Patent Grant
9963770
The invention arose under an agreement between UT-Battelle, LLC (Oak Ridge National Laboratory), Lawrence Livermore National Security, LLC, Iowa State University of Science and Technology (Ames Laboratory), and Eck Industries, Inc., funded by the Critical Materials Institute of the United States Department of Energy.
Aluminum alloys have been developed to increase the operating temperature thereof, but are at present limited to applications below 230° C. due to rapid loss of mechanical characteristics. There is a need for aluminum alloys that have good castability and maintain mechanical characteristics above that temperature.
In accordance with one aspect of the present invention, the foregoing and other objects are achieved by a cast alloy that includes aluminum and from about from about 5 to about 30 weight percent of at least one of cerium, lanthanum, and mischmetal. The cast alloy has a strengthening Al11X3 intermetallic phase in an amount in the range of from about 5 to about 30 weight percent, wherein X is at least one of cerium, lanthanum, and mischmetal. The Al11X3 intermetallic phase has a microstructure that includes at least one of lath features and rod morphological features. The morphological features have an average thickness of no more than 700 um and an average spacing of no more than 10 um, the microstructure further comprising an eutectic microconstituent that comprises more than about 10 volume percent of the microstructure.
Moreover, a method of making a cast alloy includes the steps of:
Moreover, a method of making a cast alloy includes the steps of:
Moreover, a method of making a cast alloy includes the steps of:
Moreover, a method of making a cast alloy includes the steps of:
Amounts of various constituents in the alloys described herein are expressed in weight percent unless otherwise noted.
The scale of SEM images described above is about 50 μm horizontally across the image unless stated otherwise.
For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the above-described drawings.
Ce-modified aluminum alloys described herein solve two problems, the first being an overabundance of Cerium in the Rare Earth Element (REE) market. By utilizing Cerium in the presently described alloy, the surplus supply of Cerium can be utilized.
A major advantage of high cerium content aluminum alloys is their low cost in comparison to other high-temperature aluminum alloys. Cerium is the most abundant of the rare earths and often accounts for well over half of the yield; is a plentiful, underutilized by-product of rare earth mining processes. Since there is heretofore little use for existing cerium its market value is significantly lower than other rare-earth elements, and its utilization as a primary alloying element with aluminum is advantageous. High temperature-stable alloys can now be cast using low-cost rare earth elements while utilizing traditional casting methods for less than many modern alloys which are not stable at high-temperatures.
The second problem solved by the Ce-modified aluminum alloys described herein is the lack of high temperature Aluminum alloys. Prior to the invention described herein, there are few, very expensive Aluminum alloys which maintain desirable mechanical characteristics at temperatures above 230° C. Ce-modified Aluminum alloys fill that gap by creating aluminum alloys having high temperature mechanical properties that are about 30-40% greater than that of any currently available aluminum alloys, as will be demonstrated hereinbelow.
Aluminum casting alloys are light and strong but do not often have high tolerance for elevated temperatures, and aluminum alloys that do exhibit high temperature stability are generally cost prohibitive for most applications. Through the addition of cerium in amounts in the range of about 5 to about 30 weight percent (hereinafter indicated simply as %), preferably about 5 to about 20%, or about 6 to about 16%, or about 8 to about 12%, aluminum alloys show a marked increase in high temperature mechanical properties. Cerium addition is effective in producing a highly castable aluminum alloy without the addition of silicon, leading to good ductility up to about 30% Ce addition. After which, it is believed mechanical properties will sharply degrade.
Alloys of the present invention can contain lesser additions of conventional aluminum alloying elements in order to produce desired mechanical properties thereof. For example, up to about 5% silicon can be added in order to improve yield and tensile strengths. The Al—Ce alloys containing high content of Ce with little to no silicon can be cast into complex near net shape molds at room or elevated temperatures and do not always require a chill to be present for good castability. Other additions of up to about 5% Fe, up to about 15% Mg, up to about 8% Cu, and/or up to about 8% Ni, are also useful in tailoring the alloy as desired.
