ISSN 1063-7834, Physics of the Solid State, 2014, Vol. 56, No. 3, pp. 527–530. © Pleiades Publishing, Ltd., 2014. Original Russian Text © L.I. Derkachenko, B.N. Korchunov, S.P. Nikanorov, V.N. Osipov, V.V. Shpeizman, 2014, published in Fizika Tverdogo Tela, 2014, Vol. 56, No. 3, pp. 512–515. 527 1. INTRODUCTION The structure and mechanical properties of binary Al–Ge alloys with various germanium contents are interesting when analyzing the properties of alloys with equilibrium diagram having the eutectic compo- sition and a limited solubility of the components. The structures of aluminum–silicon alloys which are the basis of many materials widely used in the automobile, tractor, and aviation engineering are studied quite completely [1–3]. The mechanical properties of Al– Ge alloys and the influence of various factors on them were studied only for specific compositions [4]. The influence of the aging of Al–Ge alloys on the mechan- ical properties due to the processes of precipitating germanium from the α-Al solid solution was studied more completely [5, 6]. The aim of this work is to study the structure and mechanical properties of Al–Ge alloys of both hypo- and hypereutectic compositions obtained at direc- tional solidification of melts. 2. SPECIMEN PREPARATION AND EXPERIMENTAL TECHNIQUE Upon traditional casting into sand or mold, the alloys have an irregular structure that is variable in vol- ume and exerts an uncontrollable influence on the properties. Because of this, we used in this work the process of directional solidification of the alloy by the Stepanov method [7]. The crystallization by this method has a number of advantages as compared to other liquid-phase methods. The process is more sta- ble than that in the case of the Czochralski method. The shape and sizes of the article pulled out from the melt are constant, the solidification occurs at a con- stant pulling rate. The interface between the liquid and solid phases and the temperature gradient near the interface are constant. This provides the structure constancy along all the specimens under studied. The ribbons about 0.5 m long with a cross section of 15 × 3 mm were pulled out from an Al–Ge melt through a shaper as a loop from a steel wire during air spray cooling. The pulling rate was about 10 2 μm/s. The high-pure (99.99 wt %) aluminum and germa- nium were used. From the ribbons with the germanium contents of 35, 43, 53, 57, and 64 wt %, the 60-mm- long tensile specimens were made having the gage length 20 mm and a cross section of 3 × 3 mm. The microstructure and the Vickers microhardness H V of the specimens were studied on the polished nonetched specimens. The microhardness was measured on a PMT-3 microhardness meter at the indentation load of 10 g. The measurement error was about 10%. The deformation tests were performed on an Instron 1342 universal test machine. The grid move- ment rate during the tension was 6 μm/s, which corre- sponds to the deformation rate of 3 × 10 –4 s –1 . MECHANICAL PROPERTIES, PHYSICS OF STRENGTH, AND PLASTICITY Structure, Microhardness, and Strength of a Directionally Crystallized Al–Ge Alloy L. I. Derkachenko, B. N. Korchunov, S. P. Nikanorov*, V. N. Osipov, and V. V. Shpeizman Ioffe Physical-Technical Institute, Russian Academy of Sciences, Politekhnicheskaya ul. 26, St. Petersburg, 194021 Russia * e-mail: s.nikanorov28@mail.ru, kolosvl@rambler.ru Received July 17, 2013 Abstract—The structure, microhardness, and strength of binary directionally crystallized aluminum alloys with 35, 43, 53, 57, and 64 wt % germanium have been investigated. It has been shown that the eutectic microhardness is constant in the composition region under study. The microstrength of primary crystals of the solid solution of germanium in aluminum with the dendrite structure increases with increasing germa- nium concentration. However, the difference in the microhardnesses of the eutectic and dendrites, which was determined for each of compositions on the same specimen, does not exceed the measurement error. It has been assumed that the change in the strength of the alloy having the composition in the hypoeutectic region is determined by the redistribution of the volume fractions of the eutectic (α-Al and eutectic germanium) and the domains of primary crystals of the solid solution. This dependence can be described by the mixture rule. Above the eutectic composition, the alloy decomposes in a brittle manner; its strength is likely dependent not only on the content of the components, but also on the form and orientation of primary germanium crystals. DOI: 10.1134/S1063783414030111