具体实施方式：
[0012]For producing small quantities of complex mechanical parts made of metal, the default approach has been machining. Machining is a skill-intensive method and thus may be costly. Increasingly, metallic 3D objects/parts can be produced by 3D printing. 3D printing however faces challenges in producing high strength parts suitable for replacing metal parts. Many of the materials that are capable of being 3D printed lack the targeted mechanical strength of metallic parts produced by common machining. 3D printing has been used to rapidly produce casting molds or “lost wax” materials to speed up the formation of metal parts. Some attempts have been made to adjust the 3D printing approach to metals by depositing metal-polymer composites. A part is formed by building up layer after layer of material. Adjusting of inkjet printing technology has offered precise deposition of multiple materials as part of a 3D printing process. After forming, the polymer-metal hybrid part is then subjected to a high temperature process to burn away the polymer and consolidate the metal part.
[0013]Two challenges presented by polymer binders are: 1) low fracture strength in the printed polymer-metal hybrid parts and 2) complete loss of fracture strength in the printed polymer-metal parts after burning away the polymeric binder. Low strength in the printed polymer-metal hybrid parts makes it difficult to handle parts; i.e., removing parts from the printer, cleaning parts, and transferring parts to a sintering furnace can lead to breakage. Loss of binding strength after burning away the polymer can cause part collapse due to gravitational forces acting on the part. Additionally, any external force experienced at this stage can damage or break the part.
[0014]There is therefore still a demand for 3D printed metal objects that have high fracture strengths. The examples described hereinbelow show that dehydrated metal salt bound 3D printed metal object can be stronger with high fracture strengths compared with a 3D printed metal object using polymeric binders.
[0015]The examples described hereinbelow also show that because of retention of the metal component (i.e., metal from the hydrated metal salt) during the entire process (e.g., printing, decomposition, reduction, or sintering), the strength of the 3D metal object can be maintained through the 3D printing process while also mitigating distortion during sintering. This is in contrast with polymeric binders that are burned off/removed during the 3D printing process and/or sintering leaving gaps in the 3D metal object structure, which makes such 3D metal object weak.
[0016]As used herein, the term “patterned 3D printed metal object” refers to an intermediate part that has a shape representative of the final 3D printed part and that includes metallic build material patterned with a fusing agent. In the patterned 3D printed metal object, the metallic build material particles may or may not be weakly bound together by at least one component of the fusing agent and/or by attractive force(s) between the metallic build material particles and the fusing agent. It is to be understood that any metallic build material that is not patterned with the fusing agent is not considered to be part of the patterned 3D printed metal object, even if it is adjacent to or surrounds the patterned 3D printed metal object.
[0017]As used herein, the term “3D printed metal object” refers to a patterned 3D printed metal object that has been exposed to a heating process that dehydrates the hydrated metal salt in the fusing agent and that may also contribute to the evaporation of the liquid components of the fusing agent. The heating process can, in some examples, decompose a portion of the dehydrated metal salt to form a corresponding metal oxide. The dehydrated metal salt binds the metallic build material particles and creates or strengthens the bond between the metallic build material particles. In other words, the “3D printed metal object” is an intermediate part with a shape representative of the final 3D printed part and that includes metallic build material bound together by at least substantially dehydrated metal salt in the fusing agent (with which the metallic build material was patterned). Compared to the patterned 3D printed metal object, the mechanical strength of the 3D printed metal object is greater, and in some instances, the 3D printed metal object can be handled or extracted from the build material platform.
