Aluminium matrix composites reinforced with fine aluminium nitride particles

Maciej Dyzia, Józef Śleziona Politechnika Śląska, Wydział Inżynierii Materiałowej i Metalurgii, Katedra Technologii Stopów Metali i Kompozytów, ul. Krasińskiego 8, 40-019 Katowice, Poland

Quarterly No. 3, 2008 pages 269-273

DOI:

keywords: in situ composites, fine reinforcement phase, aluminium nitride

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abstract Aluminium nitride is expected to be favourable reinforcement phase for aluminium matrix compostes. Reinforcement effects could be obtained when particles formed by in situ process were sized less then 1 μm and disposed uniformly in the matrix. More important is good wettability obtained AlN phases, lack of reaction with liquide aluminium and better chemical stability then AlN powder introduced to matrix by ex situ methods. During the liquid-phase process liquid-gas and liquid-solid reactions between aluminium and reacting substance containing nitride were realized. According to thermodynamically point of view, aluminium nitriding is an exothermic process and is quite energetically favourable throughout a wide range of temperatures. At 700C, the process enthalpy for reaction amounts to –658.99 kJ • mol–1, while free enthalpy amounts to 215 kJ • mol–1. The nitriding process is influenced by factors such as nitrogen’s solubility in liquid aluminium and its alloys, passivation effect, reactivity of gases or gas mixtures used for the process (N2, NH3), alloying additions, reaction atmosphere, process temperature and pressure. Proper control of synthesis process leads to the formation expected reinforcement phases and they morphology. Presented results of researches concerning possibilities of obtaining ultrafine aluminium nitride particles via in situ reaction between liquid aluminium alloys (with 3% addition of Mg) and nitrogen gas in higher pressure (300 kPa). During 1 hour nitridation process at 1000°C the layer of reaction products was obtained, while the reaction was take 5 hours components react completely. Presence of Al-N system phases were confirmed by XRD and EDS analisys.