Production method for high-strength and high-ductility next-generation al-cu and al-mg-cu casting alloys with titanium, vanadium, molybdenum, niobium, and scandium additions

Abstract

The invention pertains to a production method for a new generation aluminum-copper (Al-Cu) or aluminum-magnesium-copper (Al-Mg-Cu) casting alloy with titanium, vanadium, molybdenum, niobium, and scandium alloying additives, exhibiting high strength and high ductility properties.

Description

[0001] PRODUCTION METHOD FOR HIGH-STRENGTH AND HIGH-DUCTILITY NEXT-GENERATION AL-CU AND AL-MG-CU CASTING ALLOYS WITH TITANIUM, VANADIUM, MOLYBDENUM, NIOBIUM, AND SCANDIUM ADDITIONS

[0002] TECHNICAL FIELD

[0003] The invention pertains to a production method for a new generation aluminum-copper (Al-Cu) or aluminum-magnesium-copper (Al-Mg-Cu) casting alloy with titanium, vanadium, molybdenum, niobium, and scandium alloying additives, exhibiting high strength and high ductility properties.

[0004] BACKGROUND

[0005] In the prior art of casting alloys used in technology, alloying elements such as silicon, titanium, strontium, and zirconium are being used for alloying. In recent studies, the control of the structure have been ensured by micro-alloying and by reducing the casting volume with a smaller amount of molten metal. In the state of the art, the standard metal cleaning process is being performed by introducing gas using rotary elements within the metal melt or through the use of degassing cleaning tablets. The alloying elements do not contribute adequately to alloys with high magnesium and copper content. Titanium-strontium (Ti-Sr) alloying has reached its limit in terms of contribution. On the other hand, the control of zirconium in the structure bears difficulties. The method of adding alloying elements into the metal melt during alloying affects greatly metal cleanliness. Elements added without prior tomography analysis incorporate impurities into the metal melt structure. In degassing step which is done using rotary degasser blades, turbulence is created as the rotor blades rotates at high speed while releasing the inert gas. Additionally, gas bubble sizes are large. In case of using degassing tablets, hazardous wastes of chemical salts are formed in the end the cleaning process.

[0006] In the known state of the art, the U.S. patent document numbered US11634795B2 proposes a production method of aluminum alloys developed for structural and non-structural near-net casting process.

[0007] In the known state of the art, the Chinese patent document numbered CN108149080A addresses an aluminum alloy containing rare earth elements and its preparation method thereof.

[0008] Upon examining existing studies in the field, to overcome the aforementioned disadvantages, It has been identified that there is a need to develop a new generation aluminum-copper (Al-Cu) or aluminum-magnesium-copper (Al-Mg-Cu) casting alloy and its production method with titanium- vanadium-molybdenum and scandium additives, that provides high strength and high ductility.

[0009] AIM OF THE INVENTION

[0010] The present invention aims to develop a production method for a new generation aluminum-copper (Al-Cu) or aluminum-magnesium-copper (Al-Mg-Cu) casting alloy with titanium-vanadium- molybdenum and scandium alloying additives, to possess high strength and high ductility properties.

[0011] Another aim of the invention is to achieve a production method for a new generation aluminumcopper (Al-Cu) or aluminum-magnesium-copper (Al-Mg-Cu) casting alloy, where the grain size, dendrite size and the sub-grain sizes in the microstructure are adjusted through the use of specific element ratios in the alloy composition, which contains different alloying elements and different phases formations thereby the strength, elongation, creep, and fatigue behavior is enhanced

[0012] Another aim of the invention is to establish a proportional and thermochemical selection criteria and process criteria ensuring the production method of new generation aluminum-copper (Al-Cu) or aluminum-magnesium-copper (Al-Mg-Cu) casting alloy in the selection of earth elements, transition metals, and rare earth alloying elements content.