[0018]As used herein, the term “at least substantially hydrated metal salt free 3D printed metal object” refers to a 3D printed metal object that has been exposed to a heating process that completes dehydration of the metal salt and in some instances promotes partial thermal decomposition of the metal salt to the corresponding metal oxide of the hydrated metal salt. The result of this heating is to remove the hydrated metal salt from the 3D printed metal object leaving behind dehydrated metal salt and in some instances a small amount of the corresponding metal oxide. In some instances, any remaining liquid and/or volatile organic components from the fusing agent are completely removed. In other words, the “at least substantially hydrated metal salt free 3D printed metal object” refers to an intermediate part with a shape representative of the final 3D printed part and that includes metallic build material bound together as a result of i) weak sintering (i.e., low level necking between the particles, which is able to preserve the part shape), and/or ii) binding of the dehydrated metal salt with the metallic build material. In some examples, the “at least substantially hydrated metal salt free 3D printed metal object” is the same as the “3D printed metal object.”
[0019]As used herein, the term “metallic part” refers to the 3D printed metal object or the at least substantially hydrated metal salt free 3D printed metal object after having been subjected to a sintering temperature for at least a few minutes.
[0020]As used herein, the terms “3D printed part,”“3D part,”“part,”“3D printed object,”“3D object,” or “object” may be a completed 3D printed part or a layer of a 3D printed part.
[0021]As used herein, the terms “hydrated metal salt,”“metal salt,”“hydrated salt,” or “salt” are used interchangeably generally or specifically to refer to a metal salt that is hydrated.
[0022]As used herein, “(s)” at the end of some terms indicates that those terms/phrases may be singular in some examples or plural in some examples. It is to be understood that the terms without “(s)” may be also be used singularly or plurally in many examples.
[0023]Described herein, in some examples, is a method of forming a 3D printed metal object comprising:[0024](A) depositing a build material comprising at least one metal;[0025](B) selectively jetting a fusing agent on the build material, the fusing agent comprising:[0026](i) at least one hydrated metal salt having a dehydration temperature of from about 100° C. to about 250° C., and[0027](ii) a carrier liquid comprising at least one surfactant and water;[0028](C) heating the build material and the selectively jetted fusing agent to a temperature of from about 100° C. to about 250° C. to:[0029](a) remove the carrier liquid,[0030](b) dehydrate the hydrated metal salt, and[0031](c) bind the build material and the selectively jetted fusing agent; and[0032](D) repeating (A), (B), and (C) at least one time to form the 3D printed metal object.
[0033]In some examples, described herein is a method of forming a 3D printed metal object comprising:[0034](A) depositing a build material comprising at least one metal;[0035](B) selectively jetting a fusing agent on the build material, the fusing agent comprising:[0036](i) at least one hydrated metal salt having a dehydration temperature of from about 100° C. to about 250° C., and[0037](ii) a carrier liquid comprising at least one surfactant and water;[0038](C) repeating (A) and (B); and[0039](D) heating the build material and the selectively jetted fusing agent to a temperature of from about 100° C. to about 250° C. to:[0040](a) remove the carrier liquid,[0041](b) dehydrate the hydrated metal salt, and[0042](c) bind the build material and the selectively jetted fusing agent; at least one time to form the 3D printed metal object.
[0043]In some examples, the dehydration temperature is from about 100° C. to about 240° C., or from about 100° C. to about 230° C., or from about 100° C. to about 220° C., or from about 100° C. to about 210° C., or from about 100° C. to about 200° C., or from about 100° C. to about 190° C., or from about 100° C. to about 180° C., or from about 100° C. to about 170° C., or from about 100° C. to about 160° C., or from about 100° C. to about 150° C., or from about 100° C. to about 140° C., or from about 100° C. to about 130° C., or from about 100° C. to about 120° C., or from about 100° C. to about 110° C., or more than about 100° C., or more than about 110° C., or more than about 120° C., or more than about 130° C., or more than about 140° C., or more than about 150° C., or more than about 160° C., or more than about 170° C., or more than about 180° C., or more than about 190° C., or more than about 200° C., or more than about 210° C., or more than about 220° C., or more than about 230° C., or more than about 240° C., or less than about 250° C., or less than about 240° C., or less than about 230° C., or less than about 220° C., or less than about 210° C., or less than about 200° C., or less than about 190° C., or less than about 180° C., less than about 170° C., or less than about 160° C., or less than about 150° C., or less than about 140° C., or less than about 130° C., or less than about 120° C., or less than about 110° C.
