Abstract

To explore the cavity behavior in magnesium-lithium alloy, an ultralight superplastic Mg-9.13Li-3.74Al- 0.31Sr-0.11Y alloy has been fabricated by asymmetric rolling and friction stir processing. The cavity nucleation and growth behavior were evaluated in this alloy at 573K and 1.67×10-3s-1 by means of optical microscopy and tensile testing machine. Microstructural examination reveals that cavity nucleates at α-Mg/β-Li interphase boundary, and cavity interlinkage occurs. Estimation shows that cavity nucleation accounts for 1.14%, and net cavity growth accounts for 98.86% in this alloy. The identification of this contribution is based on the availability of Cao’s cavity nucleation model. A cavity growth equation was obtained in this alloy: 1.210 0.342drrdε= − , where r unit is micrometer. Chokshi’s cavity growth mechanism map constructed in this alloy reveals that plasticity-controlled cavity growth governs the cavity growth mechanism, which is in good agreement with the experimental result.

Keywords: Mg-Li-Al alloy; Friction stir processing; Super plasticity; Cavitation nucleation; Cavitation growth