Patent Application
20190291182
A variety of aluminum alloy compositions have been developed for use in the manufacture of three-dimensional aluminum alloy parts via casting and/or hot forming operations to impart certain desirable chemical and mechanical properties to the resulting parts. However, it has been found that when such aluminum alloy compositions are employed as a powder feed material in a powder bed fusion additive manufacturing process, the resulting aluminum alloy parts oftentimes exhibit a columnar grain structure, and thus are relatively susceptible to cracking along grain boundaries between adjacent columnar grains. Therefore, there is a need in the art for an aluminum alloy composition that can be employed in a powder bed fusion additive manufacturing process to form three-dimensional aluminum alloy parts that predominantly exhibit an equiaxed grain structure and thus are relatively resistant or impervious to solidification cracking.
In accordance with one aspect of the present disclosure, an aluminum alloy powder for manufacturing a three-dimensional high-strength aluminum alloy part by a powder bed fusion additive manufacturing process is provided. Each particle of the aluminum alloy powder may comprise an aluminum alloy that includes, by weight, 13-25% silicon, 0.1-10% copper, and 0-2% magnesium. When the aluminum alloy is heated to a first temperature greater than a liquidus temperature of the aluminum alloy and subsequently cooled to a second temperature less than the liquidus temperature of the aluminum alloy and greater than a solidus temperature of the aluminum alloy, the aluminum alloy may transition from a liquid phase to a multiphase system. The multiphase system may include a solution of liquid phase aluminum and a solid phase of silicon particles dispersed throughout the liquid phase aluminum.
In one form, the aluminum alloy may comprise, by weight, 15-22% silicon, 2-5.1% copper, and 0.6-0.8% magnesium. In another form, the aluminum alloy powder may comprise, by weight, 19-21% silicon, 3.5-4.1% copper, and aluminum as balance.
The aluminum also may comprise, by weight: greater than 0% iron and less than 9% iron, and greater than 0% manganese and less than 5% manganese. In such case, the multiphase system may include the solution of liquid phase aluminum, the solid phase of silicon particles, and another solid phase of iron-containing intermetallic particles dispersed throughout the liquid phase aluminum.
In accordance with another aspect of the present disclosure, an aluminum alloy powder for manufacturing a three-dimensional high thermal conductivity aluminum alloy part by a powder bed fusion additive manufacturing process is provided. Each particle of the aluminum alloy powder may comprise an aluminum alloy that includes, by weight: greater than 95% aluminum, and greater than 0% and less than 5% of at least one nucleating agent. The at least one nucleating agent may comprise an element or compound having a solid solubility in aluminum of, by weight, less than 0.5% at temperatures less than 530 degrees Celsius. When the aluminum alloy is heated to a first temperature greater than a liquidus temperature of the aluminum alloy and subsequently cooled to a second temperature less than the liquidus temperature of the aluminum alloy and greater than a solidus temperature of the aluminum alloy, the aluminum alloy may transition from a liquid phase to a multiphase system. The multiphase system may include a solution of liquid phase aluminum and a solid phase of particles of the at least one nucleating agent dispersed throughout the liquid phase aluminum. In one form, the at least one nucleating agent may comprise an element or compound having a solid solubility in aluminum of, by weight, less than or equal to 2.0% at the second temperature.
A method of manufacturing a three-dimensional aluminum alloy part may comprise the following step. In step (a), an aluminum alloy powder feed material may be provided. In step (b), a layer of the powder feed material may be distributed over a substrate. In step (c), selective regions of the layer of the powder feed material may be scanned with a high-energy laser or electron beam to form a pool of molten aluminum alloy material therein. The selective regions of the layer of the powder feed material may correspond to a cross-section of an aluminum alloy part being formed. In step (d), the laser or electron beam may be terminated to cool and solidify the pool of molten aluminum alloy material into a solid layer of fused aluminum alloy material. Steps (b) through (d) may be sequentially repeated to form an aluminum alloy part made up of a plurality of solid layers of fused aluminum alloy material. During solidification of the pool of molten aluminum alloy material, solid phase particles may form within a solution of liquid phase aluminum prior to formation of solid phase aluminum dendrites. Each of the solid layers of fused aluminum alloy material in the aluminum alloy part may include a continuous aluminum matrix phase that exhibits a polycrystalline structure and predominantly includes a plurality of equiaxed grains.