[0044]In some examples, the method of forming a 3D printed metal object can further comprise: (E) heating the 3D printed metal object to a sintering temperature to form a metallic part.
[0045]In some examples, the method of forming a 3D printed metal object can further comprise: forming a corresponding metal oxide of the hydrated metal salt after dehydrating the hydrated metal salt in (C)(b); and/or forming a corresponding metal of the hydrated metal salt after dehydrating the hydrated metal salt in (C)(b).
[0046]In some examples, the at least one hydrated metal salt comprises: at least one metal cation selected from the group consisting of aluminum, magnesium, copper, zinc, iron, nickel, manganese, cobalt, molybdenum, chromium, tin, vanadium, and combinations thereof; and at least one anion selected from the group consisting of hydroxide, carbonate, sulfate, nitrate, acetate, formate, borate, chloride, bromide, and combinations thereof.
[0047]In some examples, the at least one hydrated metal salt is selected from the group consisting of hydrated copper nitrate, hydrated iron nitrate, hydrated nickel nitrate, hydrated manganese nitrate, hydrated cobalt nitrate, hydrated iron acetate, and combinations thereof.
[0048]In some examples, the at least one metal in the build material is the same as the metal cation in the at least one hydrated metal salt.
[0049]In some examples, the at least one hydrated metal salt is present in the fusing agent in an amount of from about 5 wt % to about 50 wt % based on the total weight of the fusing agent, or from about 10 wt % to about 50 wt % based on the total weight of the fusing agent, or from about 15 wt % to about 50 wt % based on the total weight of the fusing agent, or from about 20 wt % to about 50 wt % based on the total weight of the fusing agent, or from about 25 wt % to about 50 wt % based on the total weight of the fusing agent, or from about 30 wt % to about 50 wt % based on the total weight of the fusing agent, or from about 35 wt % to about 50 wt % based on the total weight of the fusing agent, or from about 40 wt % to about 50 wt % based on the total weight of the fusing agent, or from about 45 wt % to about 50 wt % based on the total weight of the fusing agent, or less than about 50 wt % based on the total weight of the fusing agent, or less than about 45 wt % based on the total weight of the fusing agent, or less than about 40 wt % based on the total weight of the fusing agent, or less than about 35 wt % based on the total weight of the fusing agent, or less than about 30 wt % based on the total weight of the fusing agent, or less than about 25 wt % based on the total weight of the fusing agent, or less than about 20 wt % based on the total weight of the fusing agent, or less than about 15 wt % based on the total weight of the fusing agent, or less than about 10 wt % based on the total weight of the fusing agent.
[0050]In some examples, the 3D printed metal object has a fracture strength of from about 5 MPa to about 20 MPa, or from about 10 MPa to about 20 MPa, or from about 15 MPa to about 20 MPa, or less than about 20 MPa, or less than about 15 MPa, or less than about 10 MPa, or less than about 5 MPa, or at least 5 MPa, or at least 10 MPa, or at least 15 MPa, or at least 20 MPa.
[0051]In some examples, the 3D printed metal object comprises the dehydrated metal salt and the corresponding metal oxide.
[0052]In some examples, the dehydrated metal salt is present in the 3D printed metal object in an amount of from about 0.2 wt % to about 20 wt % based on the total weight of the 3D printed metal object, or from about 0.2 wt % to about 15 wt % based on the total weight of the 3D printed metal object, or from about 0.2 wt % to about 10 wt % based on the total weight of the 3D printed metal object, or from about 0.2 wt % to about 5 wt % based on the total weight of the 3D printed metal object, or from about 0.2 wt % to about 1 wt % based on the total weight of the 3D printed metal object, or less than about 20 wt % based on the total weight of the 3D printed metal object, or less than about 15 wt % based on the total weight of the 3D printed metal object, or less than about 10 wt % based on the total weight of the 3D printed metal object, or less than about 5 wt % based on the total weight of the 3D printed metal object, or less than about 1 wt % based on the total weight of the 3D printed metal object, or less than about 0.5 wt % based on the total weight of the 3D printed metal object, or less than about 0.02 wt % based on the total weight of the 3D printed metal object, or about 0 wt % based on the total weight of the 3D printed metal object.
