Refractory metal plates
A refractory metal plate is provided. The plate has a center, a thickness, an edge, a top surface and a bottom surface, and has a crystallographic texture (as characterized by through thickness gradient, banding severity; and variation across the plate, for each of the texture components 100//ND and 111//ND, which is substantially uniform throughout the plate.
1. A method of forming a refractory metal plate, the method comprising:
(A) providing a workpiece having a size suitable for a target plate, the workpiece comprising a refractory metal;
(B) asymmetrically rolling the workpiece one or more times at an angle of incline between 2° and 20° relative to horizontal, thereby forming a rolled plate; and
(C) annealing the rolled plate to achieve substantially full recrystallization.
2. The method of claim 1 , wherein providing the workpiece comprises separating the workpiece from an ingot.
3. The method of claim 2 , wherein the ingot is an electron-beam-melted ingot.
4. The method of claim 1 , wherein providing the workpiece comprises separating the workpiece from a powder-metallurgy billet.
5. The method of claim 4 , further comprising providing the powder-metallurgy billet by a process comprising:
(a) cold isostatically pressing a refractory metal powder to a density of 60%-90% to form a preform;
(b) hot isostatically pressing the preform to a density of approximately 100% to form a billet; and
(c) annealing the billet.
6. The method of claim 1 , wherein the angle of incline is between 3° and 7°.
7. The method of claim 1 , wherein the workpiece is asymmetrically rolled a plurality of times during step (B).
8. The method of claim 7 , wherein the workpiece is rotated at a predetermined angle about a vertical axis between rolling passes.
9. The method of claim 7 , wherein the workpiece is flipped between rolling passes.
10. The method of claim 1 , further comprising, after step (C), bonding the plate to a backing plate.
11. The method of claim 1 , wherein after step (C):
the plate has a crystallographic texture as characterized by through thickness gradient, banding severity, and variation across the plate for at least one of the texture components 100//ND or 111//ND, using electron back-scatter diffraction with a 15 μm step in both the horizontal and vertical directions for each measurement;
an average through-thickness gradient is less than or equal to 6% per mm for 111//ND; and
a maximum through-thickness gradient is less than or equal to 13% per mm for 111//ND.
12. The method of claim 1 , wherein after step (C):
the plate has a crystallographic texture as characterized by through thickness gradient banding severity, and variation across the plate for at least one of the texture components 100//ND or 111//ND, using electron back-scatter diffraction with a 15 μm step in both the horizontal and vertical directions for each measurement; and an average banding severity is less than or equal to 6% per mm for 111//ND.
13. The method of claim 1 , wherein, after step (C):
the plate has a crystallographic texture as characterized by through thickness gradient, banding severity, and variation across the plate for at least one of the texture components 100//ND or 111//ND, using electron back-scatter diffraction with a 15 μm step in both the horizontal and vertical directions for each measurement; and a maximum banding severity is less than or equal to 8% per mm for 111//ND.
14. The method of claim 1 , further comprising, after step (C):
providing a substrate; and
sputtering the plate to form a film on the substrate, the film comprising the refractory metal.
15. The method of claim 1 , wherein the refractory metal comprises tantalum.
16. The method of claim 1 , further comprising annealing the workpiece before step (B).
17. The method of claim 1 , further comprising applying a lubricant to top and bottom surfaces of the workpiece before asymmetrically rolling the workpiece.