Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/06—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of magnesium or alloys based thereon
• • 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
• • 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
  • C22C23/06—Alloys based on magnesium with a rare earth metal as the next major constituent

Definitions

• the invention relates to a method for producing a magnesium alloy high Ductility etc. through extrusion and the use of extruded semi-finished products or components.
• magnesium alloys are approximately in the range from 1.2 to 1.9 g / cm 3 , occasionally, especially in the case of particularly lithium-rich magnesium alloys, down to approximately 0.9 g / cm 3 as metallic construction materials of particular interest for vehicle and aircraft construction. In the future, they will be used more and more for the lightweight construction of motor vehicles and airplanes, in order to be able to compensate for the weight of additional elements due to increasing comfort and safety standards, especially in new low-emission automobiles. They are also of interest for transportable devices or systems that are particularly light-weight for other reasons.
• the lightweight construction enables the construction of energy-saving vehicles and planes, such as the 3-liter motor vehicle, to a particular extent.
• the cold formability of the commercially available magnesium alloys is due to the hexagonal crystal structure and the associated low ductility limited. Polycrystalline magnesium and most magnesium alloys behave becomes brittle at room temperature. For a number of applications or for certain Manufacturing process of semi-finished products from magnesium alloys is in addition to good ones mechanical properties such as high tensile strength require ductile behavior. On improved forming, energy absorption and deformation behavior requires a higher one Ductility and possibly also higher strength and toughness. For this are To develop magnesium alloys with these properties or their To further develop manufacturing processes because many material variants match the manufacturing condition have widely varying material properties.
• Ductility is the ability of a material to undergo a permanent change in shape, which, in the uniaxial state according to the stress-strain diagram, is ideally without any elastic component. This property is limited by the occurrence of the break. In general, the permanent elongation achieved in the tensile test up to fracture is considered ductility. The degree of ductility can also be seen as the constriction of fracture, impact work and notched impact work, each with a slightly different statement. These properties can be determined in accordance with EN 10 002, Part 1, or in accordance with DIN 50115 and 50116.
• a highly plastic material is called ductile.
• the elasticity denotes the elastic part of the stress-strain diagram according to Hook's law, where with ideal linear-elastic relationships no permanent change in shape occurs.
• the impact work is above all a measure of the energy consumption of a semi-finished product and for plastic behavior, i.e. for deformability and rate of deformation.
• a high impact work is therefore essential for the use of deformation elements such as Crash elements, impact absorbers, impact shields and impact carriers.
• the impact work-measured on notched specimens - is among other things due to higher absolute values for Magnesium alloys are more meaningful than the impact energy and affects one largely uniaxial load.
• the impact work, which is always on notched samples is determined also indicates the susceptibility of a material to triaxial failure Burden. Their informative value is particularly low if the execution of the Notch significantly affects the values of the impact energy.
• the values listed below measured on samples in a particular The state of manufacture therefore reflects the current material properties. she provide an indication of the forming behavior that previously occurred during the forming process was. In this state it is a conclusion about the characteristics and behavior of a person Semi-finished product or even a component with this semi-finished product, which may be further refined later use possible. Furthermore, there is a conclusion about the material properties formed alloys possible, e.g. by bending, pressing, pressure rolling, Stretch drawing, deep drawing, hydroforming or roll forming processed semi-finished products are to be shaped. Because the change in Material properties from cast to extruded condition similar to that Change in material properties from cast to forged, rolled or a similar reshaped state is therefore also an inference to one other forming condition possible.
• the elastic is usually used Properties (rigidity) lifted, unless it is e.g. in the event of an accident
• Properties rigidity
• These properties are typically for use on the respective ambient temperature, in extreme cases in the range from -40 ° C to +90 ° C individual points in the vehicle or plane, however, to the locally lower or higher Turn off temperatures.
• the load state is usually multi-axis. The Conclusion from uniaxial to multiaxial load conditions is all the more possible, ever more of an isotropic structure.
• the manufacture is particularly suitable by die casting or extrusion, forging and / or rolling.
