number of starting points for breaking and cracking increases, resulting in a decrease in strength and impact resistance.
  • the impact resistance tends to be high when the number of crystallized phases having a maximum diameter of 0.1 to 1 ⁇ m is small.
  • the number if preferably 10 or less and ideally zero.
  • the crystallized phases contain both Al and Mn.
  • the detail for measuring the maximum diameter is described below. Note that in the present invention, presence of superfine crystallized phases which are not likely to cause breaking, i.e., crystallized phases having a maximum diameter less than 0.1 ⁇ m, is allowable. However, the precipitated impurities are preferably absent.
  • An example of the invention alloy sheet is one having a microstructure with a small average crystal grain diameter, i.e., 20 ⁇ m or less.
  • a cast sheet having a microstructure is obtained by continuous casting under particular conditions, and a rolled sheet having the microstructure described above can be prepared by rolling the cast sheet under particular conditions.
  • the invention alloy sheet having such a microstructure exhibits good mechanical properties such as strength and elongation, and an enhanced impact resistance even in a low-temperature environment.
  • the invention magnesium alloy structural member made of a magnesium alloy sheet having the microstructure or a treated sheet prepared by correcting, such as leveling, the rolled sheet can also have a microstructure having an average crystal grain diameter of 20 ⁇ m or less and exhibit high impact resistance. More preferably, the average crystal grain diameter is 0.1 ⁇ m to 10 ⁇ m.
  • a twin-roll continuous casting process is employed.
  • the temperature of the rolls used as a die is adjusted to 100°C or less and the thickness of the cast sheet obtained thereby is adjusted to 5 mm or less.
  • the roll temperature is adjusted to 100°C or less by using rolls that can be subjected to forced cooling such as water-cooling. The lower the roll temperature and the thinner the cast sheet, the faster the cooling rate and more suppressed is the generation of the crystallized phases. Accordingly, the roll temperature is more preferably 60°C or less and the thickness of the cast sheet is more preferably 4.0 mm or less.
  • This casting step (including cooling step) is preferably conducted in an inert gas atmosphere to prevent oxidation of the magnesium alloy.
  • the rolling conditions are, for example, the temperature of heating the material: 200°C to 400°C, the temperature of heating the rolling rolls: 150°C to 300°C, and a reduction per pass: 5% to 50%.
  • a plurality of passes of rolling may be conducted to adjust the thickness to a desired value.
  • the controlled rolling disclosed in patent literature 1 may also be employed.
  • the cast material is rolled, the structure can be converted to a rolled structure from a metal structure formed by casting.
  • a microstructure having an average crystal grain diameter of 20 ⁇ m or less can be easily formed, internal and surface defects such as segregation, shrinkage cavities, and pores generated by casting can be reduced, and a rolled sheet with an excellent surface texture can be obtained.
  • the strength and the corrosion resistance of the resulting rolled sheet can be further enhanced by conducting a final heat treatment after final rolling whereby a fine recrystallized structure having an average crystal grain diameter of 20 ⁇ m or less is formed.
  • the invention alloy structural member is obtained by subjecting the rolled sheet (including a heat-treated rolled sheet) to plastic forming, such as press-forming (including blanking), deep-drawing, forging, blowing, or bending, into a desired shape.
  • plastic forming can suppress the structure of the rolled sheet from turning into a coarse recrystallized structure and reduce deterioration of the mechanical properties and corrosion resistance if the plastic forming is conducted in a warm process at 200°C to 280°C.
  • a heat treatment or an anticorrosion treatment may be performed or a coating layer may be formed after the plastic forming.
  • the invention magnesium alloy sheet and the invention magnesium alloy structural member have high impact resistance in a low-temperature environment.
  • the invention method for producing a magnesium alloy sheet can produce the magnesium alloy sheet of the invention.
  • Ingots (commercially available products) composed of magnesium alloys shown in Table I were used to produce magnesium alloy sheets and magnesium alloy structural members (housings) under various conditions. The structure of the resulting magnesium alloy sheets and magnesium alloy structural members was observed and a tensile test (low temperature) and an impact test (low temperature) were conducted.
  • the production conditions were as follows.
  • Each of the ingots of magnesium alloys is heated to 700°C in an inert atmosphere to prepare molten metal, and the molten metal is used to form a plurality of cast sheets each 4.0 mm ( ⁇ 5 mm) in thickness by a twin-roll continuous casting process in the inert atmosphere. This casting is conducted while cooling the rolls so that the roll temperature is 60°C ( ⁇ 100°C).
  • Each of the resulting cast sheets is used as a material and rolled a plurality of times at a material heating temperature of 200°C to 400°C, a rolling roll heating temperature of 150°C to 300°C, and a reduction ratio per pass of 5% to 50% until the thickness of the material is 0.6 mm so as to prepare a rolled sheet.
