JP5288717B2 - Wear-resistant magnesium alloy - Google Patents
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Description
本発明は、マグネシウム母相中に金属間化合物結晶体が分散されてなる低摩擦性マグネシウム合金に関する。 The present invention relates to a low-friction magnesium alloy in which intermetallic compound crystals are dispersed in a magnesium matrix.
今日、地球環境問題はますます深刻になってきている。20世紀の大量生産・大量消費を見直し、21世紀はライフサイクル全体を通して環境への影響を最小にする「持続可能な社会」の構築が緊要の課題となっている。2005年2月16日に発効した京都議定書によれば、二酸化炭素をはじめとする温暖化効果ガス削減目標を各国別に規定している。日本は、1990年基準で2008年〜2012年の間に−6%の削減率が求められている。日本においては、全二酸化炭素排出量のうち20%が自動車の排気によるものであり、自動車の軽量化による大幅な燃費向上が要求課題となっている。 Today, global environmental problems are becoming increasingly serious. Reviewing mass production and mass consumption in the 20th century, and building a “sustainable society” that minimizes environmental impact throughout the life cycle is an urgent issue in the 21st century. According to the Kyoto Protocol, which came into effect on February 16, 2005, global warming effect gas reduction targets including carbon dioxide are stipulated for each country. In Japan, a reduction rate of -6% is required between 2008 and 2012 based on the 1990 standard. In Japan, 20% of the total carbon dioxide emissions are due to automobile exhaust, and a significant improvement in fuel efficiency due to weight reduction of automobiles has become a required issue.
一方マグネシウムは実用金属中で最軽量の物質であり、比重は鉄の約1/4,アルミニウムの約2/3であることから、軽量化材として魅力的な材料である。また、マグネシウムは鉄やアルミニウムと比較して比強度、比剛性、比耐力に優れ、振動吸収性、耐くぼみ性および切削性も良好等、多くの特長を有している。さらには、リサイクルエネルギーが生産エネルギーの約4〜5%程度に抑えられることからもここ数年で使用量が急速に増加しており、自動車産業において省エネルギーに大きく貢献するものと期待されている。
現在、マグネシウム合金は自動車部品として、ステアリング部品、エンジンヘッドカバーおよびシートフレームなど構造材料分野への適用がなされている。更なる燃費改善のため、シリンダやピストンといったエンジン部材といった劣悪な環境下への適用が望まれている。摺動部に適用するためには、耐摩耗性および耐熱性を改善することが要求課題となる。
Magnesium, on the other hand, is the lightest material among practical metals and has a specific gravity of about 1/4 of iron and about 2/3 of aluminum, and is therefore an attractive material for weight reduction. Magnesium has many features such as excellent specific strength, specific rigidity, and specific strength compared to iron and aluminum, and good vibration absorption, dent resistance, and machinability. Furthermore, since the amount of recycled energy is limited to about 4 to 5% of the production energy, the amount used has increased rapidly in recent years, and it is expected to contribute greatly to energy saving in the automobile industry.
Currently, magnesium alloys are used as automotive parts in the structural material field such as steering parts, engine head covers and seat frames. In order to further improve fuel consumption, application to a poor environment such as an engine member such as a cylinder or a piston is desired. In order to apply to a sliding part, it is a required subject to improve wear resistance and heat resistance.
過去の研究において、松岡らはZK60合金の結晶粒径を粗大化させることで耐摩耗性が改善されたと報告している(非特許文献1)。吉岡らは、AZ31,AZ61およびAZ91合金を用いて、溶体化処理および人工時効が耐摩耗性に及ぼす影響について検討した結果を報告している。その結果、アルミニウム濃度を増加させることにより低摩擦を示し、溶体化処理材の耐摩耗性はアルミニウム濃度にほとんど依存しないと報告している(非特許文献2)。 In past research, Matsuoka et al. Reported that wear resistance was improved by increasing the crystal grain size of ZK60 alloy (Non-patent Document 1). Yoshioka et al. Reported the results of examining the effects of solution treatment and artificial aging on wear resistance using AZ31, AZ61 and AZ91 alloys. As a result, by increasing the aluminum concentration, low friction is exhibited, and it has been reported that the wear resistance of the solution-treated material hardly depends on the aluminum concentration (Non-patent Document 2).