• requirement for the use of semi-finished products made of magnesium alloys or of or from them Components manufactured in automobiles can meet certain property profiles depending after application such as for deformation elements, seat and door frames one Tensile strength of the light material of at least 100 MPa, preferably at least 130 MPa, together with an elongation at break measured at room temperature of at least 10%, preferably at least 15%.
• higher strength values and higher ductility are also one Relief and partly also a prerequisite for the forming of cast blanks or for the further forming of already formed blanks or semi-finished products.
• the higher these properties are in the cast state, the higher these are usually even in the deformed state.
• a higher ductility can the forming or the renewed Forming, especially extrusion, easier. Therefore an elongation at break of at least 10% also for the subsequent manufacturing steps to form elements Magnesium alloys helpful. Therefore, a tensile strength of at least 150 MPa measured at room temperature, preferably at least 180 MPa, or an elongation at break of at least 18%, preferably of at least 20%, particularly preferred of at least 25%, recommended. Usually this is Elongation at break in the commercially available magnesium alloys measured at Room temperature less than 12%.
• MgLi40at% Al6at% for example of 19% or about 260 MPa, and for MgLi40at% 42% or about 134 MPa are given. Due to the small laboratory extrusion press used for those experiments, however, the forming speed and the degree of forming were low.
• Neite describes in Materials Science and Technology, Vol. 8, ED .: K. H. Matucha, 199 ?, in Chapter 4.3.2 Manufacturing processes and mechanical properties of typical Magnesium alloys.
• Alloy M1 typically had a tensile strength in the extruded state 225 MPa and an elongation at break of 12%.
• GB 2,296,256 A gives values of elongation at break of 17.2 and 18% for alloys MgA10.5-1.1Mn0.10-0.12, which, however, had a rather low flexural strength.
• the object is achieved with a process in which the magnesium alloy contains a content of Zr in the range of 0.1 to 10% by weight and an elongation at break after extrusion of at least 18%, a compressive strength of at least 300 MPa and impact work measured at least 20 J on notched samples.
• the Zr content is in particular 0.15 to 6% by weight, preferably 0.2 to 3% by weight, particularly preferably 0.3 to 1.5% by weight.
• the task is also solved with a corresponding method, in which the Magnesium alloy including at least one rare earth element SE La and Y in the range of 0.1 to 10% by weight in total, and one after extrusion Elongation at break of at least 18%, a compressive strength of at least 300 MPa and has an impact energy measured on notched specimens of at least 50 J.
• the total content of magnesium alloys without the addition of lithium is: Rare earth elements, in particular 0.15 to 8% by weight, preferably 0.2 to 6% by weight, particularly preferably 0.3 to 4% by weight, very particularly preferably 0.4 to 3% by weight.
• That the alloy is dynamically recrystallized during extrusion, that it is additives or traces of Cd less than 1.8 wt% and traces of up to 0.1 wt% Cu, up to 0.05% by weight of Fe and up to 0.005% by weight of Ni may contain one Magnesium alloy based on AM, AS, EM, EZ, MA, ME, SA, ZA or ZE and that it is after extrusion, an elongation at break of at least 17.5%, a compressive strength of at least 300 MPa and impact work measured on unslotted samples of has at least 45 J.
• the task is also solved with a corresponding method, in which the Magnesium alloy based on AZ with at least one addition of Ca, Sr, Li, SE or / and Zr is in each case at least 0.1% by weight and in which it is one after extrusion Elongation at break of at least 17.5%, a compressive strength of at least 350 MPa and has an impact energy measured on notched specimens of at least 50 J.
• the proportion by weight of the respective additive can in particular be 0.15 to 6% by weight, preferably 0.2 to 4% by weight, particularly preferably 0.25 to 2% by weight.
• other additions can occur, preferably those that are dynamic Recrystallization behavior and fine grain influence.
• the task is also solved with a corresponding method, in which the Magnesium alloy based on MN with at least 1% by weight Mn and with the addition of SE or / and Zr of at least 0.1 wt .-% and in which they after Extrusion has an elongation at break of at least 15%, a compressive strength of at least 300 MPa, and impact work measured on unslotted samples of has at least 20 J.
• the Mn content is preferably at least 1.3% by weight.