[0013] Another aim of the invention is to propose a production method of new generation aluminumcopper (Al-Cu) or aluminum-magnesium-copper (Al-Mg-Cu) casting alloy, ensuring the control of high-quality metal cleaning and melt treatment processes.

[0014] DETAILED DESCRIPTION

[0015] Attached figures provides the results regarding the implementation of the method in order to achieve the objectives of the present invention. (The figures illustrate sections, images that were obtained by gravity casting into the sand molds. Similar trends would continue in the permanent mold castings into the steel molds and under varying / different pressures levels during a casting process. The scope of the invention cannot be limited to this brief and detailed description focusing sand mold gravity casting)

[0016] These figures;

[0017] Figure 1 a: Schematic view of the grain size distribution of the AlMgCu alloy.

[0018] Figure lb: Schematic view of the grain size distribution of the AlMgCu-Ti-V alloy.

[0019] Figure 1c: Schematic view of the grain size distribution of the AlMgCu-Ti-V-Nb alloy.

[0020] Figure Id: Schematic view of the grain size distribution of the AlMgCu-Ti-V-Sc alloy.

[0021] Figure 2a: SEM image of the AlMg7Cul-Ti-V alloy.

[0022] Figure 2b: SEM image of the AlMgCu-Nb alloy.

[0023] Figure 2c: SEM image of the AlMgCu-Ti-V-Nb alloy when the Nb content is 0.05% by weight.

[0024] Figure 2d: SEM image of the AlMgCu-Ti-V-Nb alloy when the Nb content is 0.125% by weight. Figure 3a: Optical microscope image of the AlMg7Cul.6 Ti-V-Mo-Zr alloy when the Mo and Zr contents are 0.05% by weight.

[0025] Figure 3b: Optical microscope image of the AlMg7Cul.6 Ti-V-Mo-Zr alloy when the Mo and Zr contents are 0.2% by weight. Figure 4a: Schematic view of the grain size distribution in the AlMgCu-Ti-V-Nb-Sc alloy when scandium is dominant.

[0026] Figure 4b: Schematic view of the grain size distribution in the AlMgCu-Ti-V-Nb-Sc alloy when niobium is dominant.

[0027] The invention pertains to a production method for a new generation aluminum-copper (Al-Cu) or aluminum-magnesium-copper (Al-Mg-Cu) casting alloy with high strength and high ductility, comprising these steps:

[0028] • Melting of the aluminum-copper (Al-Cu) composition by induction type or closed chamber natural gas burner type method,

[0029] • Applying a degassing process by blowing an inert gas such as Nitrogen or Argon into the molten aluminum-copper (Al-Cu) composition using a ceramic lance degasser,

[0030] • Removal of iron-based impurities by applying a magnetic field to force them toward the surface of the melt, sweeping and cleaning them from the surface by a filter,

[0031] • Subsequent to degassing process, addition of titanium-vanadium (Ti-V) to the composition and performing the degassing process once more,

[0032] • Based on the desired mechanical values of the alloy and application area, the required grain size is adjusted based on the set of ratios of niobium and scandium from the database according to the required fatigue and creep behaviors.

[0033] • Adding niobium- scandium (Nb-Sc) elements and performing the final degassing operation,

[0034] • Cleaning intermetallic particles in the structure either sweeping by induction or by filter application,

[0035] • Preparation of a sand mold or steel mold and fabrication of the casting alloy.

[0036] Generally, in alloying step, different elements are added randomly to observe their effects on properties. On this context, phases are identified using phase diagrams. Before the invention method is applied the initial metal impurity is examined through tomography and by temperature monitoring, transitional phase or intermediate phases that would be evolved are identified prior to the method of the invention begins to be carried out.

