Nanoobjects microscopy
Peculiarities of the formation of nanostructured states in heat-treatable Al-Mg alloys
A.L. Berezina1, T.O. Monastyrska1, O.A. Molebny1, S.L. Polyvoda2, A.V. Kotko3
1 G.V. Kurdyumov Institute for Metal Physics of the NAS of Ukraine. 
Vernadsky Blvd. 36, Kyiv-142, 03680, Ukraine. 
E-mail: monast@imp.kiev.ua
2 Physico-Technical Institute of Metals and Alloys of the NAS of Ukraine. 
Vernadsky Blvd. 34/1, Kyiv-142, 03680, Ukraine.
3 Frantsevich Institute for Problems of Materials Science of the NAS of Ukraine. 
Krzhizhanovskii Str. 3, Kyiv-142, 03680,Ukraine.
It is known that Al-Mg alloys with the content of Mg  wt.10% are capable of precipitation hardening during the aging due to the formation of metastable  and  phases [1]. The precipitation of  phase particles of 2-5 nm with the precipitation density ~ 1018 sm-3 during the aging (Т  100ºС) allow us to obtain a nanostructured state. Thus a significant increase in strength properties can be expected. However, hardly soluble liquations forming during crystallization cause a decreasing of the plasticity of the alloy. The effect of long time homogenization on the formation of disperse  phase particles and nanoscale  phase particles has been analyzed. Alloys solidified with the cooling rate of 10-1 ºC/s (Al-10%Mg and Al-10%Mg-0.1%Sc) and alloys melted by centrifugal casting with the cooling rate of 103 ºC/s (Al-10%Mg) were chosen for comparative analysis. Dendritic liquation and grain size of 100-200 μm are observed in the initial cast state in alloys obtained by the ingot technology. Nondendritic structure with the grain size of 30-70 μm and the stable Al3Mg2 phase on the boundaries of grains are found in alloys after centrifugal casting. Regardless of the production technology the homogenization of Al-10%Mg alloys does not cause a change in grain size in contrast to the Al-10%Mg-0.1%Sc alloy, in which the grain sizes increase to 2 mm. А significant heterogeneity of the distribution of the hardening  phase after aging is observed in Al-10%Mg alloys obtained by the ingot technology. The greatest hardening up to 40% is achieved after using the centrifugal casting due to the formation of the  phase. In Al-10%Mg-0.1%Sc alloy plasticity increases by one order of magnitude and strength on 80% in domain where  phase exists.

1.	Chuistov K. V. Starenie metallicheskih splavov // Kiev. Akademperiodika. – 2003. (in Russian).