Embodiments of the present invention include aluminum alloys modified by cerium, lanthanum, mischmetal, or any combination of the foregoing. Lanthanum modification has the potential to exhibit similar mechanical properties to that of cerium modification. However, lanthanum is much more expensive than cerium as it has other commercial uses. Ce and La exhibit very similar atomic properties with the same number of valence electrons in the 6s energy orbital. They also exhibit a very similar atomic radius. These similarities in atomic structure render their overall reactivity nearly identical in most systems. The skilled artisan will understand that the well-known Al—Ce and Al—La phase diagrams in the aluminum rich region appear identical with the only discernible schism being the depression in the primary Al11La3 liquidus temperature over that of the equivalent Al11Ce3 region. All other features of the diagrams appear near identical. Furthermore if one observes the ternary isotherm plotted by the Al—La—Ce system at 500° C. it can be observed that Ce and La form mirrored phase spaces across constant Al isopleth lines. Combining this information it is clear that in an alloy of Al—Ce, Al—La, or any rational combination of Ce and La the present phases would bear the same structure and the alloy exhibit nearly identical mechanical properties.
Natural mischmetal comprises, in terms of weight percent, about 50% cerium, 30% lanthanum, balance other rare earth elements. Thus, modification of aluminum alloys with cerium through addition of mischmetal can be a less expensive alternative to pure cerium.
Of critical importance is a strengthening Al11X3 intermetallic phase, where X is cerium, lanthanum, mischmetal, or any combination of the foregoing. The intermetallic phase is present in an amount in the range of from about 5 to about 30 weight percent. The general formula that applies is as follows: AlXa+CeX1+LaX2+MshX3= and X1+X2+X3>5 and <30 wt %. The intermetallic phase has a microstructure characterized by lath and/or rod features having an average thickness of no more than about 700 um and an average lath spacing of no more than about 10 um.
It is to be understood that wherever cerium is mentioned hereinbelow, lanthanum and/or mischmetal can be substituted for a portion of, or all of the cerium.
Moreover, other elements may be present in the alloy that do not significantly interfere with the formation and stability of the critically important Al11X3 intermetallic constituent. Such elements may include at least one of titanium, vanadium, and Zirconium.
Moreover, alloys of the present invention can contain innocuous amounts of various impurities that have no substantial effect on the chemical or mechanical properties of the alloys.
Optimal castability is found in the X range between about 8-12 wt %. However castability is not greatly reduced until cerium content drops below 6 wt % and mechanical properties are contemplated to remain viable until X exceeds 20 wt % or even 30%.
Al—Ce alloys are denser than standard aluminum alloys due to the addition of cerium, but are lighter than conventional nickel and steel alloys currently being used in many high-temperature applications where aluminum alloys with proper mechanical and thermal properties are prohibitively expensive.
Described herein are new aluminum alloys containing relatively high cerium content and relatively low silicon content with exceptional casting characteristics and mechanical property stability in temperatures at or above 230° C., and at or above 260° C.
The process for casting the Al—Ce alloys is compatible with conventional industrial practices. Little or no modification of existing equipment and infrastructure of modern aluminum foundries is necessary.
The Al metal is heated to 100° C. or about 100° C. above its melting temperature under an oxygen-excluded atmosphere. After the Al reaches a stable fully liquid state, the Ce is added in as large of ingots as possible. The large ingots and oxygen-excluded atmosphere help reduce the likely hood of the Ce causing a fire or oxidizing as a result of its reactivity. After the cerium has completely melted and once the alloys return to an appropriate temperature, a degassing step is taken to remove any present oxides or oxygen from the melt. After degassing the Al—Ce alloy can be cast into molds and allowed to solidify. Chills of various sizes can be used but are not necessary for most Al—Ce alloys.
Assessment for castability of an alloy generally depends almost entirely on three variables: presence and frequency of micro or macro voids in the casting; extent to which the mold filled; and presence of cracking or hot tearing resulting in mold failure.
Castability is an indicator of feasibility of an alloy for casting into complex shapes and can be rated in a system of 0 (poor) to 5 (excellent). Characteristics of castings are generally rated herein as follows:
All as-cast Al—Ce alloys exhibit a very complex intermetallic shown via SEM micrographs. This highly interconnected microstructure is unique to these alloys in both morphology and phase fraction. The area and volume fraction of intermetallic Al11Ce3 is very high. This high phase fraction of extremely fine laths likely leads to the exceptional ductility of the samples.