After termination of the laser or electron beam, the pool of molten aluminum alloy material may be cooled at a rate in the range of 104 Kelvin per second to 106 Kelvin per second.
During solidification of the pool of molten aluminum alloy material, the molten aluminum alloy material may transition from an entirely liquid phase to a multiphase system. In the multiphase system, the solid phase particles may be dispersed throughout the solution of liquid phase aluminum.
The solid phase particles may serve as nuclei for the subsequent formation of the solid phase aluminum dendrites. In such case, after the solid phase particles form within the solution of liquid phase aluminum, the solid phase aluminum dendrites may nucleate and grow in multiple directions on the solid phase particles. Growth of the solid phase aluminum dendrites may be arrested when neighboring aluminum dendrites impinge upon one another and form grain boundaries.
In one form, each particle of the aluminum alloy powder feed material may comprise, by weight, 13-25% silicon. In such case, the solid phase particles may comprise particles of silicon.
Each particle of the aluminum alloy powder feed material also may comprise, by weight: greater than 0% iron and less than 9% iron, and greater than 0% manganese and less than 5% manganese. In such case, the solid phase particles may comprise the particles of silicon and iron-containing intermetallic particles.
Each particle of the aluminum alloy powder feed material also may comprise, by weight, 0.1-10% copper and 0-2% magnesium. In such case, the aluminum alloy part may be heated at a temperature in the range of 180° C. to 210° C. for a duration of 0.5 hours to 7 hours to form at least one copper-containing precipitate phase within the aluminum matrix phase of each of the solid layers of fused aluminum alloy material in the aluminum alloy part.
In another form, each particle of the aluminum alloy powder feed material may comprise, by weight: greater than 95% aluminum, and greater than 0% and less than 5% of at least one nucleating agent. The at least one nucleating agent may comprise an element or compound having a solid solubility in aluminum of, by weight, less than 0.5% at temperatures less than 530 degrees Celsius.
In one specific example, each particle of the aluminum alloy powder feed material may comprise, by weight, greater than 98% aluminum and less than 2% of the at least one nucleating agent.
The at least one nucleating agent may comprise at least one element or compound of titanium (Ti), boron (B), beryllium (Be), cobalt (Co), chromium (Cr), cesium (Cs), iron (Fe), hafnium (Hf), manganese (Mn), molybdenum (Mo), niobium (Nb), lead (Pb), sulfur (S), zirconium (Zr), antimony (Sb), scandium (Sc), selenium (Se), strontium (Sr), tantalum (Ta), vanadium (V), or tungsten (W).
In one form, each particle of the aluminum alloy powder feed material may comprise, by weight, at least one of greater than 0% B and less than 5% B, greater than or equal to 0.7% Be and less than 5% Be, greater than or equal to 0.9% Co and less than 5% Co, greater than or equal to 0.3% Cr and less than 5% Cr, greater than 0% Cs and less than 5% Cs, greater than or equal to 1.7% Fe and less than 5% Fe, greater than or equal to 0.4% Hf and less than 5% Hf, greater than or equal to 1.8% Mn and less than 5% Mn, greater than 0% Mo and less than 5% Mo, greater than 0% Nb and less than 5% Nb, greater than or equal to 1.4% Pb and less than 5% Pb, greater than 0% S and less than 5% S, greater than or equal to 0.9% Sb and less than 5% Sb, greater than or equal to 0.4% Sc and less than 5% Sc, greater than 0% Se and less than 5% Se, greater than or equal to 0.5% Sr and less than 5% Sr, greater than 0% Ta and less than 5% Ta, greater than or equal to 0.12% Ti and less than 5% Ti, greater than 0% V and less than 5% V, greater than 0% W and less than 5% W, or greater than 0% Zr and less than 5% Zr.
In one specific form, each particle of the aluminum alloy powder feed material may comprise, by weight, greater than 0.12% Ti, less than 5% Ti, and aluminum as balance.