[0053]In some examples, the corresponding metal oxide is present in the 3D printed metal object in an amount of from about 0 wt % to about 10 wt % based on the total weight of the 3D printed metal object, or from about 0 wt % to about 5 wt % based on the total weight of the 3D printed metal object, or from about 0 wt % to about 1 wt % based on the total weight of the 3D printed metal object, or less than about 10 wt % based on the total weight of the 3D printed metal object, or less than about 5 wt % based on the total weight of the 3D printed metal object, or less than about 1 wt % based on the total weight of the 3D printed metal object, or less than about 0.1 wt % based on the total weight of the 3D printed metal object, or about 0 wt % based on the total weight of the 3D printed metal object.
[0054]In some examples, the 3D printed metal object is substantially free from the hydrated metal salt.
[0055]In some examples, the sintering temperature is from about 450° C. to about 1500° C., or from about 500° C. to about 1500° C., or from about 600° C. to about 1500° C., or from about 700° C. to about 1500° C., or from about 800° C. to about 1500° C., or from about 900° C. to about 1500° C., or from about 1000° C. to about 1500° C., or from about 1100° C. to about 1500° C., or from about 1200° C. to about 1500° C., or from about 1300° C. to about 1500° C., or from about 1400° C. to about 1500° C., or less than about 2500° C., or less than about 2000° C., or less than about 1500° C., or less than about 1000° C., or less than about 900° C., or less than about 800° C., or less than about 700° C., or less than about 600° C., or less than about 500° C., or at least about 500° C., or at least about 1000° C., or at least about 1500° C., or at least about 2000° C., or at least about 2500° C.
[0056]In some examples, the heating of the three-dimensional object to the sintering temperature is performed for a sintering time period ranging from about 10 minutes to about 20 hours, or at least 10 minutes, or at least 1 hour, or at least 8 hours, or at least 10 hours, or at least 15 hours, or at least 20 hours.
[0057]In some examples, (E) occurs in an environment containing (i) a vacuum or (ii) an inert gas, a low reactivity gas, a reducing gas, or a combination thereof. The inert gas, low reactivity gas, and reducing gas can include but are not limited to helium, argon, neon, xenon, krypton, nitrogen, hydrogen, carbon monoxide and combinations thereof.
[0058]In some examples, disclosed herein is a composition for 3D printing comprising: a build material comprising at least one metal; and a fusing agent comprising (i) at least one hydrated metal salt having a dehydration temperature of from about 100° C. to about 250° C., and (ii) a carrier liquid comprising at least one surfactant and water, wherein the at least one hydrated metal salt is present in an amount of at least 5 wt % in the fusing agent based on the total weight of the fusing agent, and wherein the at least one hydrated metal salt comprises: at least one metal cation selected from the group consisting of aluminum, magnesium, copper, zinc, iron, nickel, manganese, cobalt, molybdenum, chromium, tin, vanadium, and combinations thereof; and at least one anion selected from the group consisting of hydroxide, carbonate, sulfate, nitrate, acetate, formate, borate, chloride, bromide, and combinations thereof.