• the proportion by weight of the respective additive can in particular be 0.15 to 6% by weight, preferably 0.2 to 4% by weight, particularly preferably 0.25 to 2% by weight.
• other additions can occur, preferably those that are dynamic Influence recrystallization behavior.
• the Magnesium alloy based on MZ or ZM which is an addition of SE and / or Zr by each can contain at least 0.1 wt .-%, and in which they after extrusion an elongation at break of at least 15%, a compressive strength of at least 300 MPa and has an impact work of at least 40 J measured on notched specimens.
• the alloy preferably has a plastic component Stress determined in the tensile test according to the stress-strain diagram from the Difference of tensile stress and yield stress of at least 40 MPa.
• the degree of deformation characterizes the degree of Reduction of cross-section during forming and is used as the natural logarithm of the Ratio of initial cross-section to cross-section specified after forming. He is therefore often correlated with the degree of dynamic recrystallization, where possible should not yet occur stronger growth of individual grains, but one if possible fine-grain structure is sought, which is high for some magnesium alloys Ductility conditional. The more stable the structure of a magnesium alloy, the more fine-grained the structure becomes or remains during forming.
• the degree of deformation is advantageously at least 1.5, preferably at least 2, particularly preferably at least 2.5. If the degree of deformation is less than 1.5, the dynamic Recrystallization when forming is quite low. It would also have a grade of 3.5 or more can be selected in the tests.
• the extrusion speed is advantageously at least 1.5 m / min, preferably at least 2.5 m / min, particularly preferably at least 5 m / min, very particularly preferably at least 7.5 m / min. It is above all due to the decreasing quality of the extruded profiles limited.
• the magnesium alloy is selected from the group of Magnesium alloys due to dynamic recrystallization and fine grain get a higher ductility.
• the dynamic recrystallization and structural change from the original or compacted molded body to the finished semi-finished product, component or Compounding is often not only achieved through extrusion and the associated processes thermal or mechanical influences, but they are preferred performed essentially or even mainly in extrusion.
• the task is finally solved with a semi-finished product made of a magnesium alloy or with a component made of it or with it or with a composite with a such semifinished product or component that was produced according to the invention.
• the semifinished product or component according to the invention preferably consists essentially of a magnesium alloy selected from the group of alloys based AM, AS, AZ, EZ, MA, SA, ZA or ZE, EM, EZ, ME, MN, MZ, ZE and ZM with a salary on at least one rare earth element AM, AS, AZ, MA, MN, MZ, SA, ZA or EZ, MN or ZE with zirconium addition.
• semi-finished products are understood to be shaped articles which have not yet are completed and ready for use for their respective application.
• the molded articles are suitable for the intended purpose designated.
• both terms flow smoothly into one another, since it is the same shaped body for one purpose around a semi-finished product, but for the other can already be a component.
• Simplification does not strictly differentiate between semi-finished products and components throughout the text or both mentioned at the same time or only spoken of magnesium alloy, although both can be meant.
• the semifinished products made of magnesium alloys according to the invention or those thereof or therewith manufactured components or composites can be used as frame elements, Elements of the vehicle cell or vehicle outer skin, as a vehicle cell or Vehicle outer skin, cockpit support, cockpit skin, housing, floor element, floors, cover, Tank elements, tank flaps, brackets, supports, beams, angles, hollow profiles, pipes, Deformation elements, crash elements, crash absorbers, impact absorbers, impact shields, Impact beams, small parts, as a welded profile construction, for the vehicle body, for Seat, window or / and door frames, as semi-finished products, components or composites on or in Automobile or airplane.
• high-purity alloys are alloyed with additives.
• the high-purity alloys can absorb small amounts of contaminants from the crucible during the melting process.
• the alloys can be melted, for example, in a nickel and chromium-free steel crucible under a protective gas atmosphere, for example Ar or / and SF 6 .
• a protective gas atmosphere for example Ar or / and SF 6 .
• the powder-metallurgical production of green compacts possibly with subsequent annealing, can also be used.
• the process steps are known in principle, but require a different modification or optimization depending on the alloy.