[0037] The ratio of Nb and Sc components used in the present invention ensures the modifications or regulations of the microstructure. Thus, the Nb-Sc ratio is adjusted in inverse proportion, controlling the grain size, subgrain size, and the phases formation according to the Al-Cu and Al- Mg binary phase diagrams system. It is also controlled the phases formations in the binary Al-Cu, Al-Ti, Al-V, Al-Sc, Al-Nb, Cu-Nb, Cu-Sc, Al-Mo, Al-Zr, and ternary Al-Cu-Sc, Al-Cu-Nb, Al- Mg-V, Al-Mg-Cu, Al-Mg-Nb, Al-Mg-Sc equilibrium systems, adjusting the grain structure at precipitation zones and the sizes of the precipitates. The Nb and Sc ratio ensures homogeneous distribution of elements in the structure, preventing defect localization that negatively affects the damage behavior and mechanical behavior. Alloying elements form intermetallic phases. It is essential to predict these phases and eliminate the harmful ones. The proper alloy cleaning method is modulated by the degassing time-gas flow rate. Furthermore, temperature monitoring must be conducted both during the degassing step and subsequent casting operation.

[0038] In the present invention, the aluminum-copper (Al-Cu) composition is melted using induction heating type or closed chamber natural gas burner type methods. An inert gas such as N2 or Argon is blown into the molten aluminum-copper (Al-Cu) composition using a ceramic lance degasser to carry out the degassing operation. After the degassing process, titanium-vanadium (Ti-V) is added to the composition, and the degassing process is repeated. Then, niobium-scandium (Nb-Sc) is added, and the final degassing operation is performed. The intermetallic particles in the molten metal structure are cleaned either by induction sweeping or filter sweeping. Finally, the casting is manufactured.

[0039] METAL CLEANING AND METAL MELT MONITORING STEP:

[0040] In the present invention, oxide films in the structure will be removed using a micro-porous ceramic degassing lance and cleaning / sweeping filters. Alloying and cleaning are performed separately. The alloying elements are fed into the crucible.

[0041] The alloying elements, Ti-V / Nb-Sc, are fed and immersed into the metal from within an atmosphere / vacuum-controlled additional chamber, simultaneously introduced into the crucible along with a degassing lance.

[0042] As an additional step, if necessary, magnetic particles are forced to migrate toward the surface using the induction method to clean iron-based constituents. These particles, since they have neutral buoyancy, could not be cleaned in industrial practice in common furnaces or in monolithic induction furnaces.

[0043] ALLOYING STEP:

[0044] In the present invention, it has been studied and found that microstructure can be altered by the use of titanium-vanadium-molybdenum (Ti-V-Mo) with niobium / scandium (Nb / Sc) within a specific logical framework. In this context, the base Al-Cu and Al-Mg-Cu alloy matrix structure can be strengthened through the formation of Ti-V related phases such as AlxTiy, AlmTikVzalong with AICu and AlMg phases, resulting stronger particles and phases in the structure. But unless their distribution and grain size are not adjusted, those phases / particles cannot have a positive effect.

[0045] Therefore, to achieve above mentioned strength and distribution, the elements such as zirconium (Zr), scandium (Sc), and niobium (Nb), along with titanium (Ti), vanadium (V), or molybdenum (Mo) is added to alloy. However, each added alloying element increases intermetallic and porosity in the alloy structure. Therefore, niobium (Nb) and scandium (Sc) are effective only below a certain ratio and amount. Moreover, at first step, the major base composition should be adjusted in alloying step prior to alloying.

[0046] In the conventional practice, the details of the degassing method that is applied used in the process are not detailed. But the degassing lance type and the gas blowing holes / apertures are important. The ideal methodology is to use static degassing lances with gas out blowing holes smaller than 1mm or a system made of ceramic material with microcrack apertures through which the gas is blown into the metal. On the other hand, the use of slag sweeping or skimming filter provides benefits under certain circumstances.

