Accession Number:

ADA242299

Title:

The Influence of Temperature and Composition on the Activation Energy for Creep in Binary Aluminum Lithium Alloys

Descriptive Note:

Master's thesis,

Corporate Author:

NAVAL POSTGRADUATE SCHOOL MONTEREY CA

Personal Author(s):

Report Date:

1990-12-01

Pagination or Media Count:

97.0

Abstract:

With the fast pace of technology in the aerospace industry, there are increasing demands for higher strength and stiffness in structural materials but with reduced weight and improved formability. Aluminum alloys have been widely used in the construction of aerospace vehicles because of their high strength to weight ratio, forming characteristics and corrosion resistance. An investigation was conducted to determine the temperature and composition dependence on the activation energy for creep of A1-0.5wt.pct.lithium, A1-1.Owt.pct.Li, and A1-2. Owt.pc.Li alloys. A series of isothermal tests were conducted utilizing constant true stress creep tests, with nominal temperatures ranging from 300 C to 500 C. Temperature cycling tests involved a range of 10 C for each test. Experimental results indicate all three alloys behave as a class II alloy pure metal class with a stress exponent, n, approximately equal to 5. In addition, subgrain formation was observed in association with the primary stage of creep. The activation energy for creep of the A1-0.5wt.pct.Li and A1-1.Owt.pct.Li alloys was observed to b essentially the same as that for pure Aluminum.

Subject Categories:

  • Research and Experimental Aircraft
  • Metallurgy and Metallography
  • Properties of Metals and Alloys

Distribution Statement:

APPROVED FOR PUBLIC RELEASE