The presently disclosed aluminum alloys can be prepared in powder form and used in various powder bed fusion additive manufacturing processes to produce three-dimensional aluminum alloy parts that predominantly exhibit an equiaxed grain structure and relatively high resistance to solidification cracking, as compared to aluminum alloy parts that predominantly exhibit a columnar grain structure. To inhibit the formation of columnar grains within the aluminum alloy parts during the powder bed fusion process, the aluminum alloys include at least one element or compound that, during solidification of the aluminum alloys, nucleates within a solution of liquid phase aluminum and serves as nuclei for the subsequent nucleation and growth of aluminum dendrites. As the aluminum dendrites grow outward in all directions from their respective nuclei, the aluminum dendrites eventually impinge upon neighboring dendrites and form grain boundaries. Because the nucleation and growth of the aluminum dendrites occurs throughout the solidifying aluminum alloy, instead of along a single plane (e.g., on a substrate or on a layer of previously solidified aluminum alloy material), the formation of columnar grains within the solidifying alloy is prevented or inhibited.
As used herein, the term “aluminum alloy” refers to a material that comprises, by weight, greater than or equal to 50% aluminum (Al) and one or more other elements selected to impart certain desirable properties to the material that are not exhibited by pure aluminum.
In one form, an aluminum alloy composition for manufacturing a three-dimensional high-strength aluminum alloy part by an additive manufacturing process may comprise, in addition to aluminum, alloying elements of silicon (Si) and copper (Cu), and thus may be referred to herein as an “Al—Si—Cu alloy.” More specifically, the Al—Si—Cu alloy may comprise, by weight, greater than or equal to 13%, 15%, or 19% silicon; less than 25%, 22%, or 21% silicon; or between 13-25%, 15-22%, or 19-21% silicon. In addition, the Al—Si—Cu alloy may comprise, by weight, greater than or equal to 0.1%, 2%, or 3.5% copper; less than 10%, 5.1%, or 4.1%, copper; or between 0.1-10%, 2-5.1%, or 3.5-4.1% copper.
The amount of silicon in the Al—Si—Cu alloy described herein is selected so that the Al—Si—Cu alloy exhibits a hypereutectic composition and can be heated to a temperature above a liquidus temperature of the Al—Si—Cu alloy and subsequently cooled to a temperature below a solidus temperature of the Al—Si—Cu alloy to produce an entirely solid polycrystalline Al—Si—Cu alloy that predominantly exhibits an equiaxed grain structure, instead of a columnar grain structure. Without intending to be bound by theory, it is believed that the equiaxed grain structure of the resulting polycrystalline Al—Si—Cu alloy is due, at least in part, to the solidification behavior of the Al—Si—Cu alloy. In particular, it is believed that, when the hypereutectic Al—Si—Cu alloy is heated to a temperature above the liquidus temperature of the Al—Si—Cu alloy and subsequently cooled to a temperature below the liquidus temperature of the Al—Si—Cu alloy, the Al—Si—Cu alloy will transition from an entirely liquid phase to a multiphase system. During this transition, particles of solid phase silicon will nucleate throughout a solution of liquid phase aluminum to produce a multiphase system that includes a solution of liquid phase aluminum and a solid phase of silicon particles dispersed throughout the liquid phase aluminum. Nucleation of the particles of solid phase silicon may occur simultaneously throughout multiple horizontally and vertically spaced-apart regions of the solution of liquid phase aluminum, and may occur generally homogeneously throughout the solution of liquid phase aluminum. Thereafter, when the hypereutectic Al—Si—Cu alloy is further cooled to a temperature at or below the solidus temperature of the Al—Si—Cu alloy, solid phase aluminum dendrites will nucleate and grow in multiple directions on the previously formed silicon particles. Growth of these aluminum dendrites will eventually be arrested when neighboring aluminum dendrites impinge upon one another and form grain boundaries. After the hypereutectic Al—Si—Cu alloy has completely solidified, the Al—Si—Cu alloy will exhibit a polycrystalline structure including a continuous aluminum matrix phase and a dispersed phase of silicon. In addition, the resulting hypereutectic Al—Si—Cu alloy will predominantly include a plurality of randomly oriented equiaxed grains, instead of columnar grains. The equiaxed grains may have a mean grain diameter in the range of 0.1 μm to 50 μm.
