Method of processing beta-phase nickel/titanium-base alloys and articles produced therefrom

DETAILED DESCRIPTION OF THE INVENTION Disclosed according to the invention is a method for processing an essentially beta-phase nickel/titanium-base alloy.
The method comprises warm working the alloy and then annealing the alloy.
The working and annealing temperatures are in the range of about 350.
degree.
to 600.
degree.
C.
In order to effectuate the objects of the invention, it is necessary that the working and annealing temperatures, while in the range of about 350.
degree.
to 600.
degree.
C.
, should, in any event, be below the recrystallization temperature of the alloy.
The prior art problem of limited cold ductility is overcome by controlling the working temperature which should be sufficiently high enough above room temperature such that the material has improved workability (i.
e.
, sufficient ductility) and enough dynamic recovery occurs to prevent excessive work hardening on successive passes but not so high that the dislocations generated by the working are anihilated by a thermally activated climb/glide process.
Specifically, the working temperature is above that at which recovery takes place but below that at which full recrystallization occurs.
When the material is worked according to the invention, a cell structure is produced in which the cell walls are very sharp and well defined.
The fine subgrains thus produced provide material with substantially higher austenitic yield strengths than conventionally hot-worked material, i.
e.
, material where the working and annealing temperatures are above those at which recrystallization occurs.
In order to complete the subgrain or cell formation, the warm-worked material is annealed at a temperature similar to the working temperature.
When the material is warm worked in the upper part of the 350.
degree.
to 600.
degree.
C.
temperature range, the material may be annealed at the same time due to the warm working so that a separate annealing step is not necessary and, in fact, is optional.
While the perferred working and annealing temperatures of the alloy are in the range of about 350