Three-dimensional printing

1 . A method for generating a site-specific alloyed section of a three-dimensional (3D) object during three-dimensional printing, the method comprising:

based on a digital 3D object model of the 3D object, patterning individual layers of a metal-based build material with a binder agent to form an intermediate structure;

based on the digital 3D object model, patterning a first portion of at least one of the individual layers with an alloying agent to form a pattern of the site-specific alloyed section;

based on the digital 3D object model, patterning a second portion of at least one of the individual layers with a diffusion barrier agent to form a perimeter pattern at an edge of at least a portion of the pattern of the site-specific alloyed section; and

exposing the intermediate structure to a heat treatment to form the 3D object.

2 . The method as defined in claim 1 , wherein the diffusion barrier agent includes a diffusion barrier component that is to restrict diffusion of an alloying element that is contained in the alloying agent.

3 . The method as defined in claim 2 , wherein the diffusion barrier component is selected from the group consisting of silicon, nickel, copper, chromium, vanadium, titanium, tantalum, carbon, aluminum, tantalum nitride, titanium nitride, titanium dioxide, titanium carbide, tungsten-titanium, yttria stabilized zirconia, a metal silicide, an amorphous alloy, hexagonal boron nitride, molybdenum disulfide, and ruthenium-titanium dioxide.

4 . The method as defined in claim 2 , wherein a concentration of the diffusion barrier component in the diffusion barrier agent ranges from about 0.1 wt % to about 10 wt %.

5 . The method as defined in claim 2 , wherein one of:

i) the metal-based build material is an iron-based steel;

the alloying element in the alloying agent is carbon; and

the diffusion barrier component is selected from the group consisting of silicon, nickel, copper, and tantalum; or

ii) the metal-based build material is an aluminum-based build material;

the alloying element in the alloying agent is silicon; and

the diffusion barrier component is a metal silicide selected from the group consisting of Ni 2 Si, NiSi, Ni 5 Si 2 , Ni 3 Si, Co 2 Si, CoSi, CoSi 2 , PtSi, Pd 2 Si, TiSi 2 , CoSi 3 , MoSi, TaSi 2 , WSi 2 ; or

iii) the metal-based build material is a copper-based build material;

the alloying element in the alloying agent is silicon; and

the diffusion barrier component is selected from the group consisting of tantalum, tantalum nitride, and titanium-tungsten; or

iv) the metal-based build material is an iron-chromium alloy;

the alloying element in the alloying agent is palladium; and

the diffusion barrier component is yttria stabilized zirconia; or

v) the metal-based build material is an aluminum-based build material;

the alloying element in the alloying agent is silicon; and

the diffusion barrier component is selected from the group consisting of chromium, vanadium, titanium, tantalum nitride, titanium nitride, titanium carbide, titanium-tungsten, and an amorphous alloy; or

vi) the metal-based build material is an iron-based steel;

the alloying element in the alloying agent is nickel; and

the diffusion barrier component is carbon; or

vii) the metal-based build material is selected from the group consisting of martensitic stainless steel, austenitic stainless steel, and carbon-manganese steel;

the alloying element in the alloying agent is copper; and

the diffusion barrier component is selected from the group consisting of tantalum, tantalum nitride, titanium nitride, aluminum, hexagonal boron nitride, molybdenum disulfide, and ruthenium-titanium dioxide.

6 . The method as defined in claim 1 , wherein the diffusion barrier agent is selectively applied so that the perimeter pattern is defined around an entire pattern of the site-specific alloyed section.

7 . The method as defined in claim 1 , wherein the heat treatment involves:

exposure to a de-binding temperature for a first predetermined time; and

then exposure to a sintering temperature for a second predetermined time.

8 . The method as defined in claim 1 , wherein:

the diffusion barrier agent includes a diffusion barrier component;

a percentage of the metal-based build material is a same type of diffusion barrier component that is present in the diffusion barrier agent; and

the method further comprises adjusting an amount of the diffusion barrier agent that is applied during patterning of the second portion based on the percentage of the diffusion barrier component in the metal-based build material.

9 . A method for generating a site-specific alloyed section of a three-dimensional (3D) object during three-dimensional printing, the method comprising:

applying a metal-based build material to form a build material layer, wherein a predetermined portion of the build material layer includes an alloying element;

based on a digital 3D object model of the 3D object, patterning a portion of the build material layer with a diffusion barrier agent to form a perimeter pattern at an edge of at least part of the predetermined portion; and

using a localized heat source to scan the build material layer based on the digital 3D object model, thereby forming a layer of the 3D object.

10 . The method as defined in claim 9 , wherein the diffusion barrier agent includes a diffusion barrier component that is to restrict diffusion of the alloying element out of the predetermined portion.

11 . The method as defined in claim 10 , wherein one of:

i) the metal-based build material is an iron-based steel;

the alloying element is carbon; and

the diffusion barrier component is selected from the group consisting of silicon, nickel, copper, and tantalum; or

ii) the metal-based build material is an aluminum-based build material;

the alloying element is silicon; and

the diffusion barrier component is a metal silicide selected from the group consisting of M 2 Si, MSi, MSi 2 , Ni 2 Si, NiSi, Ni 5 Si 2 , Ni 3 Si, Co 2 Si, CoSi, CoSi 2 , PtSi, Pd 2 Si, TiSi 2 , CoSi 3 , MoSi, TaSi 2 , WSi 2 ; or

iii) the metal-based build material is a copper-based build material;

the alloying element is silicon; and

the diffusion barrier component is selected from the group consisting of tantalum, tantalum nitride, and titanium-tungsten; or

iv) the metal-based build material is an iron-chromium alloy;

the alloying element is palladium; and

the diffusion barrier component is yttria stabilized zirconia; or

v) the metal-based build material is an aluminum-based build material;

the alloying element is silicon; and

the diffusion barrier component is selected from the group consisting of chromium, vanadium, titanium, tantalum nitride, titanium nitride, titanium carbide, titanium-tungsten, and an amorphous alloy; or

vi) the metal-based build material is an iron-based steel;

the alloying element is nickel; and

the diffusion barrier component is carbon; or

vii) the metal-based build material is selected from the group consisting of martensitic stainless steel, austenitic stainless steel, and carbon-manganese steel;

the alloying element is copper; and

the diffusion barrier component is selected from the group consisting of tantalum, tantalum nitride, titanium nitride, aluminum, hexagonal boron nitride, molybdenum disulfide, and ruthenium-titanium dioxide.

12 . The method as defined in claim 9 , further comprising generating the predetermined portion by patterning a section of the build material layer with an alloying agent that contains the alloying element.

13 . The method as defined in claim 9 , further comprising generating the predetermined portion by:

mixing the alloying element with some of the metal-based build material to generate a mixed build material; and

applying the mixed build material instead of the metal-based build material at a predetermined location for the predetermined portion.

14 . The method as defined in claim 9 , wherein the metal-based build material includes a percentage of a diffusion barrier component present in the diffusion barrier agent, and wherein the method further comprises adjusting an amount of the diffusion barrier agent that is applied during patterning of the portion based on the percentage of the diffusion barrier component in the metal-based build material.