JP2013011474A - EVALUATION METHOD OF FINE TISSUE STRUCTURE OF Mg-Li ALLOY - Google Patents
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本発明は、Ｍｇ−Ｌｉ系合金の新規評価方法に関する。 The present invention relates to a novel evaluation method for Mg-Li alloys.
Ｍｇ材料は軽量な金属材料であり、自動車部品や電子機器のボディ等への適用が期待されている。しかしながら、Ｍｇ材料は冷間加工性に劣るという課題を有しており、当該課題を解決すべく種々の研究がなされている。 Mg material is a lightweight metal material, and is expected to be applied to automobile parts, bodies of electronic devices, and the like. However, Mg material has a problem that it is inferior in cold workability, and various studies have been made to solve the problem.
Ｍｇ材料の冷間加工性を向上させる技術として、大量のＬｉを添加してＭｇ−Ｌｉ合金とするものがある。ＭｇにＬｉを約１６ａｔ％以上添加すると、結晶構造が最密六方構造（ｈｃｐ）から体心立方構造（ｂｃｃ）へと変化するため、冷間加工性が向上する。また、Ｌｉの添加によって密度が低下するため、一層軽量化することができる。しかしながら、Ｍｇ−Ｌｉ合金は強度や耐食性に劣るという課題を有しており、当該課題を解決するための様々な技術が開示されている。例えば、特許文献１〜３や非特許文献１等に開示されているように、Ｍｇ−Ｌｉ合金において、さらにＡｌやＺｎ等の第三元素を添加してＭｇ−Ｌｉ系合金とすることにより、強度等を向上させることができる。 As a technique for improving the cold workability of the Mg material, there is a technique in which a large amount of Li is added to form an Mg—Li alloy. When about 16 at% or more of Li is added to Mg, the crystal structure changes from the close-packed hexagonal structure (hcp) to the body-centered cubic structure (bcc), so that cold workability is improved. Further, since the density is reduced by the addition of Li, the weight can be further reduced. However, the Mg—Li alloy has a problem that it is inferior in strength and corrosion resistance, and various techniques for solving the problem are disclosed. For example, as disclosed in Patent Documents 1 to 3 and Non-Patent Document 1, etc., in the Mg-Li alloy, by adding a third element such as Al or Zn to make an Mg-Li alloy, Strength etc. can be improved.
このように優れた特性を有するＭｇ−Ｌｉ系合金ではあるが、第三元素を含ませたことにより当該Ｍｇ−Ｌｉ系合金がどのように強化されるのか等、強化機構の詳細について解明されていない点が多く、Ｍｇ−Ｌｉ系合金の強化機構を評価・解明可能な方法が求められている。 Although it is an Mg-Li alloy having such excellent characteristics, details of the strengthening mechanism have been elucidated, such as how the Mg-Li alloy is strengthened by including a third element. There are many points, and there is a need for a method that can evaluate and elucidate the strengthening mechanism of Mg-Li alloys.
そこで本発明は、ＺｎやＡｌ等の第三元素を含むＭｇ−Ｌｉ系合金の強化機構を解明可能であり、Ｍｇ−Ｌｉ系合金を適切に評価することが可能な方法を提供することを課題とする。 Therefore, the present invention is capable of elucidating the strengthening mechanism of an Mg—Li based alloy containing a third element such as Zn or Al and providing a method capable of appropriately evaluating the Mg—Li based alloy. And
本発明者は、Ｍｇ−Ｌｉ合金に少量の第三元素を添加することによって合金強化を図った際の強化機構を解明すべく、Ｘ線回折法や透過電子顕微鏡法（ＴＥＭ法）による微細組織・構造の評価を行った。そして、本発明者が鋭意研究を進めたところ、高角度円環状検出器暗視野走査型透過電子顕微鏡法（ＨＡＡＤＦ−ＳＴＥＭ法）にて取得したＨＡＡＤＦ−ＳＴＥＭ像によれば、Ｍｇ−Ｌｉ系合金の結晶構造の変化に加えて、軽元素であるＬｉやＺｎなどの第三元素の偏在状態を容易かつ正確に確認することができることを知見した。これにより、Ｍｇ−Ｌｉ合金の微視的な時効析出挙動を確認することができ、Ｍｇ−Ｌｉ合金の強化機構を評価することが可能となった。 In order to elucidate the strengthening mechanism when the alloy is strengthened by adding a small amount of a third element to the Mg-Li alloy, the present inventor has made a fine structure by X-ray diffraction method or transmission electron microscopy (TEM method).・ The structure was evaluated. And when this inventor advanced earnest research, according to the HAADF-STEM image acquired by the high angle annular detector dark field scanning transmission electron microscopy (HAADF-STEM method), it is Mg-Li type alloy. In addition to the change in the crystal structure, it has been found that the uneven distribution state of the third elements such as Li and Zn, which are light elements, can be easily and accurately confirmed. Thereby, the microscopic aging precipitation behavior of the Mg—Li alloy can be confirmed, and the strengthening mechanism of the Mg—Li alloy can be evaluated.
本発明において、「ＨＡＡＤＦ−ＳＴＥＭ法」とは、国内では１９９５年頃よりハード面での商用化が始まった比較的新しい電子顕微鏡技術で、「デジタル走査像観察装置」と「円環状検出器」を搭載した「電界放出型透過電子顕微鏡」を用いて、２Å程度に細く絞った電子ビームで対象試料（Ｍｇ−Ｌｉ合金）上をスキャンし、試料内で散乱された電子を検出して二次元分布像を得る方法をいう。当該方法にあっては、電子ビームを走査させた際に生じる散乱電子のうち、特に高角度（＞７０ｍｒａｄ）に散乱された弾性散乱電子を円環状検出器で捕獲し、それを電子線強度として２次元的に記録する。このとき検出される電子線強度は、原子番号の２乗に比例することが知られ、観察像はＺコントラスト像とも呼ばれる。当該方法により得られるＺコントラスト像は、非干渉像であるため、従来の高分解能電子顕微鏡像に現れる電子波の干渉像と異なり、像解釈が容易になる。つまり、ＨＡＡＤＦ−ＳＴＥＭ法によって取得した画像を見る場合、相対的に明るく写っている箇所が大きなＺから成る重元素の濃化領域に対応し、逆に暗い箇所が軽元素の濃化領域に対応するとの解釈が可能になる。そこで、本発明者は、Ｍｇ−Ｌｉ系合金の時効析出挙動を調査する際に、通常のＴＥＭ法（汎用ＴＥＭ法）に加えてＨＡＡＤＦ−ＳＴＥＭ法を併用することにより、同系合金の時効析出挙動に関してより詳細な情報を取得すること、つまり、時効の進行に伴って変化する重元素（原子番号Ｚの大きな添加元素）や軽元素(Ｌｉ)の分布状態をより容易かつ正確に評価することが可能になると考えた。 In the present invention, the “HAADF-STEM method” is a relatively new electron microscope technology that has been commercialized in hardware since around 1995 in Japan. “Digital scanning image observation device” and “annular detector” Using the on-board "field emission transmission electron microscope", the target sample (Mg-Li alloy) is scanned with an electron beam narrowed down to about 2 mm, and the electrons scattered in the sample are detected to obtain a two-dimensional distribution. A method of obtaining an image. In this method, among the scattered electrons generated when the electron beam is scanned, elastic scattered electrons scattered particularly at a high angle (> 70 mrad) are captured by an annular detector, and this is used as the electron beam intensity. Record in two dimensions. The electron beam intensity detected at this time is known to be proportional to the square of the atomic number, and the observed image is also called a Z contrast image. Since the Z contrast image obtained by this method is a non-interfering image, it is easy to interpret an image unlike an interference image of an electron wave that appears in a conventional high-resolution electron microscope image. In other words, when viewing an image acquired by the HAADF-STEM method, a relatively bright spot corresponds to a heavy element enriched region composed of large Z, and conversely, a dark spot corresponds to a light element enriched region. Then interpretation becomes possible. Therefore, the present inventor used the HAADF-STEM method in combination with the normal TEM method (general-purpose TEM method) when investigating the aging precipitation behavior of the Mg-Li alloy, thereby aging precipitation behavior of the alloy of the same type. To obtain more detailed information on, that is, to more easily and accurately evaluate the distribution of heavy elements (additive elements with a large atomic number Z) and light elements (Li) that change with the progress of aging I thought it would be possible.