• a bolt with a very large diameter can be cast are then turned into round bolts using a high-performance extrusion press can be pressed with a diameter that corresponds to the recipient diameter.
• the segregation is reduced by the thermomechanical treatment.
• the cast bolts can first be subjected to heat treatment depending on the Alloy composition in e.g. 350 ° C homogenized in the range from 6 h to 12 h to eliminate segregations in the structure, some of which heterogeneous structure too improve and increase the pressability. Then the homogenized bolts machined to the required dimensions.
• the extrusion of the magnesium alloys can be carried out in the same extrusion plants take place, which are used for the extrusion of aluminum alloys, both via direct as well as indirect extrusion. Only with the Tool design (die), the deformation behavior must be specifically taken into account. There are sharp-edged inlets, such as those used in aluminum alloys Avoid magnesium alloys, otherwise there is a risk of surface cracks. In many cases e.g. for matrices of round profiles an entry angle of approx. 50 ° for Magnesium alloys used. A round profile was used in the tests.
• the most important parameter besides the extrusion temperature is the extrusion speed, because they have the properties and surface quality of the Extruded profiles significantly influenced.
• a high pressure also means a high one Extrusion speed, which is aimed for economic reasons.
• a high Extrusion speed is usually with an even better surface quality connected.
• the extrusion speed is very different from the geometry of the strand dependent.
• the pressability of the magnesium alloys is comparable to that heavy-duty aluminum alloys.
• a high extrusion speed is true Desired from an economic point of view, but is not the case with magnesium alloys always feasible. It may also be used at particularly high extrusion speeds there are no cracks or burning of the magnesium alloy.
• the Degree of deformation of great importance. It goes along with the change in the structure.
• the extrusion can advantageously be followed by a heat treatment.
• the Semi-finished products can be straightened if necessary, e.g. by bending, pressing, pressure rolling, stretch drawing, Deep drawing, hydroforming or roll forming further deformed, e.g. by Cutting, drilling, milling, grinding, lapping, polishing, machining, joining and / or e.g. by Etching, pickling, painting or other coating are surface treated.
• Alloys according to the invention can be solid and extruded profiles in simple or complicated cross sections can be extruded without problems.
• you can Semi-finished products are improved or components can be produced from them or, if necessary, from them.
• the semi-finished product or the component made therefrom or with it can pass through at least one low-heat joining process such as Gluing, riveting, plugging, pressing, Pressing in, clinching, folding, shrinking or screwing and / or at least one heat-generating joining process such as Composite casting, composite forging, Composite extrusion, composite rolling, soldering or welding, in particular Beam welding or fusion welding, with a similar or different type Semi-finished product or component can be connected.
• the different semi-finished product or component can likewise essentially of a magnesium alloy or of another alloy or also consist of a non-metallic material. It can be the same or one have a different geometry than the semi-finished product or component according to the invention.
• the Joining methods can serve in particular to create a housing from several elements, to manufacture an apparatus, a system, a profile construction and / or a cladding.
• a Al, E indicates at least one of the alloy designations used Rare earth element SE, whereby Y is also counted among the rare earth elements, M or MN Mn, S Si and Z Zn - usually with content in% by weight, unless otherwise is noted.
• alloy information such as AZ31 are made by the numbers as usual for the respective alloy only in the order of magnitude specified, which can vary to a relatively wide extent as is customary in the industry.
• modified alloys based on AZ have a low manganese content. All Examples showed traces of less than 0.1 wt% Cd, less than 0.05 wt% Cu, less than 0.04 wt% Fe and less than 0.003 wt% Ni.
• the alloys were made as high-purity, commercially available alloys or usually from high-purity starting alloys such as, for example, AM, AS or AZ alloys or by adding high-purity magnesium HP-Mg, a rare earth element-containing master alloy with a ratio of Nd to other rare earths, including yttrium of 0.92, a zirconium-containing master alloy and / or of calcium or strontium.
• the standard alloys contained an Mn content of up to about 0.2% by weight.
• the alloys were melted in a steel crucible under the protective gas atmosphere of an Ar-SF 6 mixture.
• the blanks required for the subsequent extrusion were cast in a cylindrical steel mold with machining allowance. The element contents achieved were checked spectroscopically.
