JP5590413B2 - High thermal conductivity magnesium alloy - Google Patents
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- JP5590413B2 JP5590413B2 JP2011062771A JP2011062771A JP5590413B2 JP 5590413 B2 JP5590413 B2 JP 5590413B2 JP 2011062771 A JP2011062771 A JP 2011062771A JP 2011062771 A JP2011062771 A JP 2011062771A JP 5590413 B2 JP5590413 B2 JP 5590413B2
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- 229910000861 Mg alloy Inorganic materials 0.000 title claims description 62
- 239000011701 zinc Substances 0.000 claims description 54
- 239000011572 manganese Substances 0.000 claims description 15
- 239000011777 magnesium Substances 0.000 claims description 11
- 229910052710 silicon Inorganic materials 0.000 claims description 7
- 229910052748 manganese Inorganic materials 0.000 claims description 6
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 5
- 239000012535 impurity Substances 0.000 claims description 5
- 229910052749 magnesium Inorganic materials 0.000 claims description 5
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 4
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 4
- 239000010703 silicon Substances 0.000 claims description 4
- JBQYATWDVHIOAR-UHFFFAOYSA-N tellanylidenegermanium Chemical compound [Te]=[Ge] JBQYATWDVHIOAR-UHFFFAOYSA-N 0.000 claims description 2
- 238000012360 testing method Methods 0.000 description 25
- 229910045601 alloy Inorganic materials 0.000 description 17
- 239000000956 alloy Substances 0.000 description 17
- 239000000203 mixture Substances 0.000 description 17
- 230000035882 stress Effects 0.000 description 15
- 229910019018 Mg 2 Si Inorganic materials 0.000 description 14
- 229910052751 metal Inorganic materials 0.000 description 9
- 239000002184 metal Substances 0.000 description 9
- 229910052725 zinc Inorganic materials 0.000 description 7
- 238000005259 measurement Methods 0.000 description 6
- 238000009864 tensile test Methods 0.000 description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 238000005211 surface analysis Methods 0.000 description 5
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 4
- 239000013078 crystal Substances 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- 230000014759 maintenance of location Effects 0.000 description 4
- 238000005266 casting Methods 0.000 description 3
- 230000007423 decrease Effects 0.000 description 3
- 238000007542 hardness measurement Methods 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 229910052742 iron Inorganic materials 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- 229910017706 MgZn Inorganic materials 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000000523 sample Substances 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000032683 aging Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 239000003963 antioxidant agent Substances 0.000 description 1
- 230000003078 antioxidant effect Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 229910052790 beryllium Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052791 calcium Inorganic materials 0.000 description 1
- 229910052801 chlorine Inorganic materials 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000006073 displacement reaction Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000000921 elemental analysis Methods 0.000 description 1
- 230000004907 flux Effects 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000003921 oil Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000004576 sand Substances 0.000 description 1
- 239000011856 silicon-based particle Substances 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 229910052712 strontium Inorganic materials 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 239000013585 weight reducing agent Substances 0.000 description 1
- 238000004876 x-ray fluorescence Methods 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
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Description
本発明は、高温下での使用に好適な高熱伝導性マグネシウム合金に関する。 The present invention relates to a highly thermally conductive magnesium alloy suitable for use at high temperatures.
アルミニウム合金よりもさらに軽量なマグネシウム合金は、軽量化の観点から航空機材料や車両材料などとして広く用いられつつある。しかしながら、マグネシウム合金は、用途によっては要求される特性が十分に発揮されないため、さらなる特性の向上が求められている。 Magnesium alloys that are lighter than aluminum alloys are being widely used as aircraft materials and vehicle materials from the viewpoint of weight reduction. However, the magnesium alloy does not sufficiently exhibit the required characteristics depending on the application, and therefore further improvement of the characteristics is required.