The Al—Si—Cu alloy may have a liquidus temperature in the range of 570° C. to 850° C., and a solidus temperature in the range of 500° C. to 540° C. As such, the Al—Si—Cu alloy may exhibit a multiphase system of liquid phase aluminum and solid phase silicon at a temperature in the range of 500° C. to 850° C.
As used herein, the term “predominantly” means something, for example, a grain structure, that is present in the greatest amount by volume, as compared to other similar things, for example, as compared to other grain structures.
The amount of copper in the Al—Si—Cu alloy is selected to provide the alloy with the ability to develop one or more Cu-containing precipitate phases within the aluminum matrix phase when the Al—Si—Cu alloy is subjected to a heat treatment process. For example, the amount of copper in the Al—Si—Cu alloy may be selected to provide the alloy with the ability to develop an Al- and Cu-based precipitate (referred to herein as an “AlCu precipitate”) phase within the aluminum matrix phase when the Al—Si—Cu alloy is subjected to a heat treatment process that includes an aging heat treatment stage and optionally a solution heat treatment stage. The AlCu precipitate phase is Al- and Cu-based, meaning that Al and Cu constitute the largest constituents of the precipitate phase by weight. Formation of the AlCu precipitate phase within the aluminum matrix phase may provide the Al—Si—Cu alloy with high strength at relatively low temperatures, e.g., at ambient temperature (e.g., 25° C.) and at temperatures up to about 200° C.
In some embodiments, the Al—Si—Cu alloy also may comprise alloying elements of magnesium (Mg), iron (Fe), and/or manganese (Mn). When present, the Al—Si—Cu alloy may comprise, by weight, greater than or equal to 0%, 0.5%, or 0.6% magnesium; less than 2%, 1.5%, or 0.8% magnesium; or between 0-2%, 0.5-1.5%, or 0.6-0.8% magnesium. The Al—Si—Cu alloy may comprise, by weight, greater than or equal to 0% or 7% iron; less than 10% or 9% iron; or between 0-10% or 7-9% iron. The Al—Si—Cu alloy may comprise, by weight, greater than or equal to 0% or 3% manganese; less than 6% or 5% manganese; or between 0-6% or 3-5% manganese.
The amount of magnesium in the Al—Si—Cu alloy may be selected to provide the alloy with the ability to develop an Al-, Cu-, Mg-, and Si-based precipitate (referred to herein as an “AlCuMgSi precipitate”) phase within the aluminum matrix phase when the Al—Si—Cu alloy is subjected to a heat treatment process that includes an aging heat treatment stage and optionally a solution heat treatment stage. The AlCuMgSi precipitate phase is Al-, Cu-, Mg-, and Si-based, meaning that Al, Cu, Mg, and Si constitute the largest constituents of the precipitate phase by weight. Formation of the AlCuMgSi precipitate phase within the aluminum matrix phase may provide the Al—Si—Cu alloy with high strength at ambient temperature and at elevated temperatures (e.g., up to about 300° C.).
The amount of iron and manganese in the Al—Si—Cu alloy may be selected to promote the formation of at least one intermetallic phase within the Al—Si—Cu alloy during solidification thereof. In particular, the amount of iron and/or manganese in the Al—Si—Cu alloy may be selected so that at least one intermetallic phase nucleates within the liquid phase aluminum during solidification of the Al—Si—Cu alloy and provides additional nucleation sites (in addition to the nucleation sites provided by the silicon particles) for the subsequent nucleation and equiaxed growth of aluminum dendrites. For example, the at least one intermetallic phase may comprise an Fe-containing intermetallic phase and/or a Mn-containing intermetallic phase. In one specific example, the amount of iron in the Al—Si—Cu alloy may be selected to promote the formation of solid particles of an Al-, Fe-, and Si-based intermetallic (referred to herein as an “AlFeSi intermetallic”) phase within the liquid phase aluminum during solidification of the Al—Si—Cu alloy. The AlFeSi intermetallic phase is Al-, Fe-, and Si-based, meaning that Al, Fe, and Si are the largest constituents of the intermetallic phase. For example, the combined amounts of Al, Fe, and Si in the AlFeSi intermetallic phase may account for, by weight, greater than 50% of the AlFeSi intermetallic phase and, in some cases, greater than 90% of the AlFeSi intermetallic phase.