また、Ｍｇ−Ｌｉ合金は、酸化や窒化の影響及び電子線やアルゴンイオンなどによる照射ダメージの影響を受けやすく、従来技術においてはＴＥＭ法の適用はおろか、ＴＥＭ観察用の薄片試料を作製することが極めて困難であると考えられていた。一般の金属材料に対するＴＥＭ観察用試料の作製法としては、高エネルギーのアルゴンイオンを試料にぶつけて薄片化する「イオン衝撃研磨法」と化学液によるエッチング作用を利用した「電解研磨法」に大別されるが、いずれの方法もＭｇ−Ｌｉ系合金にそのまま適用しようとすると、構造劣化や被膜の形成などの悪影響が生じることが問題であった。これに対し、本発明者は鋭意研究により、Ｍｇ−Ｌｉ系合金をＴＥＭ観察に供するよう薄片化する際に、同材料の構造劣化を最小限に抑えるべく液体窒素で冷却させながらイオン衝撃研磨を行う等の工夫を施し、良質なＴＥＭ観察試料片を得ることに成功した。 In addition, Mg-Li alloys are susceptible to the effects of oxidation and nitridation and irradiation damage due to electron beams, argon ions, etc., and in the prior art, not only the TEM method is applied, but also a thin piece sample for TEM observation is prepared. Was considered extremely difficult. There are two major methods for preparing TEM observation samples for general metal materials: the “ion impact polishing method” in which high-energy argon ions are struck against the sample and thinned, and the “electropolishing method” using the etching action of a chemical solution. Although different from each other, if any of the methods is applied to the Mg—Li alloy as it is, there is a problem that adverse effects such as structural deterioration and formation of a film occur. On the other hand, the present inventor has conducted ionic impact polishing while cooling with liquid nitrogen to minimize the structural deterioration of the same material when slicing the Mg-Li alloy for TEM observation by diligent research. We have succeeded in obtaining a high-quality TEM observation sample piece.
従来の電子顕微鏡技術によれば、ＬｉやＯなどの軽元素は電子線との相互作用が極めて小さく、可視化することはおろか、それらの結晶状態を調べることは困難とされてきた。ところが今回、良質なＴＥＭ観察試料片に仕上げられたＭｇ−Ｌｉ系合金に対してＨＡＡＤＦ−ＳＴＥＭ法を適用した場合、同系合金内に形成したリチウム化合物粒子（リチウム酸化物や亜鉛化リチウム）が効果的に顕在化することを見出し、リチウムの偏在状態に関する具体的な評価が可能になり、従来常識では想到し得なかった本発明を完成させたのである。 According to the conventional electron microscope technology, light elements such as Li and O have a very small interaction with an electron beam, and it has been difficult to examine their crystal state as well as visualization. However, this time, when the HAADF-STEM method is applied to the Mg-Li alloy that has been finished into a high-quality TEM observation specimen, lithium compound particles (lithium oxide and lithium zincide) formed in the alloy are effective. As a result, the present invention, which could not be conceived by conventional common sense, has been completed.
すなわち本発明は、少なくともＭｇとＬｉと第三元素とを含んでなるＭｇ−Ｌｉ系合金の評価方法であって、高角度円環状検出器暗視野走査型透過電子顕微鏡法（ＨＡＡＤＦ−ＳＴＥＭ法）によって、Ｍｇ−Ｌｉ系合金のＨＡＡＤＦ−ＳＴＥＭ像を取得し、当該Ｍｇ−Ｌｉ系合金の微細組織・構造、及び／又は、当該Ｍｇ−Ｌｉ系合金における重・軽元素の偏在状態を確認することを特徴とする、Ｍｇ−Ｌｉ系合金の評価方法である。本発明によれば、Ｍｇ−Ｌｉ系合金の微細組織・構造、及び／又は、当該Ｍｇ−Ｌｉ系合金におけるＬｉや第三元素の偏在状態を迅速かつ正確に評価することができる。 That is, the present invention is a method for evaluating an Mg-Li alloy containing at least Mg, Li, and a third element, and is a high-angle annular detector dark field scanning transmission electron microscope (HAADF-STEM method). Obtain HAADF-STEM image of Mg-Li alloy and confirm the microstructure and structure of the Mg-Li alloy and / or the uneven distribution of heavy and light elements in the Mg-Li alloy It is the evaluation method of Mg-Li type alloy characterized by these. According to the present invention, the microstructure and structure of an Mg—Li alloy and / or the uneven distribution of Li and third elements in the Mg—Li alloy can be evaluated quickly and accurately.
