The Effect of Microstructure on the Creep behavior of Ti-6Al-2Nb-1Ta-0.8Mo.
Abstract
The effects of microstructure, temperature, stress level and crystallographic orientation on the creep response of Ti-6211 have been investigated. A variety of microstructures simulating the heat affected zone of a weld (HAZ) as well as the as-received structure were tested in a temperature range of 298K to 873K. At stress levels below the tensile yield strength, creep curves level off and saturate in the ambient temperature regime. The colony tupe Widmanstatten alpha + beta as received structure exhibited the highest creep strains at ambient temperatures (T<0.2Tm). Steady state creep was attained at elevated temperature (T>0.4Tm) where wavy dislocation lines and dislocation loops were more homogeneously distributed than at ambient temperatures. Activation energy determinations indicate that creep mechanisms are dependent on a creep rate/temperature relationship. Above 778K the activation energy of creep is close to that of self-diffusion in titanium, suggesting that diffusion-controlled dislocation mechanisms are the rate-controlling processes at elevated temperatures. Creep rupture at elevated temperatures occurred by microwave nucleation and growth. Cyclic creep with a loading-unloading sequence was performed at room temperature and cyclic creep acceleration was observed. The reduction of internal stress in the unloading period enhanced the creep rate in subsequent loading.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1985
- Accession Number
- ADA159532
Entities
People
- E. A. Starke Jr.
- W. H. Miller Jr.
Organizations
- University of Virginia