Accession Number : ADA018645

Title :   Investigation of Basic Creep Mechanisms.

Descriptive Note : Final rept. 1 Sep 74-1 Sep 75,


Personal Author(s) : Mahoney,Murray W. ; Paton,Neil E.

Report Date : 15 SEP 1975

Pagination or Media Count : 60

Abstract : The effect of processing variables on the creep resistance of Ti-5Al-5Zr-0.5Si was studied at 1000F (811K). Variables studied included solution temperature, cooling rate from the solution temperature, time at solution temperature, and metal working processes of cold swaging and hot rolling. The effects of these variables on both creep resistance and alloy stability (post-creep ductility) were evaluated. Optimum parameters for creep resistance with attendant residual ductility proved to be a solution temperature of 2192F (1473K)0.5 hr followed by an air cool. In addition, it was shown that the creep rate controlling mechanism goes through a transition at approximately 0.00005/hr creep rate. This transition is marked by an increase in apparent activation energy at creep rates above 0.00005/hr. The creep rate controlling mechanism at low creep rates (< or = 0.00005/hr) is not however permanently altered by brief overload periods during which the creep rate is increased to levels up to 0.001/hr. Conversely, overload conditions resulting in creep rates approximately = or > 0.003/hr were shown to have a lasting effect on subsequent steady state creep rates.

Descriptors :   *Titanium alloys, *Creep, High temperature, Aluminum alloys, Zirconium alloys, Silicon alloys, Processing

Subject Categories : Metallurgy and Metallography

Distribution Statement : APPROVED FOR PUBLIC RELEASE