In embodiments where the Al—Si—Cu alloy comprises iron, the amount of manganese in the Al—Si—Cu alloy may be selected to promote the formation of an Al-, Fe-, Mn-, and Si-based intermetallic (referred to herein as an “AlFeMnSi intermetallic”) phase within the liquid phase aluminum during solidification of the Al—Si—Cu alloy and to inhibit the formation of an Al-, Fe-, and Si-based intermetallic (referred to herein as an “AlFeSi intermetallic”) phase.
The hypereutectic Al—Si—Cu alloy does not require addition of scandium (Sc) to achieve an equiaxed grain structure during solidification thereof. As such, the amount of Sc in the Al—Si—Cu alloy may be less than 0.2%, preferably less than 0.05%, and more preferably less than 0.01% by weight of the Al—Si—Cu alloy.
Additional elements not intentionally introduced into the composition of the Al—Si—Cu alloy nonetheless may be inherently present in the alloy in relatively small amounts, for example, less than 0.2%, preferably less than 0.05%, and more preferably less than 0.01% by weight of the Al—Si—Cu alloy. Such elements may be present, for example, as impurities in the raw materials used to prepare the Al—Si—Cu alloy composition. In embodiments were the Al—Si—Cu alloy is referred to as comprising one or more alloying elements (e.g., one or more of Si, Cu, Mg, Fe, and Mn) and aluminum as balance, the term “as balance” does not exclude the presence of additional elements not intentionally introduced into the composition of the Al—Si—Cu alloy but nonetheless inherently present in the alloy in relatively small amounts, e.g., as impurities.
In another form, an aluminum alloy composition for manufacturing a three-dimensional high thermal conductivity aluminum alloy part by an additive manufacturing process may comprise, by weight, greater than or equal to 95% aluminum and less than 5% of at least one nucleating agent, and thus may be referred to as a “high-purity Al alloy.” In one specific example, the high-purity Al alloy may comprise, by weight, greater than or equal to 98% aluminum and less than 2% of at least one nucleating agent.
The at least one nucleating agent included in the high-purity Al alloy may comprise an element or compound that exhibits relatively low solid solubility (e.g., less than 1 wt % or, more preferably, less than 0.5 wt %) in aluminum at temperatures less than 530° C. The composition and amount of the at least one nucleating agent included in the high-purity Al alloy may be selected so that the high-purity Al alloy can be heated to a temperature above a liquidus temperature of the high-purity Al alloy and subsequently cooled to a temperature below a solidus temperature of the high-purity Al alloy to produce an entirely solid polycrystalline high-purity Al alloy that predominantly exhibits an equiaxed grain structure, instead of a columnar grain structure.
