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US20070204936A1 - Magnesium Alloy - Google Patents

Magnesium Alloy Download PDF

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Publication number
US20070204936A1
US20070204936A1 US11/663,298 US66329805A US2007204936A1 US 20070204936 A1 US20070204936 A1 US 20070204936A1 US 66329805 A US66329805 A US 66329805A US 2007204936 A1 US2007204936 A1 US 2007204936A1
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US
United States
Prior art keywords
magnesium alloy
crystal
strength
magnesium
quasicrystal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US11/663,298
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English (en)
Inventor
Akira Kato
An-pang Tsai
Masaki Watanabe
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
National Institute for Materials Science
Toyota Motor Corp
Original Assignee
National Institute for Materials Science
Toyota Motor Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by National Institute for Materials Science, Toyota Motor Corp filed Critical National Institute for Materials Science
Assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA, NATIONAL INSTITUTE FOR MATERIALS SCIENCE reassignment TOYOTA JIDOSHA KABUSHIKI KAISHA ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KATO, AKIRA, TSAI, AN-PANG, WATANABE, MASAKI
Publication of US20070204936A1 publication Critical patent/US20070204936A1/en
Abandoned 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
    • C22C23/04—Alloys based on magnesium with zinc or cadmium as the next major constituent

Definitions

  • the present invention relates to a magnesium alloy having superior high-temperature strength. More particularly, the invention relates to a particle-dispersed magnesium alloy having superior high-temperature strength.
  • Magnesium has the specific gravity of 1.74 and is the lightest among the metal materials for industrial purposes. Its mechanical property is comparable to that of aluminum alloy, and for that reason it has drawn attention as a material suitable for aircraft and automobiles, particularly as a material contributing to light weight and improved mileage.
  • magnesium alloy has already been used as the material for automotive wheels or engine head covers.
  • Applications of magnesium alloy under consideration include structural components, such as engine blocks, and even functional components such as pistons, that experience high temperature. If the piston is made of magnesium alloy instead of aluminum alloy, not only the piston becomes lighter in weight but also other components can be made lighter because of the decrease in inertia weight or the like.
  • Magnesium alloy products are usually made of cast products including die-cast products.
  • Mg—Al alloys (ASTM standards—AM60B, AM50A, AM20A, for example) contain 2 to 12% Al, to which small amounts of Mn are added.
  • the Mg component consists of eutectic crystal of ⁇ -Mg solid solution and ⁇ -Mg 17 Al 12 compound, in which age hardening is caused by the precipitation of a Mg 17 Al 12 mesophase upon heat treatment. Strength and toughness also improve by solution heat treatment.
  • Mg—Al—Zn alloys in which 5 to 10% Al and 1 to 3% Zn are contained, there is a wide ⁇ -solid solution region on the Mg side, where a Mg—Al—Zn compound crystallizes. While they are strong and highly anticorrosive in the as-cast condition, their mechanical property can be improved by aging heat treatment, and a pearlite-like compound phase is precipitated at the grain boundary by hardening and tempering.
  • Mg—Zn alloys the maximum strength and elongation can be obtained in the as-cast condition when 2% Zn is added to Mg. In order to improve castability and obtain a robust cast product, greater amounts of Zn are added.
  • the as-cast Mg-6% Zn alloy has a tensile strength on the order of 17 kg/mm 2 , which, although it can be improved by the T6 treatment, is much inferior to that of Mg—Al alloys.
  • Mg—Zn alloys is ZCM630A (Mg-6% Zn-3% Cu-0.2Mn).
  • an alloy to which a rare earth element (R.E.) is added provides a mechanical property that, although somewhat inferior to that of aluminum alloys in room temperature, is comparable to that of aluminum alloys at high temperatures from 250 to 300° C.
  • R.E. rare earth element
  • Examples of alloys that contain R.E. that have been put to practical use include EK30A alloy (2.5 to 4% R.E.-0.2% Zr) which contains no Zn, and ZE41A alloy (1% R.E.-2.0% Zn-0.6% Zr) that contains Zn.
  • JP Patent Publication (Kokai) No. 2002-309332 A after casting an Mg—Zn—Y alloy, a quasicrystal phase that forms eutetic crystal with ⁇ -Mg is uniformly and finely dispersed in the microstructure by hot forming.
  • the quasicrystal is a quasicrystal-phase-reinforced magnesium alloy that is much harder than a crystalline compound with an approximate composition and that has superior strength and elongation property.
  • the composition is limited to Mg, 1-10 at. % Zn, 0.1-3 at. % Y.
  • an eutetic crystal microstructure of quasicrystal is formed at the ⁇ -Mg crystal grain boundary.
  • sand casting Mg alloys such as AZ91C and ZE41
