Accession Number:

ADA243186

Title:

A Powder X-Ray Diffraction Study of Two Aluminum-Lithium Based Alloys

Descriptive Note:

Master's thesis,

Corporate Author:

NAVAL POSTGRADUATE SCHOOL MONTEREY CA

Personal Author(s):

Report Date:

1991-03-01

Pagination or Media Count:

63.0

Abstract:

The microstructures of solution treated, quenched and aged A1-2.5 wt. Li and A1-2.0 wt.Li-2.76 wt.Mg-1.03 wt.Cu alloys were studied by powder X- ray diffraction. The as-quenched alloys showed extensive X-ray line broadening due to particle size effects and the intensity measurements indicated a significant amount ordering in the as-quenched state. These results were interpreted using a spinodal ordering model which suggests that A1-Li-based alloys order during quenching and then spinodally decompose into regions of order and disorder so that the final microstructure comprises small ordered regions size 40 nm in a disordered matrix Studies on the aged A1-2.5 wt.Li alloy indicated that after initial short-time aging, particle growth follows Ostwald ripening kinetics in agreement with previous work. Studies on the aged quaternary alloy indicated that T1 and S phases grow in this system so that precipitates are not a dominant strengthening mechanism in this alloy.

Subject Categories:

  • Metallurgy and Metallography

Distribution Statement:

APPROVED FOR PUBLIC RELEASE