In particular, the composition and amount of the at least one nucleating agent in the high-purity Al alloy may be selected so that, when the high-purity Al alloy is melted and subsequently cooled from an entirely liquid phase to an entirely solid phase, particles of the at least one nucleating agent will form within a solution of liquid phase aluminum prior to formation of a solid aluminum matrix phase. More specifically, when the high-purity Al alloy is heated to a temperature above the liquidus temperature of the high-purity Al alloy and subsequently cooled to a temperature below the liquidus temperature of the high-purity Al alloy, the high-purity Al alloy will transition from an entirely liquid phase to a multiphase system. During this transition, solid particles of the at least one nucleating agent will nucleate throughout a solution of liquid phase aluminum to produce a multiphase system that includes a solution of liquid phase aluminum and a solid phase of particles of the at least one nucleating agent dispersed throughout the liquid phase aluminum. In the multiphase system, the solid particles of the at least one nucleating agent may exhibit a solubility in liquid aluminum of, by weight, less than or equal to 2%, which may help maximize the number if solid particles within the liquid phase aluminum. Nucleation of the solid particles of the at least one nucleating agent may occur simultaneously throughout multiple horizontally and vertically spaced-apart regions of the solution of liquid phase aluminum, and may occur generally homogeneously throughout the solution of liquid phase aluminum. Thereafter, as the high-purity Al alloy continues to cool, solid phase aluminum dendrites will nucleate and grown in multiple directions on the previously formed nuclei (i.e., on the solid particles of the at least one nucleating agent). Growth of these aluminum dendrites within the solidifying high-purity Al alloy will eventually be arrested when neighboring aluminum dendrites impinge upon one another and form grain boundaries. After the high-purity Al alloy has been cooled to a temperature below the solidus temperature of the high-purity Al alloy and is completely solidified, the high-purity Al alloy will exhibit a polycrystalline structure including a continuous aluminum matrix phase and a dispersed phase of particles of the at least one nucleating agent. In addition, the resulting high-purity Al alloy will predominantly include a plurality of randomly oriented equiaxed grains, instead of columnar grains. The equiaxed grains may have a mean diameter in the range of 0.1 μm to 50 μm.
The high-purity Al alloy may have a liquidus temperature in the range of 660° and 1300° C. and a solidus temperature in the range of 650° and 680° C. As such, the high-purity Al alloy may exhibit a multiphase system of liquid phase aluminum and solid particles of the at least one nucleating agent at a temperature in the range of 650° and 1300° C.
Due to the relatively low solubility of the at least one nucleating agent in solid aluminum, limited amounts of the at least one nucleating agent will be present in solid solution in the aluminum matrix phase after complete solidification of the high-purity Al alloy. As such, inclusion of the at least one nucleating agent in the high-purity Al alloy will have little to no adverse effect on the thermal conductivity of the high-purity Al alloy. For example, after complete solidification, the high-purity Al alloy may exhibit a thermal conductivity in the range of 120 watts per meter-Kelvin (W/(m·K)) to 220 W/(m·K).
In some embodiments, the at least one nucleating agent may comprise an element that, when present in the high-purity Al alloy, exhibits a eutectic point or a peritectic point at a concentration of, by weight, less than 5% of the high-purity Al alloy. In such case, the element may be present in the high-purity Al alloy in an amount that is greater than the amount of the same element in the eutectic or peritectic composition of the Al alloy.
For example, in one form, the at least one nucleating agent may comprise titanium (Ti). A binary Al—Ti alloy exhibits a peritectic point at a composition of, by weight, about 0.12% Ti and a temperature of about 665° C. Therefore, in one form, the high-purity Al alloy may comprise a high-purity Al—Ti alloy including, by weight, greater than or equal to 95% aluminum, greater than 0.12% titanium, and less than 5% titanium. In such case, when this high-purity Al—Ti alloy is melted and subsequently cooled from an entirely liquid phase to an entirely solid phase, solid particles of Al3Ti will nucleate within a solution of liquid phase aluminum at the liquidus temperature of the alloy. Thereafter, aluminum dendrites will nucleate and grown in all directions on the previously formed Al3Ti particles, resulting in the formation of a polycrystalline structure that predominantly includes a plurality of randomly oriented equiaxed grains, instead of columnar grains.
Some examples of elements (in addition to Ti) that can be used as the at least one nucleating agent in the high-purity Al alloy include boron (B), beryllium (Be), cobalt (Co), chromium (Cr), cesium (Cs), iron (Fe), hafnium (Hf), manganese (Mn), molybdenum (Mo), niobium (Nb), lead (Pb), sulfur (S), zirconium (Zr), antimony (Sb), scandium (Sc), selenium (Se), strontium (Sr), tantalum (Ta), vanadium (V), tungsten (W), and combinations thereof. For example, the high-purity Al alloy may include, by weight, equal to or greater than 0% B to 5% B, 0.7-5% Be, 0.9-5% Co, 0.3-5% Cr, equal to or greater than 0% Cs to 5% Cs, 1.7-5% Fe, 0.4-5% Hf, 1.8-5% Mn, equal to or greater than 0% Mo to 5% Mo, equal to or greater than 0% Nb to 5% Nb, 1.4-5% Pb, equal to or greater than 0% S to 5% S, 0.9-5% Sb, 0.4-5% Sc, equal to or greater than 0% Se to 5% Se, 0.5-5% Sr, equal to or greater than 0% Ta to 5% Ta, 0.12-5% Ti, equal to or greater than 0% V to 5% V, equal to or greater than 0% W to 5% W, and/or equal to or greater than 0% Zr to 5% Zr, and the balance Al.
