EP0465376A1 - High strength magnesium alloy containing strontium and process for its manufacture by rapid solidification - Google Patents
High strength magnesium alloy containing strontium and process for its manufacture by rapid solidification Download PDFInfo
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- EP0465376A1 EP0465376A1 EP91420177A EP91420177A EP0465376A1 EP 0465376 A1 EP0465376 A1 EP 0465376A1 EP 91420177 A EP91420177 A EP 91420177A EP 91420177 A EP91420177 A EP 91420177A EP 0465376 A1 EP0465376 A1 EP 0465376A1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C45/00—Amorphous alloys
- C22C45/005—Amorphous alloys with Mg as the major constituent
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C23/00—Alloys based on magnesium
- C22C23/02—Alloys based on magnesium with aluminium as the next major constituent
Definitions
- the present invention relates to magnesium alloys with high mechanical strength containing strontium and their manufacturing process. It relates in particular to the commercial magnesium alloys listed under the names AZ 31, AZ 61, AZ 80 (wrought alloys) and AZ 91, AZ 92 (casting alloys), according to the ASTM standard (or alternatively G-A3Z1, G-A6Z1, G-A8Z, G-A9Z1, G-A9Z2 according to French standard NFA 02-004) to which strontium has been added. These alloys can contain manganese and / or calcium as addition elements.
- the rare earths must be refined to contain very little Fe, Ni or Cu, which significantly increases their price. They are also difficult to introduce into the liquid magnesium bath because of their high reactivity with oxygen. Due to their high density, it is more difficult to obtain good homogeneity of the bath during their introduction.
- This alloy may also contain, as an addition, at least one of the elements Zn and / or Ca in the following proportions:
- the matrix consists of fine magnesium grains with an average size of less than 3 ⁇ m or more advantageously not exceeding approximately 1 ⁇ m; it is reinforced by precipitates of intermetallic compounds dispersed homogeneously, preferably at the grain boundaries, of variable size and nature depending on the chemical composition of the alloy.
- Al4Sr, Mg2Sr, Mg17Sr2 and / or Mg17Al12 are preferably found in the grains for sizes less than 0.1 ⁇ m and at grain boundaries for larger sizes between 0.1 and 1 ⁇ m; this is the case for the Mg17Al12 compounds.
- Sr can also be found in solid solution in Mg and Mg17Al12.
- Ca is present in sufficient quantity in the alloy, it is found in solid solution in Mg17Al12 and in the form of fine metastable globules rich in Al and Ca of size less than 0.1 ⁇ m, dispersed in the matrix of Mg and possibly transform into Al2Ca by heat treatment.
- the alloy according to the invention is usually obtained by the rapid solidification processes and the various modes of implementation, described in application EP 89-903172, which form an integral part of the description.
- the alloy in the liquid state is subjected to rapid solidification, at a speed at least equal to 104K sec ⁇ 1, generally less than 107K sec ⁇ 1, so as to obtain a solidified product, of which at least one dimensions is less than 150 ⁇ m, said product then being consolidated directly by precompaction and compacting or by direct compacting, the compacting taking place at a temperature between 200 and 350 ° C.
- the solidified product undergoes no other operation conditioning such as grinding before being consolidated by direct precompaction and / or compacting, this operation may be such as to alter the mechanical characteristics of the consolidated alloy obtained.
- the first two modes of application make it possible to obtain a solid in the form of ribbons, scales or platelets, while the latter gives powder. These processes are described in detail in application EP 89-903 172.
- the rapidly solidified product can be degassed under vacuum at a temperature less than or equal to 350 ° C. before consolidation.
- Consolidation is carried out, according to the invention, directly on the products which solidify rapidly, in particular directly on the scales or plates.
- Consolidation is important to avoid long exposures to high temperatures. We therefore chose to operate a warm spinning which minimizes the time spent at high temperature.
- the spinning temperature is between 200 and 350 ° C; the spinning ratio is generally between 10 and 40, preferably between 10 and 20, and simultaneously the speed of advance of the pestle is preferably between 0.5 and 3 mm / sec, but it can be higher (for example 5 mm / sec).