• the bolts were then turned to a diameter of 70 mm and to a length of 120 mm brought.
• the bolts were then subjected to homogenization treatment in e.g. 350 ° C exposed for 4 h or 12 h to eliminate segregations in the structure and the Increase pressability. Segregations can lead to uneven deformation and critical extrusion conditions lead to cracks or local melting, which can cause poor surface qualities. With less well homogenized bolts an unnecessarily high pressing pressure is required during extrusion.
• the homogenized bolts were then well prepared for extrusion.
• the homogenized bolts were then brought up to the respective extrusion temperature heated, warmed up and directly in a 400 t horizontal press Extrusion process extruded.
• the temperature of the bolt is the temperature which the bolt has when it enters the extrusion press.
• the semifinished product or component according to the invention preferably consists essentially of a Magnesium alloy, which is selected from the group of alloys based on AM, AS, AZ, EZ, MA, SA, ZA or ZE, EM, EZ, ME, MN, MZ, ZE and ZM containing with at least one rare earth element AM, AZ, MA, MN, MZ, ZA or EZ, MN or ZE Zirkoniumzusatz.
• the strength values determined on the cast and extruded samples were much higher than expected.
• the deformability was also surprising of these alloys very high. It was also surprising that the material properties of the modified alloys surprisingly little depending on the Extrusion conditions varied, which is advantageous for production. Furthermore, it was Surprisingly, the impact energy of the ZE10 alloy was so high.
• the measurement results of the Brinell hardness determinations did not allow any special ones Statement.
• the Brinell hardness of the extruded samples was found to be 7 to 22% greater than the cast samples. The hardness increased with the aluminum content.
• Casting the stud The melt was at a temperature in the range of 780 to 820 ° C, once also at 750 ° C, kept and cast.
• the shape showed depending on the experiment a diameter of 90 or 110 mm and a mold temperature in the range of 80 to 320 ° C.
• the element contents achieved were checked spectroscopically.
• the castings were homogenized at 350 ° C. over 12 h.
• By turning bolts usually made 70 mm in diameter and 120 mm in length; with 6 samples of Alloy AZ31Ca0.3, however, was chosen to have a diameter of 74 mm.
• an extrusion temperature in the range of 200 to 450 ° C and a time to Heating and warming set in the range from 60 to 150 min.
• the parameter spectrum showed good compressibility with a large scope with regard to pressing force and pressing speed.
• the structure formation and the achieved Elongation at break correlated with the deformation parameters.
• the extrusion pressures that occurred varied depending on the alloy used and set parameters in a wide range.
• the final pressures reached were for Alloys without the addition of SE or Zr in the range around 10 ⁇ 2 MPa Extrusion temperatures greater than 300 ° C and for alloys containing SE or Zr up to 4 MPa higher.
• Cause for the higher extrusion pressures and thus for the increased resistance to deformation of magnesium alloys with SE or Zr addition is a higher proportion of stable excretions than magnesium alloys without this addition.
• the properties of the ZE10 alloy become essential from the rare earths influenced and can vary in the variation of rare earth elements including yttrium or their contents can be further optimized.
• Medium occurred with the ZE10 alloy Grain sizes in the range from 6.5 to 13 ⁇ m, which again with the extrusion temperature rather increased; however, this alloy warmed with increasing Extrusion speed relatively strong, which at higher extrusion speed also led to somewhat larger average grain sizes.
• nb nb nb 10.7 62.0 Mainly occurring grain sizes in the as-cast state after homogenization at 350 ° C for 4 h or after extrusion with the modified lithium-free magnesium alloys and their starting alloys.
• sample alloy average grain sizes ⁇ m B 20a MN150Zr0.7 extr. 6.4 - 6.5 VB 21 ZE10 Molding 85 B 21 ZE10 extr. 6.7 - 13.3 VB 22 ZE10Zr0,7 Molding 94 B 22 ZE10Zr0,7 extr. 2.3 - 4.6 B 24 ZM21SE0.7 extr. 6.8 - 10.3 B 25 ZM21Zr0.7 extr.

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• 1999
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