たとえば、一般的なマグネシウム合金として、ＡＺ９１Ｄ（ＡＳＴＭ記号）がある。ＡＺ９１Ｄの熱伝導率は６０Ｗ／ｍＫ程度であるため、使用環境が高温であったり使用中に発熱したりする部材に用いられると、放熱が良好に行われず、部材に熱変形が生じることがある。特に、内燃機関のシリンダヘッドやシリンダブロックに用いられるマグネシウム合金として熱伝導率の低いマグネシウム合金を用いると、シリンダヘッドが熱変形したり、シリンダブロック内に熱がこもりシリンダボアが変形することで、摩擦が増大したり気密性が低下したりするなどの悪影響が生じる。そのため、高い熱伝導率をもつマグネシウム合金が求められている。また、一般的なマグネシウム合金は、その延性についても十分とは言えない。 For example, as a general magnesium alloy, there is AZ91D (ASTM symbol). Since the thermal conductivity of AZ91D is about 60 W / mK, when used in a member that is used in a high temperature environment or generates heat during use, heat dissipation is not performed well, and the member may be thermally deformed. . In particular, if a magnesium alloy with low thermal conductivity is used as the magnesium alloy used in the cylinder head or cylinder block of an internal combustion engine, the cylinder head is thermally deformed, the heat is accumulated in the cylinder block, and the cylinder bore is deformed. Adverse effects such as increase in the airtightness and decrease in airtightness occur. Therefore, a magnesium alloy having a high thermal conductivity is demanded. Moreover, it cannot be said that a general magnesium alloy has sufficient ductility.
高温環境での使用を前提としたマグネシウム合金は、これまでにも開発されている。特許文献１には、高温での使用を目的としたマグネシウム合金が開示されている。実施例１３のマグネシウム合金は、亜鉛を６．１重量％、珪素を１．０重量％、マンガンを０．３０重量％含む。 Magnesium alloys premised on use in high temperature environments have been developed so far. Patent Document 1 discloses a magnesium alloy intended for use at high temperatures. The magnesium alloy of Example 13 contains 6.1 wt% zinc, 1.0 wt% silicon, and 0.30 wt% manganese.
また、特許文献２には、実施例１３よりも亜鉛含有量を大きく低減させた、延性に優れたマグネシウム合金が開示されている。表２には、亜鉛を０．２〜１．０重量％、珪素を０．４〜１．４重量％、マンガンを０．２〜０．４重量％含むマグネシウム合金が示されている。 Patent Document 2 discloses a magnesium alloy excellent in ductility in which the zinc content is greatly reduced as compared with Example 13. Table 2 shows a magnesium alloy containing 0.2 to 1.0% by weight of zinc, 0.4 to 1.4% by weight of silicon, and 0.2 to 0.4% by weight of manganese.
特許文献１では、実施例１３のマグネシウム合金に対して、１５０℃において引張試験を行い、高温での強度を評価している。しかしながら、マグネシウム合金の熱伝導率については全く触れられていない。また、特許文献２では、マグネシウム合金の延性を改善するために亜鉛の含有量を０．５〜１．３重量％とすることが記載されているが、高温での特性については評価されていない。つまり、高温で使用するマグネシウム合金に必要とされる熱伝導性および高温耐クリープ性、さらには延性を、十分なレベルで満足するマグネシウム合金は得られていないのが現状である。 In Patent Document 1, a tensile test is performed on the magnesium alloy of Example 13 at 150 ° C. to evaluate strength at high temperature. However, no mention is made of the thermal conductivity of the magnesium alloy. Patent Document 2 describes that the zinc content is 0.5 to 1.3% by weight in order to improve the ductility of the magnesium alloy, but the properties at high temperatures are not evaluated. . That is, the present situation is that a magnesium alloy satisfying a sufficient level of thermal conductivity, high temperature creep resistance, and ductility required for a magnesium alloy used at a high temperature has not been obtained.
本発明は、延性および耐クリープ性を両立する高熱伝導性マグネシウム合金を提供することを目的とする。 An object of the present invention is to provide a highly heat-conductive magnesium alloy having both ductility and creep resistance.
本発明の高熱伝導性マグネシウム合金は、全体を１００質量％としたときに（以下単に「％」という。）、
１．５％以上４．３％以下の亜鉛（Ｚｎ）と、
０．３％以上２％以下の珪素（Ｓｉ）と、
０．１％以上０．５％以下のマンガン（Ｍｎ）と、
残部がマグネシウム（Ｍｇ）と不可避不純物および／または改質元素とからなることを特徴とする。
The high thermal conductivity magnesium alloy of the present invention is 100% by mass as a whole (hereinafter simply referred to as “%”).
1.5% to 4.3% zinc (Zn);
0.3% or more and 2% or less of silicon (Si);
0.1% to 0.5% manganese (Mn);
The balance is made of magnesium (Mg) and inevitable impurities and / or modifying elements.
