The advantages and disadvantages of the Aluminium base alloys are well known, and the methods of elimination of problems and increasing of the good properties are also well known. One of the wrong properties of the Al base alloys is the relative high thermal expansion. Si alloying could decrease the thermal expansion coefficient. However, the remarkable high value of decreasing requires so much Si alloying, that primary Si phase appearing on microstructure results remarkable deterioration of the mechanical properties. The quantity of the primary Si phase and the grain sizes of them could decrease by high speed cooling from the melted material (Rapid Solidification, RS), and by adding other alloying elements, in our case nickel, improving the mechanical properties. The rapid solidification might execute by atomisation (spraying) from overheated, homogenous liquid material. The powder resulted by this way could be worked to machine parts by methods of the Powder Metallurgy (PM). Because of the rapid solidification, a typical non-equilibrium state of the material has been produced. Question, the necessary heat effects during the following working steps how influences the properties of the alloy.

The authors try to find the answer to the question; heat-treated the material, which was made by a special version of the described technology above, in a wide range of the parameters like time and temperature. The changes of the phases’ morphology and the mechanical properties as the functions of the heat treatment parameters investigated by electron microscopy and mechanical testing. The space of technological parameters was limited by the criterion of the non-loses of the extra-ordinary good properties of the material at the using.

The experiments were done in the frame of CT 96 0750 “MicroAlu” INCO-COPERNICUS project supporting by European Community. The authors and their colleagues worked together with universities and research institutes of Germany, The Netherlands, Poland and Slovakia on this project.