Effects of Ti addition on cleavage fracture in Nb-Cr-Ti solid-solution alloys

Journal Article · Thu Apr 01 04:00:00 EST 1999 · Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science

DOI:https://doi.org/10.1007/s11661-999-0146-1· OSTI ID:347477

Chan, K S; Davidson, D L ^[1]

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1. Southwest Research Inst., San Antonio, TX (United States)

The fracture toughness of Nb-Cr-Ti solid-solution alloys has been shown to be greatly improved by Ti addition, but the mechanism of toughness enhancement has not been established. In this study, critical experiments were performed on the tough Nb-Cr-Ti alloy to characterize the crack-tip fracture process and to investigate the origin of fracture toughness. In addition, theoretical calculations of the unstable stacking energy (USE) and the Peierls-Nabarro (P-N) energy and stress were performed as a function of Ti content in the Nb-Cr-Ti alloys. The experimental results indicate that the fracture toughness in the tough Nb-Cr-Ti alloy originates from extensive dislocation emission that suppresses cleavage crack propagation from the crack tip. The theoretical calculation indicates that Ti addition lowers the P-N energy and stress, but has little effect on the USE. These results are used to elucidate the effects of Ti addition on cleavage fracture in Nb-Cr-Ti alloys by considering the influence of the P-N energy and stress values on (1) dislocation mobility, (2) crack-tip dislocation emission, (3) fracture toughness, and (4) brittle-to-ductile fracture transition. It is concluded that dislocation emission in the Nb-Cr-Ti alloys appears to be controlled by the P-N energy, which influences dislocation mobility, rather than by the USE, which influences dislocation nucleation. Ti increases the fracture toughness of Nb-Cr-Ti alloys by increasing dislocation mobility and dislocation emission from the crack tip through a reduction of the P-N energy and stress.

• Sponsoring Organization: USDOE
• OSTI ID: 347477
• Journal Information: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science Journal Issue: 4 Vol. 30; ISSN 1073-5623; ISSN MMTAEB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CHROMIUM ALLOYS
DISLOCATIONS
FRACTURE PROPERTIES
METALLURGICAL EFFECTS
NIOBIUM ALLOYS
PEIERLS-NABARRO FORCE
SOLID SOLUTIONS
STRESSES
TITANIUM ALLOYS