<p class="Adressess">The preparation of a large number of materials trough the propagating exothermic reactions has been the objective of numerous investigation. Self-propagating reactions are typically associated with high temperatures and extremely steep thermal gradients and thus offer the opportunity to investigate the formation of intermediate and metastable phases. Such reactions are also of interest from a practical point of view since, as has been described in numerous literature accounts, they provide the opportunity to prepare materials with unique properties.</p><p class="Adressess">In this study the thermal effects of dissolution on the solid nickel in liquid aluminum and formation intermetallic phases was studied by simple experimental procedure. The thermal effects generated by exothermic solid-liquid metal interaction was judged by the rise of temperature in the system. Depending on experimental conditions, two different regimes of behavior were found: solid-liquid interaction leading to the considerable rise of the temperature in the system, and characterized by continuos decrease of the temperature in the system with time. The results of the experiments on the heat effects during the interaction of solid nickel with different particle size and liquid aluminum, with and without external mixing, are presented. It has been shown that, depending on experimental conditions, the evolved heat may influence the structure of a zone near to the solid-liquid interface. The experimental procedure correlates with the practical conditions of semi-industrial production of aluminum-nickel master alloys with relatively high percentage of nickel.</p>

Zirconium is one of those few metals which are capable of dissolving relatively large quantities of oxygen. When heated in air at elevated temperatures, an oxide layer is built up at the metal surface. The oxidation of mechanically polished zirconium was studied in the range 500-900oC in air atmosphere, at temperature intervals of 100oC, for exposure times from 5 min to 1860 min for each temperature. The weight gain of the oxidized species was the reacted amount of oxygen with zirconium for the formation of the ZrO2. The weight gain and thickness of the oxide film increase with the increasing of the oxidation time and temperature. The oxidation initially followed a parabolic rate at all temperatures. At temperatures higher than 700oC oxide "breakaway" appears at the longest oxidation times. Microstructural investigations have shown that the oxide layers are compact and with good adhesion to the metal surface, but at temperatures over 700oC, radial micro-cracks appear. Raman spectra of the formed oxides at the investigated temperatures are characteristic for monoclinic phase.