Accession Number:

ADA159532

Title:

The Effect of Microstructure on the Creep behavior of Ti-6Al-2Nb-1Ta-0.8Mo.

Descriptive Note:

Final rept. 1 Feb 83-31 Mar 85,

Corporate Author:

VIRGINIA UNIV CHARLOTTESVILLE DEPT OF MATERIALS SCIENCE

Report Date:

1985-09-01

Pagination or Media Count:

133.0

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 T0.2Tm. Steady state creep was attained at elevated temperature T0.4Tm 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 ratetemperature 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.

Subject Categories:

  • Properties of Metals and Alloys
  • Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE