Microstructural refinement of cast titanium
AssigneeHowmet Turbine Components Corporation
InventorsRobert J. Smickley, Louis E. Dardi
Life of this patent
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Abstract
The microstructure of titanium is refined by inducing a high temperature transformation from .alpha.+.beta. to .beta. and back to .alpha.+.beta. by diffusing hydrogen into and then out of the metal while maintaining the metal above the temperature of hydride formation. The titanium is heated to a temperature just below the .alpha.+.beta. to .beta. transformation temperature, and hydrogen is diffused into the metal thereby inducing the phase change. The hydrogen is diffused out of the metal again inducing a phase change. When the hydrogen has been removed, the metal is allowed to cool to room temperature.
Claims15
A method of treating a metal casting comprised of titanium, said method comprising the steps of:
- heating said casting to a treatment temperature in the range of from 800.degree. F. to 2000.degree. F., said treatment temperature being below the beta transus temperature for said metal;
- diffusing hydrogen into said metal casting at said treatment temperature such that hydrogen is present in said metal in an amount in the range of from 0.2% to 5% by weight, said hydrogen thereby inducing the transformation of (HCP) alpha in said casting to (BCC) beta;
- removing said hydrogen at an average rate greater than 0.01%/hour to transform said beta to alpha at a rate sufficient to refine the microstructure of the alpha formed from beta upon removal of said hydrogen;
- and
- throughout said method maintaining the temperature of said metal casting, when hydrogen is present in more than trace amounts, above the temperature at which metal hydrides would be formed.
Dependencies are inferred from the claim text.