本発明者等は、Ｚｎ、ＳｉおよびＭｎを含むマグネシウム合金が、一般的なＡＺ９１Ｄよりも熱伝導性に優れることを新たに見出した。さらに、Ｚｎ含有量を上記の範囲とすることで、延性および耐クリープ性を両立する本発明のマグネシウム合金が得られることがわかった。Ｚｎを含まずＳｉを含むマグネシウム合金は、α−Ｍｇ結晶粒の粒界にＭｇ２Ｓｉが三次元網目状に晶出するが、このような構造は、耐クリープ性に有利に働かないことがわかった。そして、ＳｉとともにＺｎを含むマグネシウム合金は、粒状のＭｇ２Ｓｉが均一に分散する金属組織が得られやすいことがわかった。上記の範囲でＺｎを含む本発明のマグネシウム合金は、Ｚｎがマグネシウムのα相に固溶してマグネシウム合金が固溶強化されるとともに、Ｍｇ２Ｓｉが金属組織に均一に分散することで、マグネシウム合金の延性および耐クリープ性がともに高く維持される。 The present inventors have newly found that a magnesium alloy containing Zn, Si, and Mn has better thermal conductivity than general AZ91D. Furthermore, it turned out that the magnesium alloy of this invention which makes ductility and creep resistance compatible is obtained by making Zn content into said range. In a magnesium alloy that does not contain Zn but contains Si, Mg 2 Si crystallizes in a three-dimensional network at the grain boundaries of α-Mg crystal grains. However, such a structure may not work favorably in creep resistance. all right. Then, it was found that a magnesium alloy containing Zn together with Si can easily obtain a metal structure in which granular Mg 2 Si is uniformly dispersed. In the magnesium alloy of the present invention containing Zn within the above range, Zn is solid-solved in the α phase of magnesium, the magnesium alloy is solid-solution strengthened, and Mg 2 Si is uniformly dispersed in the metal structure. Both the ductility and creep resistance of the alloy are maintained high.
本発明のマグネシウム合金は、熱伝導性が高く、延性および耐クリープ性を両立する。 The magnesium alloy of the present invention has high thermal conductivity, and achieves both ductility and creep resistance.
以下に実施形態を挙げて本発明をより詳しく説明する。 Hereinafter, the present invention will be described in more detail with reference to embodiments.
本発明の高熱伝導性マグネシウム合金は、Ｚｎと、Ｓｉと、Ｍｎと、残部がマグネシウム（Ｍｇ）と不可避不純物および／または改質元素とからなる。 The high thermal conductivity magnesium alloy of the present invention is composed of Zn, Si, Mn, the balance being magnesium (Mg), unavoidable impurities and / or modifying elements.
Ｚｎは、α相に固溶して、マグネシウム合金の機械的強度を向上させる元素である。Ｚｎの含有量が多いと機械的強度および耐クリープ性は向上するが、１．５％以上とすることで十分な耐クリープ性を確保することができる。好ましいＺｎ含有量は、１．８％以上、１．９％以上、２．５％以上、２．７％以上、さらに好ましくは２．８％以上、特に好ましくは２．９％以上である。しかし、Ｚｎが過多であると、粗大なＭｇＺｎ２が晶出したり、Ｍｇ２Ｓｉを粗大化させたり、といった延性を低下させる要因となる。また、過剰なＺｎの添加は、熱伝導率を低下させる。そのため、Ｚｎ含有量は４．３％以下とする。好ましくは３．６％以下、３．４％以下、さらに好ましくは３．２％以下、特に好ましくは３．１％以下である。 Zn is an element that improves the mechanical strength of the magnesium alloy by dissolving in the α phase. When the Zn content is large, mechanical strength and creep resistance are improved, but by setting the content to 1.5% or more, sufficient creep resistance can be ensured. A preferable Zn content is 1.8% or more, 1.9% or more, 2.5% or more, 2.7% or more, more preferably 2.8% or more, and particularly preferably 2.9% or more. However, when Zn is excessive, coarse MgZn 2 is crystallized or Mg 2 Si is coarsened, which causes a reduction in ductility. Moreover, addition of excess Zn reduces thermal conductivity. Therefore, the Zn content is set to 4.3% or less. Preferably it is 3.6% or less, 3.4% or less, More preferably, it is 3.2% or less, Most preferably, it is 3.1% or less.
