Use of variable beam parameters to control solidification of a material
A method for forming an article includes providing a material having a first material property; forming a melt pool by exposing the material to an optical beam having at least one beam characteristic, wherein the melt pool has at least one melt pool property determinative of a second material property of the material; and modifying the at least one beam characteristic in response to a change in the melt pool property.
1. A method for forming an article using a laser beam, the method comprising:
providing a material comprising a first material property;
forming a melt pool by exposing the material to the laser beam, wherein the melt pool comprises at least one melt pool property determinative of a second material property of the material; and
modifying at least one beam characteristic of the laser beam in response to a change in the melt pool property, the modifying of the at least one beam characteristic of the laser beam including:
perturbing an optical beam propagating within a first section of fiber to adjust the at least one characteristic of the laser beam in the first section of fiber or a second section of fiber or a combination thereof;
coupling the perturbed optical beam into the second section of fiber; and
maintaining at least a portion of one or more adjusted beam characteristics within the second section of fiber having two or more confinement regions, wherein the first section of fiber and the second section of fiber form at least a portion of a continuous length of fiber.
2. The method of claim 1 , wherein the first section of fiber and the second section of fiber have different refractive index profiles (RIPs).
3. The method of claim 1 , wherein the modifying of the at least one beam characteristic of the laser beam occurs prior to or during the exposing of the material to the laser beam.
4. The method of claim 1 , wherein the material comprises a raw material feed.
5. The method of claim 4 , wherein the raw material feed comprises a plurality of solid particles.
6. The method of claim 1 , wherein the material comprises a metal.
7. The method of claim 1 , wherein the material property comprises grain size, grain orientation, solidification direction, or a combination thereof.
8. The method of claim 1 , wherein the first material property is different than the second material property.
9. The method of claim 8 , wherein the first material property comprises a first grain structure, and wherein the second material property comprises a second grain structure that is different than the first grain structure.
10. The method of claim 9 , wherein the second grain structure comprises smaller equiaxed grain structures than in the first grain structure.
11. The method of claim 1 , wherein the second material property comprises directional solidification of the material.
12. The method of claim 1 , wherein the melt pool property comprises a melt pool cross-sectional area.
13. The method of claim 1 , wherein the modifying of the at least one beam characteristic is performed continuously over a range of values.
14. The method of claim 1 , wherein the modifying of the at least one beam characteristic is performed by oscillating between a plurality of discrete values.
15. The method of claim 1 , wherein the at least one beam characteristic includes a beam parameter product (BPP).
16. The method of claim 1 , wherein the melt pool property comprises incandescent light emitted by the material in response to the exposing to the laser beam.
17. The method of claim 16 , further comprising providing the incandescent light to a sensor configured to generate a signal representative of a signature of the incandescent light.
18. The method of claim 17 , further comprising providing the signal to a processor, wherein the processor is in communication with the sensor and with a beam delivery device, wherein the processor is configured to access a memory that stores data and instructions, and wherein the processor is configured to execute the instructions, wherein the instructions comprise:
retrieving a stored value from the data stored by the memory, the stored value corresponding to a known property of a melt pool;
converting the signal generated by the sensor to a signature value corresponding to the melt pool property;
calculating a difference between the stored value and the signature value; and
modifying the at least one beam characteristic when the difference is greater than a predetermined threshold value.
19. The method of claim 1 , further comprising forming at least a portion of the melt pool as a build layer.
20. The method of claim 1 , wherein the forming of the melt pool comprises a step in an additive manufacturing process.
21. The method of claim 1 , further comprising forming of at least a portion of the melt pool as a weld.
22. The method of claim 1 , wherein the forming of the melt pool comprises a step in a laser-welding process.
23. An optical beam system, comprising:
an optical beam delivery device, including:
one or more optical beam sources configured to generate one or more optical beams; and
a perturbation device configured to modify one or more beam characteristics of the generated one or more optical beams in a first section of fiber, in a second section of fiber, or combinations thereof, the second section of fiber having two or more confinement regions;
wherein the second section of fiber is configured to confine one or more portions of the modified one or more beam characteristics within the two or more confinement regions, and wherein the first section of fiber and the second section of fiber form at least a portion of a continuous length of fiber;
a sensor that generates a signal in response to sensing a signature of a melt pool property; and
a feedback subsystem in communication with the optical beam delivery device and the sensor, wherein the feedback subsystem comprises:
at least one memory to store data and instructions; and
at least one processor configured to receive the signal, access the at least one memory, and execute the instructions.
24. The optical beam system of claim 23 , wherein the instructions comprise:
retrieving a stored value from the memory, the stored value corresponding to a known property of a melt pool;
converting the signal generated by the sensor to a signature value corresponding to the melt pool property;
calculating a difference between the stored value and the signature value; and
modifying the at least one beam characteristic using the optical beam delivery device when the difference is greater than a predetermined threshold value.
25. The system of claim 23 , wherein the system comprises an additive manufacturing system.
26. The system of claim 23 , wherein the system comprises a laser-welding system.