Application of a standard (ASTM) T6 heat-treatment causes the as-cast sample's microstructure to undergo a shift from a complex interconnected structure to a more island like fiber structure. The composition of the intermetallic (Al11Ce3) is unique to Al alloys. In the case of alloy ALC-500 described hereinbelow, a hypereutectic binary alloy, and samples containing Mg or Si large primary crystals are also present. These primary crystals do not undergo any changes after heat-treatment. The crystals are surrounded by the complex intermetallic which does undergo the standard transition after heat-treatment. ASTM T4 and T7 treatments were also tested. A person having ordinary skill in the art will recognize ASTM standard treatments as well-known methods; such methods are standardized and readily available to the public.
The critically important Al11Ce3 intermetallic phase present in the described binary Al—Ce alloys has been shown to be very stable at high temperatures present in the T6 heat treatment cycles. The microstructure does make a slight change in morphology but phase fraction is almost unaffected. The XRD and DSC plots (curves) described hereinbelow show overlays of the as-cast data and T6 heat-treated data. These plots reinforce the high-temperature stability of the intermetallic strengthening phase by noting that the profiles do not have any appreciable differences between the heat-treated and the as-cast and no present phase transition until the onset of melting at ˜640° C. Testing showed the alloys to be stable up to 230° C. or about 230° C., which is not expected for aluminum alloys.
In the case of quaternary alloys containing Si addition, present phases appear to change after heat-treatment. Prior to heat-treatment Al11Ce3 is the major intermetallic constituent whereas following heat-treatment ternary Al—Ce—Si compounds dominate the composition. Once precipitated these phases are stable up to the melting temperature.
Alloy ALC-400 having a composition of 12% Ce, balance Al was made as follows: Aluminum ingots were melted in a resistive furnace under and oxygen excluded environment and brought to a temperature above 750° C. Once the temperature in the crucible was stable ingots of cerium were added and mixed until melted. Once melted the alloy was degassed and mixed further. After the temperature in the crucible again stabilized above 750° C. the melt was poured into various molds, including at least one of: a preheated permanent test-bar mold, a near net shape sand hot-tear mold, and a step-plate mold. The molds employed for testing were kept at room temperature; the step-plate molds contained either and iron chill or a copper chill.
After the alloy was cast and broken from the mold test-bars were heat-treated using a T6 heat-treatment.
Alloy ALC-200 having a composition of 8% Ce, balance Al was made and tested as described above in Example I.
Mechanical properties of as-cast and heat-treated alloy ALC-200 are presented in Table 2.
Alloy ALC-300 having a composition of 10% Ce, balance Al was made and tested as described above in Example I.
Mechanical properties of as-cast and heat-treated alloy ALC-300 are presented in Table 3.
Alloy ALC-100 having a composition of 6% Ce, balance Al was made and tested as described above in Example I.
Mechanical properties of as-cast and heat-treated alloy ALC-100 are presented in Table 4.
Alloy ALC-500 having a composition of 16% Ce, balance Al was made and tested as described above in Example I.
Mechanical properties of as-cast and heat-treated alloy ALC-500 are presented in Table 5.
A specimen of alloy ALC-500 was characterized by its magnetic properties near and below room temperature, as shown in
XRD spectra in
Referring to
The measured values of the moment at 2 K and the susceptibility at 300 K support the presence of Ce3Al11 as the primary Ce containing phase in ALC-500 and the temperature dependence and transition temperatures indicates this phase is present in well-ordered grains which behave very similarly to bulk single crystal Ce3Al11.
Alloy ALC-315 having a composition of 8% Ce, 1% Ni, balance Al was made and tested as described above in Example I.
Mechanical properties of as-cast and heat-treated alloy ALC-315 are presented in Table 6.
Alloy ALC-412 having a composition of 12% Ce, 0.4% Mg, balance Al was made and tested as described above in Example I.
Alloy ALC-413 having a composition of 12% Ce, 1% Fe, balance Al was made and tested as described above in Example I.
Alloy ALC-322 having a composition of 8% Ce, 1% Ni, 1% Si, balance Al was made and tested as described above in Example I.
Mechanical properties of as-cast and heat-treated alloy ALC-322 are presented in Table 8.
The samples described hereinabove were tested and compared to show the unique and unexpected properties and characteristics thereof. In some cases, the samples were compared to conventional, well-known alloy A-7075.