  • the resulting rolled sheets are used as samples (sheets).
  • the resulting rolled sheets are subjected to a rectangular cup drawing at a heating temperature of 250°C to prepare a box having a square-bracket-shaped cross-section. This box (magnesium alloy structural member) is used as a sample (housing).
  • a heat treatment (solution treatment) or aging treatment may be performed after the casting to homogenize the structure, an intermediate heat treatment may be performed during the rolling, or a final heat treatment may be performed after the final rolling.
  • the rolled sheet may be subjected to a leveling process or a polishing process to improve the flatness by correction or may be polished to make the surface smooth.
  • a commercially available die-cast product is used (box having a square-bracket-shaped cross-section, thickness of the bottom portion: 0.6 mm)
  • a commercially available sheet (thickness: 0.6 mm) composed of an AZ31 alloy is used.
  • a box (commercially available product) having a square-bracket-shaped cross-section (thickness of the bottom portion: 0.6 mm) prepared by subjecting a sheet (thickness: 0.6 mm) composed of an AZ31 alloy to a rectangular cup drawing is used.
  • the metal structure was observed as below to study crystallized phases.
  • the sample (sheet) is cut in the thickness direction, and the section is observed with a transmission electron microscope (20,000 magnification).
  • Five 50 ⁇ m 2 sub-regions are arbitrarily selected from the surface region, and the size of all crystallized phases present in each of each sub-regions is measured. Identification of the crystallized phases is conducted on the basis of the composition.
  • the composition of the grains present in the section is determined by qualitative analysis and semiquantitative analysis such as energy dispersive X-ray spectroscopy (EDX), and grains containing Al and Mg are identified as crystallized phases.
  • EDX energy dispersive X-ray spectroscopy
  • the ratio Al/Mn of the mass of the Al to the mass of Mn is measured.
  • the Al/Mn was 2 to 5 in all Samples 1-1 and 1-2.
  • parallel lines are drawn in the section and the maximum value of the lengths of each grain traversing the straight lines is determined to be the maximum diameter of that grain.
  • the number of crystallized phases having a maximum diameter of 0.1 ⁇ m to 1 ⁇ m is defined to be the number of crystallized phases in the sub-region.
  • the average number of the five sub-regions is defined to be the number of the crystallized phases in this sample per 50 ⁇ m 2 .
  • a bottom portion which is a flat portion not subjected to drawing deformation in the sample, is cut in the sheet thickness direction, and the section is observed as with the sample (sheet) above to count the number of crystallized phases per 50 ⁇ m 2 .
  • each sub-region is changed to 200 ⁇ m 2 and the maximum diameter of the crystallized phases in this 200 ⁇ m 2 and the number of the crystallized phases per 200 ⁇ m 2 are measured.
  • the shape of each sub-region may be any as long as the area satisfies the description above, but a rectangular shape (typically square) is easy to use. The measurement results are shown in Table I.
  • JIS 13B sheet specimen JIS Z 2201 (1998) was taken from each sample (thickness: 0.6 mm) and subjected to a tensile test in accordance with a metal material tensile test method of JIS Z 2241 (1998).
  • the gage distance GL is set to 50 mm for the sample (sheet) and to 15 mm for the sample (housing).
  • a 30 mm ⁇ 30 mm sheet piece is cut out from each sample and used as a specimen.
  • a support table 20 having a circular hole 21 having a diameter d of 20 mm in a horizontal surface was prepared.
  • the depth of the circular hole 21 was large enough to allow insertion of a circular cylinder rod 10.
  • a specimen 1 was placed to cover the circular hole 21 and a ceramic circular cylinder rod 10 having a weight of 100 g and a tip r of 5 mm was arranged at a position with a height of 200 mm from the specimen 1 so that the center axis of the specimen 1 and the center axis of the circular hole 21 were coaxial.
  • the circular cylinder rod 10 was allowed to freely drop from the position (height of 200 mm) described above toward the specimen 1 and the amount of dent of the specimen 1 is measured.
  • the amount of dent (mm) was measured by drawing a straight line connecting two opposing sides of the specimen 1 and measuring the distance from the straight line to a portion that had dented most with a point micrometer.
  • the impact test was conducted in a low-temperature environment at -30°C. The results are shown in Table I.
  • the rating ⁇ is given for samples with an amount of dent of 0.5 mm or less and the rating X is given for samples with an amount of dent of more than 0.5 mm. For samples in which the amount of dent could not be measured due to breaking, "Breaking" is indicated.
  • the thickness of the 30 mm ⁇ 30 mm specimen prepared from the sample (housing) was measured at four arbitrary points.
  • the thickness (thickness of the specimen: 0.6 mm) was equal to the thickness (0.6 mm) of the sheet of the material at all positions.