  • a predetermined strength is obtained by heat treatment such as T6 or T5.
  • Such alloys are precipitation hardening alloys and that is why they require heat treatment such as T6 or T5 in order to adjust them to a predetermined strength and obtain long-term-stability in their characteristics. If exposed to temperatures above room temperature (generally 50° C. or higher) for a long time, aging precipitation of dissolved elements might occur, resulting in a gradual change in alloy microstructure and characteristics.
  • Mg alloys for forging such as AZ61A and AZ31B
  • the crystal grain is made finer by recrystallization caused by intense processing such as rolling and extrusion, thereby enhancing strength.
  • the major reinforcing mechanism for such alloys is the refinement of crystal grains. Refinement of crystal grains, however, triggers a decrease in strength at high temperatures of 1000° C. and above where a strong grain boundary sliding unique to Mg occurs. Furthermore, grain growth occurs at high temperatures, so that such alloys, once exposed to high temperature, would potentially not be able to regain their original strength even after the temperature is lowered.
  • the Mg—Zn—Y alloy cast material disclosed in JP Patent Publication (Kokai) No. 2002-309332 is a general eutetic crystal alloy, and it has a strength comparable to that of commercially available alloys with a similar composition, such as ZE41.
  • ZE41 a similar composition
  • Mg alloys for forging such as AZ61A and AZ31B, have no mechanism for pinning the grain boundary or controlling grain growth at high temperatures.
  • the high-strength magnesium alloy of the invention has been made in view of the aforementioned problems, and it is an object of the invention to improve the strength, particularly high-temperature strength, of a Mg—Zn-RE alloy.
  • the invention is based on the inventors' realization that by substituting a part of RE in an Mg—Zn-RE alloy with a particular element, a high-strength magnesium alloy can be obtained that has such a microstructure that nanoparticles having a complex structure deriving from a quasicrystal are dispersed in the crystalline magnesium parent phase.
  • the invention provides a high-strength magnesium alloy which comprises 2.0 to 10 at. % zinc, 0.05 to 0.2 at. % zirconium, 0.2 to 1.50 at. % rare earth element, and the balance being magnesium and unavoidable impurities.
  • the rare earth element (RE) is yttrium (Y).
  • the magnesium alloy of the invention is expressed by the following general formula: Mg 100 ⁇ (a+b+c) Zn a Zr b RE c where RE is a rare earth element, and a, b, and c are atomic percentages of zinc (Zn), zirconium (Zr), and rare earth element (RE), respectively, where the following relationship is satisfied: a 12 ⁇ b + c ⁇ a 3 1.5 ⁇ a ⁇ 10 0.05 ⁇ b ⁇ 0.25 ⁇ c .
  • the ⁇ -Mg crystal grains occupy 50% or more in volume, and the alloy contains nanoparticles having a complicated structure, such as quasicrystal or approximate crystal, at the ⁇ -Mg crystal grain boundary.
  • the quasicrystal herein refers to a new ordered structure having no translational symmetry but having fivefold or tenfold symmetry and quasiperiodicity, which are not crystallographically allowed. Alloys known to produce quasicrystal include Al—Pd—Mn, Al—Cu—Fe, Cd—Yb, and Mg—Zn—Y, for example. Because of its specific structure, the quasicrystal has specific characteristics, such as high degree of hardness, high melting point, and low ⁇ , as compared with ordinary crystals.
  • Fine precipitates (1 ⁇ m or smaller) are uniformly dispersed within the ⁇ -Mg crystal grains. Such fine precipitates enhance the strength of the magnesium alloy of the invention.
  • the major fine precipitates are approximate crystals and MgY intermetallic compounds.
  • the approximate crystal which is related to quasicrystal, herein refers to an intermetallic compound having a structure and composition similar to those of the quasicrystal (Mg 3 Zn 6 Y 1 ).
  • the quasicrystal or approximate crystal phase of the ⁇ -Mg crystal grain boundary pins the shifting of the crystal grain boundary. Therefore, growth of crystal grain is controlled, and the decrease in strength due to the coarsening of the crystal grain does not occur even at high temperature of 300° C. or above.
  • the ⁇ -Mg phase occupies 50% or more of the volume, and quasicrystal or approximate crystal particles exist in the ⁇ -Mg crystal grain boundary. These particles pins the shifting of the crystal grain boundary, so that the growth of crystal grain can be controlled. Thus, no decrease in strength due to the coarsening of the crystal occurs even at high temperature. Further, fine crystals are also precipitated within the grains. The major fine precipitates are approximate crystals and Mg—Y intermetallic compounds.
  • FIG. 1A shows an SEM microstructure image of Example 1.
  • FIG. 1B shows an SEM microstructure image of Comparative Example.
  • FIG. 2 shows enlarged images of the inside of a grain of a Mg-6Zn-0.1Zr-0.9Y (at. %) cast material according to Example 1.
  • FIG. 3 shows enlarged images of the grain boundary (more strictly, an eutetic crystal-like portion) of a Mg-6Zn-0.1Zr-0.9Y (at. %) cast material according to Example 1.
