Correlation between S' precipitation and the PortevinLe Chatelier effect in an Al-Li-Cu-Mg-Zr alloy
Serrated yielding, also known as the Portevin-le Chatelier effect, occurs in a variety of aluminum alloys when solutes such as Mg or Cu are present in solid solution. Despite frequent observations of serrated yielding in Al-Li alloys, the phenomenon has not been extensively investigated in these alloys. Tamura, Mori and Nakamura reported finding serrated yielding in Al-3 wt.% Li single crystals deformed at room temperature at a strain rate near 10/sup -3/ 5/sup -1/. However, similar polycrystalline samples did not exhibit serrated yielding, a observation which Tamura et al ascribed to interference of the primary slip system by grain boundaries or by operation of multiple slip systems. Although the cause of serrated yielding in Al-Li single crystals was not discussed, an interaction between dislocations and Li atoms in solid solution is consistent with results reported by Tamura et al. The goal of the present investigation was to show that occurrence of serrated yielding of an Al-Li-Cu-Mg-Zr alloy coincides with absence of S' precipitates (precursor to Al/sub 2/CuMg) in the microstructure. Evidence is presented to show that when Cu and Mg remain in solid solution (S' absent), serrated yielding is observed. However, aging treatments that lead to copious precipitation of S' inhibit serrated yielding in this alloy. Thus, links are established between aging treatment, microstructure and the Portevin-le Chatelier effect in an Al-Li-Cu-Mg-Zr alloy.
- Research Organization:
- Rockwell International Science Center, Thousand Oaks, CA
- OSTI ID:
- 6490491
- Journal Information:
- Scr. Metall.; (United States), Vol. 19:4
- Country of Publication:
- United States
- Language:
- English
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