The high-purity Al alloy may include one or more additional elements that may or may not be intentionally introduced into the composition of the high-purity Al alloy, with such additional elements being present in the high-purity Al alloy in amounts less than 0.2%, preferably less than 0.05%, and more preferably less than 0.01% by weight of the high-purity Al alloy. Additional elements not intentionally introduced into the composition of the high-purity Al alloy may be present, for example, as impurities in the raw materials used to prepare the high-purity Al alloy composition. In embodiments were the high-purity Al alloy is referred to as comprising at least one nucleating agent (e.g., at least one element or compound of Ti, B, Be, Co, Cr, Cs, Fe, Hf, Mn, Mo, Nb, Pb, S, Zr, Sb, Sc, Se, Sr, Ta, V, or W) and aluminum as balance, the term “as balance” does not exclude the presence of additional elements not intentionally introduced into the composition of the high-purity Al alloy but nonetheless inherently present in the alloy in relatively small amounts, e.g., as impurities.
A volume of the aluminum alloy powder feed material 110 may be distributed over a surface of the building platform 114, for example, by a blade 122 to form a layer 124 of aluminum alloy powder feed material 110. In one form, the aluminum alloy powder feed material 110 may have a mean particle diameter in the range of 5 micrometers to 100 micrometers and the layer 124 of aluminum alloy powder feed material 110 may have a thickness in the range of 20 micrometers to 100 micrometers. In
Referring now to
In embodiments where the aluminum alloy powder feed material 110 comprises the Al—Si—Cu alloy, the resulting alloy part 108 may be heat treated to dissolve into solid solution any coarse intermetallic phases that may have formed during solidification and/or to promote the formation of one or more Cu-containing precipitate phases (e.g., an AlCu precipitate phase and/or AlCuMgSi precipitate phase) within the aluminum matrix phase. The heat treatment process may include an aging heat treatment stage and optionally a solution heat treatment stage. If performed, the solution heat treatment stage may be performed prior to the aging heat treatment stage. During the optional solution heat treatment stage, the alloy part 108 may be heated to a temperature in the range of 490° C. to 550° C. for a duration of 10 minutes to 10 hours. In one form, the alloy part 108 may be heated during the solution heat treatment stage to a temperature in the range of 490° C. to 550° C. for a duration of 3 hours to 10 hours. In another form, the alloy part 108 may be heated during the solution heat treatment stage to a temperature in the range of 490° C. to 550° C. for a duration of less than 1 hours, for example, for a duration of 10 minutes to 30 minutes. After the optional solution heat treatment stage, the alloy part 108 may be cooled or quenched to a temperature less than 100° C., e.g., ambient temperature, at a cooling rate sufficient to prevent diffusion and precipitation of alloying elements dissolved in into solid solution during the solution heat treatment stage. In the aging heat treatment stage, the alloy part 108 may be heated to a temperature in the range of 180° C. to 210° C. for a duration of 0.5 hours to 7 hours. After the aging heat treatment stage, the alloy part 108 may be cooled or quenched to a temperature less than 100° C., e.g., ambient temperature.
As described in further detail above, the Al—Si—Cu alloy and the high-purity Al alloy each include at least one element or compound that, during solidification of the alloy, nucleates within a solution of liquid phase aluminum and provides sites for the subsequent nucleation and growth of aluminum dendrites. However, referring now to
As shown in
The above description of preferred exemplary embodiments, aspects, and specific examples are merely descriptive in nature; they are not intended to limit the scope of the claims that follow. Each of the terms used in the appended claims should be given its ordinary and customary meaning unless specifically and unambiguously stated otherwise in the specification.