- the solid product before consolidation can be: either introduced directly into the container of a press and then spun, either cold or warm pre-compacted (temperature below 350 ° C.
- a press for example in the form of a billet whose density is close to 99% of the theoretical density of the alloy, this billet being subsequently spun, either introduced by cold pre-compacting them up to 70% of the theoretical density in a sheath made of magnesium or magnesium alloy or aluminum or aluminum alloy, itself introduced into the container of the spinning press; we can then, after spinning, remove the sheath by machining.
- the sheath can be thin-walled (less than 1 mm) or thick (up to 4 mm). In all cases, it is preferable that the alloy constituting the sheath has a flow limit not exceeding the order of magnitude of that of the product to be spun, at the spinning temperature.
- the process according to the invention makes it possible to unexpectedly obtain a consolidated magnesium alloy which has, as already described, a structure of fine grains (less than 3 ⁇ m) stabilized by intermetallic compounds, and / or by metastable dispersoids and high mechanical characteristics.
- the structure and mechanical properties of said alloy remain unchanged after prolonged maintenance of 24 h and more at a temperature reaching 250 ° C., or even 300 ° C. in certain cases, for example when the alloy contains calcium.
- the matrix consists essentially of magnesium containing approximately 1% (atomic) of Al in solid solution; the grain size is very fine, and usually between 0.3 and 1 ⁇ m; it depends on the consolidation conditions.
- the intermetallic phases observed depend on the composition of the alloy and can be Mg17Al12 optionally containing Sr and / or Zn, Mg32 (Al, Zn) 49, Mg17Sr2, Mg2Sr, Al4Sr, and when the alloy contains Ca Al2Ca. Rapid cooling allows the formation of metastable phases.
- the breaking loads obtained with the alloys according to the invention are high; they generally exceed 400 MPa and are at least of the same level as those obtained for example with the alloys described in the aforementioned applications; moreover, there is an improvement in ductility and hardness.
- strontium makes it possible to significantly improve the breaking strength, sometimes at the expense of ductility.
- the corrosion resistance is also very good, because, in addition to a low weight loss in a saline aqueous medium, there is the absence of pitting; the alloys according to the invention retain a very shiny appearance; only a few shallow localized corrosions are observed, having the appearance of antlers.
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Abstract
Description
La présente invention concerne des alliages de magnésium à haute résistance mécanique contenant du strontium et leur procédé de fabrication. Elle concerne en particulier les alliages commerciaux de magnésium répertoriés sous les dénominations AZ 31, AZ 61, AZ 80 (alliages de corroyage) et AZ 91, AZ 92 (alliages de moulage), selon la norme ASTM (ou encore respectivement G-A3Z1, G-A6Z1, G-A8Z, G-A9Z1, G-A9Z2 selon la norme française NFA 02-004) auxquels on a ajouté du strontium. Ces alliages peuvent contenir du manganèse et/ou du calcium comme éléments d'addition.The present invention relates to magnesium alloys with high mechanical strength containing strontium and their manufacturing process. It relates in particular to the commercial magnesium alloys listed under the names AZ 31, AZ 61, AZ 80 (wrought alloys) and AZ 91, AZ 92 (casting alloys), according to the ASTM standard (or alternatively G-A3Z1, G-A6Z1, G-A8Z, G-A9Z1, G-A9Z2 according to French standard NFA 02-004) to which strontium has been added. These alloys can contain manganese and / or calcium as addition elements.
La demanderesse a déjà proposé dans la demande EP 89-903 172 des alliages de magnésium obtenus par solidification rapide disposant de caractéristiques mécaniques améliorées; ces alliages peuvent contenir du calcium. Dans la demande FR 89-11357, elle a également proposé des alliages de magnésium de caractéristiques mécaniques améliorées contenant du Ca et des terres rares avec lesquels on note en plus une meilleure tenue à la corrosion.The Applicant has already proposed in Application EP 89-903,172 magnesium alloys obtained by rapid solidification having improved mechanical characteristics; these alloys may contain calcium. In application FR 89-11357, it also proposed magnesium alloys with improved mechanical characteristics containing Ca and rare earths with which there is in addition a better resistance to corrosion.