Ｓｉは、α−Ｍｇ結晶粒の粒界にＭｇ２Ｓｉとして晶出し、マグネシウム合金の機械的強度を向上させる元素である。Ｚｎを含有しないマグネシウム合金では、Ｍｇ２Ｓｉが三次元網目状に晶出するが、前述のとおり、本発明のマグネシウム合金では、ＳｉとともにＺｎが存在することで、粒界に晶出するＭｎ２Ｓｉは粒状に分断されて均一に分散される。このような金属組織を有する本発明のマグネシウム合金は、機械的強度を大きく低下させることなく、延性および耐クリープ性を十分に維持できると考えらえる。Ｍｇ２Ｓｉの晶出量を確保する観点から、Ｓｉ含有量は０．３％以上とする。好ましくは、０．４％以上さらに好ましくは０．５％以上である。しかし、Ｓｉが過多であると、Ｍｇ２Ｓｉが粗大な初晶として晶出して延性を低下させる。また、Ｓｉ量の増加とともに液相温度が上昇し、鋳造の際の湯流れが悪くなる。そのため、Ｓｉ含有量は２％以下とする。好ましくは、１．８％以下さらに好ましくは１．５％以下である。 Si is an element that crystallizes as Mg 2 Si at the grain boundary of α-Mg crystal grains and improves the mechanical strength of the magnesium alloy. In a magnesium alloy not containing Zn, Mg 2 Si crystallizes in a three-dimensional network, but as described above, in the magnesium alloy of the present invention, Mn 2 crystallizes at grain boundaries due to the presence of Zn together with Si. Si is divided into particles and uniformly dispersed. It can be considered that the magnesium alloy of the present invention having such a metal structure can sufficiently maintain ductility and creep resistance without greatly reducing the mechanical strength. From the viewpoint of securing the crystallization amount of Mg 2 Si, the Si content is set to 0.3% or more. Preferably, it is 0.4% or more, more preferably 0.5% or more. However, if Si is excessive, Mg 2 Si is crystallized as a coarse primary crystal and the ductility is lowered. In addition, the liquidus temperature rises as the Si amount increases, and the hot water flow during casting deteriorates. Therefore, the Si content is 2% or less. Preferably, it is 1.8% or less, more preferably 1.5% or less.
Ｍｎは、Ｚｎと同様にα相に固溶して、マグネシウム合金の機械的強度を向上させる元素である。そのため、Ｍｎは、高い熱伝導性および高い延性を維持するために添加を抑制したＺｎ量を補う役割を果たす。しかし、Ｍｎが過多であると、粒界に粗大な塊状の化合物が晶出して延性が低下する。そのため、望ましいＭｎ含有量は０．１％以上０．５％以下である。 Mn is an element that improves the mechanical strength of the magnesium alloy by being dissolved in the α phase in the same manner as Zn. Therefore, Mn plays a role of supplementing the Zn content that is suppressed from being added in order to maintain high thermal conductivity and high ductility. However, when Mn is excessive, a coarse massive compound crystallizes at the grain boundary and the ductility is lowered. Therefore, the desirable Mn content is 0.1% or more and 0.5% or less.
本発明のマグネシウム合金に含まれる不可避不純物としては、たとえば、Ａｌ、Ｆｅ、Ｎｉ、Ｃｕ、Ｃｌ、Ｃａ、Ｋ、Ｂｅ等が挙げられる。これらの各不可避不純物は、０．０２％以下さらには０．０１％以下とするのが好ましい。 Examples of the inevitable impurities contained in the magnesium alloy of the present invention include Al, Fe, Ni, Cu, Cl, Ca, K, and Be. Each of these inevitable impurities is preferably 0.02% or less, more preferably 0.01% or less.
また、本発明のマグネシウム合金は、金属組織、耐酸化性、耐腐食性、電気的特性等、種々の特性を改善するための改質元素を添加してもよい。つまり、本発明のマグネシウム合金に対して、公知の改質元素の添加を妨げるものではない。改質元素としては、たとえば、Ｓｒ、Ｙ、Ｚｒ等が挙げられる。これら各元素の含有量は、マグネシウム合金に要求される特性によって適宜調整される。コストや基本組成への影響等の観点から、改質元素は含有総量で１％以下、０．８％以下さらには０．６％以下程度が好ましい。 In addition, the magnesium alloy of the present invention may contain modifying elements for improving various characteristics such as metal structure, oxidation resistance, corrosion resistance, and electrical characteristics. That is, it does not prevent the addition of a known modifying element to the magnesium alloy of the present invention. Examples of the modifying element include Sr, Y, Zr, and the like. The content of each of these elements is appropriately adjusted according to the characteristics required for the magnesium alloy. From the viewpoint of cost, influence on the basic composition, etc., the total content of the modifying element is preferably 1% or less, 0.8% or less, more preferably about 0.6% or less.