本発明において「第三元素」とは、Ｚｎ、Ａｌ、Ｓｎ、Ａｇ等の金属元素をいう。好ましくはＺｎ、Ａｌ、より好ましくはＺｎである。また、本発明において「Ｍｇ−Ｌｉ系合金における重・軽元素」とは、重元素として上記第三元素を挙げることができ、軽元素として、Ｌｉを挙げることができる。本発明では、Ｍｇ−Ｌｉ系合金のＨＡＡＤＦ−ＳＴＥＭ像から、例えば、Ｍｇ−Ｌｉ系合金において、Ｌｉや第三元素の濃化領域の大きさや分散の度合い（第三元素が濃化して析出した析出粒子の大きさや分散の規則性等）を確認することにより、Ｍｇ−Ｌｉ系合金の時効硬化現象の成因を適切に評価することができる。より具体的には、例えば、Ｍｇ−Ｌｉ−Ｚｎ合金において、汎用ＴＥＭ法（明視野法、暗視野法、電子回折法など）によって同合金の構成相ならびにそれらの集合状態を確認し（この場合では、体心立方構造相（bcc相）−最密六方構造相（hcp相）−斜方晶構造相（orthorhombic相）の混合組織からなるヘテロ構造の形成）、さらにＨＡＡＤＦ−ＳＴＥＭ法によって、ＬｉならびにＺｎの偏在状態がある程度確認された場合（例えば、１０ｎｍ以上の粒子径を有する濃化粒子が確認された場合）、当該Ｍｇ−Ｌｉ系合金における時効硬化の進行度を評価することができる。 In the present invention, the “third element” refers to a metal element such as Zn, Al, Sn, or Ag. Zn and Al are preferable, and Zn is more preferable. In the present invention, the “heavy / light element in the Mg—Li alloy” may include the third element as a heavy element, and may include Li as a light element. In the present invention, from the HAADF-STEM image of the Mg—Li based alloy, for example, in the Mg—Li based alloy, the size of the concentrated region of Li and the third element and the degree of dispersion (the third element is concentrated and precipitated). By confirming the size of the precipitated particles, the regularity of the dispersion, etc., the cause of the age hardening phenomenon of the Mg—Li alloy can be appropriately evaluated. More specifically, for example, in a Mg—Li—Zn alloy, the constituent phases of the alloy and their aggregate state are confirmed by a general-purpose TEM method (bright field method, dark field method, electron diffraction method, etc.) (in this case) Then, formation of a heterostructure composed of a mixed structure of a body-centered cubic structure phase (bcc phase) -close-packed hexagonal structure phase (hcp phase) -orthorhombic structure phase (orthorhombic phase)), and further by HAADF-STEM method, Li In addition, when the uneven distribution state of Zn is confirmed to some extent (for example, when concentrated particles having a particle diameter of 10 nm or more are confirmed), the progress of age hardening in the Mg-Li alloy can be evaluated.
本発明の効果は、以下のように概説される。つまり、一般に材料開発のプロセスとは、「材料合成−特性評価−構造解析」から成るサイクルの繰り返しによって展開し、現代の構造解析作業の中核を担っている技術が透過電子顕微鏡法である。特にナノテクノロジーという概念が一般的になった今日、材料の組織・構造を原子レベルで正当に評価し、これらの情報を迅速かつ有効利に材料プロセッシングにフィードバックすることが、最適な材料を生み出すために必須の作業となっている。Ｍｇ−Ｌｉ系合金に照らして換言すれば、従来技術において有効な構造解析法が存在しなかったことが、これまで同材料の開発研究が遅れた主因と考えられる。本発明によれば、Ｍｇ−Ｌｉ系合金の構造解析に際してＨＡＡＤＦ−ＳＴＥＭ法を適用することにより、同系合金の時効析出挙動を容易かつ正確に評価できるようになり、これにより当該Ｍｇ−Ｌｉ系合金における強化機構を正しく解釈することができる。そして、本発明に係る評価方法により、合金成分や組織・構造制御の視点から、従来技術では果たせなかった強度性能と延性能を両立させた新Ｍｇ-Ｌｉ合金開発の大幅な進展が期待できる。また、それとは別に、もともとＨＡＡＤＦ−ＳＴＥＭ法はその実用化が始まった当初から、「軽金属中に含まれる重元素の偏在状態」を感度良く知ることができる技術として注目され普及が進んできたが、本発明者は、ＨＡＡＤＦ−ＳＴＥＭ法が「軽金属中（Ｍｇ）に含まれる軽元素（Ｌｉ）の偏在状態」を知るうえでも有効であることを知見・実証し、本発明を完成させたのであり、この点についても特筆に値する。つまり、本発明の方法は、Ｍｇ−Ｌｉ合金以外のリチウム含有材料（例えばリチウムイオン電池等）にも適用可能な評価法になり得ることを示唆している。 The effects of the present invention are outlined as follows. In other words, the material development process is generally developed by repeating a cycle consisting of “material synthesis-characteristic evaluation-structural analysis”, and transmission electron microscopy is the core technology of modern structural analysis work. Today, especially when the concept of nanotechnology has become commonplace, to properly evaluate the structure and structure of materials at the atomic level, and to feed back this information to material processing quickly and effectively, it is necessary to produce optimal materials. It is essential work. In other words, in light of the Mg—Li alloy, the lack of an effective structural analysis method in the prior art is considered to be the main cause of delay in the development of the same material so far. According to the present invention, by applying the HAADF-STEM method in the structural analysis of the Mg—Li based alloy, it becomes possible to easily and accurately evaluate the aging precipitation behavior of the similar alloy, thereby the Mg—Li based alloy. Can be interpreted correctly. The evaluation method according to the present invention can be expected to make significant progress in developing a new Mg—Li alloy that achieves both strength performance and ductility that cannot be achieved by the prior art from the viewpoint of alloy composition and structure / structure control. Apart from that, the HAADF-STEM method has been attracting attention and spread as a technology capable of knowing “the uneven distribution state of heavy elements contained in light metals” with high sensitivity since the beginning of its practical use. The present inventor has found and verified that the HAADF-STEM method is effective for knowing “the uneven distribution state of light elements (Li) contained in light metal (Mg)”, and has completed the present invention. Yes, and this point deserves special mention. That is, it is suggested that the method of the present invention can be an evaluation method applicable to lithium-containing materials (for example, lithium ion batteries) other than Mg—Li alloy.
本発明に係るＭｇ−Ｌｉ系合金の評価方法は、少なくともＭｇとＬｉと第三元素とを含んでなるＭｇ−Ｌｉ系合金の評価方法であって、高角度円環状検出器暗視野走査型透過電子顕微鏡法（ＨＡＡＤＦ−ＳＴＥＭ法）によって、Ｍｇ−Ｌｉ系合金のＨＡＡＤＦ−ＳＴＥＭ像を取得し、当該Ｍｇ−Ｌｉ系合金の微細組織・構造、及び／又は、当該Ｍｇ−Ｌｉ系合金における軽元素（Ｌｉ）や第３元素（特にＺｎなどの重元素）の偏在状態を確認することに特徴を有する。本発明によれば、Ｍｇ−Ｌｉ系合金における時効析出組織を容易かつ正確に評価することができ、例えば、Ｍｇ−Ｌｉ系合金について強度試験を行うことなく、当該Ｍｇ−Ｌｉ系合金が強度に優れるものであるのか否かをある程度予見することができるようになる。 An evaluation method of an Mg-Li alloy according to the present invention is an evaluation method of an Mg-Li alloy comprising at least Mg, Li, and a third element, and is a high-angle annular detector dark-field scanning transmission HAADF-STEM images of Mg-Li alloys are obtained by electron microscopy (HAADF-STEM method), and the microstructure and structure of the Mg-Li alloys and / or light elements in the Mg-Li alloys It is characterized by confirming the uneven distribution of (Li) and the third element (particularly heavy elements such as Zn). According to the present invention, it is possible to easily and accurately evaluate an aging precipitation structure in an Mg—Li alloy. For example, the Mg—Li alloy can be strengthened without performing a strength test on the Mg—Li alloy. Whether it is excellent or not can be predicted to some extent.