[0059]In some examples, the at least one hydrated metal salt is present in the fusing agent in an amount of from about 5 wt % to about 50 wt % based on the total weight of the fusing agent, or from about 10 wt % to about 50 wt % based on the total weight of the fusing agent, or from about 15 wt % to about 50 wt % based on the total weight of the fusing agent, or from about 20 wt % to about 50 wt % based on the total weight of the fusing agent, or from about 25 wt % to about 50 wt % based on the total weight of the fusing agent, or from about 30 wt % to about 50 wt % based on the total weight of the fusing agent, or from about 35 wt % to about 50 wt % based on the total weight of the fusing agent, or from about 40 wt % to about 50 wt % based on the total weight of the fusing agent, or from about 45 wt % to about 50 wt % based on the total weight of the fusing agent, or less than about 50 wt % based on the total weight of the fusing agent, or less than about 45 wt % based on the total weight of the fusing agent, or less than about 40 wt % based on the total weight of the fusing agent, or less than about 35 wt % based on the total weight of the fusing agent, or less than about 30 wt % based on the total weight of the fusing agent, or less than about 25 wt % based on the total weight of the fusing agent, or less than about 20 wt % based on the total weight of the fusing agent, or less than about 15 wt % based on the total weight of the fusing agent, or less than about 10 wt % based on the total weight of the fusing agent.
[0060]In some examples, the dehydration temperature is from about 100° C. to about 240° C., or from about 100° C. to about 230° C., or from about 100° C. to about 220° C., or from about 100° C. to about 210° C., or from about 100° C. to about 200° C., or from about 100° C. to about 190° C., or from about 100° C. to about 180° C., or from about 100° C. to about 170° C., or from about 100° C. to about 160° C., or from about 100° C. to about 150° C., or from about 100° C. to about 140° C., or from about 100° C. to about 130° C., or from about 100° C. to about 120° C., or from about 100° C. to about 110° C., or more than about 100° C., or more than about 110° C., or more than about 120° C., or more than about 130° C., or more than about 140° C., or more than about 150° C., or more than about 160° C., or more than about 170° C., or more than about 180° C., or more than about 190° C., or more than about 200° C., or more than about 210° C., or more than about 220° C., or more than about 230° C., or more than about 240° C., or less than about 250° C., or less than about 240° C., or less than about 230° C., or less than about 220° C., or less than about 210° C., or less than about 200° C., or less than about 190° C., or less than about 180° C., less than about 170° C., or less than about 160° C., or less than about 150° C., or less than about 140° C., or less than about 130° C., or less than about 120° C., or less than about 110° C.
[0061]Turning now to the figures:
[0062]Referring now to FIG. 1, an example of a 3D printing system 10 is depicted. It is to be understood that the 3D printing system 10 may include additional components and that some of the components described herein may be removed and/or modified. Furthermore, components of the 3D printing system 10 depicted in FIG. 1 may not be drawn to scale and thus, the 3D printing system 10 may have a different size and/or configuration other than as shown therein.
[0063]The three-dimensional (3D) printing system 10 generally includes a supply 14 of metallic build material 16; a build material distributor 18; a supply of a fusing agent 36, the fusing agent 36 including a liquid vehicle and hydrated metal salt dispersed in the liquid vehicle; an inkjet applicator 24 for selectively dispensing the fusing agent 36 (FIG. 2C); at least one heat source 32, 32′; a controller 28; and a non-transitory computer readable medium having stored thereon computer executable instructions to cause the controller 28 to: utilize the build material distributor 18 and the inkjet applicator 24 to iteratively form multiple layers 34 (FIG. 2B) of metallic build material 16 which are applied by the build material distributor 18 and have received the fusing agent 36, thereby creating a patterned 3D printed metal object 42′ (FIG. 2E), and utilize the at least one heat source 32, 32′ to heat 46 the patterned 3D printed metal object 42′ to about a dehydration temperature of the hydrated metal salt thereby affecting binding of the metallic build material particles 16 by creating a 3D printed metal object 42′, continue heating the patterned 3D printed metal object 42′ to the dehydration temperature of the hydrated metal salt, thereby creating an at least substantially hydrated metal salt free 3D printed metal object 42, and heat 52 the at least substantially hydrated metal salt free 3D printed metal object 42 to a sintering temperature to form a metallic part 50.