In Al—Ce alloys there exists a unique oxide layer. X-ray photoelectron spectroscopy (XPS) analysis was employed to provide further evidence of the distinction between non-cerium aluminum alloys and the new alloys described herein. XPS data spectra were obtained for all the as-cast ternary and quaternary samples. After measuring the as-received samples, the samples were etched using an ar-ion beam. They were then measured again. Data profiles were plotted for the Al—Ce alloys, shown in
An alloy having a composition of 8% Ce, 1% Cu, balance Al (commonly written as Al-8Ce-1Cu) is made as described above in Example I. Properties are contemplated to be similar to alloy ALC-315 described hereinabove in Example VI
Graphs were prepared to compare mechanical properties of various alloys described hereinabove.
Alloy ALC-217 having a composition of Al-8Ce-0.25Zr was made and tested as described above in Example I.
Mechanical properties of as-cast and heat-treated alloy ALC-217 are presented in Table 12.
Alloy ALC-217.1 having a composition of Al-8Ce-0.25Zr was made and tested as described above in Example I.
Alloy ALC-218 having a composition of Al-8Ce-1.3Ti was made and tested as described above in Example I.
Mechanical properties of as-cast and heat-treated alloy ALC-218 are presented in Table 13.
Alloy ALC-216 having a composition of Al-8Ce-0.75Mn was made and tested as described above in Example I.
Mechanical properties of as-cast and heat-treated alloy ALC-216 are presented in Table 14.
Alloy ALC-413.1 having a composition of Al-2Ce-4Fe was made and tested as described above in Example I.
Mechanical properties of as-cast and heat-treated alloy ALC-413.1 are presented in Table 15.
Alloy ALC-223 having a composition of Al-8Ce-10Mg-2.5Zn was made and tested as described above in Example I.
Mechanical properties of as-cast and heat-treated alloy ALC-223 are presented in Table 16.
Further illustrations are provided as follows:
Referring again to
Further comparative illustrations are provided as follows:
Heat treating cast Al—Ce alloys that contain Mg can reversibly transfer the Mg between the main phase Al1-xMgx and the intermetallic (Ce1-yMgy)3(Al1-zMgz)11. This is observed by thermal analysis, x-ray diffraction, and magnetization measurements. Similar behavior is seen in alloys that contain Al, Ce, Mg, and Zn.
Magnesium and Zn can be incorporated into the fcc-Al phase in the Ce3Al11 containing alloys. This is apparent from the behavior of the unit cell volume determined from x-ray diffraction shown in Table 17, which shows unit cell (u.c.) volumes of the Ce3Al11 intermetallic and the FCC—Al matrix phases determined by x-ray diffraction.
Referring to
The thermal signature is present on both heating and cooling, indicating that this is a reversible phase transition.
Referring to
As-cast Al-8Ce-7Mg shows a lower ferromagnetic ordering temperature, by about 1 K. This sample also does not show the downturn at low temperatures seen in the other, which corresponds to a ferromagnetic to antiferromagnetic transition reported in single crystals.
The magnetic data suggests the chemistry of the Al-8Ce-7Mg sample in the as-cast state is different than Al-8Ce and Al-8Ce-10Mg, which appear to be quite similar. This is consistent with the lattice parameter results shown above in Table 17, which give a smaller unit cell volume for Al-8Ce-7Mg (574.9 Å3) vs Al-8Ce and Al-8Ce-10Mg (576.5 Å3 and 576.6 Å3, respectively).
Results of annealing the as cast samples at 375° C. and 475° C. are shown in
Annealing at 375° C. has little influence on the magnetic behavior of either sample. Annealing at 475° C. has a strong effect on Al-8Ce-7Mg and little effect on Al-8Ce-10Mg. This is consistent with measured unit cell volume shown above in Table 17. Among as-cast, 375° C. annealed, and 475° C. annealed specimens, the cell volume changes little in Al-8Ce-10Mg (576.6 Å3, 576.1 Å3, 576.3 Å3, respectively), but considerable changes are seen in Al-8Ce-7Mg (574.9 Å3, 573.6 Å3, 574.4 Å3, respectively). Those changes suggest the chemical composition of the intermetallic phase can be changed with thermal treatment.
Evidence for these chemical composition variation is also seen in the FCC—Al phase in Table 17. Annealing at 475° C. results in a small reduction of the unit cell volume of this phase, suggesting a small fraction of the Mg migrates from the FCC—Al phase into the Ce3Al11 or another secondary phase at this temperature. Table 17 data indicates significant changes are seen in the Ce3Al11 phase unit cell volume during these thermal treatments as well.