Au vu de ces bons résultats elle a cependant cherché à s'affranchir de l'emploi d'éléments comme les terres rares qui sont des produits coûteux et nécessitent des précautions d'emploi. En particulier les terres rares doivent être affinées pour ne contenir que très peu de Fe, Ni ou Cu, ce qui accroît significativement leur prix.
Elles sont par ailleurs délicates à introduire dans le bain de magnésium liquide du fait de leur grande réactivité avec l'oxygène. Du fait de leur forte densité il est de plus difficile d'obtenir une bonne homogénéité du bain lors de leur introduction.In view of these good results, however, it has sought to overcome the use of elements such as rare earths which are expensive products and require precautions for use. In particular, the rare earths must be refined to contain very little Fe, Ni or Cu, which significantly increases their price.
They are also difficult to introduce into the liquid magnesium bath because of their high reactivity with oxygen. Due to their high density, it is more difficult to obtain good homogeneity of the bath during their introduction.
La demanderesse a donc cherché à éviter l'emploi de ces éléments tout en cherchant à obtenir des caractéristiques mécaniques au moins équivalentes, voire améliorées (la résistance à la rupture et surtout la ductilité) et une tenue à la corrosion également améliorée.The plaintiff therefore sought to avoid the use of these elements while seeking to obtain mechanical characteristics that are at least equivalent, or even improved (breaking strength and above all ductility) and also improved corrosion resistance.
L'invention est un alliage à base de magnésium ayant une charge à la rupture au moins égale à 290 MPa, un allongement à la rupture d'au moins 5%, caractérisé en ce qu'il a la composition suivante (en poids) :
avec les teneurs en impuretés principales (en poids) :
- Silicium
- < 0,6 %
- Cuivre
- < 0,2 %
- Fer
- < 0,1 %
with the main impurity contents (by weight):
- Silicon
- <0.6%
- Copper
- <0.2%
- Iron
- <0.1%
Cet alliage peut également contenir, comme addition, au moins l'un des éléments Zn et/ou Ca dans les proportions suivantes :
La microstructure habituelle des alliages obtenus peut être caractérisée de la façon suivante : la matrice est constituée de grains fins de magnésium de dimension moyenne inférieure à 3 µm ou plus avantageusement ne dépassant pas approximativement 1 µm ; elle est renforcée par des précipités de composés intermétalliques dispersés de façon homogène, de préférence aux joints de grains, de taille et nature variables selon la composition chimique de l'alliage.The usual microstructure of the alloys obtained can be characterized as follows: the matrix consists of fine magnesium grains with an average size of less than 3 μm or more advantageously not exceeding approximately 1 μm; it is reinforced by precipitates of intermetallic compounds dispersed homogeneously, preferably at the grain boundaries, of variable size and nature depending on the chemical composition of the alloy.
Ainsi on trouve généralement Al₄Sr, Mg₂Sr, Mg₁₇Sr₂ et/ou Mg₁₇Al₁₂ selon les teneurs respectives en Al et Sr ; ces dispersoïdes se trouvent de préférence dans les grains pour des tailles inférieures à 0,1 µm et aux joints de grains pour des tailles plus élevées comprise entre 0,1 et 1 µm ; ceci est le cas pour les composés Mg₁₇Al₁₂. Sr peut également se trouver en solution solide dans Mg et Mg₁₇Al₁₂. Quand Ca est présent en quantité suffisante dans l'alliage, on le trouve en solution solide dans Mg₁₇Al₁₂ et sous forme de fins globules métastables riches en Al et Ca de taille inférieure à 0,1 µm, dispersés dans la matrice de Mg et pouvant se transformer en Al₂Ca par traitement thermique.Thus one generally finds Al₄Sr, Mg₂Sr, Mg₁₇Sr₂ and / or Mg₁₇Al₁₂ according to the respective contents in Al and Sr; these dispersoids are preferably found in the grains for sizes less than 0.1 μm and at grain boundaries for larger sizes between 0.1 and 1 µm; this is the case for the Mg₁₇Al₁₂ compounds. Sr can also be found in solid solution in Mg and Mg₁₇Al₁₂. When Ca is present in sufficient quantity in the alloy, it is found in solid solution in Mg₁₇Al₁₂ and in the form of fine metastable globules rich in Al and Ca of size less than 0.1 μm, dispersed in the matrix of Mg and possibly transform into Al₂Ca by heat treatment.