本発明に係る評価対象であるＭｇ−Ｌｉ系合金において、Ｍｇ、Ｌｉ及び第三元素の組成比は特に限定されるものではない。従来公知のＭｇ−Ｌｉ系合金を対象とすることができる。Ｍｇ−Ｌｉ系合金は、酸化や窒化の影響及び電子線やアルゴンイオンによる照射ダメージの影響を受けやすく、透過電子顕微鏡法の適用が難しいとされてきた。よって、従来技術によれば、同系合金の微視的な時効硬化機構の解明は極めて困難であると考えられていたが、本発明では当該従来常識とは相反して、ＨＡＡＤＦ−ＳＴＥＭ法によってＭｇ−Ｌｉ系合金の時効析出組織に関する詳細な評価が可能になり、ひいては微視的強化機構の解釈までが可能になったことに特徴を有する。 In the Mg—Li-based alloy that is an evaluation object according to the present invention, the composition ratio of Mg, Li, and the third element is not particularly limited. Conventionally known Mg-Li alloys can be used. Mg-Li alloys are susceptible to the effects of oxidation and nitriding and irradiation damage due to electron beams and argon ions, and it has been difficult to apply transmission electron microscopy. Therefore, according to the prior art, it was thought that it was extremely difficult to elucidate the microscopic age-hardening mechanism of the same alloy, but in the present invention, contrary to the conventional common sense, the HAADF-STEM method is used to produce Mg. It is characterized in that a detailed evaluation of the aging precipitation structure of a Li-based alloy can be performed, and that even a microscopic strengthening mechanism can be interpreted.
本発明において、Ｍｇ−Ｌｉ系合金に含まれる第三元素とは、Ｚｎ、Ａｌ、Ｓｎ、Ａｇ等の金属元素をいう。好ましくはＺｎ、Ａｌ、より好ましくはＺｎである。第三元素としてＺｎを添加した場合に、特に大きな時効硬化を得ることができ、強度に優れたＭｇ−Ｌｉ系合金とすることができる。そして、本発明に係る評価方法により、第三元素、特にＺｎのように主構成元素（Ｍｇ）に対して相対的に大きな原子量Ｚを有する元素を添加した場合のＭｇ−Ｌｉ系合金の時効析出組織を正確に評価することができ、同添加操作によるＭｇ−Ｌｉ系合金の微視的強化機構に関する正しい理解が可能になる。 In the present invention, the third element contained in the Mg—Li-based alloy refers to a metal element such as Zn, Al, Sn, or Ag. Zn and Al are preferable, and Zn is more preferable. When Zn is added as the third element, particularly large age hardening can be obtained, and an Mg—Li alloy having excellent strength can be obtained. And, by the evaluation method according to the present invention, the aging precipitation of the Mg—Li alloy in the case where an element having a relatively large atomic weight Z with respect to the main constituent element (Mg) such as Zn is added. The structure can be accurately evaluated, and a correct understanding of the microscopic strengthening mechanism of the Mg—Li alloy by the addition operation can be realized.
本発明においては、Ｍｇ−Ｌｉ系合金のＨＡＡＤＦ−ＳＴＥＭ像から、例えば、Ｍｇ−Ｌｉ系合金における軽元素（Ｌｉや自然酸化に伴って取り込まれた酸素Ｏ）ならびに第三元素（特にＺｎのような重元素）の濃化領域の形状、大きさ、密度等の情報収集が可能になる。これによって、Ｍｇ−Ｌｉ系合金の時効硬化挙動を適切に評価し、ひいては同合金の時効硬化機構の正しい理解が可能になる。これらの情報を元に、新たな材料合成に対する設計指針の提示、つまり、Ｍｇ−Ｌｉ合金組成、第３元素の種類や量、時効処理の温度や処理時間などの条件設定が可能になり、効果的なフィードバックが達せられる。 In the present invention, from a HAADF-STEM image of an Mg—Li based alloy, for example, a light element (Li or oxygen O incorporated with natural oxidation) and a third element (particularly Zn) in an Mg—Li based alloy. It is possible to collect information on the shape, size, density, etc. of the concentrated region of the heavy elements. This makes it possible to appropriately evaluate the age hardening behavior of the Mg—Li based alloy and thus to correctly understand the age hardening mechanism of the alloy. Based on this information, it becomes possible to present design guidelines for new material synthesis, that is, to set conditions such as Mg-Li alloy composition, type and amount of the third element, aging treatment temperature and treatment time, etc. Feedback can be reached.
以下、実施例により、本発明に係る評価方法についてさらに詳述するが、本発明は以下の実施例に記載された具体的な形態に限定されるものではない。 Hereinafter, the evaluation method according to the present invention will be described in more detail by way of examples, but the present invention is not limited to the specific modes described in the following examples.
まず、第三元素を含むＭｇ−Ｌｉ系合金における強化向上に大きく寄与する、Ｍｇ−Ｌｉ系合金の時効硬化について、時効硬化曲線を用いて説明する。 First, age hardening of an Mg—Li alloy that greatly contributes to strengthening improvement in an Mg—Li alloy containing a third element will be described using an age hardening curve.
下記表１に示す組成比及び条件にて、Ｍｇ−Ｌｉ合金或いはＭｇ−Ｌｉ系合金を作製した。 An Mg—Li alloy or an Mg—Li alloy was prepared under the composition ratio and conditions shown in Table 1 below.