  • the magnesium alloy of the invention is manufactured by adding all predetermined additive elements in molten Mg, mixing them uniformly, and casting the mixture in a casting mold.
  • the casting method is not particularly limited and a variety of methods, such as gravity casting, die-casting, or rheocast, may be employed.
  • the magnesium alloy of the invention is not just cast but subjected to heating process after casting, or to hot working and heating process after casting, so as to improve strength.
  • Examples of the rare earth element of which the magnesium alloy of the invention is composed include scandium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu), gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb), and lutetium (Lu), of which yttrium (Y) is preferable.
  • An alloy of Mg-6Zn-0.1Zr-0.9Y (at. %) cast material was manufactured by the following steps.
  • Pure Mg was dissolved in an iron crucible, and molten metal was maintained at 700° C. Other constituent materials were added in the molten metal, which was stirred while its temperature was maintained at approximately 700° C. until all the materials were uniformly dissolved. The order of addition of the constituent materials in the molten metal does not affect characteristics and is therefore not specified.
  • the alloy molten metal whose temperature was maintained at approximately 700° C. was cast in a JIS 4 boat-shaped mold which had been preheated to about 100° C.
  • Mg-3Zn-0.5Y which is a conventional material, was cast in the same way as in Example 1 except that the following materials were used.
  • FIG. 1A shows an SEM microstructure image of Example 1
  • FIG. 1B shows an SEM microstructure image of Comparative Example.
  • Example 1 and Comparative Example have similar exterior, having an eutetic crystal structure of approximate crystal (Example 1) or Mg 3 Zn 6 Y, quasicrystal (Comparative Example) at the ⁇ -Mg crystal grain boundary.
  • the shape of the eutetic crystal structure is different between Example 1 and Comparative Example; in Example 1, the eutetic crystal structure is generally finer and more uniformly dispersed.
  • FIG. 2 shows an enlarged image of the inside of a grain of the Mg-6Zn-0.1Zr-0.9Y (at. %) cast material of Example 1.
  • the image shows the ⁇ -Mg phase, a MgY intermetallic compound that could be either Mg 24 Y 5 or Mg 12 Y, and an unidentifiable phase.
  • FIG. 3 shows an enlarged image of the grain boundary (or, to be more precise, the eutetic crystal-like portion) of the Mg-6Zn-0.1Zr-0.9Y (at. %) cast material of Example 1.
  • the image shows the W phase (cubic crystal z Zn 3 Mg 3 Y 2 ), a Zn 6 Y 4 binary compound, a hexagonal compound, and an unidentifiable phase.
  • Example 1 From ingots of the above JIS 4 boat-shaped mold according to Example 1 (Mg-6Zn-0.1Zr-0.9Y) and Comparative Example (Mg-3Zn-0.5Y), cylindrical tensile specimens measuring ⁇ 5 ⁇ 25 mm at the parallel portion were acquired and subjected to tensile test at room temperature and 150° C. Similar tensile tests were conducted on Examples 2 to 4 with various composition ratios and on AZ91C-T6 and ZE41A-T5, which are conventional materials. The tests were conducted using AG-250kND manufactured by Shimadzu Corporation as a tensile tester, at the pulling rate of 0.8 mm/min. The results are shown in Table I below.
  • Example 1 to 4 show superior to the conventional cast materials such as Comparative Example in terms of tensile strength at 150° C. Further, Examples 1 to 4 show much lower decrease in strength associated with the temperature increase from room temperature to 150° C.
  • One cause for these results is believed to be an increase in the fine precipitates in the ⁇ -Mg crystal grains. Since fine precipitates, such as approximate crystals and MgY intermetallic compounds, have high thermal stability, they are supposedly functioning as an effective dislocation barrier even at 150° C.
  • magnesium alloy of the invention nanoparticles deriving from quasicrystal are present at the Mg crystal grain boundary, and fine crystals are precipitated even within the grains. As a result, there is no decrease in strength due to the coarsening of crystals at high temperature. Thus, high strength can be maintained at high temperature.
  • high-temperature strength can be increased by increasing the content of rare earth element. This, nevertheless, results in an increased cost.
  • WE54 can exhibit high strength by increasing the rare earth content to nearly 10% and carrying out T6 heat treatment, although at very high cost.
  • high-temperature strength comparable to the strength of conventional heat-treated material can be achieved in the as-cast condition; namely, without heat treatment.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Forging (AREA)
  • Powder Metallurgy (AREA)
US11/663,298 2004-09-21 2005-09-21 Magnesium Alloy Abandoned US20070204936A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2004-273364 2004-09-21
JP2004273364A JP2006089772A (ja) 2004-09-21 2004-09-21 マグネシウム合金
PCT/JP2005/017912 WO2006033458A1 (fr) 2004-09-21 2005-09-21 Alliage de magnésium

