Friction stir fabrication
A low-temperature friction-based coating method termed friction stir fabrication (FSF) is disclosed, in which material is deposited onto a substrate and subsequently stirred into the substrate using friction stir processing to homogenize and refine the microstructure. This solid-state process is capable of depositing coatings, including nanocrystalline aluminum and/or metal matrix composites and the like, onto substrates such as aluminum at relatively low temperatures. A method of making rod stock for use in the FSF process is also disclosed.
1 . A method of forming a surface layer on a substrate, the method comprising:
depositing a coating material on the substrate; and
friction stirring the deposited coating material.
2 . The method of claim 1 , wherein the coating material is deposited on the substrate by rotating a tool comprising the coating material against the substrate.
3 . The method of claim 2 , wherein the tool comprises a solid rod of the coating material.
4 . The method of claim 3 , wherein the coating material is nanocrystalline.
5 . The method of claim 3 , wherein the coating material comprises a metal matrix composite.
6 . The method of claim 5 , wherein the metal matrix composite comprises at least one discontinuous ceramic phase dispersed in the metal matrix.
7 . The method of claim 6 , wherein the at least one discontinuous ceramic phase comprises a carbide, boride, nitride and/or oxide.
8 . The method of claim 6 , wherein the discontinuous ceramic phase comprises SiC, TiB 2 and/or Al 2 O 3 .
9 . The method of claim 5 , wherein the metal matrix comprises Al, Ni, Mg, Ti and/or Fe.
10 . The method of claim 5 , wherein the metal matrix comprises Al.
11 . The method of claim 1 , wherein the coating material comprises Al, Ni, Mg, Ti and/or Fe.
12 . The method of claim 1 , wherein the coating material comprises Al.
13 . The method of claim 1 , wherein the substrate comprises a metal.
14 . The method of claim 1 , wherein the substrate comprises Al.
15 . The method of claim 1 , wherein the step of depositing the coating material on the substrate is performed at a temperature below a melting temperature of the coating material.
16 . The method of claim 1 , wherein the coating material is deposited on the substrate in solid form.
17 . The method of claim 1 , wherein the coating material comprises Al and is deposited on the substrate at a temperature below about 500°.
18 . The method of claim 17 , wherein the coating material is deposited on the substrate at a temperature below about 400° C.
19 . The method of claim 1 , wherein the step of friction stirring is performed with a substantially non-consumable rotating tool.
20 . The method of claim 19 , wherein the step of friction stirring includes multiple passes of the rotating tool across a surface of the substrate.
21 . The method of claim 1 , wherein the step of friction stirring is performed at a temperature below a melting temperature of the coating material.
22 . The method of claim 1 , wherein the step of friction stirring is performed at a temperature below a melting temperature of the substrate.
23 . The method of claim 1 , wherein the substrate comprises aluminum and the step of friction stirring is performed at a temperature below about 500° C.
24 . The method of claim 23 , wherein the coating material comprises aluminum and has a nanocrystalline structure after the friction stirring.
25 . A substrate having a surface layer formed by the method of claim 1 .
26 . A method of filling a hole in a substrate, the method comprising:
placing powder of a fill material in the hole; and
friction stirring the fill material powder in the hole to consolidate the fill material.
27 . The method of claim 26 , wherein the step of friction stirring is performed at a temperature below a melting temperature of the fill material.
28 . The method of claim 26 , wherein the step of friction stirring is performed at a temperature below a melting temperature of the substrate.
29 . The method of claim 26 , further comprising:
placing additional powder of a fill material in the hole after the step of friction stirring; and
friction stirring the additional fill material powder in the hole to consolidate the additional fill material powder.
30 . The method of claim 29 , wherein the fill material powder and the additional fill material powder are the same composition.
31 . The method of claim 29 , wherein the fill material powder and the additional fill material powder are different compositions.
32 . The method of claim 26 , wherein the consolidated fill material is nanocrystalline.
33 . The method of claim 26 , wherein the consolidated fill material comprises a metal matrix composite.
34 . A method of making consumable friction stirring rod stock, the method comprising:
placing powder of a coating material in a die;
friction stirring the coating material powder in the die to consolidate the coating material; and
recovering a rod comprising the consolidated coating material.
35 . The method of claim 34 , wherein the step of friction stirring is performed at a temperature below a melting temperature of the coating material.
36 . The method of claim 34 , further comprising:
placing additional powder of a coating material in the die after the step of friction stirring; and
friction stirring the additional coating material powder in the die to consolidate the additional coating material powder.
37 . The method of claim 36 , wherein the coating material powder and the additional coating material powder are the same composition.
38 . The method of claim 36 , wherein the coating material powder and the additional coating material powder are different compositions.