図１に、表１に示した第三元素を含まないＭｇ−Ｌｉ合金、及び、第三元素としてＺｎ、Ａｌ、Ａｇ又はＳｎを添加したＭｇ−Ｌｉ系合金それぞれに対して所定の溶体化処理を施した後、室温下（２３℃）で調査した等温時効硬化測定の結果を示す。図１から明らかなように、第三元素を添加することによって、ビッカース硬さ値（ＨＶ）が上昇し時効硬化が高まることが分かる。中でも、Ｚｎを添加した場合には、汎用の高強度Ｍｇ合金材に匹敵するほどの大きな時効硬化が得られた。一方、Ｚｎ添加の場合と比べると控えめではあるものの、第三元素としてＡｌを添加した場合でも、良好な時効硬化性能が得られた。 FIG. 1 shows a predetermined solution treatment for each of the Mg—Li alloy not containing the third element shown in Table 1 and the Mg—Li alloy to which Zn, Al, Ag, or Sn is added as the third element. The results of isothermal age hardening measurement investigated at room temperature (23 ° C.) are shown. As is clear from FIG. 1, it can be seen that the addition of the third element increases the Vickers hardness value (HV) and age hardening. In particular, when Zn was added, age hardening large enough to be comparable to a general-purpose high-strength Mg alloy material was obtained. On the other hand, although it is modest compared with the case of adding Zn, good age hardening performance was obtained even when Al was added as the third element.
Ｍｇ−Ｌｉ合金は、室温下で時効が自発的に進行し（自然時効）、これに伴って結晶構造が変化するものと考えられた。図２に、第三元素を添加していないＭｇ−Ｌｉ合金の自然時効に伴うＸＲＤスペクトルの変化を示す。初期時効段階では、ｂｃｃ構造のβ−Ｌｉ相を示すピークが多く確認できるが、時効が進行するとともに、ｈｃｐ構造のα−Ｍｇ相を示すピークが徐々に大きくなることが分かる。その他、Ｌｉ酸化物、水酸化物、窒化物に起因するとみられるピークも確認できるが、これらは大気との接触によって試料表面に生じた反応生成物とみられた。 The Mg-Li alloy was considered to undergo aging spontaneously at room temperature (natural aging), and the crystal structure changed accordingly. FIG. 2 shows changes in the XRD spectrum associated with natural aging of the Mg—Li alloy to which no third element is added. In the initial aging stage, many peaks indicating a β-Li phase having a bcc structure can be confirmed, but it can be seen that the peak indicating an α-Mg phase having an hcp structure gradually increases as aging progresses. In addition, although peaks that can be attributed to Li oxide, hydroxide, and nitride can also be confirmed, these were considered to be reaction products generated on the sample surface by contact with the atmosphere.
図３に、第三元素としてＺｎを添加したＭｇ−Ｌｉ系合金の自然時効に伴うＸＲＤスペクトルの変化を示す。Ｚｎ添加合金では、時効の進行に伴ってｂｃｃ構造を擁するβ−Ｌｉ相に加え、ｈｃｐ構造のα−Ｍｇ相、さらには第三の化合物相に対応するピークの高まりが観測された。当該第三の化合物相の詳細については未解明であるものの、従来の報告に照らせば、ＭｇＬｉ２Ｚｎ型化合物相を含んでいる可能性がある。いずれにせよ、第三元素としてＺｎを添加したＭｇ−Ｌｉ合金の時効硬化の原因は、ｂｃｃ母相内における複数の異相析出物の出現が関与していると考えられた。この解釈は、後述のＴＥＭならびにＨＡＡＤＦ−ＳＴＥＭ法による観察データによってより具体的に支持されることとなった。 FIG. 3 shows changes in the XRD spectrum associated with natural aging of an Mg—Li alloy containing Zn as a third element. In the Zn-added alloy, as the aging progresses, in addition to the β-Li phase having the bcc structure, the peaks corresponding to the α-Mg phase having the hcp structure and the third compound phase were observed. Although the details of the third compound phase are not yet elucidated, in light of conventional reports, there is a possibility that an MgLi 2 Zn type compound phase is included. In any case, it was considered that the cause of age hardening of the Mg—Li alloy with Zn added as the third element is related to the appearance of a plurality of heterogeneous precipitates in the bcc matrix. This interpretation was more specifically supported by observation data obtained by the TEM and HAADF-STEM methods described later.
上記の通り、Ｍｇ−Ｌｉ系合金における時効硬化は、ｂｃｃ母相中に複数の析出物が発生したことに起因したものと言える。図２、３のＸ線回折測定結果では、その一つがｈｃｐ相析出物であることが示唆されたが、Ｘ線回折測定では十分且つ容易にＭｇ−Ｌｉ系合金を評価できるとは言えない。そこで、本発明者は、ＴＥＭ法によって、Ｍｇ−Ｌｉ系合金における母相や析出物などの対象物を直接に拡大観察することで、Ｍｇ−Ｌｉ系合金を適切に評価できるのではと考えた。実際の観察作業の際には、析出強化の一般理論を念頭に置いて、析出物の種類、析出物の密度、析出物の大きさ、析出物の形態、析出物の発生による結晶格子のひずみ、析出物の硬さ（母相との整合性、剛性率の違い）等に着目しながらデータ収集に努めた。 As described above, it can be said that the age hardening in the Mg—Li alloy is caused by the occurrence of a plurality of precipitates in the bcc matrix. The X-ray diffraction measurement results in FIGS. 2 and 3 suggest that one of them is an hcp phase precipitate, but it cannot be said that the Mg—Li alloy can be evaluated sufficiently and easily by X-ray diffraction measurement. Therefore, the present inventor considered that the Mg-Li based alloy can be appropriately evaluated by directly magnifying the target object such as a parent phase and precipitates in the Mg-Li based alloy by the TEM method. . In the actual observation work, with the general theory of precipitation strengthening in mind, the type of precipitate, the density of the precipitate, the size of the precipitate, the form of the precipitate, and the distortion of the crystal lattice due to the occurrence of the precipitate We tried to collect data while paying attention to the hardness of the precipitates (consistency with the parent phase, difference in rigidity).
まず、通常のＴＥＭ観察によって、第三元素を含まないＭｇ−Ｌｉ合金、或いは、第三元素を含むＭｇ−Ｌｉ系合金を観察した場合について説明する。 First, a case where an Mg—Li alloy not containing a third element or an Mg—Li alloy containing a third element is observed by ordinary TEM observation will be described.
図４（Ａ）、（Ｂ）は、第三元素を含まないＭｇ−Ｌｉ合金の母相に対する[１００]方位から撮影されたＴＥＭ写真画像、及び電子回折図形を示す図である。図４（Ａ）、（Ｂ）から明らかなように、第三元素を含まないＭｇ−Ｌｉ合金の組織状態は、均一なコントラストからなる母相領域が大半を占め、析出物や結晶格子のひずみはそれほど目立たなかった。ところが図４（Ａ）の画像を注意深くみると、多数の線状欠陥が２方向に走っていることが分かった。これらはいずれもｂｃｃやｈｃｐとは異なる構造相の形成が関与して現れた「双晶境界」と考えられた。そしてこの双晶境界の発生に伴って、回折スポットに細かな分裂が現れたものと解釈された（図４（Ｂ））。 4A and 4B are diagrams showing a TEM photograph image and an electron diffraction pattern taken from the [100] orientation with respect to the parent phase of the Mg—Li alloy not containing the third element. As apparent from FIGS. 4A and 4B, the structure of the Mg—Li alloy not containing the third element occupies most of the parent phase region having a uniform contrast, and the distortion of precipitates and crystal lattices. Was not so noticeable. However, when the image of FIG. 4A was carefully examined, it was found that many linear defects were running in two directions. All of these were considered to be “twin boundaries” that appeared due to the formation of a structural phase different from bcc and hcp. It was interpreted that fine splitting appeared in the diffraction spot with the occurrence of the twin boundary (FIG. 4B).