  • magnesium alloy sheets and magnesium alloy structural members in which the number of Al-Mn crystallized phases having a maximum diameter of 0.1 to 1 ⁇ m per 50 ⁇ m 2 arbitrarily selected from the surface region is 15 or less, the amount of dent is small and the impact resistance is high even in a low-temperature environment at -30°C compared to cast materials and expanded materials (AZ31 alloys) having the same composition.
  • the reason therefor is presumably that the mechanical properties such as tensile strength and elongation were excellent even in a low-temperature environment.
  • Samples 1-1 and 1-2 having high impact resistance contain only crystallized phases having a maximum diameter of 0.5 ⁇ m or less.
  • Ingots (commercially available products) composed of magnesium alloys shown in Table II were used to produce magnesium alloy sheets and magnesium alloy structural members (housings) under various conditions. The structure of the resulting magnesium alloy sheets and magnesium alloy structural members was observed and the impact test (low temperature) was performed as in Test Example 1. The results are shown in Table II.
  • the casting is conducted by a twin-roll continuous casting process and the conditions of the roll temperature and the thickness of the cast sheet are set as shown in Table II. Rolling is conducted under the same rolling conditions as Test Example 1. However, in this test, the total length of time the material is retained in the temperature range of 150°C to 250°C is adjusted to 45 minutes or 90 minutes by adjusting the time of heating the material, the rolling velocity, the cooling rate during the rolling, etc. Note that in Test Example 1, this total length of time is set to about 60 minutes.
  • the shape "Sheet” indicates that the sample is a rolled sheet (magnesium alloy sheet) and "Housing” indicates that the sample is a box (magnesium alloy structural member) produced from the rolled sheet under the same conditions as Test Example 1.
  • Condition B Die casting
  • Condition C Commercially available sheet
  • Condition D Commercially available housing
  • Table II shows that magnesium alloy sheets and magnesium alloy structural members containing 15 or less of Al-Mn crystallized phases having a maximum diameter of 0.1 to 1 ⁇ m per 50 ⁇ m 2 arbitrarily selected from the surface region can be obtained by rolling cast sheets cast by a twin-roll continuous casting process at a roll temperature of 100°C or less to a cast sheet thickness of 5 mm or less. In contrast, coarse crystallized phases will occur unless the particular coasting conditions are observed.
  • the results show that as with Test Example 1, the magnesium alloy sheets and magnesium alloy structural members containing 15 or less of Al-Mn crystallized phases having a maximum diameter of 0.1 to 1 ⁇ m per 50 ⁇ m 2 arbitrarily selected from the surface region exhibit high impact resistance even in a low-temperature environment of -30°C.
  • the Al/Mn was measured in all Samples 2-1 to 2-6 and was all 2 to 5.
  • the test has found that (1) when the thickness of the cast materials prepared is the same, the amount of crystallized phases can be reduced by decreasing the roll temperature; and (2) when the roll temperature is the same, the amount of crystallized phases can be reduced by decreasing the thickness of the cast material prepared.
  • the embodiments described above are subject various modification without departing from the scope of the present invention and the scope of the present invention is not limited by the structures described above.
  • the composition of the magnesium alloy, the thickness of the sheet after casting and after rolling, the roll temperature during casting, etc. may be modified as needed.
  • the obtained rolled sheet or pressed structural member may be subjected to anticorrosion treatment or coated with a coating layer.
  • the invention magnesium alloy structural member has high impact resistance in a low-temperature environment, it is suitable for use in various housings and parts used in low-temperature environment.
  • the invention magnesium alloy sheet is suitable for use as a structural material of the invention magnesium alloy structural member.
  • the invention method for producing a magnesium alloy sheet is suitable for use in production of the invention magnesium alloy sheet. According to the present invention,.

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EP10791969.8A 2009-06-26 2010-06-08 Platte aus magnesiumlegierung Withdrawn EP2447381A4 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2009152849A JP2011006754A (ja) 2009-06-26 2009-06-26 マグネシウム合金板
PCT/JP2010/059710 WO2010150651A1 (ja) 2009-06-26 2010-06-08 マグネシウム合金板

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EP2447381A1 true EP2447381A1 (de) 2012-05-02
EP2447381A4 EP2447381A4 (de) 2016-03-09

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EP10791969.8A Withdrawn EP2447381A4 (de) 2009-06-26 2010-06-08 Platte aus magnesiumlegierung

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US (1) US20120100035A1 (de)
EP (1) EP2447381A4 (de)
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KR (1) KR20120031008A (de)
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TW201111521A (en) 2011-04-01
BRPI1015407A2 (pt) 2016-08-09
JP2011006754A (ja) 2011-01-13
CN102803533B (zh) 2016-01-20
KR20120031008A (ko) 2012-03-29
RU2012102620A (ru) 2013-08-10
EP2447381A4 (de) 2016-03-09
US20120100035A1 (en) 2012-04-26
WO2010150651A1 (ja) 2010-12-29
CN102803533A (zh) 2012-11-28

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