Cette structure demeure inchangée après maintien de 24 h à 250° C.This structure remains unchanged after 24 hours at 250 ° C.
L'alliage selon l'invention est habituellement obtenu par les procédés de solidification rapide et les différents modes de mise en oeuvre, décrits dans la demande EP 89-903172, qui font partie intégrante de la description. En résumé, l'alliage à l'état liquide est soumis à une solidification rapide, à une vitesse au moins égale à 10⁴K sec⁻¹, généralement inférieure à 10⁷K sec⁻¹, de façon à obtenir un produit solidifié, dont au moins une des dimensions est inférieure à 150 µm, ledit produit étant ensuite consolidé directement par précompactage et compactage ou par compactage direct, le compactage ayant lieu à une température comprise entre 200 et 350° C. Il est préférable que le produit solidifié ne subisse aucune autre opération de conditionnement telle que le broyage avant d'être consolidé par précompactage et/ou compactage direct, cette opération pouvant être de nature à altérer les caractéristiques mécaniques de l'alliage consolidé obtenu.The alloy according to the invention is usually obtained by the rapid solidification processes and the various modes of implementation, described in application EP 89-903172, which form an integral part of the description. In summary, the alloy in the liquid state is subjected to rapid solidification, at a speed at least equal to 10⁴K sec⁻¹, generally less than 10⁷K sec⁻¹, so as to obtain a solidified product, of which at least one dimensions is less than 150 μm, said product then being consolidated directly by precompaction and compacting or by direct compacting, the compacting taking place at a temperature between 200 and 350 ° C. It is preferable that the solidified product undergoes no other operation conditioning such as grinding before being consolidated by direct precompaction and / or compacting, this operation may be such as to alter the mechanical characteristics of the consolidated alloy obtained.
Le refroidissement rapide pour solidification peut être obtenu :
- soit par coulée sous forme de ruban sur un appareil dit "d'hypertrempe sur rouleau" (procédés connus sous le nom de "free jet melt spinning" ou "planar flow casting"), constitué habituellement d'un tambour refroidi énergiquement sur lequel on coule le métal sous forme d'un ruban d'épaisseur inférieure à 150 µm, de préférence de l'ordre de 30 à 50 µm;
- soit par fusion d'une électrode ou par jet de métal liquide; le métal liquide est alors mécaniquement divisé ou atomisé et projeté sur une surface énergiquement refroidie et maintenue dégagée,
- soit par atomisation de l'alliage liquide dans un jet de gaz inerte.
- either by casting in the form of a ribbon on an apparatus known as "hyper-quenching on a roll" (processes known as "free jet melt spinning" or "planar flow casting"), usually consisting of an energetically cooled drum on which flows the metal in the form of a ribbon with a thickness of less than 150 μm, preferably of the order of 30 to 50 μm;
- either by fusion of an electrode or by jet of liquid metal; the liquid metal is then mechanically divided or atomized and projected onto an energetically cooled surface and kept clear,
- either by atomization of the liquid alloy in a jet of inert gas.
Les deux premiers modes d'application permettent d'obtenir un solide sous forme de rubans, écailles ou plaquettes, tandis que le dernier donne de la poudre. Ces procédés sont décrits en détail dans la demande EP 89-903 172. Le produit solidifié rapidement peut être dégazé sous vide à une température inférieure ou égale à 350° C avant consolidation.The first two modes of application make it possible to obtain a solid in the form of ribbons, scales or platelets, while the latter gives powder. These processes are described in detail in application EP 89-903 172. The rapidly solidified product can be degassed under vacuum at a temperature less than or equal to 350 ° C. before consolidation.