図５に、第三元素を含まないＭｇ−Ｌｉ合金の典型的な微細組織を写す高分解能像を示す。図５から明らかなように、平行な縞状コントラストからなるモアレ縞の形成に加え、双晶の形成によるドメイン（分域）構造領域が発達した様子が確認できる。この場合の双晶境界は、シャープな格子面からなるものではなく、３ｎｍから５ｎｍ程度の幅をもった乱れた構造領域を境界として、その両側にｂｃｃやｈｃｐとは異なる斜方晶系（orthorhombic）の構造領域が「鏡映対称」の関係をとりながら存在する。モアレ縞の周囲に発生する「ひずみ場」や「双晶境界」等の格子欠陥はいずれも、転位のすべりに対する運動障害として機能し、強度上昇をもたらす重大な影響因子とみなせる。以上より、Ｍｇ−Ｌｉ合金の構造とは、母相のｂｃｃ構造に加え、ｈｃｐ構造ならびに多数の双晶境界によって分域化された斜方晶構造から成る混合組織（ヘテロ構造）として特徴付けられることが分かった。この現象は、第３元素を添加した場合でも、その種類や量によって程度を変えながら再現することが確かめられた。 FIG. 5 shows a high-resolution image showing a typical microstructure of an Mg—Li alloy not containing a third element. As can be seen from FIG. 5, it can be confirmed that the domain (domain) structure region has developed due to the formation of twins in addition to the formation of moire fringes composed of parallel striped contrast. In this case, the twin boundary is not composed of a sharp lattice plane, and has a disordered structural region having a width of about 3 nm to 5 nm as a boundary, and an orthorhombic system different from bcc and hcp on both sides thereof. ) Exists in a “mirror symmetry” relationship. Lattice defects such as “strain field” and “twin boundary” generated around the moire fringe function as kinetic obstacles to dislocation slip, and can be regarded as serious influencing factors that increase the strength. From the above, the structure of the Mg—Li alloy is characterized as a mixed structure (heterostructure) consisting of an hcp structure and an orthorhombic structure divided by a number of twin boundaries in addition to the bcc structure of the parent phase. I understood that. It was confirmed that this phenomenon was reproduced while changing the degree depending on the type and amount even when the third element was added.
図６、７に、第三元素としてＺｎを添加したＭｇ−Ｌｉ系合金のＴＥＭ写真画像を示す。尚、図６に示したＴＥＭ写真画像は、初期時効材に対して母相の［１００］方位から撮影したものであり、図７に示したＴＥＭ写真画像は、ピーク時効材に対するものである。図６、７を見ると明らかなように、図４に示した第三元素を含まないＭｇ−Ｌｉ合金の写真と比較して、Ｚｎ添加合金のほうが微細且つ複雑なコントラストを示しており、Ｚｎ添加によってＭｇ−Ｌｉ合金に大きな組織変化が生じたことが分かる。しかしながら、図６と図７とを比較しても、組織的に大きな違いは認められず、単に通常のＴＥＭ画像を観察するのみでは、第三元素を添加した場合におけるＭｇ−Ｌｉ合金の強化機構を評価することは困難であった。 6 and 7 show TEM photographic images of Mg—Li based alloys to which Zn is added as a third element. The TEM photographic image shown in FIG. 6 is taken from the [100] orientation of the parent phase with respect to the initial aging material, and the TEM photographic image shown in FIG. 7 is for the peak aging material. As apparent from FIGS. 6 and 7, the Zn-added alloy shows a finer and more complex contrast than the photograph of the Mg—Li alloy not containing the third element shown in FIG. It can be seen that a large structural change occurred in the Mg—Li alloy by the addition. However, even when FIG. 6 and FIG. 7 are compared, no significant structural difference is recognized, and the mechanism of strengthening the Mg—Li alloy in the case where the third element is added simply by observing a normal TEM image. It was difficult to evaluate.
本発明者は、ＴＥＭ写真において複雑に分裂した回折スポットに注目し、汎用観察技術の一つである暗視野法を適用して画像取得を行い、Ｚｎを添加したＭｇ−Ｌｉ合金の構成相粒子の分散状態を比較した。 The present inventor paid attention to the diffraction spots complicatedly divided in the TEM photograph, applied the dark field method, which is one of general-purpose observation techniques, and obtained constituent images of Mg-Li alloy containing Zn. The dispersion states of were compared.
図８に、「初期時効材」の母相に対する[１００]入射の電子回折図形を示す。ここに分裂して存在する６つの回折スポットに注目して対物レンズ絞りを挿入し、暗視野像を取得して、それぞれのスポットに起因する粒子の分布情報を調査した。まず、図９（Ａ）に、スポット１とスポット２に対応した暗視野像を示す。図９（Ａ）は、それぞれｈｃｐ相及びそのバリアント晶（結晶構造は等価であるが、成長方位の異なる析出結晶粒子の総称）に起因するものである。図９（Ａ）において、明るく光っている粒子がｈｃｐ相粒子に対応し、一粒子当たり数ｎｍ程度の粒子径からなる小さな粒子であることが分かる。また、図９（Ｂ）、（Ｃ）に、スポット３〜６に対応した暗視野像を示す。図９（Ｂ）、（Ｃ）は、双晶関係にあるorthorhombic相及びそのバリアント晶に起因するものである。これらはｈｃｐ相粒子よりも粒子径が大きく、数十ｎｍのサイズを有することが分かる。 FIG. 8 shows an [100] incident electron diffraction pattern for the parent phase of the “initial aging material”. Focusing on the six diffracted spots split and present, an objective lens stop was inserted, a dark field image was acquired, and the distribution information of the particles resulting from each spot was investigated. First, FIG. 9A shows dark field images corresponding to spot 1 and spot 2. FIG. 9A is attributed to the hcp phase and its variant crystal (generic name for precipitated crystal grains having the same crystal structure but different growth orientations). In FIG. 9A, it can be seen that brightly shining particles correspond to hcp phase particles and are small particles having a particle diameter of about several nanometers per particle. 9B and 9C show dark field images corresponding to the spots 3 to 6, respectively. FIGS. 9B and 9C are due to the orthohomhombic phase having a twin relationship and its variant crystals. It can be seen that these particles have a particle size larger than that of hcp phase particles and have a size of several tens of nm.
