Elevated temperature compressive steady state deformation and failure in the oxide dispersion strengthened alloy MA 6000
- PDF / 3,119,126 Bytes
- 10 Pages / 594 x 774 pts Page_size
- 9 Downloads / 238 Views
I.
INTRODUCTION
THE oxide
dispersion strengthened (ODS) alloy MA 6000(E)* represents the latest step in the logical progression *The designation E has been used by INCO to signify that the alloy was under experimental development. With the establishment of a commercial manufacturing process, the E was deleted.
to develop ODS materials for high temperature, rotating gas turbine engine blade applications. Through incorporation of a high volume fraction of the intermetallic y' as well as a proper distribution of small diameter inert particles, MA 6000E possesses strength capabilities from room temperature to at least 1500 K well in excess of all previous commercial ODS alloys. Although MA 6000E has a directional structure due to a complex thermomechanical processing history, the elevated temperature creep testing undertaken to date j'2'3 has generally concentrated on the longitudinal properties of this alloy. In addition, testing temperatures have usually been restricted to 1033 and 1366 K where the dominant hardening mechanisms are thought to be from y' and the inert dispersoid, respectively. Although the principal stress in actual turbine engine blades is along their length (the longitudinal bar direction), these components must possess adequate strength in all directions and temperatures up to 1366 K. Therefore, a study of the elevated temperature slow plastic flow behavior as a function of orientation and temperature seemed appropriate. The specific objectives of this work were to determine the steady state strain rate-flow stress values over the temperature range where dispersoid strengthening effects become increasingly important, use existing steady state creep models in an effort to describe mechanical behavior, and develop a microstructural model of failure. To this end constant cross head velocity compression tests at 1144, 1255, and 1366 K were conducted on MA 6000E specimens taken parallel and perpendicular to the major axis of working. Compression testing was selected as it can utilize small specimens and tends to minimize the J. DANIEL WHITTENBERGER is with NASA-Lewis Research Center, Cleveland, OH 44135. Manuscript submitted August 15, 1983.
METALLURGICAL TRANSACTIONS A
role of transverse grain boundaries which generally serve as the failure sites for ODS alloys in tension.
II.
EXPERIMENTAL PROCEDURE
A. Material
The MA 6000E utilized in this work was commercially procured as thermomechanically processed bar: appropriate materials were mechanically alloyed to produce powder containing the evenly dispersed oxide particles. The powder was vacuum sealed in steel cans and hot extruded at 1283 K and a 10:1 reduction ratio to 25 by 25 mm bar. This material was then rolled at 1283 K parallel to the extrusion axis in two passes for a total reduction of --40 pct. Directional recrystallization was accomplished by zone annealing with a maximum temperature of 1533 K and a furnace travel velocity of 6 cm per hour. To develop the optimum "y' distribution the standard heat treatment was performed: 1505 K/0.5
Data Loading...