[0047] In the present invention, the initial composition adjustment of the Al-Cu alloy and degassing operation are performed by raising the temperature so that the slag and metal oxides in this composition are removed through degassing cleaning. This should not be done when other alloying elements, particularly Mg and Ti, V, Mo, Nb, and Sc, are present in the metal alloy melt. Ti-V and Nb-Sc are not added at this stage because there is a risk of metal loss due to thermodynamic equilibrium in high temperature.

[0048] In another embodiment of the invention, alternative approach of Mg alloying is performed in the next step. The top of the crucible is insulated if necessary. Therefore, the formation of Mg oxides is allowed so that they sustain equilibrium state within the metal melt. Degassing operation, skimming / scraping by filter application and slag removal are carried out to achieve a homogeneous composition.

[0049] In another embodiment of the invention, melt stabilization is done for 10-15 minutes, followed by 5-8 minutes of degassing operation. If the elements such as Ti-V-Nb-Sc are added along with Mg, this stage could be extended, and the risk of metal loss also increases in this case. In alloying stage, if the alloying content in percentage weight to the molten metal increase, correspondingly, it becomes more difficult to control the temperature and achieve stabilization and homogenization. Therefore, 3 or 4 stages of alloying and degassing are applied. In the final stage, the final elements are added gradually, followed by an additional degassing operation and crucible insulation is performed. The results related to the assessment and evaluation of the alloys manufactured by the method of production of the present invention are provided in the tables below:

[0050] *Except for transition metals, rare earth metals.

[0051] Table 1 : Details of the alloy composition obtained by the method of the present invention

[0052] Table 2: Yield strength, tensile strength, and elongation of the alloy with the addition of molybdenum and zirconium"

[0053] Table 3: Yield strength, tensile strength, and elongation of the alloy with the addition of niobium

[0054] Table 4: Results of the sample specimens with the use of the extensometer in tests

[0055] Table 5: Yield strength, tensile strength, and elongation of the alloy with the addition of Nb and Sc

[0056] Table 6: Comparison of the properties of the alloys manufactured by the method of the present invention with existing alloys in the state of the art

Claims

CLAIMS1. The invention pertains to a production method for a new generation aluminum-copper (Al-Cu) or aluminum-magnesium-copper (Al-Mg-Cu) casting alloy with high strength and high ductility, characterized in that, a. Melting operation of the aluminum-copper (Al-Cu) composition alloy using an induction heating method or a closed-chamber natural gas burner heating method, b. Appliying degassing of the melted aluminum-copper (Al-Cu) composition by blowing an inert gas through a ceramic lance degasser, c. Use of a magnetic field to remove iron-based content by sweeping it toward the surface of the melt, then perform its filtration and cleaning, d. After the degassing process, applying titanium-vanadium (Ti-V) addition to the melted alloy composition, and repeating of the degassing process, e. Adding niobium-scandium (Nb-Sc) subsequently and applying a final degassing process , f. Cleaning intermetallic particles of the structure by sweeping using induction method or cleaning by filtering, g. Preparing a sand mold or steel mold to produce the casting alloy.

2. A method production method for a casting alloy according to claim 1, characterized in that, the use of aluminum-magnesium-copper (Al-Mg-Cu) composition instead of the initial aluminum-copper (Al-Cu) composition.

3. A method production method for a casting alloy according to claim 1, characterized in that, the inert gas being nitrogen (N2) or argon.

4. A method production method for a casting alloy according to claim 1, characterized in that, the holes in the degassing lance used in the method being less than 1 mm in size and the apertures in the degassing lance used in the method being less than 1 mm, the degasser being ceramic -based.

5. A method production method for a casting alloy according to claim 1, characterized in that, use of molybdenum-zirconium (Mo-Zr) is substitutable for niobium-scandium (Nb-Sc)6. A method production method for a casting alloy according to claim 1, characterized in that, the weight ratios of Nb-Sc and Mo-Zr can be adjusted based on direct or inverse proportionality coefficients, enabling the adjustment of phase distributions, grain sizes, and sub-grain sizes.

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