図１０に、「ピーク時効材」の母相に対する[１００]入射の電子回折図形を示す。ここに分裂して存在する６つの回折スポットに注目して対物レンズ絞りを挿入し、暗視野像を取得して、それぞれのスポットに起因する粒子の分布情報を調査した。まず、図１１（Ａ）に、スポット１とスポット２に対応した暗視野像を示す。図１１（Ａ）は、それぞれｈｃｐ相及びそのバリアント晶に起因するものである。図１１（Ａ）から明らかなように、初期時効材においては数ｎｍ程度の粒子径であったｈｃｐ相粒子が、ピーク時効材においては１００ｎｍを上回るほどに拡大成長していることがわかる。また、図１１（Ｂ）、（Ｃ）に、スポット３〜６に対応した暗視野像を示す。図１１（Ｂ）、（Ｃ）から明らかなように、双晶関係にある斜方晶相及びそのバリアント晶に起因する析出物粒子についても、若干の粒成長が確認できる。すなわち、ｈｃｐ相及び斜方晶相からなるそれぞれの析出物粒子が、「１００ｎｍ程度の大きさに及ぶ粒成長を遂げたこと」が、Ｍｇ−Ｌｉ合金の強度向上に大きな影響を与えたと判断することができる。 FIG. 10 shows an [100] incident electron diffraction pattern for the parent phase of the “peak aging material”. Focusing on the six diffracted spots split and present, an objective lens stop was inserted, a dark field image was acquired, and the distribution information of the particles resulting from each spot was investigated. First, FIG. 11A shows dark field images corresponding to spot 1 and spot 2. FIG. 11A is attributed to the hcp phase and its variant crystals, respectively. As is clear from FIG. 11A, it can be seen that hcp phase particles having a particle diameter of about several nanometers in the initial aging material expand and grow to exceed 100 nm in the peak aging material. FIGS. 11B and 11C show dark field images corresponding to the spots 3 to 6. As is clear from FIGS. 11B and 11C, some grain growth can be confirmed also for the precipitate particles resulting from the orthorhombic phase in the twinning relationship and the variant crystals. That is, it is judged that the fact that the respective precipitate particles composed of the hcp phase and the orthorhombic phase “growth about 100 nm in size” had a great influence on the strength improvement of the Mg—Li alloy. be able to.
図１２に、Ｚｎ添加のＭｇ−Ｌｉ系合金に係る初期時効材の同一視野に対して実施した汎用ＴＥＭ法ならびにＨＡＡＤＦ−ＳＴＥＭ法による観察例を示す。図１２（Ａ）がＺｎ添加の初期時効材から得られた汎用ＴＥＭ像で、図１２（Ｂ）がＨＡＡＤＦ−ＳＴＥＭ像である。図１２（Ａ）に示すＴＥＭ像のコントラストは、電子の散乱・吸収コントラストからなるもので、試料の厚さや密度、ひずみなど様々な条件の影響を受けて現れるため、その像解釈は容易でない。一方、図１２（Ｂ）に示すＨＡＡＤＦ−ＳＴＥＭ像のコントラストは、原子番号Ｚの２乗に比例して現れるため、像解釈が容易である。すなわち、明るく見える場所が重元素（すなわちＺｎ）の濃化領域であり、暗く見える場所が軽元素（Ｌｉ）の濃化領域である。図１２（Ｂ）の一部を拡大した写真を図１３に示す。図１３において暗い領域がＬｉ（もしくはその化合物）の濃化領域で、明るい領域がＺｎの濃化領域と言える。 FIG. 12 shows an example of observation by the general-purpose TEM method and the HAADF-STEM method performed on the same field of view of the initial aging material related to the Zn-added Mg—Li alloy. FIG. 12 (A) is a general-purpose TEM image obtained from the Zn-added initial aging material, and FIG. 12 (B) is a HAADF-STEM image. The contrast of the TEM image shown in FIG. 12A is made up of electron scattering / absorption contrast, and appears under the influence of various conditions such as the thickness, density, and strain of the sample, so that the image interpretation is not easy. On the other hand, since the contrast of the HAADF-STEM image shown in FIG. 12B appears in proportion to the square of the atomic number Z, image interpretation is easy. That is, a place that appears bright is a heavy element (ie, Zn) concentration region, and a place that appears dark is a light element (Li) concentration region. FIG. 13 shows an enlarged photograph of a part of FIG. In FIG. 13, it can be said that the dark region is a concentrated region of Li (or a compound thereof) and the bright region is a concentrated region of Zn.
図１４に、Ｚｎ添加のＭｇ−Ｌｉ系合金に係るピーク時効材の同一視野に対して実施した汎用ＴＥＭ法ならびにＨＡＡＤＦ−ＳＴＥＭ法による観察例を示す。図１４（Ａ）がＺｎ添加のピーク時効材から得られた汎用ＴＥＭ像で、図１４（Ｂ）がＨＡＡＤＦ−ＳＴＥＭ像である。図１４（Ｂ）から分かるように、ＺｎとＬｉそれぞれの濃化領域が白黒のコントラストとなっており、図１２の初期時効材とは大きく異なる組織の特徴、つまりＺｎとＬｉに関する特異な偏析状態が顕在化している。図１４（Ｂ）において、ＨＡＡＤＦ−ＳＴＥＭ像に見える微細な明るい粒子は、Ｚｎの濃化粒子であり、一様な方向性、すなわち母相の＜１００＞方向に沿って分散析出していることが分かる。一方、黒色の比較的大きな粒子はＬｉの濃化粒子であり、ＥＤＳ分析によれば酸化リチウム或いは亜鉛化リチウムの粒子と推測された（図１５）。図１３と図１４とを比較すると明らかなように、Ｚｎ添加のＭｇ−Ｌｉ合金においては特に、微細且つ高濃度に現れるＺｎの濃化粒子の析出、あるいはそれに加えてＬｉの濃化粒子の析出が、当該合金の大きな時効硬化をもたらす影響因子になっていると判断された。 FIG. 14 shows an example of observation by a general-purpose TEM method and a HAADF-STEM method performed on the same field of view of a peak aging material related to a Zn-added Mg—Li-based alloy. FIG. 14 (A) is a general-purpose TEM image obtained from a Zn-added peak aging material, and FIG. 14 (B) is a HAADF-STEM image. As can be seen from FIG. 14B, the concentrated regions of Zn and Li each have a black and white contrast, and the feature of the structure greatly different from the initial aging material of FIG. 12, that is, a unique segregation state regarding Zn and Li. Has become apparent. In FIG. 14 (B), the fine bright particles that can be seen in the HAADF-STEM image are Zn-enriched particles, and are distributed in a uniform direction, that is, along the <100> direction of the parent phase. I understand. On the other hand, the relatively large black particles were concentrated Li particles, and were estimated to be lithium oxide or lithium zincated particles according to EDS analysis (FIG. 15). As is clear from comparison between FIG. 13 and FIG. 14, precipitation of Zn-concentrated particles appearing in a fine and high concentration, or precipitation of Li-concentrated particles in addition to that, particularly in a Zn-added Mg—Li alloy. However, it has been determined that this is an influential factor that causes a large age hardening of the alloy.