Changes in the unit cell volume of the FCC—Al/Mg solid solution Al1-xMgx phase can be used to estimate the Mg concentration changes that occur during thermal treatment.
Thus, an Al—Ce—Mg alloy has been made that includes an Al—Mg solid solution and Ce3Al11-based intermetallic in which the Mg can be made to move in and out of the Al—Mg phase by heat treating at temperatures above 300° C.
Moreover, an Al—Ce—Zn alloy has been made that includes an Al—Zn solid solution and Ce3Al11-based intermetallic in which the Zn can be made to move in and out of the Al—Zn phase by heat treating at temperatures above 300° C.
Moreover, an Al—Ce—Mg—Zn alloy has been made that includes an Al—Mg—Zn solid solution and Ce3Al11-based intermetallic in which the at least one of the Mg and the Zn can be made to move in and out of the Al—Mg—Zn phase by heat treating at temperatures above 300° C.
Any of the cast alloys described herein can have an eutectic microconstituent that comprises more than 10 volume percent of the microstructure, preferably at least 20 volume percent of the microstructure. A eutectic microconstituent is element of the microstructure having a distinctive lamellar or rod structure consisting on two or more phases that form through coupled growth from the liquid phase. The eutectic constituent forms through an isothermal invariant reaction involving the co-precipitation and growth of two or more phases with a distinct composition. In the examples discussed here the relevant phases are the FCC Al phase with space group FM-3M, the orthorhombic Al11Ce3 phase with space group IMMM, the body centered tetragonal CeAlSi phase with space group I41MD, the primitive cubic phase NiAl with space group PM-3M and the face centered Si phase with the Fd-3m space group. Typically, intermetallics precipitates in an Al matrix that are larger than 5 um do not effectively transfer load to the matrix phase and do not result in effective strengthening of the alloy. Additionally, intermetallics will decrease the ductility of the material related toughness. The formation of the said intermetallic as a phase or phases within the eutectic microconstituent with the specified dimensions leads to effective load transfer between the intermetallic and Al phase that comprise the eutectic microconstituent. This enables strengthening of the alloy while maintaining high ductility and toughness. In particular,
Moreover, any of the cast alloys described herein can have a strengthening Al11X3 intermetallic phase in an amount in the range of from about 5 to about 30 weight percent, from about 5 to about 20 weight percent, from about 6 to about 16 weight percent, or from about 8 to about 12 weight percent. Moreover, Any of the cast alloys described herein can include up to about 7 weight percent of an element selected from the group consisting of silicon and zinc, up to about 5 weight percent of an element selected from the group consisting of iron, titanium, zirconium, and vanadium, and up to about 8 weight percent of at least one element selected from the group consisting of copper and nickel. Moreover, Any of the cast alloys described herein can include up to about 20 weight percent magnesium, preferably up to about 15 weight percent, or up to about 12 weight percent.
Any of the cast alloys described herein can have a room-temperature ductility of at least 1%, at least 5%, at least 10%, or at least 20%. Moreover, any of the cast alloys described herein may retain at least 60% of its room-temperature tensile yield strength and at least 60% of its ultimate tensile strength at about 200° C., and may retain at least 50% of its room-temperature tensile yield strength and at least 30% of its ultimate tensile strength at about 300° C. Moreover, any of the cast alloys described herein may retain at least 80% of its room temperature tensile yield strength and at least 80% of its ultimate tensile strength at room temperature after being held at about 50° C. for 40 hours.
Moreover, in any of the cast alloys described herein, the lath or rod spacing and thickness may not increase by more than 20% after being held at about 550° C. for 40 hours. Moreover, in any of the cast alloys described herein, the lath or rod spacing and thickness may not increase by more than 20% after being held at about 400° C. for 40 hours.
Any of the cast alloys described herein may have a castability rating of at least 3. Moreover, any of the cast alloys described herein may exhibit an anti-ferromagnetic transition at a temperature between 2K and 12K, or between 4K and 10K. Moreover, any of the cast alloys described herein may include a rare-earth containing surface oxide. Moreover, any of the cast alloys described herein may exhibit a solid state transformation and associated exothermic thermal signature at a temperature between 250 and 500° C.
