| A study was made of the effects of alloying elements on the structure and mechanical properties of high Li($gt;3wt%) containing RSP Al-Li-X(X=Zr, Cu, Mg) alloys. Particular emphasis was placed on the role of Mg and Cu, which are the major alloying elements in ingot metallurgy (IM) Al-Li alloys. RSP Al-Li-X alloys with several alloy compositions were subjected to various thermal treatments without any pre-aging cold working such as stretching. It has been found that, in the case of plain Al-Li-Zr alloy, the deformation behavior and the resultant mechanical properties are mainly controlled by the presence of uniformly distributed composite Al₃Li/Al₃Zr precipitates. Composite precipitates are also the major strengthening precipitates which control the deformation behavior of the alloys containing Cu and Mg. Addition of Cu and Mg to Al-Li-Zr alloys, when subjected to thermal treatment without any mechanical working, do not promote the precipitation of other strengthening phases such as T₁ and S` as expected ; however, they have a very important effect on increasing the ultimate tensile strength of Al-Li-Zr alloys due to their solid solution strengthening effects. Comparison of the present results with those of IM Al-Li alloys indicates that optimum mechanical properties can be achieved in high Li and Zr containing Al-Li alloys by simple thermal treatment without stretching, and this is due to the presence of uniformly distributed composite precipitates. |
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