また、図１６に、Ｚｎ添加のＭｇ−Ｌｉ系合金に係るピーク時効材について、電子線の入射方位を精密に［１００］晶帯軸に平行に調整したうえで、高倍率にてＨＡＡＤＦ−ＳＴＥＭ像を取得した場合の図を示す。図１６から明らかなように、より微細なコントラストの発生を観察することができる。図１６においては、９０°の回転関係にある２つの等価な＜１１０＞方向に沿って延びた直線状の細いコントラスト（線部分）からなるものであることがわかる。この析出物の実体については未解明であるが、ｂｃｃ母相の＜１１０＞に平行な格子点をＺｎ原子が２次元的に置換したできた板状の整合析出物、つまりＧＰゾーンである可能性が考えられた。 FIG. 16 shows the HAADF-STEM at a high magnification after adjusting the incident direction of the electron beam precisely in parallel with the [100] zone axis for the peak-aged material related to the Zn-added Mg—Li alloy. The figure at the time of acquiring an image is shown. As is apparent from FIG. 16, the generation of finer contrast can be observed. In FIG. 16, it can be seen that it consists of two thin linear contrasts (line portions) extending along two equivalent <110> directions having a 90 ° rotational relationship. Although the substance of this precipitate is not yet elucidated, it may be a plate-like matched precipitate in which Zn atoms are two-dimensionally substituted at lattice points parallel to <110> of the bcc matrix, that is, a GP zone. Sex was considered.
以上より、Ｍｇ−Ｌｉ系合金について、ＨＡＡＤＦ−ＳＴＥＭ像を取得することにより、Ｍｇ−Ｌｉ系合金における第三元素（Ｚｎ）や軽元素（Ｌｉ）の化学的偏析状態を可視化することができ、Ｍｇ−Ｌｉ系合金の時効硬化に直結する組織学的特徴を適切に解明・評価することが可能と言える。言い換えれば、硬度試験や強度試験において優れた性能を示したＭｇ−Ｌｉ系合金に対して本発明に係る評価を実施し、その構造の変化や重・軽元素の分布状態を評価し、時効硬化メカニズムを正しく理解することにより、新たな材料合成に対する設計指針の提示、つまり、Ｍｇ−Ｌｉ合金組成、第三元素の種類や量、時効処理の温度や処理時間などの条件設定が可能になり、効果的なフィードバックが達せられることとなった。 From the above, it is possible to visualize the chemical segregation state of the third element (Zn) and the light element (Li) in the Mg-Li alloy by acquiring the HAADF-STEM image for the Mg-Li alloy. It can be said that it is possible to appropriately elucidate and evaluate the histological characteristics directly related to age hardening of the Mg—Li alloy. In other words, an evaluation according to the present invention is performed on an Mg-Li alloy that has shown excellent performance in hardness tests and strength tests, the structural changes and the distribution state of heavy and light elements are evaluated, and age hardening is performed. By correctly understanding the mechanism, it becomes possible to present design guidelines for new material synthesis, that is, to set conditions such as Mg-Li alloy composition, type and amount of third element, temperature of aging treatment and treatment time, Effective feedback was achieved.
以上、現時点において、最も実践的であり、且つ、好ましいと思われる実施形態に関連して本発明を説明したが、本発明は、本願明細書中に開示された実施形態に限定されるものではなく、請求の範囲及び明細書全体から読み取れる発明の要旨あるいは思想に反しない範囲で適宜変更可能であり、そのような変更を伴うＭｇ−Ｌｉ系合金の評価方法もまた本発明の技術範囲に包含されるものとして理解されなければならない。 Although the present invention has been described with reference to the most practical and preferred embodiments at the present time, the invention is not limited to the embodiments disclosed herein. The invention can be appropriately changed without departing from the scope or spirit of the invention that can be read from the claims and the entire specification, and a method for evaluating an Mg—Li alloy with such a change is also included in the technical scope of the present invention. Must be understood as being.
本発明によれば、Ｍｇ−Ｌｉ系合金における強化機構の詳細を適切に評価することができる。これを活用することで、硬度試験や強度試験において優れた性能を示したＭｇ−Ｌｉ系合金について、本発明に係る評価方法によってその構造の変化や重・軽元素（ＺｎやＬｉ）の分布状態を評価し、時効硬化メカニズムを正しく理解することにより、新たな材料合成に対する設計指針の提示、つまり、Ｍｇ−Ｌｉ合金組成、第三元素の種類や量、時効処理の温度や処理時間などの条件設定が可能になり、効果的なフィードバックが達せられこととなった。 According to the present invention, the details of the strengthening mechanism in the Mg—Li alloy can be appropriately evaluated. By utilizing this, regarding Mg-Li alloys that showed excellent performance in hardness tests and strength tests, the structural changes and the distribution of heavy and light elements (Zn and Li) by the evaluation method according to the present invention By evaluating the age hardening mechanism and correctly understanding the age-hardening mechanism, presentation of design guidelines for new material synthesis, that is, conditions such as Mg-Li alloy composition, type and amount of third element, temperature and time of aging treatment, etc. Setting is now possible and effective feedback is achieved.
Claims (3)
高角度円環状検出器暗視野走査型透過電子顕微鏡法（ＨＡＡＤＦ−ＳＴＥＭ法）によって、前記Ｍｇ−Ｌｉ系合金のＨＡＡＤＦ−ＳＴＥＭ像を取得し、該Ｍｇ−Ｌｉ系合金の微細組織・構造、及び／又は、該Ｍｇ−Ｌｉ系合金における重・軽元素の偏在状態を確認することを特徴とする、
Ｍｇ−Ｌｉ系合金の評価方法。 A method for evaluating an Mg-Li alloy comprising at least Mg, Li, and a third element,
HAADF-STEM image of the Mg-Li alloy was obtained by high-angle annular detector dark field scanning transmission electron microscopy (HAADF-STEM method), and the microstructure and structure of the Mg-Li alloy, and / Or characterized by confirming the uneven distribution of heavy and light elements in the Mg-Li-based alloy,
Evaluation method of Mg-Li alloy.
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