Deformation processing of the Nb-10 a/o Si in-situ composite
Isothermal constant strain rate compressive deformation of the Nb-10 a/o Si in-situ composite was studied in order to establish the conditions under which the alloy deformed uniformly. The microstructure of the alloy was modified by hot extrusion. The different microstructures obtained were: as-cast (AC-I Generation), once-extruded (E1-II Generation), and twice-extruded (E2-III Generation). In the as-cast condition, the alloy undergoes uniform deformation only at very high temperatures (approx. 1800 deg C) or at very slow strain rates epsilon (less than or equal to) 10 (exp -4)/s. Through microstructural modification it was possible to change the conditions for uniform deformation to lower temperatures and faster strain rates. The thermomechanical processing of Nb-10 a/o Si alloy resulted in the recrystallization and the morphological alignment of the Nb3Si and Nb phases in the extrusion direction. A consequence of these microstructural modifications was an improvement in the mechanical properties of the alloy. Room temperature fracture toughness of the alloy increased from about 11 MPa m in the AC condition to 21 MPa m in the E1 condition, and to 26 MPa m in the E2 condition. Thermomechanical processing also resulted in considerable increases in both the room temperature and the elevated temperature strength of the alloy.
- Research Organization:
- Wright State Univ., Dayton, OH (United States). Dept. of Mechanical and Materials Engineering
- OSTI ID:
- 371111
- Report Number(s):
- AD-A--307987/8/XAB; CNN: Contract AFOSR-90-0204
- Country of Publication:
- United States
- Language:
- English
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