Any of the cast alloys described herein may exhibit a complex load sharing relationship between an Al face-centered-cubic phase and the strengthening Al11X3 inter-metallic phase, the complex load sharing relationship characterized by a three-stage deformation mechanism that includes load partitioning preference to the strengthening Al11X3 inter-metallic, and wherein, in a first stage, both of the Al face-centered-cubic phase and the strengthening Al11X3 inter-metallic phase deform elastically, in a second stage, the Al face-centered-cubic phase deforms plastically and the strengthening Al11X3 inter-metallic phase deforms elastically, and in a third stage, the Al face-centered-cubic phase and the strengthening Al11X3 inter-metallic phase deforming plastically, load sharing relationship characterized by a common tangent between the first stage and the second stage, the transition from the elastic to the plastic deformation in the Al face-centered-cubic phase having an onset at no less than 0.025 lattice strain, or no less than 0.05 lattice strain.
Alloy 206 was re-alloyed to make a new alloy comprising up to about 0.1 weight percent Si, up to about 0.15 weight percent Fe, about 4.2-5.0 weight percent Cu, about 0.2-0.5 weight percent Mn, about 0.15-0.35 weight percent Mg, up to about 0.05 weight percent Ni, up to about 0.1 weight percent, about 0.15-0.30 weight percent Ti, from about 6 to about 30 wt weight percent of at least one material selected from the group consisting of cerium, lanthanum, and mischmetal, up to about 0.15 weight percent total other impurities, and balance aluminum.
Alloy 356 is re-alloyed to make a new alloy comprising about 6.5-7.5 weight percent Si, up to about 0.6 weight percent Fe, up to about 0.25 weight percent Cu, up to about 0.35 weight percent Mn, about 0.20-0.45 weight percent Mg, up to about 0.35 weight percent Zn, up to about 0.25 weight percent Ti, from about 6 to about 30 wt weight percent of at least one material selected from the group consisting of cerium, lanthanum, and mischmetal, up to about 0.15 weight percent total other impurities, and balance aluminum.
Alloy 319 is re-alloyed to make a new alloy comprising about 5.5-6.5 weight percent Si, about 1 weight percent Fe, about 3.0-4.0 weight percent Cu, about 0.5 weight percent Mn, up to about 0.1 weight percent Mg, up to about 1 weight percent Zn, up to about 0.25 weight percent Ti, from about 6 to about 30 wt weight percent of either Cerium lanthanum Mischmetal or any mixture of the three, up to about 0.15 weight percent total other impurities, and balance aluminum.
Alloy 535 is re-alloyed to make a new alloy comprising up to about 0.15 weight percent Si, up to about 0.15 weight percent Fe, up to about 0.05 weight percent Cu, about 0.1-0.25 weight percent Mn, about 6.2-7.5 weight percent Mg, about 0.10-0.25 weight percent Ti, from about 6 to about 30 wt weight percent of at least one material selected from the group consisting of cerium, lanthanum, and mischmetal, up to about 0.15 weight percent total other impurities, and balance aluminum.
Alloy 206 was diluted to make a new alloy comprising up to about 0.1 weight percent Si, up to about 0.15 weight percent Fe, about 4.2-5.0 weight percent about Cu, 0.2-0.5 weight percent Mn, about 0.15-0.35 weight percent Mg, up to about 0.05 weight percent Ni, up to about 0.1 weight percent, about 0.15-0.30 weight percent Ti, up to about 0.15 weight percent total other impurities, and balance aluminum, to which from about 6 to about 30 weight percent of at least one material selected from the group consisting of cerium, lanthanum, and mischmetal is added.
Alloy 356 is diluted to make a new alloy comprising about 6.5-7.5 weight percent Si, up to about 0.6 weight percent Fe, up to about 0.25 weight percent Cu, up to about 0.35 weight percent Mn, about 0.20-0.45 weight percent Mg, up to about 0.35 weight percent Zn, up to about 0.25 weight percent Ti, up to about 0.15 weight percent total other impurities, and balance aluminum, to which from about 6 to about 30 weight percent of at least one material selected from the group consisting of cerium, lanthanum, and mischmetal is added.
Alloy 319 is diluted to make a new alloy comprising about 5.5-6.5 weight percent Si, about 1 weight percent Fe, about 3.0-4.0 weight percent Cu, about 0.5 weight percent Mn, up to about 0.1 weight percent Mg, up to about 1 weight percent Zn, up to about 0.25 weight percent Ti, up to about 0.15 weight percent total other impurities, and balance aluminum, to which from about 6 to about 30 weight percent of at least one material selected from the group consisting of cerium, lanthanum, and mischmetal is added.
Alloy 535 is diluted to make a new alloy comprising up to about 0.15 weight percent Si, up to about 0.15 weight percent Fe, up to about 0.05 weight percent Cu, about 0.1-0.25 weight percent Mn, about 6.2-7.5 weight percent Mg, about 0.10-0.25 weight percent Ti, up to about 0.15 weight percent total other impurities, and balance aluminum, to which from about 6 to about 30 weight percent of at least one material selected from the group consisting of cerium, lanthanum, and mischmetal is added.
Any of the cast compositions described hereinabove can be made by the respective casting processes described hereinbelow.
Referring to
Step 1: Aluminum is heated to a molten state, which is to be understood throughout the specification as being heated to a temperature suitable for pouring. At this point, any desired additional alloying elements, including silicon, zinc, iron, titanium, zirconium, vanadium, magnesium, copper, and nickel, but excluding cerium, lanthanum, and mischmetal, can be added to the melt.
Step 2: Degassing (generally rotary degassing) is performed using a reactive gas such as, for example, nitrous oxide (N.O.S.) in order to purge the melt of undesirable dissolved materials.
Step 3: The reactive gas is replaced with a non-reactive gas such as, for example, argon or nitrogen. Purging is continued until the reactive gas is removed and the melt exceeds 90% theoretical density.
Step 4: The melt is fluxed with an alkaline based flux to remove dissolved gases and undesirable solids. If the theoretical density does not exceed 90% at this point, then repeat Steps 3 and 4. If the theoretical density does not exceed 70% at this point, then it may be beneficial to repeat Steps 2, 3 and 4. When the theoretical density exceeds 90%, continue to Step 5.
Step 5: Cerium, lanthanum, and/or mischmetal is added to the melt; heating continues until the temperature returns to the desired pouring temperature.
Step 6: Degassing is performed using a non-reactive gas.
Step 7: The melt is fluxed with an alkaline based flux to remove dissolved gases and undesirable solids. If the theoretical density does not exceed 90% at this point, then repeat Steps 6 and 7. When the theoretical density exceeds 90%, continue to Step 8.
Step 8: The melt can be held under alkaline based flux or a cover gas until ready to pour.
Step 9: The melt is poured (transferred) into a casting mold.
Referring to
Step 1: Aluminum is heated to a molten state—to a temperature suitable for pouring.
Step 2: Degassing (generally rotary degassing) is performed using a reactive gas such as, for example, nitrous oxide (N.O.S.) in order to purge the melt of undesirable dissolved materials.
Step 3: The reactive gas is replaced with a non-reactive gas such as, for example, argon or nitrogen. Purging is continued until the reactive gas is removed. If the theoretical density does not exceed 90% at this point, then repeat Step 3. If the theoretical density does not exceed 70% at this point, then it may be beneficial to repeat Steps 2 and 3. When the theoretical density exceeds 90%, continue to Step 4.
Step 4: Cerium is added to the melt; heating continues until the temperature returns to the desired pouring temperature.
Step 5: Degassing is performed using a non-reactive gas.
Step 6: The melt is fluxed with an alkaline based flux to remove dissolved gases and undesirable solids. If the theoretical density does not exceed 90% at this point, then repeat Steps 5 and 6. When the theoretical density exceeds 90%, continue to Step 7.
Step 7: Any desired additional alloying elements, including silicon, zinc, iron, titanium, zirconium, vanadium, magnesium, copper, and nickel, but excluding cerium, lanthanum, and mischmetal, can be added.
Step 8: Degassing is performed using a non-reactive gas.
Step 9: The melt is fluxed with an alkaline based flux to remove dissolved gases and undesirable solids. If the theoretical density does not exceed 90% at this point, then repeat Steps 8 and 9. When the theoretical density exceeds 90%, continue to Step 10.
Step 10: The melt can be held under alkaline based flux or a cover gas until ready to pour.
Step 11: The melt is poured (transferred) into a casting mold.
Referring to
Step 1: Aluminum is heated to a molten state—to a temperature suitable for pouring. At this point, any desired additional alloying elements, including silicon, iron, titanium, zirconium, vanadium, copper, and nickel, but excluding cerium, magnesium, and zinc, can be added to the melt.