村田らは時効処理温度によるAZ91合金の析出形態の最適化により、低摩擦および耐摩耗性は改善されると報告している(非特許文献3)。しかし、これら既存のマグネシウム合金の耐摩耗性は実用上不十分であり、さらなる耐摩耗性の改善が必要である。また商業用ベースであることを考慮すれば、耐摩耗性を有したマグネシウム合金の開発が不可欠であると言える。 Murata et al. Have reported that low friction and wear resistance are improved by optimizing the precipitation form of the AZ91 alloy according to the aging temperature (Non-patent Document 3). However, the wear resistance of these existing magnesium alloys is insufficient in practice, and further improvement of the wear resistance is necessary. Considering that it is a commercial base, it can be said that it is indispensable to develop a magnesium alloy having wear resistance.
さらに、摺動部に適用するためには耐熱性を有することも要求される。現在、高温時の耐クリープ性の問題から、マグネシウム合金をエンジンまわりなど高温にさらされる部位への適用は限定されている。
近年、耐熱性マグネシウム合金の開発において、コストパフォーマンスおよびダイカスト性の観点から、銅およびケイ素等を添加することで耐熱性を向上させる研究が行われている(非特許文献4、5)。これらの元素添加により構成されるマグネシウム合金の組織は、AZ91合金の析出相であるMg17Al12の融点と比較して高融点な金属間化合物(非特許文献6)がデンドライト状に形成される(非特許文献7〜8)ことが知られている。
Furthermore, in order to apply to a sliding part, it is also required to have heat resistance. Currently, due to the problem of creep resistance at high temperatures, the application of magnesium alloys to parts exposed to high temperatures such as around engines is limited.
In recent years, in the development of heat-resistant magnesium alloys, studies have been made to improve heat resistance by adding copper, silicon and the like from the viewpoint of cost performance and die-casting properties (Non-Patent Documents 4 and 5). In the structure of the magnesium alloy formed by the addition of these elements, an intermetallic compound (Non-patent Document 6) having a higher melting point than the melting point of Mg 17 Al 12 which is a precipitation phase of the AZ91 alloy is formed in a dendrite shape. (Non-Patent Documents 7 to 8) are known.
耐熱性と摩擦・摩耗特性との関連性も加藤ら(非特許文献9)および松岡ら(非特許文献1)によって指摘されている。一般に、摩耗挙動を支配する重要な因子として摩耗面間での温度上昇が知られている。これらの報告例では、摩耗面温度が上昇するに従い、摩耗表面における母材強度も低下し始める。それに伴い、摩耗形態はアブレシブ摩耗から凝着摩耗へ移行すると報告されている。上記の報告から、高温時においても十分な強度を有する耐熱性マグネシウム合金を用いれば、低摩擦および耐摩耗性の改善に貢献するものと期待される。さらに、高融点金属間化合物の分散形態を制御することによって、マグネシウム合金における耐摩耗性の改善が期待される。
しかし、実用上十分な耐摩耗性を有するものについては未だほ報告されていない。
However, there has not been reported yet what has practically sufficient wear resistance.
本発明は、このような実情に鑑み、高温時でも耐摩耗性を十分に維持できる低摩擦性マグネシウム合金を提供することを目的とする。 In view of such circumstances, an object of the present invention is to provide a low-friction magnesium alloy that can sufficiently maintain wear resistance even at high temperatures.
発明1の低摩擦性マグネシウム合金は、Mg−Cu、Mg−Zn−Cu、Mg−Si又はMg−Zn−Siよりなり、前記金属間化合物結晶体が球若しくは楕円のように鋭角な角を持たない微粒子状であり、前記金属間化合物結晶体の平均直径が1〜20μmであり、前記母相の473Kにおける降伏強度が85MPa以上であり、前記母相中に針状のβ相が析出されてなり、かつ時効材又は過時効材であることを特徴とする。 The low friction magnesium alloy of the invention 1 is made of Mg—Cu, Mg—Zn—Cu, Mg—Si, or Mg—Zn—Si, and the intermetallic compound crystal has an acute angle like a sphere or an ellipse. And the average diameter of the intermetallic compound crystal is 1 to 20 μm, the yield strength of the parent phase at 473 K is 85 MPa or more, and a needle-like β phase is precipitated in the parent phase. And is an aging material or an overaging material.
