Accession Number:

ADA237784

Title:

Strengthening Mechanisms, Creep and Fatigue Processes in Dispersion Hardened Niobium Alloy

Descriptive Note:

Annual technical rept. 1 Feb 90-31 Jan 91,

Corporate Author:

CALIFORNIA UNIV DAVIS DIV OF MATERIALS SCIENCE AND ENGINEERING

Report Date:

1991-05-01

Pagination or Media Count:

24.0

Abstract:

The creep properties of Nb-1 Zr alloy was investigated at intermediate temperatures. A model is proposed based on the operation of two parallel mechanisms. The first mechanism is based on dislocation glide- controlled creep and controls creep rate at higher stresses where the influence of the threshold stress due to the particles is negligible. At lower stresses below 135 MPa, the threshold stress of the particles come into play and becomes the rate-controlling mechanism. The resultant effect of the operation of these two parallel mechanisms produced quite satisfactory correlation between theoretical predictions and experimental data. We have also studied the cyclic deformation of commercially pure niobium and Nb-1Zr at ambient temperature. We have conducted tests at slow strain rates, where these materials exhibit high temperature dislocation glide kinetics, and at fast strain rates, where the behavior is characteristic of the low temperature regime. We are presently exploring additional aspects of the fatigue response using a Bauschinger analysis and by testing at very low plastic strain amplitudes to see if a fatigue limit is observed. The focus of this research program is on the development and characterization of refractory metals for advanced aerospace craft and structural applications at elevated temperatures. These applications include space nuclear power reactors and hypersonic vehicles such as the National Aerospace Plane.

Subject Categories:

  • Research and Experimental Aircraft
  • Properties of Metals and Alloys
  • Nuclear Radiation Shielding, Protection and Safety

Distribution Statement:

APPROVED FOR PUBLIC RELEASE