Step 2: Degassing (generally rotary degassing) is performed using a reactive gas such as, for example, nitrous oxide (N.O.S.) in order to purge the melt of undesirable dissolved materials.
Step 3: The melt is fluxed with an alkaline based flux to remove dissolved gases and undesirable solids. If the theoretical density does not exceed 90% at this point, then repeat Steps 2 and 3. When the theoretical density exceeds 90%, continue to Step 5.
Step 4: Magnesium and/or zinc are added to the melt; heating continues until the temperature returns to the desired pouring temperature.
Step 5: Degassing (generally rotary degassing) is performed using a reactive gas such as, for example, nitrous oxide (N.O.S.) in order to purge the melt of undesirable dissolved materials.
Step 6: The reactive gas is replaced with a non-reactive gas such as, for example, argon or nitrogen. Purging is continued until the reactive gas is removed.
Step 7: The melt is fluxed with an alkaline based flux to remove dissolved gases and undesirable solids. If the theoretical density does not exceed 90% at this point, then repeat Steps 6 and 7. If the theoretical density does not exceed 70% at this point, then it may be beneficial to repeat Steps 5, 6 and 7. When the theoretical density exceeds 90%, continue to Step 8.
Step 8: Cerium is added to the melt; heating continues until the temperature returns to the desired pouring temperature.
Step 9: Degassing (generally rotary degassing) is performed using a non-reactive gas such as, for example, argon or nitrogen.
Step 10: The melt is fluxed with an alkaline based flux to remove dissolved gases and undesirable solids. If the theoretical density does not exceed 90% at this point, then repeat Step 10. When the theoretical density exceeds 90%, continue to Step 11.
Step 11: The melt can be held under alkaline based flux or a cover gas until ready to pour.
Step 12: The melt is poured (transferred) into a casting mold.
Referring to
Step 1: Aluminum is heated to a molten state—to a temperature suitable for pouring. At this point, any desired additional alloying elements, including silicon, iron, titanium, zirconium, vanadium, copper, and nickel, but excluding cerium, magnesium, and zinc, can be added to the melt.
Step 2: Degassing (generally rotary degassing) is performed using a reactive gas such as, for example, nitrous oxide (N.O.S.) in order to purge the melt of undesirable dissolved materials.
Step 3: The reactive gas is replaced with a non-reactive gas such as, for example, argon or nitrogen. Purging is continued until the reactive gas is removed.
Step 4: The melt is fluxed with an alkaline based flux to remove dissolved gases and undesirable solids. If the theoretical density does not exceed 90% at this point, then repeat Steps 2, 3 and 4. When the theoretical density exceeds 90%, continue to Step 5.
Step 5: Cerium is added to the melt; heating continues until the temperature returns to the desired pouring temperature.
Step 6: Degassing (generally rotary degassing) is performed using a non-reactive gas such as, for example, argon or nitrogen.
Step 7: The melt us fluxed with an alkaline based flux to remove dissolved gases and undesirable solids. If the theoretical density does not exceed 90% at this point, then repeat Steps 6 and 7. When the theoretical density exceeds 90%, continue to Step 8.
Step 8: Magnesium and/or zinc are added to the melt; heating continues until the temperature returns to the desired pouring temperature.
Step 9: Degassing (generally rotary degassing) is performed using a non-reactive gas such as, for example, argon or nitrogen.
Step 10: The melt is fluxed with an alkaline based flux to remove dissolved gases and undesirable solids. If the theoretical density does not exceed 90% at this point, then repeat Steps 9 and 10. When the theoretical density exceeds 90%, continue to Step 11.
Step 11: The melt can be held under alkaline based flux or a cover gas until ready to pour.
Step 12: The melt is poured (transferred) into a casting mold.
Heat-treating can follow any of the casting methods described hereinabove. Moreover, such heat treatment can include ASTM T6 heat treatment.
While there has been shown and described what are at present considered to be examples of the invention, it will be obvious to those skilled in the art that various changes and modifications can be prepared therein without departing from the scope of the inventions defined by the appended claims.
This invention was made with Government support under DE-AC05-00OR22725 and DE-AC02-07CH11358, and DE-AC52-07NA27344 awarded by the United States Department of Energy. The Government has certain rights in the invention.
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