発明2は、発明1の低摩擦性マグネシウム合金において、前記母相の473Kにおける降伏強度が90MPa以上であることを特徴とする。 Invention 2 is characterized in that in the low friction magnesium alloy of Invention 1, the yield strength at 473 K of the parent phase is 90 MPa or more .
本発明により、摩擦時の表面破壊が押さえられて、従来に比べ摩耗率を低減することができ、今までには期待できなかった耐摩耗性を有するに至った。
この原因は、金属間化合物結晶体の形状が、母相との界面での集中応力を抑えるような形状にしたから、及び鋭利な角部により相手材を損傷することが抑えられたからと考えられる。
According to the present invention , surface destruction during friction can be suppressed, the wear rate can be reduced as compared with the prior art, and the wear resistance that has not been expected so far has been achieved.
This is thought to be because the shape of the intermetallic compound crystal is such that the concentrated stress at the interface with the matrix phase is suppressed, and damage to the mating material due to sharp corners is suppressed. .
また、上記のような応力分散作用を母相全体に及ぼすことができ、全体として破壊を少なくすることが出来た。 In addition, the stress dispersion action as described above can be exerted on the entire matrix phase, and the fracture can be reduced as a whole.
また、高温時でも高い降伏強度を母相に持たせることで、耐摩耗性を高温時でも発揮でき、実用上要求されていた高温時での低摩擦性を有することができた。 In addition, by providing the matrix with a high yield strength even at high temperatures , the wear resistance can be exhibited even at high temperatures, and the low friction properties at high temperatures required for practical use can be achieved.
さらに、母相を組織的にも強固にして、耐摩耗性を向上すると共に、耐摩擦性を確保するに至った。 Furthermore, the matrix was strengthened systematically to improve wear resistance and to ensure friction resistance.
溶体化処理
合金中に存在する金属間化合物を母材中に過飽和に固溶化させ、化合物の均質化を図るため、溶体化処理を施した。各材料における処理温度および保持時間については実施例に示すとおりである。酸化や燃焼を防ぐため、炭酸ガス雰囲気中にて溶体化処理を行った。
Solution treatment In order to solidify the intermetallic compound present in the alloy into a super-saturated solution in the base material and to homogenize the compound, a solution treatment was performed. The processing temperature and holding time for each material are as shown in the examples. In order to prevent oxidation and combustion, solution treatment was performed in a carbon dioxide atmosphere.
人工時効処理
固溶度が温度の低下とともに減少する場合は、溶体化処理によって得られた過飽和固溶状態を解消するため時効析出が起こる。時効析出過程および析出組織は合金系や時効温度、合金組成、および成型方法等によって変化する。そのため、溶体化処理を施した各試験片における時効処理条件について検討する必要がある。処理温度を150℃、175℃および200℃の3条件とし、保持温度を10分、1時間、2時間、6時間、24時間および48時間の6条件に設定した。ただし、時効曲線の極大値が見られた場合、時効時間はそれまでとした。空気循環炉を用いて時効処理を実施した後、空冷した。
Artificial aging treatment When the solid solubility decreases with decreasing temperature, aging precipitation occurs to eliminate the supersaturated solid solution state obtained by solution treatment. The aging precipitation process and the precipitation structure vary depending on the alloy system, the aging temperature, the alloy composition, the molding method, and the like. Therefore, it is necessary to examine aging treatment conditions for each test piece subjected to solution treatment. The treatment temperature was set to three conditions of 150 ° C., 175 ° C., and 200 ° C., and the holding temperature was set to six conditions of 10 minutes, 1 hour, 2 hours, 6 hours, 24 hours, and 48 hours. However, when the maximum value of the aging curve was observed, the aging time was set to that. After performing an aging treatment using an air circulation furnace, it was air-cooled.