La consolidation, également décrite dans ladite demande, est effectuée, selon l'invention, directement sur les produits solidifiés rapidement, en particulier directement sur les écailles ou plaquettes. Pour préserver la structure fine et originale obtenue par solidification rapide, il est important d'éviter les longues expositions à des températures élevées. On a donc choisi d'opérer un filage à tiède qui permet de minimiser la durée de passage à température élevée.Consolidation, also described in said application, is carried out, according to the invention, directly on the products which solidify rapidly, in particular directly on the scales or plates. To preserve the fine and original structure obtained by rapid solidification, it is important to avoid long exposures to high temperatures. We therefore chose to operate a warm spinning which minimizes the time spent at high temperature.
La température de filage est comprise entre 200 et 350° C; le rapport de filage est généralement compris entre 10 et 40, de préférence entre 10 et 20, et simultanément la vitesse d'avance du pilon est de préférence située entre 0,5 et 3 mm/sec, mais elle peut être supérieure (par exemple 5 mm/sec ).
Comme cela est décrit dans ladite demande, le produit solide avant consolidation peut être :
soit introduit directement dans le conteneur d'une presse puis filé,
soit précompacté à froid ou à tiède (température inférieure par exemple à 350° C), à l'aide d'une presse, sous forme par exemple de billette dont la densité est voisine de 99 % de la densité théorique de l'alliage, cette billette étant par la suite filée,
soit introduit en les précompactant à froid jusqu'à 70 % de la densité théorique dans une gaine en magnésium ou alliage de magnésium ou en aluminium ou alliage d'aluminium, elle-même introduite dans le conteneur de la presse à filer; on peut ensuite, après filage, éliminer la gaine par usinage.The spinning temperature is between 200 and 350 ° C; the spinning ratio is generally between 10 and 40, preferably between 10 and 20, and simultaneously the speed of advance of the pestle is preferably between 0.5 and 3 mm / sec, but it can be higher (for example 5 mm / sec).
As described in said application, the solid product before consolidation can be:
either introduced directly into the container of a press and then spun,
either cold or warm pre-compacted (temperature below 350 ° C. for example), using a press, for example in the form of a billet whose density is close to 99% of the theoretical density of the alloy, this billet being subsequently spun,
either introduced by cold pre-compacting them up to 70% of the theoretical density in a sheath made of magnesium or magnesium alloy or aluminum or aluminum alloy, itself introduced into the container of the spinning press; we can then, after spinning, remove the sheath by machining.
La gaine peut être à paroi fine (inférieure à 1 mm) ou épaisse (jusqu'à 4 mm). Dans tous les cas, il est préférable que l'alliage constituant la gaine ait une limite d'écoulement ne dépassant pas l'ordre de grandeur de celle du produit à filer, à la température de filage.The sheath can be thin-walled (less than 1 mm) or thick (up to 4 mm). In all cases, it is preferable that the alloy constituting the sheath has a flow limit not exceeding the order of magnitude of that of the product to be spun, at the spinning temperature.
En variante, on peut mettre en oeuvre d'autres procédés de compactage ne produisant pas une élévation de température du produit au-delà de 350° C : parmi ces procédés optionnels, on peut citer le filage hydrostatique, le forgeage, le laminage et le formage superplastique, la compression isostatique à chaud (HIP).As a variant, it is possible to implement other compacting methods which do not produce a rise in temperature of the product beyond 350 ° C.: among these optional methods, mention may be made of hydrostatic spinning, forging, rolling and superplastic forming, hot isostatic compression (HIP).
