Fracture toughness and fatigue crack growth in rapidly quenched Nb-Cr-Ti in situ composites

• Published in: Metallurgical and materials transactions. A, Physical metallurgy and materials science Vol. 28; no. 9; pp. 1797 - 1808
• Main Authors: CHAN, K. S, DAVIDSON, D. L, ANTON, D. L
• Format: Journal Article
• Language: English
• Published: New York, NY Springer 01-09-1997
• Subjects: Applied sciences; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Fatigue, corrosion fatigue, embrittlement, cracking, fracture and failure; Fatigue, embrittlement, and fracture; Materials science; Metals. Metallurgy; Physics; Treatment of materials and its effects on microstructure and properties; Elaboration; Intermetallic compounds; Mechanical properties; Niobium alloys; Liquid state quenching; Chromium alloys; Experimental study; Dispersion strengthened metal; Fatigue crack; Crack propagation; Quenching; Fracture toughness; Titanium alloys; Composite materials; Extremely rapid cooling; Rapidly solidified alloy; Microstructure; Fractography; Transition element alloys
• ISSN: 1073-5623; 1543-1940
• DOI: 10.1007/s11661-997-0110-x

In situ composites based on the Nb-Cr-Ti ternary system were processed by rapid solidification in order to reduce the size of the reinforcing intermetallic phase. Two-phase microstructures with small Cr sub 2 Nb particles in a Nb(Cr,Ti) solid solution alloy matrix were produced for several compositions that previous work showed to produce high toughness composites in cast materials. The fracture and fatigue behaviors of these composites were characterized at ambient temperature. The results indicate that the fracture resistance increases with a decreasing volume of Cr sub 2 Nb particles. Fracture toughnesses of the rapidly solidified materials with their smaller particle sizes were lower than for conventionally processed composites with larger particles of the intermetallic compound. The fatigue crack growth rate curves exhibit steep slopes and a low critical stress intensity factor at fracture. The lack of fracture and fatigue resistance is attributed to the contiguity of the intermetallic particles and the absence of plastic flow in the Nb solid solution matrix. The matrix alloy appears to be embrittled by (1) the rapid solidification processing that prevented plastic relaxation of residual stresses, (2) a high oxygen content, and (3) the constraint caused by the hard Cr sub 2 Nb particles.