本発明のマグネシウム合金は、高熱伝導性であって、延性および耐クリープ性を両立する。具体的に規定するのであれば、本発明のマグネシウム合金の熱伝導率は、１００Ｗ／ｍＫ以上さらには１２０Ｗ／ｍＫ以上であるとよい。延性は、伸びが５．５％以上、６．０％以上さらには６．５％以上であるとよい。なお、熱伝導率の測定にはレーザフラッシュ法、伸びの測定にはＪＩＳに規定の引張試験、を行うとよい。また、耐クリープ性は、後述の方法により算出される応力保持率が５５％以上さらには６０％以上であるとよい。 The magnesium alloy of the present invention has high thermal conductivity, and achieves both ductility and creep resistance. If specifically defined, the thermal conductivity of the magnesium alloy of the present invention is preferably 100 W / mK or more, more preferably 120 W / mK or more. As for the ductility, the elongation is preferably 5.5% or more, 6.0% or more, and more preferably 6.5% or more. In addition, it is good to perform the laser flash method for the measurement of thermal conductivity and the tensile test prescribed in JIS for the measurement of elongation. The creep resistance is preferably 55% or more, more preferably 60% or more, with a stress retention calculated by a method described later.
マグネシウム合金は、上述した組成を有するものであれば、溶製材でも焼結材でもよい。溶製または焼結中のマグネシウム合金の酸化を防止するために、酸化防止雰囲気さらには真空雰囲気で鋳造または焼結されてもよい。また、マグネシウム合金を鋳造する場合、その冷却速度に特に限定はなく、たとえば、大気中で徐冷するとよい。また、砂型、金型のいずれを使用して鋳造を行ってもよい。 The magnesium alloy may be a melted material or a sintered material as long as it has the above-described composition. In order to prevent oxidation of the magnesium alloy during melting or sintering, the magnesium alloy may be cast or sintered in an antioxidant atmosphere or a vacuum atmosphere. Moreover, when casting a magnesium alloy, there is no limitation in particular in the cooling rate, For example, it is good to anneal slowly in air | atmosphere. Moreover, you may cast using either a sand mold or a metal mold | die.
本発明のマグネシウム合金は、熱伝導性が高く、延性および耐クリープ性に優れることから、高温下で使用される部材に好適である。具体的には、自動車エンジン用シリンダブロック、ベッドプレート、オイルパン、コンプレッサ用ハウジング、シリンダ等が挙げられる。なお、本発明のマグネシウム合金を使用する温度領域に特に限定はなく、０〜２００℃程度であれば、その特性を良好に発揮する。また、高温下とは、８０〜２００℃さらには１００〜２００℃程度を想定している。 The magnesium alloy of the present invention has high thermal conductivity and is excellent in ductility and creep resistance. Therefore, the magnesium alloy is suitable for members used at high temperatures. Specific examples include a cylinder block for an automobile engine, a bed plate, an oil pan, a compressor housing, a cylinder, and the like. In addition, there is no limitation in particular in the temperature range which uses the magnesium alloy of this invention, If it is about 0-200 degreeC, the characteristic will be exhibited favorably. Moreover, under high temperature, 80-200 degreeC and also about 100-200 degreeC are assumed.
以上、本発明の実施形態を説明したが、本発明は、上記実施形態に限定されるものではない。本発明の要旨を逸脱しない範囲において、当業者が行い得る変更、改良等を施した種々の形態にて実施することができる。 As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment. The present invention can be implemented in various forms without departing from the gist of the present invention, with modifications and improvements that can be made by those skilled in the art.
実施例を挙げて本発明をより具体的に説明する。 The present invention will be described more specifically with reference to examples.
マグネシウム合金中の合金元素の含有量を変更した試験片を複数製作し、それらの特性の評価および金属組織の観察を行った。 A plurality of test pieces having different alloy element contents in the magnesium alloy were manufactured, their characteristics were evaluated, and the metal structure was observed.
