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The application of the electromagnetic casting (EMC) to aluminum alloys is capable of producing structures, hardly obtainable by the conventional methods of casting due to the constant stirring of the crystallizing alloy and high cooling rate (~10³ K/s). For the first time we study EMC high purity binary Al-0.5Fe and Al-2.5Fe (wt.%) alloys in the as-cast state as well as after equal-channel angular pressing (ECAP) and cold rolling (CR). We demonstrate that EMC process leads to formation of metastable Al2Fe-alike intermetallic phase which does not decompose by further straining and annealing. Combined deformation by ECAP and CR results in the formation of ultrafine grained structure in which providing the increase in ultimate tensile strength up to 200 MPa in Al-0.5Fe and up to 340 MPa in Al-2.5Fe. Electrical conductivity level of Al-0.5Fe alloy increases up to 58.5% IACS, while the conductivity of Al-2.5Fe alloy decreases to 47.9% IACS. Both alloys demonstrate thermal stability of microstructure, mechanical and electrical properties under annealing up to 230 °C for 1h. These effects are discussed in terms of as-cast and strain-induced microstructures. [ABSTRACT FROM AUTHOR]

Solid solution treated Al-Zn alloys with different Zn contents (10 and 30 wt.%) have been nanostructured by severe plastic deformation (SPD) via equal-channel angular pressing method. In-situ transmission electron microscopy observations have been used to follow microstructure evolutions upon annealing. It was shown that SPD leads to the precipitation of Zn particles and that this partial solid solution decomposition was more pronounced in the Al- 30%Zn alloy. Annealing at temperatures in range of 200 to 250 °C led to visible dissolution of Zn particles in both alloys and to formation of extensive grain boundary segregations of Zn. This approach helped to design short term annealing treatments leading to specific ultrafine grain structures that could be achieved by static annealing on bulk samples. Last, the tensile behavior of these materials has been investigated with a special emphasis on the influence of the strain rate on the yield stress and on the elongation to failure. It is shown that in any case the yield stress is mainly controlled by the grain size, while a low volume fraction of Zn phase leads to a relatively modest ductility. [ABSTRACT FROM AUTHOR]

Investigations of an ultrafine-grained (UFG) Cr-Ni austenitic stainless steel produced by high pressure torsion (HPT) at room and elevated (400 °C) temperatures followed by series of annealing up to 700 °C are reported. The grain size of the alloy processed at room temperature (55 nm) was found to be about twice lower than the grain size of the alloy (90 nm) processed at elevated temperature. Besides, both as-processed states demonstrated a very high value of microhardness (~590 Hv), while the steel in initial quenched state had the microhardness about 155 Hv. It is shown that the hardness of the steel in both UFG states does not decrease with annealing up to 650 °C, and even a certain increase in hardness was observed for the steel produced at room temperature. At higher temperature (700 °C), the recrystallization starts, and precipitation was observed. [ABSTRACT FROM AUTHOR]

This work investigates the possibility of achieving superior ductility at room temperature (RT) in the binary Al-Zn alloys with different content of Zn from 5 to 30 wt.% thanks to the formation of ultrafine-grained (UFG) structures with a grain size below 500 nm by the high pressure torsion (HPT) techniques. The supersaturated solid solutions in investigated Al-Zn alloys decomposed during HPT processing resulting in nucleation and growth of secondary Zn precipitates and/or formation of grain boundary Zn segregations. The studied HPT deformed UFG Al-30Zn alloy demonstrates a ductility of 35%. The maximal elongation-to-failure was reached by applying a strain rate of 10-4 s-1. The observed strain rate sensitivity values are close to ones typical of superplastic behavior and were usually observed only at high temperatures above 0.5 Tm. The UFG Al-30Zn alloy becomes superductile at RT. At the same time the ductility of UFG Al-5Zn, Al-10Zn alloys was found to be considerably lower and did not exceed 50% at RT. It is suggested that it is the Al-30Zn alloy that contains a volume fraction of Zn-wetted grain boundaries which is sufficient to provide active grain boundary sliding in an UFG material. [ABSTRACT FROM AUTHOR]