Metallic build material granules

1. A three-dimensional (3D) printing method, comprising:

applying build material granules, each of the build material granules consisting of a plurality of metal particles agglomerated together by a temporary binder that is at least partially soluble in a patterning fluid,

wherein the temporary binder is selected from the group consisting of sugars, sugar alcohols, polymeric or oligomeric sugars, and combinations thereof;

selectively applying the patterning fluid on at least a portion of the build material granules to dissolve the temporary binder and form a layer of a patterned green part, the layer including a slurry of the metal particles;

repeating the applying of the build material granules and the selectively applying of the patterning fluid to create the patterned green part; and

heating the patterned green part to sinter the metal particles to form a metallic part, wherein the heating of the patterned green part includes:

heating the patterned green part to a densification temperature to create a densified green part;

heating the densified green part to a thermal decomposition temperature of the temporary binder to remove the temporary binder and create an at least substantially binder-free, gray part; and

heating the at least substantially binder-free, gray part to a sintering temperature to sinter the metal particles to form the metallic part.

2. The method as defined in claim 1 wherein:

the metal particles are non-shape memory metal particles selected from the group consisting of iron, stainless steel, steel, copper, bronze, aluminum, tungsten, molybdenum, silver, gold, platinum, titanium, nickel, cobalt, non-shape memory alloys of any of these metals, and combinations thereof; and

the temporary binder is present in an amount ranging from about 0.01 wt % to about 4.0 wt % based on a wt % of the metal particles.

3. The method as defined in claim 1 wherein:

the densification temperature ranges from about 50° C. to about 250° C.;

the thermal decomposition temperature ranges from about 250° C. to about 600° C.; and

the sintering temperature ranges from about 600° C. to about 1800° C.

4. The method as defined in claim 1 wherein the sintering temperature is below a solidus temperature of the metal particles, and wherein the heating of the at least substantially binder-free, gray part to the sintering temperature is performed for a sintering time period less than or equal to 3 hours.

5. The method as defined in claim 1 wherein:

the applying of the build material granules, the selectively applying of the patterning fluid, the repeating of the applying and the selectively applying, and the heating of the patterned green part to the densification temperature are accomplished on a build area platform; and

after the heating of the patterned green part to the densification temperature, the method further comprises:

removing the densified green part from the build area platform; and

placing the densified green part in a heating mechanism.

6. The method as defined in claim 1 wherein the heating of the densified green part to the thermal decomposition temperature and the heating of the at least substantially binder-free gray part to the sintering temperature are accomplished in an environment containing an inert gas, a low reactivity gas, a reducing gas, or a combination thereof.

7. The method as defined in claim 1 wherein prior to applying the build material granules, the method further comprises:

dispersing the metal particles in a mixture containing the temporary binder; and

spray drying the mixture containing the metal particles dispersed therein to create the build material granules.

8. The method as defined in claim 1 wherein:

each of the build material granules has a granule size ranging from about 10 μm to about 200 μm; and

each of the metal particles has a particle size ranging from about 1 μm to about 20 μm.

9. The method as defined in claim 1 wherein the patterning fluid consists of water.

10. The method as defined in claim 1 wherein the temporary binder is the sugar, and the sugar is selected from the group consisting of glucose (C 6 H 12 O 6 ), sucrose (C 12 H 22 O 11 ), and fructose (C 6 H 12 O 6 ).

11. The method as defined in claim 1 wherein the temporary binder is the sugar alcohol, and the sugar alcohol is selected from the group consisting of sorbitol (C 6 H 14 O 6 ), erythritol (C 4 H 10 O 4 ), and mannitol (C 6 H 14 O 6 ).

12. The method as defined in claim 1 wherein the temporary binder is the polymeric or oligomeric sugars, and the polymeric or oligomeric sugars are maltodextrines with a chain length ranging from 2 units to 20 units.

13. The method as defined in claim 1 wherein the patterning fluid includes water or a non-aqueous solvent and a radiation absorber present in an amount ranging from about 0.1 wt % to about 20 wt % based on a total weight of the patterning fluid.

14. The method as defined in claim 13 wherein the radiation absorber includes metal nanoparticles.