[0064]In some examples, depending on the heating temperatures and choice of hydrated metal salt, the hydrated metal salt can be dehydrated, then decomposed to the corresponding metal oxide, and then decomposed to the corresponding metal all prior to heating to a sintering temperature. In some examples, decomposition to the corresponding metal oxide and then the corresponding metal can occur during sintering. In some examples, a portion of decomposition to the corresponding metal oxide and then the corresponding metal can occur during sintering.
[0065]As shown in FIG. 1, the printing system 10 includes a build area platform 12, the build material supply 14 containing metallic build material particles 16, and the build material distributor 18.
[0066]The build area platform 12 receives the metallic build material 16 from the build material supply 14. The build area platform 12 may be integrated with the printing system 10 or may be a component that is separately insertable into the printing system 10. For example, the build area platform 12 may be a module that is available separately from the printing system 10. The build area platform 12 that is shown is also one example, and could be replaced with another support member, such as a platen, a fabrication/print bed, a glass plate, or another build surface.
[0067]The build area platform 12 may be moved in a direction as denoted by the arrow 20, e.g., along the z-axis, so that metallic build material 16 may be delivered to the platform 12 or to a previously formed layer of metallic build material 16 (see FIG. 2D). In an example, when the metallic build material particles 16 are to be delivered, the build area platform 12 may be programmed to advance (e.g., downward) enough so that the build material distributor 18 can push the metallic build material particles 16 onto the platform 12 to form a layer 34 of the metallic build material 16 thereon (see, e.g., FIGS. 2A and 2B). The build area platform 12 may also be returned to its original position, for example, when a new part is to be built.
[0068]The build material supply 14 may be a container, bed, or other surface that is to position the metallic build material particles 16 between the build material distributor 18 and the build area platform 12. In some examples, the build material supply 14 may include a surface upon which the metallic build material particles 16 may be supplied, for instance, from a build material source (not shown) located above the build material supply 14. Examples of the build material source may include a hopper, an auger conveyer, or the like. Additionally, or alternatively, the build material supply 14 may include a mechanism (e.g., a delivery piston) to move the metallic build material particles 16 from a storage location to a position to be spread onto the build area platform 12 or onto a previously formed layer of metallic build material 16.
[0069]The build material distributor 18 may be moved in a direction as denoted by the arrow 22, e.g., along the y-axis, over the build material supply 14 and across the build area platform 12 to spread a layer of the metallic build material 16 over the build area platform 12. The build material distributor 18 may also be returned to a position adjacent to the build material supply 14 following the spreading of the metallic build material 16. The build material distributor 18 may be a blade (e.g., a doctor blade), a roller, a combination of a roller and a blade, and/or any other device capable of spreading the metallic build material particles 16 over the build area platform 12. For instance, the build material distributor 18 may be a counter-rotating roller.
[0070]The metallic build material 16 may be any particulate metallic material. In an example, the metallic build material 16 may be a powder. In another example, the metallic build material 16 may have the ability to sinter into a continuous body to form the metallic part 50 (see, e.g., FIG. 2F) when heated 52 to the sintering temperature (e.g., a temperature ranging from about 850° C. to about 1400° C.). In some examples, discrete metallic build material 16 powder particles should no longer be visible in the metallic part 50 (FIG. 2F). After sintering the powder particles and metal from the metal salt merge together to form a dense solid metallic part.
[0071]By “continuous body,” it is meant that the metallic build material particles are merged together with the corresponding metal from the metal salt to form a single part with little or no porosity and with sufficient mechanical strength to meet target properties of the final metallic part 50.
[0072]While an example sintering temperature range is described, it is to be understood that this temperature may vary, depending, in part, upon the composition and phase(s) of the metallic build material 16.
[0073]In an example, the metallic build material 16 is a single phase metallic material composed of one element. In this example, the sintering temperature may be below the melting point of the single element.