Ainsi le procédé selon l'invention permet d'obtenir de façon inattendue un alliage de magnésium consolidé qui a, comme déjà décrit, une structure de grains fins (inférieurs à 3 µm) stabiliséé par des composés intermétalliques, et/ou par des dispersoïdes métastables et des caractéristiques mécaniques élevées. La structure et les propriétés mécaniques dudit alliage restent inchangées après maintien prolongé de 24 h et plus à une température atteignant 250° C, voire 300° C dans certains cas, par exemple quand l'alliage contient du calcium.Thus the process according to the invention makes it possible to unexpectedly obtain a consolidated magnesium alloy which has, as already described, a structure of fine grains (less than 3 μm) stabilized by intermetallic compounds, and / or by metastable dispersoids and high mechanical characteristics. The structure and mechanical properties of said alloy remain unchanged after prolonged maintenance of 24 h and more at a temperature reaching 250 ° C., or even 300 ° C. in certain cases, for example when the alloy contains calcium.
Cette structure fine a été observée en utilisant la microscopie optique, la diffraction des rayons X et la microscopie électronique en transmission. La matrice est constituée essentiellement de magnésium contenant approximativement 1 % (atomique) d'Al en solution solide; la taille de grains est très fine, et comprise habituellement entre 0,3 et 1 µm; elle dépend des conditions de consolidation.This fine structure was observed using optical microscopy, X-ray diffraction and transmission electron microscopy. The matrix consists essentially of magnesium containing approximately 1% (atomic) of Al in solid solution; the grain size is very fine, and usually between 0.3 and 1 μm; it depends on the consolidation conditions.
Les phases intermétalliques observées dépendent de la composition de l'alliage et peuvent être Mg₁₇Al₁₂ contenant éventuellement Sr et/ou Zn, Mg₃₂(Al,Zn)₄₉, Mg₁₇Sr₂, Mg₂Sr, Al₄Sr, et lorsque l'alliage contient Ca Al₂Ca. Le refroidissement rapide permet la formation de phases métastables.The intermetallic phases observed depend on the composition of the alloy and can be Mg₁₇Al₁₂ optionally containing Sr and / or Zn, Mg₃₂ (Al, Zn) ₄₉, Mg₁₇Sr₂, Mg₂Sr, Al₄Sr, and when the alloy contains Ca Al₂Ca. Rapid cooling allows the formation of metastable phases.
La dimension des composés intermétalliques est inférieure à 1 µm et la distribution de leur taille est généralement bimodale :
- un premier mode est généralement compris entre 0,1 et 1 µm et les particules correspondantes se trouvent aux joints de grains ; c'est souvent le cas de Mg₁₇Al₁₂.
- un deuxième mode est inférieur à 0,1 µm et est constitué de globules dispersés de façon homogène dans tout l'alliage (dans les grains et aussi aux joints de grains) ; c'est le cas par exemple pour Al₄Sr, Mg₁₇Sr₂, Al₂Ca...
- a first mode is generally between 0.1 and 1 μm and the corresponding particles are found at the grain boundaries; this is often the case with Mg₁₇Al₁₂.
- a second mode is less than 0.1 μm and consists of globules dispersed homogeneously throughout the alloy (in the grains and also at the grain boundaries); this is the case for example for Al₄Sr, Mg₁₇Sr₂, Al₂Ca ...
Toutes ces phases contribuent au durcissement des alliages. Celles dont le point de fusion est le plus élevé (par exemple Al₄Sr) garantissent la stabilité thermique de caractéristiques de l'alliage obtenu.All these phases contribute to the hardening of the alloys. Those with the highest melting point (for example Al₄Sr) guarantee the thermal stability of the characteristics of the alloy obtained.
Les charges à la rupture obtenues avec les alliages selon l'invention sont élevées; elles dépassent en général 400 MPa et sont au moins du même niveau que celles obtenu par exemple avec les alliages décrits dans les demandes précitées; de plus on note une amélioration de la ductilité et de la dureté.The breaking loads obtained with the alloys according to the invention are high; they generally exceed 400 MPa and are at least of the same level as those obtained for example with the alloys described in the aforementioned applications; moreover, there is an improvement in ductility and hardness.
Avec certains alliages de magnésium, en particulier ceux contenant du calcium ou encore les alliages commerciaux du type AZ91, le strontium permet d'améliorer significativement la résistance à la rupture, parfois au détriment de la ductilité.With certain magnesium alloys, in particular those containing calcium or even commercial alloys of the AZ91 type, strontium makes it possible to significantly improve the breaking strength, sometimes at the expense of ductility.
