The effect of Nb sub 3 Si precipitates on the deformation of the primary Nb phase in Nb-10 a/o Si in-situ composite

Journal Article · Sun Mar 01 04:00:00 EST 1992 · Scripta Metallurgica; (United States)

OSTI ID:5526780

Cockeram, B; Srinivasan, R; Weiss, I ^[1]

---

1. Mechanical and Materials Engineering Dept., Wright State Univ., Dayton, OH (US)

This paper reports that upon solidification at normal cooling rates, the microstructure of the Nb - 10 a/o Si alloy consists of primary Nb dendrites, containing Nb{sub 3}Si precipitates in a continuous Nb{sub 3}Si matrix. The matrix consists of Nb{sub 3}Si with dispersed eutectic Nb particles. Nb{sub 3}Si, is a metastable phase and is observed at room temperature due to the sluggish nature of the Nb{sub 3}Si--{gt}Nb{sub 5}Si{sub 3} + Nb eutectoid reaction. The solubility of silicon in niobium is at a maximum, ({approx}3.5 a/o) at the eutectic temperature and decreases dramatically with lowering temperature. The dissolved silicon is almost completely rejected by Nb during cooling to form Nb{sub 3}Si precipitates in the primary Nb phase. The presence of stable precipitates has ben shown to affect recrystallization of Nb, and reduce the ductility. Pervious studies have shown that the Nb phase in Nb-Nb{sub 5}Si{sub 3} composite can undergo both ductile and cleavage failure, and brittle failure was observed in regions with higher silicon content, as detected by EDS.

• OSTI ID: 5526780
• Journal Information: Scripta Metallurgica; (United States), Journal Name: Scripta Metallurgica; (United States) Vol. 26:5; ISSN 0036-9748; ISSN SCRMB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
360203* -- Ceramics
Cermets
& Refractories-- Mechanical Properties
ALLOYS
CHEMICAL COMPOSITION
COMPOSITE MATERIALS
CRYSTAL STRUCTURE
CRYSTALS
DEFORMATION
DENDRITES
DUCTILITY
HEAT RESISTANT MATERIALS
HEAT RESISTING ALLOYS
MATERIALS
MECHANICAL PROPERTIES
MICROSTRUCTURE
NIOBIUM ALLOYS
NIOBIUM BASE ALLOYS
ORGANIC COMPOUNDS
ORGANOMETALLIC COMPOUNDS
PHASE STABILITY
PHASE STUDIES
PHASE TRANSFORMATIONS
PRECIPITATION
SEPARATION PROCESSES
SILICON ALLOYS
SOLIDIFICATION
STABILITY
TENSILE PROPERTIES