Nanoobjects microscopy

Effect of microalloying by transition and post-transition metals on the aging of precipitation-hardened Al-Cu alloys
A.L. Berezina1, T.O. Monastyrska1, O.A. Molebny1, V.N. Fikssen2, O.D. Rud1
1G.V. Kurdyumov Institute for Metal Physics, Natl. Acad. of Sci. of Ukraine, Vernadsky Blvd. 36, Kyiv-142, 03680, Ukraine 
E-mail: monast@imp.kiev.ua
2 Physico-Technical Institute of Metals and Alloys, Natl. Acad. of Sci. of Ukraine, 34/1 Vernadsky Blvd., Kyiv-142, 03680, Ukraine..

For modern engineering, high-strength casting aluminum alloys with properties identical to those of wrought alloys are of great interest. The main advantage of casting alloys in comparison with wrought ones is the possibility of obtaining parts of complex shape with a high degree of isotropy of material properties. Their less labor-consuming manufacture and processing is a great advantage too.
An effective alloying system for providing improved mechanical and technological properties of model cast Al-Cu alloys (Al-4.6%Cu-0.4%Mn-0.2%Ti), using magnetohydrodynamic (MHD) melt mixing, is chosen in this research.
It was shown that MHD processing provides a non-dendritic (globular) ingot structure and can be applied to ensure thixotropy in the mass production of high-precision cast parts.
Small additives of alloying elements that modify both grain structure (Mn, Zr) and reinforcing phases (Sn, In, Sc) are used. It is shown that the most effective alloying element which improved the strength characteristics of the alloy is Sn. The introduction of 0.1-0.2% Sn followed by heat treatment led to the 50% increasing in the yield strength, 15% increasing in the tensile strength. Sn modified the kinetics of the decomposition providing high density of precipitate and slow coalescence of nano-sized particles of the strengthening phase, which resulted in higher strength characteristics of the alloy.