晶出物の形態
鋳造まま材(As−cast材)および前記溶体化処理を施した各マグネシウム合金に対する組織観察を行うため、試験片をバフ研磨した。
その後、光学顕微鏡((株)ニコン;ECLIPSE LV150)により組織観察を行った。
Form of crystallized material In order to observe the structure of the as-cast material (As-cast material) and each magnesium alloy subjected to the solution treatment, the test piece was buffed.
Thereafter, the structure was observed with an optical microscope (Nikon Corp .; ECLIPSE LV150).
時効硬化挙動の検証
前記溶体化処理後、前記人工時効処理を施したときの各温度における時効硬化曲線を図1に示す。
Verification of age hardening behavior FIG. 1 shows age hardening curves at various temperatures when the artificial aging treatment is performed after the solution treatment.
硬さ試験
摩耗面の硬さは摩擦・摩耗特性に大きく影響を及ぼす。
そこでビッカース微小硬度計((株)アカシ(現(株)Mitutoyo);MVK−H2)を用いて、摩擦・摩耗試験前の試験片摩耗面の硬度について検討した。圧子には頂角136°のダイヤモンド正四角錘を用い、室温環境の下100gfで15秒間押しつけた。硬さはビッカース硬さとし、各試験片について底辺からの距離が一定の範囲で、10箇所を無作為に選んで測定し、最大値および最小値を除去した8点の平均値を採用した。
Hardness test The hardness of the worn surface has a significant effect on the friction and wear characteristics.
Therefore, the hardness of the specimen wear surface before the friction / wear test was examined using a Vickers micro hardness tester (Akashi Co., Ltd. (currently Mitutoyo Co., Ltd .; MVK-H2)). A diamond regular square pyramid having a vertex angle of 136 ° was used as the indenter, and it was pressed at 100 gf for 15 seconds in a room temperature environment. The hardness was Vickers hardness, and each test piece was measured by randomly selecting 10 points within a certain distance from the bottom, and adopting an average value of 8 points from which the maximum and minimum values were removed.
高温圧縮試験
本発明で用いる試験片の高温強度について検討するため、高温圧縮試験を実施した。Pin−on−desk型摩擦・摩耗試験の荷重作用環境に近いものとするため、圧縮試験とした。
また、摩耗面温度は150〜200℃程度に達するため、150℃および200℃にて高温圧縮試験を実施した。
比較のため、室温(25℃)環境下における圧縮試験も行った。高温圧縮試験にはインストロン材料試験機5567型、室温圧縮試験には同5569型により圧縮試験を実施した。試験片形状は直径6mm×高さ9mmの円柱型試験片とし、ひずみ速度10−3sec−1の条件下で試験した。
High temperature compression test In order to examine the high temperature strength of the test piece used in the present invention, a high temperature compression test was conducted. In order to make it close to the load acting environment of the Pin-on-desk type friction / wear test, the compression test was used.
Moreover, since the wear surface temperature reached about 150 to 200 ° C., a high temperature compression test was performed at 150 ° C. and 200 ° C.
For comparison, a compression test in a room temperature (25 ° C.) environment was also performed. The compression test was conducted with an Instron material tester 5567 type for the high temperature compression test and the 5569 type for the room temperature compression test. The shape of the test piece was a cylindrical test piece having a diameter of 6 mm and a height of 9 mm, and the test was performed under a strain rate of 10 −3 sec −1 .