La résistance à la corrosion est également très bonne, car, en plus d'une faible perte de poids en milieu aqueux salin, on note l'absence de piqûres; les alliages selon l'invention conservent un aspect très brillant; on n'observe seulement que quelques corrosions localisées peu profondes ayant l'aspect de ramures.The corrosion resistance is also very good, because, in addition to a low weight loss in a saline aqueous medium, there is the absence of pitting; the alloys according to the invention retain a very shiny appearance; only a few shallow localized corrosions are observed, having the appearance of antlers.
Plusieurs alliages ont été produits par solidification rapide dans des conditions identiques à celles utilisées dans les exemples de la demande EP 89-903 172 précitée : coulée sur roue, vitesse périphérique de la roue 10 à 40 m/s, vitesse de refroidissement comprise entre 10⁵ et 10⁶K s⁻¹. Les rubans obtenus ont été ensuite directement introduits dans le conteneur d'une presse à filer pour obtenir un alliage consolidé sur lequel ont été faits les essais de caractérisation : examen microscopique, mesure des caractéristiques mécaniques, tenue à la corrosion.Several alloys were produced by rapid solidification under conditions identical to those used in the examples of the above-mentioned application EP 89-903 172: casting on wheel, peripheral speed of the wheel 10 to 40 m / s, cooling speed between 10⁵ and 10⁶K s⁻¹. The ribbons obtained were then directly introduced into the container of a spinning press to obtain a consolidated alloy on which were carried out the characterization tests: microscopic examination, measurement of mechanical characteristics, resistance to corrosion.
dans le tableau 1, on donne les conditions opératoires du filage, et les caractéristiques des alliages obtenus :
- Hv
- = dureté Vickers exprimée en Kg/mm2
- TYS
- = limite élastique mesurée à 0,2 % d'allongement résiduel, exprimée en MPa
- UTS
- = charge de rupture exprimé en MPa
- e
- = allongement de la rupture exprimé en %
- H v
- = Vickers hardness expressed in Kg / mm2
- TYS
- = elastic limit measured at 0.2% residual elongation, expressed in MPa
- UTS
- = breaking load expressed in MPa
- e
- = elongation at break expressed in%
Dans ce tableau on voit que les alliages des essais 30, 31 et 32, avec comme éléments d'addition Al et Sr, offrent de très bonnes résistances à la rupture conjuguées à une ductilité très élevée.In this table we see that the alloys of tests 30, 31 and 32, with the addition elements Al and Sr, offer very good tensile strengths combined with a very high ductility.
Dans l'essai 33, on a introduit Ca comme élément d'addition supplémentaire ; cet essai permet également de comparer le remplacement, par Sr, d'une terre rare (Nd) dans l'alliage de l'art antérieur de l'essai 20. On observe un net gain de caractéristiques mécaniques, la résistance à la rupture atteignant la valeur record de 628 MPa, en conservant un niveau comparable de ductilité.In run 33, Ca was introduced as an additional addition; this test also makes it possible to compare the replacement, by Sr, of a rare earth (Nd) in the alloy of the prior art of test 20. A clear gain in mechanical characteristics is observed, the resistance to rupture reaching the record value of 628 MPa, while maintaining a comparable level of ductility.
De même si on ajoute Sr à un alliage AZ 91 (essais 34-35) et qu'on le compare à un alliage AZ 91 tel quel (essai 23), on voit qu'on améliore sa résistance à la rupture pour une même ductilité. Si on le compare à un alliage AZ 91 contenant Ca (essai 12), on voit que la ductilité est améliorée dans des proportions considérables : à teneurs égales, l'alliage au Sr est près de 80 % plus ductile que l'alliage au Ca.Similarly if we add Sr to an AZ 91 alloy (tests 34-35) and compare it to an AZ 91 alloy as it is (test 23), we see that we improve its tensile strength for the same ductility . If we compare it to an AZ 91 alloy containing Ca (test 12), we see that the ductility is improved in considerable proportions: at equal contents, the Sr alloy is almost 80% more ductile than the Ca alloy .
