SYMPOSIA PAPER Published: 01 January 1986
STP33027S

Al Li Precipitate Modification in an Al-Li-Zr Alloy

Source

An Al-2.34Li-1.07Zr (weight percent) alloy was produced using rapid solidification processing in an attempt to modify the δ′ (Al3Li) precipitate found in the Al-Li binary system to a complex Al3(Li,Zr) phase. Such a modification is expected to increase fracture toughness and ductility by decreasing shear localization, which is a major drawback in Al-Li alloys. A novel microstructure is presented in which a zirconium-rich phase present as fine spheres or discontinuously precipitated rods (with diameters of 6 to 20 nm) is subsequently enveloped by δ′ during aging at 190°C.

Electron diffraction effects, energy-dispersive X-ray analysis in scanning transmission electron microscopy, and preliminary electron energy loss spectroscopy results indicate that the precipitate phase stable at 500°C is Al3(Lix,Zr1−x), where x appears to be 0.45 to 0.8. This is in contrast to the Al-Li and Al-Zr binary systems, in which the equilibrium phases at 500°C for these solute levels are aluminum solid solution and Al3Zr in an aluminum matrix, respectively. The alloy shows longitudinal strength-ductility combinations which are significantly better than those of a low-zirconium control alloy and which compare quite favorably with those of other Al-Li alloys.

Author Information

Gayle, FW
Reynolds Metals Co., Richmond, VA
Vander Sande, JB
Reynolds Metals Co., Richmond, VA
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Details
Developed by Committee: B09
Pages: 137–153
DOI: 10.1520/STP33027S
ISBN-EB: 978-0-8031-4961-8
ISBN-13: 978-0-8031-0442-6