〔試験片＃０１〜＃０８、＃１１、＃１２、＃２１および＃２２の作製〕
電気炉中で予熱した鉄製るつぼの内面に塩化物系のフラックスを塗布し、その中に秤量した純マグネシウム地金、純Ｓｉおよび純Ｍｎ、必要に応じて純Ｚｎを投入して７５０℃で溶解した。この溶湯を十分に攪拌し、原料を完全に溶解させた後、７００℃でしばらく沈静保持した。こうして得た各種の合金溶湯を所定の形状の鉄製鋳型に流し込み、大気中で空冷して凝固させて、各試験片（マグネシウム合金鋳物）を鋳造した。なお、得られた試験片は、２０ｍｍ×３０ｍｍ×２００ｍｍであった。
[Production of test pieces # 01 to # 08, # 11, # 12, # 21 and # 22]
Apply a chloride flux to the inner surface of an iron crucible preheated in an electric furnace, and weigh in pure magnesium ingot, pure Si and pure Mn, and if necessary, add pure Zn and melt at 750 ° C did. The molten metal was sufficiently stirred to completely dissolve the raw material, and then kept calm at 700 ° C. for a while. The various alloy melts thus obtained were poured into iron molds of a predetermined shape, air-cooled in the atmosphere and solidified, and each test piece (magnesium alloy casting) was cast. In addition, the obtained test piece was 20 mm x 30 mm x 200 mm.
各試験片の化学組成を表１に示した。表１の「分析組成」は、蛍光Ｘ線（ＸＲＦ）分析による元素分析により測定した。 The chemical composition of each test piece is shown in Table 1. “Analytical composition” in Table 1 was measured by elemental analysis by X-ray fluorescence (XRF) analysis.
〔熱伝導率の測定〕
上記の手順で作製した各試験片に加え、市販のＡＺ９１Ｄから作製した同様の試験片について、レーザフラッシュ法により熱伝導率を求めた。試験結果を表１および図１に示した。
(Measurement of thermal conductivity)
In addition to each test piece produced by the above procedure, thermal conductivity was determined by a laser flash method for the same test piece produced from commercially available AZ91D. The test results are shown in Table 1 and FIG.
〔応力緩和試験〕
表１に示した各試験片について、応力緩和試験を行い、マグネシウム合金の耐クリープ性を調べた。応力緩和試験は、試験片に試験時間中、所定の変形量まで荷重を加えたときの応力が、時間とともに減少する過程を測定した。具体的には、１５０℃の大気雰囲気中において、試験片に１００ＭＰａの圧縮応力を負荷し、そのときの試験片の変位が一定に保たれるように、時間の経過に併せてその圧縮応力を低下させていった。試験開始から４０時間後の圧縮応力の値を、初期の値に対する割合（応力保持率）として表１および図２に示した。
[Stress relaxation test]
About each test piece shown in Table 1, the stress relaxation test was done and the creep resistance of the magnesium alloy was investigated. In the stress relaxation test, a process in which the stress when a load was applied to a test piece up to a predetermined deformation amount during the test time decreased with time was measured. Specifically, in an air atmosphere at 150 ° C., a compressive stress of 100 MPa is applied to the test piece, and the compressive stress is adjusted with the passage of time so that the displacement of the test piece is kept constant. It was lowered. The compressive stress values after 40 hours from the start of the test are shown in Table 1 and FIG.
〔引張り試験〕
表１に示した各試験片からＪＩＳＺ２２０１の１４号引張試験片を作製し、ＪＩＳＺ２２４１の引張試験を室温にて行い、引張強さ、伸び、０．２％耐力およびヤング率を求めた。結果を表１に示した。また、Ｚｎ含有量に対する引張強さを図３に、伸びを図４に、０．２％耐力を図５に、それぞれ示した。
[Tensile test]
A No. 14 tensile test piece of JISZ2201 was prepared from each test piece shown in Table 1, and a tensile test of JISZ2241 was performed at room temperature to determine tensile strength, elongation, 0.2% proof stress and Young's modulus. The results are shown in Table 1. Further, FIG. 3 shows the tensile strength with respect to the Zn content, FIG. 4 shows the elongation, and FIG. 5 shows the 0.2% proof stress.
〔ビッカース硬さ測定〕
表１に示した各試験片について、ビッカース硬さ測定を行った。ビッカース硬さ測定は、試験片中央部の断面に対して、ビッカース硬さ計を用いて測定荷重１０ｋｇｆで室温にて行った。測定結果を表１および図６に示した。
[Vickers hardness measurement]
Each test piece shown in Table 1 was measured for Vickers hardness. The Vickers hardness measurement was performed at room temperature with a measurement load of 10 kgf using a Vickers hardness tester on the cross section of the central part of the test piece. The measurement results are shown in Table 1 and FIG.
また、図１〜図６のグラフに示したＡＺ９１Ｄの熱伝導率等は、比較のための参考値であって、Ｚｎ量に依存する値ではない。 Moreover, the thermal conductivity and the like of AZ91D shown in the graphs of FIGS. 1 to 6 are reference values for comparison, and are not values depending on the amount of Zn.