摩擦・摩耗試験
試験片寸法および表面粗さ
摩擦・摩耗試験を実施するため、試験片を直径4mm×長さ12mmの円筒ピン形状に加工した。摩擦・摩耗試験時の接触面表面は、#400−600の耐水研磨紙を取り付けた研磨機(ビューラー;エコメット研磨機3型)を用いて、端面が水平になるように研磨し、表面計測装置((株)Mitutoyo;SURFTEST SV−400)を用いて、算術平均粗さがRa=0.40〜0.60μmとなるように調節した。摩擦・摩耗試験開始直後から終了時まで常に一定の接触面積を得るため、エッジ部に面取りは施さなかった。
Friction / Abrasion Test Specimen Dimensions and Surface Roughness To conduct the friction / abrasion test, the test piece was processed into a cylindrical pin shape having a diameter of 4 mm and a length of 12 mm. The surface of the contact surface during the friction / abrasion test is polished by using a polishing machine (Buhler; Ecomet polishing machine type 3) with water resistant abrasive paper of # 400-600, and a surface measuring device. (Mitutoyo; SURFTEST SV-400) was used to adjust the arithmetic average roughness to Ra = 0.40-0.60 μm. In order to always obtain a constant contact area from immediately after the start of the friction / wear test to the end, the edge portion was not chamfered.
相手材の選定
摩擦・摩耗試験のディスク相手材には一般性を考慮し、汎用的な軸受鋼の一つであり良好なすべり特性が得られる高炭素クロム軸受鋼(以下、SUJ2もしくは相手材)を選択した。
SUJ2には無酸化ズブ焼入れ焼戻し処理を施した。寸法形状は、直径60mm×厚さ14mmのディスク型とし、ビッカース硬さはHV=720のものを用いた。摩擦・摩耗試験時における試験片との接触面は、#240−400の耐水研磨紙を取り付けた研磨機(ビューラー;エコメット研磨機3型)を用いて研磨し、表面計測装置((株)Mitutoyo;SURFTEST SV−400)を用いて、算術平均粗さがRa=0.08〜0.12μmとなるように仕上げた。
Selection of mating material Considering generality, the disc mating material for friction and wear tests is one of the general-purpose bearing steels, and a high-carbon chromium bearing steel that can provide good sliding characteristics (hereinafter referred to as SUJ2 or mating material). Selected.
SUJ2 was subjected to a non-oxidizing quenching and tempering treatment. The dimensional shape was a disk type having a diameter of 60 mm and a thickness of 14 mm, and a Vickers hardness of HV = 720 was used. The contact surface with the test piece at the time of the friction / wear test was polished by using a polishing machine (Buhler; Ecomet polishing machine type 3) attached with water resistant abrasive paper of # 240-400, and a surface measuring device (Mitutoyo Co., Ltd.). Using SURFTEST SV-400), the arithmetic average roughness was Ra = 0.08 to 0.12 μm.
摩擦・摩耗試験機
本発明では、試験機にPin−on−Disk型摩擦摩耗試験機((株)村山製作所製)を用いた。この試験機は、主として空気シリンダ、回転機構および計測機器により構成されている。
空気シリンダ(CKD(株)製)には、載荷用空気供給減コンプレッサ(アネスト岩田(株)製)より随時圧縮空気が供給されている。この空気シリンダによって、スライディング機構を通して、ピン試験片側が上下移動する仕組みになっている。空気シリンダ内に存在する圧縮空気の圧力を制御することにより、試験片および相手材間に作用する荷重を調節することができる。回転機構は、三相誘電電動機(三菱電機(株)製)および回転台から構成されている。
電動機は回転台に接続されているため、回転台に固定したディスクの回転数を調節することができる。ディスクの回転数は1rpm間隔で1500rpmまで制御可能なため、低速から高速まで広範囲の摩擦・摩耗試験が可能である。計測機器には、トルクセルLT−8NSおよびロードセルCLZ−5KNS(ともに(株)東京測器研究所製)を用いた。これにより、試験中に変動するトルクおよび垂直荷重を任意の時間間隔で測定することができるため、正確な摩擦係数を算出することが可能である。
Friction / Abrasion Tester In the present invention, a Pin-on-Disk type frictional wear tester (manufactured by Murayama Seisakusho Co., Ltd.) was used as the tester. This testing machine is mainly composed of an air cylinder, a rotating mechanism, and a measuring device.
Compressed air is supplied to the air cylinder (manufactured by CKD Co., Ltd.) as needed from a loading air supply reducing compressor (manufactured by Anest Iwata Co., Ltd.). With this air cylinder, the pin test piece side moves up and down through a sliding mechanism. By controlling the pressure of the compressed air existing in the air cylinder, the load acting between the test piece and the counterpart material can be adjusted. The rotation mechanism is composed of a three-phase dielectric motor (manufactured by Mitsubishi Electric Corporation) and a turntable.
