engleski

The Al-2.5wt%Mg-0.7wt%Li alloy mechanical properties

Nature and volume fraction of strengthening precipitates, amount of co-precipitates that alter the planar slip deformation behavior, width of precipitation free zone (PFZ) and the content size and distribution of coarse and angular equilibrium precipitates are several microstructural features unique for Al-Li based alloys. Chemical composition, grain structure and thermodynamical parameters influence the nature, structure, size and distribution of the precipitates. In return, this precipitates have pronounced effect on the mechanical behavior of an alloy. The microstructural evaluation of as- cast aluminum alloy containing 2.5wt.% of Mg and 0.7wt.% of Li was done combining Computer aided thermodynamic diagram calculation (CALPHAD) under both equilibrium and non-equilibrium conditions, and differential scanning calorimetry (DSC). Results were compared with microstructural observations of optical and electron microscopy. During solidification sequence, led by low Li/Mg ratio, δ’(Al3Li), T(Al2LiMg) and Al3Mg2 intermetallic phases have precipitated at the boundaries of bulked α-Al. Besides confirming presence of the aforementioned phases, X-ray Powder Diffraction (XRD) had found traces of stable δ (AlLi) phase that precipitated despite unsuitable chemical composition (low Li/Mg ratio) due to non- equilibrium solidification conditions. By using Gleeble, thermo-mechanical properties of Al- 2.5wt%Mg-0.7wt%Li alloy were measured at the deformation rate of 100 mm/min and room and elevated temperatures. To summarize, by enhancing solid solution strengthening, increasing volume fraction of metastable δ’ phase and even partly substituting Li in δ’ phase, Mg has indirect role in improving strength of Al- 2.5wt%Mg-0.7wt%Li alloy.

Al-2, 5wt.Mg-0, 7wt.%Li alloy, lithium, magnesium, phase precipitate, thermo-mechanical properties, room and elevated temperatures, deformation rate

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