〔金属組織の観察〕
表１に示した試験片のうち、Ｚｎ含有量の異なる＃０１〜＃０８、＃２１および＃２２の金属組織を観察した。各試験片から切り出された断面からＥＰＭＡ（エレクトロンプローブマイクロアナライザ）の反射電子像（組成像）を得た。また、同じ表面を、ＥＰＭＡにより面分析した。観察結果を図７〜図２０に示した。
[Observation of metal structure]
Among the test pieces shown in Table 1, metal structures of # 01 to # 08, # 21 and # 22 having different Zn contents were observed. A reflected electron image (composition image) of EPMA (electron probe microanalyzer) was obtained from the cross section cut out from each test piece. The same surface was analyzed by EPMA. The observation results are shown in FIGS.
〔鋳放し材の測定結果について〕
熱伝導性は、いずれの試験片もＡＺ９１Ｄよりも優れた（図１）。しかし、Ｚｎ含有量が増加するにしたがい熱伝導率は徐々に低下し、図示していないが、Ｚｎ含有量が１２％になるとＡＺ９１Ｄに近づく。つまり、熱伝導性の観点からは、Ｚｎの含有量は、少ないほうが好ましいと言える。また、同程度の量のＺｎを含む場合には、Ｓｉ量の差は熱伝導率の値に影響しないことがわかった。
[Measurement results of as-cast material]
All the test pieces were superior to AZ91D in thermal conductivity (FIG. 1). However, as the Zn content increases, the thermal conductivity gradually decreases and is not shown, but approaches AZ91D when the Zn content reaches 12%. That is, from the viewpoint of thermal conductivity, it can be said that the smaller the Zn content, the better. It was also found that the difference in the amount of Si did not affect the value of thermal conductivity when the same amount of Zn was included.
応力保持率は、Ｚｎ含有量が多いほど高くなる傾向にあった（図２）。特に、Ｚｎ含有量が１．４％以下の＃０１および＃０２では、４０時間後の応力が初期の応力の半分程度であった。耐クリープ性の観点からは、Ｚｎ含有量が１．５％以上必要であることがわかった。なお、６０％以上の応力保持率を安定しているためには、Ｚｎ含有量を１．８〜３．２％さらには１．９〜３．１％とするのが好ましいことがわかった。また、同程度の量のＺｎを含む場合には、Ｓｉ量の差は耐クリープ性に影響しないことがわかった。 The stress retention rate tended to increase as the Zn content increased (FIG. 2). In particular, in # 01 and # 02 having a Zn content of 1.4% or less, the stress after 40 hours was about half of the initial stress. From the viewpoint of creep resistance, it was found that the Zn content is required to be 1.5% or more. In addition, in order to stabilize the stress retention of 60% or more, it was found that the Zn content is preferably 1.8 to 3.2%, more preferably 1.9 to 3.1%. It was also found that the difference in Si amount did not affect the creep resistance when the same amount of Zn was included.
引張強さおよび伸びは、Ｓｉ含有量が３％を越えると極端に低下することがわかった。しかし、Ｓｉ含有量を適切な量とすることで、引張強さおよび伸びは、Ｚｎ含有量が３％付近で最も優れ、Ｚｎ含有量が過少でも過多でも低下する傾向があった（図３および図４）。Ｚｎ量が４．６％の＃０７の伸びは、延性に乏しいＡＺ９１Ｄと同等であった。さらに、Ｚｎ量が６．０％である＃０８は、引張強さも伸びも大きく低下した。Ｚｎ含有量を２．８〜３．２％さらには２．９〜３．１％とすることで、高い延性を示すことがわかった。 It was found that the tensile strength and elongation are extremely lowered when the Si content exceeds 3%. However, by setting the Si content to an appropriate amount, the tensile strength and the elongation were most excellent when the Zn content was around 3%, and there was a tendency to decrease when the Zn content was too low or too high (FIG. 3 and FIG. 3). FIG. 4). The elongation of # 07 with a Zn content of 4.6% was equivalent to AZ91D with poor ductility. Furthermore, # 08 with Zn content of 6.0% greatly decreased both the tensile strength and the elongation. It was found that high ductility was exhibited by setting the Zn content to 2.8 to 3.2%, and further 2.9 to 3.1%.