Since the electric motor is connected to the turntable, the number of rotations of the disk fixed to the turntable can be adjusted. Since the rotational speed of the disk can be controlled to 1500 rpm at 1 rpm intervals, a wide range of friction and wear tests from low speed to high speed are possible. Torque cell LT-8NS and load cell CLZ-5KNS (both manufactured by Tokyo Sokki Kenkyujo Co., Ltd.) were used as measuring instruments. Thereby, since the torque and vertical load which fluctuate during a test can be measured at arbitrary time intervals, it is possible to calculate an accurate friction coefficient.
摩擦・摩耗試験条件
試験中、ピン−ディスク間に発生するトルクおよび荷重を1秒間隔で測定した。試験条件はすべり速度80mm/sec、荷重50Nとした。ディスク中心からピン中心までの距離であるピンの回転半径は15mmであり、すべり速度は回転数に換算すると51rpmである。試験時間は1時間としたため、すべり距離を計算すると288mである。試験環境は室温23±2℃とし、室温無潤滑下にてすべり摩擦・摩耗試験を実施した。
Friction / wear test conditions During the test, the torque and load generated between the pin and the disk were measured at 1 second intervals. The test conditions were a sliding speed of 80 mm / sec and a load of 50N. The rotation radius of the pin, which is the distance from the center of the disk to the center of the pin, is 15 mm, and the sliding speed is 51 rpm when converted to the rotation speed. Since the test time was 1 hour, the sliding distance was calculated to be 288 m. The test environment was a room temperature of 23 ± 2 ° C., and a sliding friction / abrasion test was performed under non-lubrication at room temperature.
摩擦・摩耗特性の評価方法
耐摩耗性の評価には、過去の研究との比較を考慮し、以下に示す「単位すべり距離当たりの摩耗体積」である摩耗率wを算出した。ただし、mは摩耗量、pは密度、Lはすべり距離である。(非特許文献10参照)
(数式1)
また、実験中、ピン−ディスク間に発生するトルクTおよび垂直荷重Wを用いて、以下に示す摩擦係数μを算出した。ただし、rはピンの回転半径である。
(数式2)
Evaluation Method of Friction / Wear Characteristics For the evaluation of wear resistance, the wear rate w, which is the “wear volume per unit slip distance” shown below, was calculated in consideration of comparison with past studies. Here, m is the amount of wear, p is the density, and L is the slip distance. (See Non-Patent Document 10)
(Formula 1)
During the experiment, the friction coefficient μ shown below was calculated using the torque T generated between the pin and the disk and the vertical load W. Here, r is the rotation radius of the pin.
(Formula 2)
摩耗粉の評価
摩耗粉は摩擦・摩耗特性に大きく影響したと考えられる。
そこで、摩耗粉がトライボロジー特性に与える影響を検討するため、各試験片により脱落した摩耗粉をSEMにより観察した。
さらに詳細に摩耗粉について検討するため、SEMに付属しているエネルギー分散型X線分析装置(EDAX製;Genesis、以下EDAX)を用いて、摩耗粉の成分分析を行った。
Evaluation of wear powder It is considered that the wear powder had a great influence on the friction and wear characteristics.
Therefore, in order to examine the influence of the wear powder on the tribological characteristics, the wear powder dropped off by each test piece was observed by SEM.
In order to examine the wear powder in more detail, a component analysis of the wear powder was performed using an energy dispersive X-ray analyzer (manufactured by EDAX; Genesis, hereinafter referred to as EDAX) attached to the SEM.