[0074]In another example, the metallic build material 16 is composed of two or more elements, which may be in the form of a single phase metallic alloy or a multiple phase metallic alloy. In these other examples, melting generally occurs over a range of temperatures. For some single phase metallic alloys, melting begins just above the solidus temperature (where melting is initiated) and is not complete until the liquidus temperature (temperature at which all the solid has melted) is exceeded. For other single phase metallic alloys, melting begins just above the peritectic temperature. The peritectic temperature is defined by the point where a single phase solid transforms into a two phase solid plus liquid mixture, where the solid above the peritectic temperature is of a different phase than the solid below the peritectic temperature. When the metallic build material 16 is composed of two or more phases (e.g., a multiphase alloy made of two or more elements), melting generally begins when the eutectic or peritectic temperature is exceeded. The eutectic temperature is defined by the temperature at which a single phase liquid completely solidifies into a two phase solid. Generally, melting of the single phase metallic alloy or the multiple phase metallic alloy begins just above the solidus, eutectic, or peritectic temperature and is not complete until the liquidus temperature is exceeded. In some examples, sintering can occur below the solidus temperature, the peritectic temperature, or the eutectic temperature. In other examples, sintering occurs above the solidus temperature, the peritectic temperature, or the eutectic temperature. Sintering above the solidus temperature is known as super solidus sintering, and this technique may be useful when utilizing larger build material particles and/or to achieve high density. It is to be understood that the sintering temperature may be high enough to offer sufficient energy to allow atom mobility between adjacent particles.
[0075]Single elements or alloys may be used as the metallic build material 16. Some examples of the metallic build material 16 include steels, stainless steel, bronzes, brasses, titanium (Ti) and alloys thereof, aluminum (Al) and alloys thereof, nickel (Ni) and alloys thereof, cobalt (Co) and alloys thereof, iron (Fe) and alloys thereof, gold (Au) and alloys thereof, silver (Ag) and alloys thereof, platinum (Pt) and alloys thereof, and copper (Cu) and alloys thereof. Some specific examples include AlSi10Mg, 2xxx series aluminum, 4xxx series aluminum, CoCr MP1, CoCr SP2, MaragingSteel MS1, Hastelloy C, Hastelloy X, NickelAlloy HX, Inconel IN625, Inconel IN718, SS GP1, SS 17-4PH, SS 316L, Ti6Al4V, and Ti-6Al-4V ELI7. While several example alloys have been described, it is to be understood that other alloy build materials may be used, such as refractory metals.
[0076]Any metallic build material 16 may be used that is in powder form at the outset of the 3D printing method(s) disclosed herein. As such, the melting point, solidus temperature, eutectic temperature, and/or peritectic temperature of the metallic build material 16 may be above the temperature of the environment in which the patterning portion of the 3D printing method is performed (e.g., above 80° C.). In some examples, the metallic build material 16 may have a melting point ranging from about 850° C. to about 3500° C. In other examples, the metallic build material 16 may be an alloy having a range of melting points. Alloys may include metals with melting points as low as 30° C. (e.g., gallium) or 157° C. (indium).
[0077]The metallic build material 16 may be made up of similarly sized particles or differently sized particles. In some examples, the metallic build material 16 has an average particle size of from about 5 to about 20 microns.
[0078]In the examples shown herein (FIG. 1 and FIGS. 2A-2F), the metallic build material 16 includes similarly sized particles (e.g., from about 5 to about 20 microns). The term “size”, as used herein with regard to the metallic build material 16, refers to the diameter of a substantially spherical particle (i.e., a spherical or near-spherical particle having a sphericity of >0.84), or the average diameter of a non-spherical particle (i.e., the average of multiple diameters across the particle).
[0079]In some examples, substantially spherical particles of a particle size of from about 5 microns to about 20 microns have good flowability and can be spread relatively easily. As an example, the average particle size of the partic