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US20070204936A1 true US20070204936A1 (en) 2007-09-06

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US11/663,298 Abandoned US20070204936A1 (en) 2004-09-21 2005-09-21 Magnesium Alloy

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US (1) US20070204936A1 (fr)
EP (1) EP1813689A4 (fr)
JP (1) JP2006089772A (fr)
WO (1) WO2006033458A1 (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090320967A1 (en) * 2006-09-15 2009-12-31 An Pang Tsai High strength magnesium alloy and method of production of the same
US20120067463A1 (en) * 2009-03-24 2012-03-22 Alok Singh Mg ALLOY
US20120160206A1 (en) * 2010-12-28 2012-06-28 Hitachi Automotive Systems, Ltd. Piston of Internal Combustion Engine, Producing Method of Piston, and Sliding Member
RU2562190C1 (ru) * 2014-11-10 2015-09-10 Федеральное государственное унитарное предприятие "Всероссийский научно-исследовательский институт авиационных материалов" (ФГУП "ВИАМ") Сплав на основе магния
US10544487B2 (en) 2015-12-30 2020-01-28 The Florida International University Board Of Trustees Age-hardenable magnesium alloys
CN112458349A (zh) * 2020-11-06 2021-03-09 重庆大学 一种含钕和钇的低稀土高强度变形镁合金及其制备方法
CN117660819A (zh) * 2024-01-25 2024-03-08 龙南龙钇重稀土科技股份有限公司 高强可溶镁合金及其制备方法