1:Mg−Cu合金
銅と純マグネシウム(純度:99.95 %)を二酸化炭素雰囲気にて完全に溶解し、鉄製鋳型に鋳込み、Mg−4.5wt.%Cu合金を作製した(以下、この試料をas−cast材と示す)。得られた鋳造合金を温度440℃にて24時間炉中保持後、水冷することにより、溶体化処理を施した。その後、150, 175, 200℃、10分、1,2,6,24,48時間にて熱処理を行い、時効材および過時効材を作成した(以下、この試料をそれぞれ、peak−aged材、over−aged材と示す)。Over−aged材の光学顕微鏡組織観察結果を図2に示す。Mg−Cu組成からなる金属間化合物の形成が確認できる。これらの試料を、機械加工により、直径4mm×長さ12mmの円柱試験片を作成し、Pin−on−disk型摩耗試験機を使用し、摩耗特性を調査した。その結果を表1に示す(摩耗率の値が低い程、特性が良い)。表1には比較のため、最も一般的に使用されているマグネシウム合金であるMg−9wt.%Al−1wt.%Zn(AZ91)合金の値も併せて示す。本発明で用いた試料の摩耗率の方が、従来材より優れていることが確認できる。摩耗試験後の試料を走査型電子顕微鏡で観察した結果を図3に示す。すべり方向に平行な削り傷が観察されるが、摩耗粉の固着も併せて確認できたことから凝着摩耗の形成が予測される。
1: Mg—Cu alloy copper and pure magnesium (purity: 99.95%) were completely dissolved in a carbon dioxide atmosphere, cast into an iron mold, and Mg-4.5 wt. % Cu alloy was produced (hereinafter, this sample is referred to as an as-cast material). The obtained cast alloy was kept in a furnace at a temperature of 440 ° C. for 24 hours, and then cooled with water to give a solution treatment. Thereafter, heat treatment was performed at 150, 175, 200 ° C., 10 minutes, 1, 2, 6, 24, and 48 hours to prepare an aging material and an overaged material (hereinafter, this sample was a peak-aged material, Over-aged material). FIG. 2 shows the results of observation of the optical microscope structure of the over-aged material. The formation of an intermetallic compound having a Mg—Cu composition can be confirmed. These samples were machined to produce cylindrical test pieces having a diameter of 4 mm and a length of 12 mm, and the wear characteristics were investigated using a Pin-on-disk type wear tester. The results are shown in Table 1 (the lower the wear rate value, the better the characteristics). Table 1 shows, for comparison, Mg-9 wt., Which is the most commonly used magnesium alloy. % Al-1 wt. The value of% Zn (AZ91) alloy is also shown. It can be confirmed that the wear rate of the sample used in the present invention is superior to that of the conventional material. FIG. 3 shows the results of observation of the sample after the abrasion test with a scanning electron microscope. Scratches parallel to the slip direction are observed, but adhesion of wear powder can also be confirmed, and the formation of adhesive wear is predicted.
2:Mg−Cu−Zn合金
銅と亜鉛と純マグネシウム(純度:99.95 %)を二酸化炭素雰囲気にて完全に溶解し、鉄製鋳型に鋳込み、Mg−4.5wt.%Cu−6.0wt.%合金を作製した(as−cast材)。その後、実施例1と同様の熱処理条件にてpeak−aged材およびover−aged材を準備・加工し、摩耗試験を実施した。表1より、本発明で用いた試料の摩耗率の方が、従来材より優れていることが確認できる。また、as−cast、peak−agedおよびover−aged材を、機械加工により平行部直径4mm×長さ8mmの円柱試験片を作成し、室温、150℃、200℃にて圧縮試験を行った。得られた応力−ひずみ曲線、およびその時の結果を図4と表2に示す。150℃では、室温の圧縮強度と同等またはそれ以上であり、優れた耐熱性を示すことが分かる。また、表2よりMg−9wt.%Al−1wt.%Znの圧縮強度よりも高い値を示し、耐熱性に優れていることが分かる。
2: Mg—Cu—Zn alloy copper, zinc and pure magnesium (purity: 99.95%) were completely dissolved in a carbon dioxide atmosphere, cast into an iron mold, and Mg-4.5 wt. % Cu-6.0 wt. % Alloy was produced (as-cast material). Thereafter, a peak-aged material and an over-aged material were prepared and processed under the same heat treatment conditions as in Example 1, and an abrasion test was performed. From Table 1, it can be confirmed that the wear rate of the sample used in the present invention is superior to that of the conventional material. In addition, cylindrical test pieces having a parallel part diameter of 4 mm × length of 8 mm were prepared by machining the as-cast, peak-aged, and over-aged materials, and subjected to a compression test at room temperature, 150 ° C., and 200 ° C. The obtained stress-strain curve and the results at that time are shown in FIG. It can be seen that at 150 ° C., it is equal to or higher than the compressive strength at room temperature and exhibits excellent heat resistance. From Table 2, Mg-9 wt. % Al-1 wt. It shows a value higher than the compressive strength of% Zn, indicating that the heat resistance is excellent.