図７および図８は、耐クリープ性が不十分である＃０１のＥＰＭＡ反射電子像（組成像）および面分析結果である。図７および図８より、α−Ｍｇ結晶粒の粒界にＭｇ２Ｓｉが晶出していることがわかった。この構造は、図２のグラフから、耐クリープ性の向上には寄与しないことがわかった。また、＃０１はＺｎを含まないため十分に固溶強化されず、引張強さの値は低かった（図３）。＃０２のようにＺｎを少量添加しても、固溶強化による引張強さの向上は見られたものの、図９および図１０には＃０１に見られた連続的な網目構造は観察されなかったため、耐クリープ性はさらに悪化したと推測される。＃０２よりもＺｎ量が多い＃０３〜０６では、網目構造が細かく分断されて粒状のＭｇ２Ｓｉが均一に分散している様子が観察された（図９〜図１５）。細かいＭｇ２Ｓｉが均一に分散した＃０３〜０６は、耐クリープ性および延性を両立し、引張強さも高かった。さらにＺｎ量が多い＃０７および＃０８では、網目構造が分断されて分散している様子が観察されたが、大きな塊状であった（図１６および図１８）。ＥＰＭＡより、これらの塊は、Ｍｇ２ＳｉおよびＭｇＺｎ２であることがわかった（図１７）。＃２１および＃２２は、Ｚｎ含有量およびＭｎ含有量は同じであるが、Ｓｉ含有量が異なる。Ｓｉ含有量の少ない＃２１では、粗大なＭｇ２Ｓｉ粒の形成が抑制され、耐クリープ性も延性も良好であったと考えられる。一方、過剰にＳｉを含む＃２２は、粗大なＭｇ２Ｓｉが形成され、延性が極端に低下したと考えられる。 FIG. 7 and FIG. 8 show the EPMA backscattered electron image (composition image) and surface analysis results of # 01 with insufficient creep resistance. 7 and 8, it was found that Mg 2 Si was crystallized at the grain boundaries of the α-Mg crystal grains. From the graph of FIG. 2, it was found that this structure does not contribute to the improvement of creep resistance. Moreover, # 01 did not contain Zn, so it was not sufficiently solid solution strengthened, and the tensile strength value was low (FIG. 3). Even when a small amount of Zn was added as in # 02, the tensile strength was improved by solid solution strengthening, but the continuous network structure observed in # 01 was not observed in FIGS. Therefore, it is estimated that the creep resistance was further deteriorated. In # 03 to 06, where the amount of Zn was larger than # 02, it was observed that the network structure was finely divided and the particulate Mg 2 Si was uniformly dispersed (FIGS. 9 to 15). # 03 to 06, in which fine Mg 2 Si was uniformly dispersed, had both creep resistance and ductility and high tensile strength. Further, in # 07 and # 08 having a large amount of Zn, it was observed that the network structure was divided and dispersed, but it was a large lump (FIGS. 16 and 18). EPMA revealed that these lumps were Mg 2 Si and MgZn 2 (FIG. 17). # 21 and # 22 have the same Zn content and Mn content, but different Si contents. In # 21 having a small Si content, it is considered that the formation of coarse Mg 2 Si particles was suppressed, and the creep resistance and ductility were good. On the other hand, # 22 containing excessive Si is considered that coarse Mg 2 Si was formed and the ductility was extremely lowered.
また、いずれの試験片も、ＡＺ９１Ｄに近い耐力と硬さを示した。 Moreover, any test piece showed the yield strength and hardness close | similar to AZ91D.
組成によっては、Ｔ５の熱処理をすることで、機械的強度が向上することがわかった。特に＃０６は、Ｔ５熱処理の影響が顕著に表れ、熱処理後の引張強さおよび硬さが向上することがわかった。 It was found that depending on the composition, the mechanical strength is improved by heat treatment of T5. In particular, in # 06, the influence of the T5 heat treatment appeared remarkably, and it was found that the tensile strength and hardness after the heat treatment were improved.
Claims (5)
１．５％以上４．３％以下の亜鉛（Ｚｎ）と、
０．３％以上２％以下の珪素（Ｓｉ）と、
０．１％以上０．５％以下のマンガン（Ｍｎ）と、
残部がマグネシウム（Ｍｇ）と不可避不純物とからなることを特徴とする高熱伝導性マグネシウム合金。 When the total is 100% by mass (hereinafter simply referred to as “%”),
1.5% to 4.3% zinc (Zn);
0.3% or more and 2% or less of silicon (Si);
0.1% to 0.5% manganese (Mn);
High thermal conductivity magnesium alloy, characterized in that the balance of magnesium and (Mg) and inevitable impurities.
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