La résistance à la corrosion de différents alliages a été évaluée par immersion dans une solution aqueuse à 0,05 % NaCl tamponnée à la magnésie à pH = 10,2. Dans le tableau 2 sont reportées les pertes de poids enregistrées, rapportées à la perte de poids de l'alliage conventionnel le plus résistant à la corrosion qui est un alliage AZ 91 de l'art antérieur (essai 23) élaboré dans les mêmes conditions.
On constate que les alliages contenant du Sr selon l'invention (essai 30-36) présentent une très bonne résistance à la corrosion dans ce milieu, meilleure que celle des alliages de l'art antérieur (essais 23-9).It is found that the alloys containing Sr according to the invention (test 30-36) have very good resistance to corrosion in this medium, better than that of the alloys of the prior art (tests 23-9).
Claims (14)
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9007299 | 1990-06-01 | ||
| FR9007299A FR2662707B1 (en) | 1990-06-01 | 1990-06-01 | HIGH MECHANICAL STRENGTH-CONTAINING MAGNESIUM ALLOY AND PROCESS FOR OBTAINING BY RAPID SOLIDIFICATION. |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0465376A1 true EP0465376A1 (en) | 1992-01-08 |
| EP0465376B1 EP0465376B1 (en) | 1994-10-26 |
Family
ID=9397519
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP91420177A Expired - Lifetime EP0465376B1 (en) | 1990-06-01 | 1991-05-30 | High strength magnesium alloy containing strontium and process for its manufacture by rapid solidification |
Country Status (6)
| Country | Link |
|---|---|
| US (1) | US5147603A (en) |
| EP (1) | EP0465376B1 (en) |
| JP (1) | JPH04231435A (en) |
| CA (1) | CA2043723A1 (en) |
| DE (1) | DE69104784T2 (en) |
| FR (1) | FR2662707B1 (en) |
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| EP1183402B1 (en) * | 1999-04-03 | 2003-11-26 | Volkswagen Aktiengesellschaft | Method for producing a magnesium alloy by extrusion moulding and use of the extrusion moulded semifinished products and components |
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- 1991-05-23 US US07/704,620 patent/US5147603A/en not_active Expired - Fee Related
- 1991-05-29 JP JP3126062A patent/JPH04231435A/en active Pending
- 1991-05-30 DE DE69104784T patent/DE69104784T2/en not_active Expired - Fee Related
- 1991-05-30 EP EP91420177A patent/EP0465376B1/en not_active Expired - Lifetime
- 1991-05-31 CA CA002043723A patent/CA2043723A1/en not_active Abandoned
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| US2233266A (en) * | 1939-12-26 | 1941-02-25 | Dow Chemical Co | Magnesium base alloy |
| DE2526024B1 (en) * | 1975-06-11 | 1976-07-15 | Mahle Gmbh | Use of magnesium-aluminum die-cast alloys for the production of die-cast parts at risk of hot cracks |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0549998A1 (en) * | 1991-12-26 | 1993-07-07 | Ykk Corporation | High-strength magnesium-based alloy |
| US5340416A (en) * | 1991-12-26 | 1994-08-23 | Tsuyoshi Masumoto | High-strength magnesium-based alloy |
| EP1183402B1 (en) * | 1999-04-03 | 2003-11-26 | Volkswagen Aktiengesellschaft | Method for producing a magnesium alloy by extrusion moulding and use of the extrusion moulded semifinished products and components |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH04231435A (en) | 1992-08-20 |
| DE69104784D1 (en) | 1994-12-01 |
| US5147603A (en) | 1992-09-15 |
| CA2043723A1 (en) | 1991-12-02 |
| FR2662707B1 (en) | 1992-07-31 |
| FR2662707A1 (en) | 1991-12-06 |
| EP0465376B1 (en) | 1994-10-26 |
| DE69104784T2 (en) | 1995-03-02 |
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