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5429702B2 (ja) * 2006-08-03 2014-02-26 独立行政法人物質・材料研究機構 マグネシウム合金とその製造方法
US8435444B2 (en) 2009-08-26 2013-05-07 Techmag Ag Magnesium alloy
JP5714436B2 (ja) * 2011-07-11 2015-05-07 株式会社神戸製鋼所 マグネシウム合金材の製造方法およびこれにより製造されたマグネシウム合金材
CN103849799A (zh) * 2012-11-28 2014-06-11 沈阳工业大学 一种高韧性变形Mg-Zn-Nd-Zr镁合金及其制备方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3183083A (en) * 1961-02-24 1965-05-11 Dow Chemical Co Magnesium-base alloy
US3183086A (en) * 1963-05-03 1965-05-11 Kulite Tungsten Co Method of making porous body with imperviously sealed surface
US3419385A (en) * 1964-10-22 1968-12-31 Dow Chemical Co Magnesium-base alloy
US5501748A (en) * 1992-06-10 1996-03-26 Norsk Hydro A.S. Procedure for the production of thixotropic magnesium alloys

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1525759A (en) * 1975-12-22 1978-09-20 Magnesium Elektron Ltd Magnesium alloys
JPH07126790A (ja) * 1993-10-29 1995-05-16 Kobe Steel Ltd 高耐食性Ｍｇ基合金
JPH07138689A (ja) * 1993-11-09 1995-05-30 Shiyoutarou Morozumi 高温強度のすぐれたＭｇ合金

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3183083A (en) * 1961-02-24 1965-05-11 Dow Chemical Co Magnesium-base alloy
US3183086A (en) * 1963-05-03 1965-05-11 Kulite Tungsten Co Method of making porous body with imperviously sealed surface
US3419385A (en) * 1964-10-22 1968-12-31 Dow Chemical Co Magnesium-base alloy
US5501748A (en) * 1992-06-10 1996-03-26 Norsk Hydro A.S. Procedure for the production of thixotropic magnesium alloys

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090320967A1 (en) * 2006-09-15 2009-12-31 An Pang Tsai High strength magnesium alloy and method of production of the same
US20120067463A1 (en) * 2009-03-24 2012-03-22 Alok Singh Mg ALLOY
US8728254B2 (en) * 2009-03-24 2014-05-20 National Institute For Materials Science Mg alloy
US20120160206A1 (en) * 2010-12-28 2012-06-28 Hitachi Automotive Systems, Ltd. Piston of Internal Combustion Engine, Producing Method of Piston, and Sliding Member
RU2562190C1 (ru) * 2014-11-10 2015-09-10 Федеральное государственное унитарное предприятие "Всероссийский научно-исследовательский институт авиационных материалов" (ФГУП "ВИАМ") Сплав на основе магния
US10544487B2 (en) 2015-12-30 2020-01-28 The Florida International University Board Of Trustees Age-hardenable magnesium alloys
CN112458349A (zh) * 2020-11-06 2021-03-09 重庆大学 一种含钕和钇的低稀土高强度变形镁合金及其制备方法
CN117660819A (zh) * 2024-01-25 2024-03-08 龙南龙钇重稀土科技股份有限公司 高强可溶镁合金及其制备方法

Also Published As

Publication number Publication date
EP1813689A4 (fr) 2007-12-26
JP2006089772A (ja) 2006-04-06
WO2006033458A1 (fr) 2006-03-30
EP1813689A1 (fr) 2007-08-01

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