3:Mg−Si合金
ケイ素と純マグネシウム(純度:99.95 %)を二酸化炭素雰囲気にて完全に溶解し、鉄製鋳型に鋳込み、Mg−2.0wt.%Si合金を作製した(as−cast材)。得られた鋳造合金を温度590℃にて24時間炉中保持後、水冷することにより、溶体化処理を施した。その後、実施例1と同様の熱処理条件にてpeak−aged材およびover−aged材を準備・加工し、摩耗試験を実施した。表1より、本発明で用いた試料の摩耗率の方が、従来材より優れていることが確認できる。
3: Mg—Si alloy silicon and pure magnesium (purity: 99.95%) were completely dissolved in a carbon dioxide atmosphere, cast into an iron mold, and Mg-2.0 wt. % Si alloy was produced (as-cast material). The obtained cast alloy was held in a furnace at a temperature of 590 ° C. for 24 hours, and then cooled with water to give a solution treatment. Thereafter, a peak-aged material and an over-aged material were prepared and processed under the same heat treatment conditions as in Example 1, and an abrasion test was performed. From Table 1, it can be confirmed that the wear rate of the sample used in the present invention is superior to that of the conventional material.
4:Mg−Si−Zn合金
ケイ素と亜鉛と純マグネシウム(純度:99.95 %)を二酸化炭素雰囲気にて完全に溶解し、鉄製鋳型に鋳込み、Mg−2.0wt.%Si−6.0wt.%合金を作製した(as−cast材)。その後、実施例1と同様の熱処理条件にてpeak−aged材およびover−aged材を準備・加工し、摩耗試験および圧縮試験を実施した。Over-aged材の典型的な透過型電子顕微鏡を用いた組織観察の結果を図5に示す。楕円形の金属間化合物がMg2Si相であり、また、マグネシウム母相に対し針状に析出している金属間化合物がb相である。図6に圧縮試験により得られた応力-ひずみ曲線を示す。図6ならびに表1・2より、本発明で用いた試料は耐摩耗性と耐熱性に優れていることが分かる。摩耗試験後の試料を走査型電子顕微鏡で観察した結果を図7に示す。すべり方向に平行な削り傷が観察されるが、図3のような凝着摩耗の形態が見られないため、耐摩耗性がさらに良好となったものと考えられる。
4: Mg—Si—Zn alloy silicon, zinc and pure magnesium (purity: 99.95%) were completely dissolved in a carbon dioxide atmosphere, cast into an iron mold, and Mg-2.0 wt. % Si-6.0 wt. % Alloy was produced (as-cast material). Thereafter, a peak-aged material and an over-aged material were prepared and processed under the same heat treatment conditions as in Example 1, and an abrasion test and a compression test were performed. FIG. 5 shows the result of the structure observation using a typical transmission electron microscope of the over-aged material. The oval intermetallic compound is the Mg 2 Si phase, and the intermetallic compound precipitated in a needle shape with respect to the magnesium matrix is the b phase. Fig. 6 shows the stress-strain curve obtained by the compression test. 6 and Tables 1 and 2, it can be seen that the sample used in the present invention is excellent in wear resistance and heat resistance. FIG. 7 shows the result of observation of the sample after the abrasion test with a scanning electron microscope. Although scratches parallel to the slip direction are observed, it is considered that the wear resistance is further improved because the form of adhesive wear as shown in FIG. 3 is not observed.
表1は摩耗試験の結果を示し、表2は圧縮試験の結果を示す。
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